csnl an environment friendly alternative

8/18/2019 CSNL an Environment Friendly Alternative

1/15

RE VI E W A RT I C L E

CNSL: an environment friendly alternative for the moderncoating industry

Dinesh Balgude, Anagha S. Sabnis

American Coatings Association & Oil and Colour Chemists’ Association 2013

Abstract Considering ecological and economical

issues in the new generation coating industries, themaximum utilization of naturally occurring materialsfor polymer synthesis can be an obvious option. In thesame line, one of the promising candidates for substi-tuting partially, and to some extent totally, petroleum-based raw materials with an equivalent or evenenhanced performance properties, is the Cashew NutShell Liquid (CNSL). This dark brown-colored viscousliquid obtained from shells of the cashew nut can beutilized for a number of polymerization reactions dueto its reactive phenolic structure and a meta-substi-tuted unsaturated aliphatic chain. Therefore, a widevariety of resins can be synthesized from CNSL, such

as polyesters, phenolic resins, epoxy resins, polyure-thanes, acrylics, vinyl, alkyds, etc. The present articlediscusses the potential of CNSL and its derivatives asan environment friendly alternative for petroleum-based raw materials as far as polymer and coatingindustries are concerned.

Keywords CNSL, Renewable resources, Resins,Functional chemicals, Coatings

Introduction

Until now, a number of chemistries have been exploredin the coatings industry, such as epoxy, alkyd, poly-urethane, phenolic, acrylic, polyester, silicates, etc.Generally, these chemistries are derived from petro-leum-based stocks. Though these petroleum-derivedpolymers/resins have played a vital role in the coating

industry, their uses have been overshadowed by eco-

nomical and ecological aspects of the modern coatingindustry. These aspects involve exponentially risingprices and high depletion rate, handling issues, toxicityand health hazards of material derived from petroleumstocks, and volatile organic compound (VOC) that areemitted in the environment during synthesis andapplication of petroleum-derived chemistries as theyare volatile in nature. So, considering these issues, it isnecessary to search and explore the new sustainable,economical, nontoxic, and nonhazardous alternatives.

One of the possible solutions is the use of bio-basedmaterials for polymer/resin synthesis. The increasingworldwide interest in the use of biomaterials is mainly

due to the fact that these materials are derived fromnatural sources which are abundantly available andtheir use would also contribute to global sustainabilitywithout depletion of scarce resources. Also, biomate-rials are comparatively easy to handle with no or lesstoxicity and health-related issues. Unlike petroleum-derived polymers, the polymers synthesized from suchbio-based materials can degrade in a controlled waywhen they come in contact with the biological envi-ronment due to the enzymatic action of some micro-organisms, thus promoting the conversions to biomass,methane, carbon dioxide, water, and other naturalsubstances.1,2 Thus, less environmental impact, ease of availability, more economical, and easy biodegradabil-

ity makes bio-based material an attractive topic foracademic as well as for industrial research on synthe-sizing polymers and functional chemicals for thecoatings industry.3

The utilization of bio-based materials as such or bychemical modifications for various applications likeresin synthesis, adhesives, paints, coatings, composites,etc., has been well reported.4–10 Such materials includecellulose, starch, sucrose, sugar, lignin, plant andanimal oils, etc. However, there exists a compoundsuch as Cashew Nut Shell Liquid (CNSL), which can

D. Balgude, A. S. Sabnis (&)Department of Polymer & Surface Engineering, Instituteof Chemical Technology, Mumbai 400 019, Indiae-mail: [email protected];[email protected]

J. Coat. Technol. Res., 11 (2) 169–183, 2014

DOI 10.1007/s11998-013-9521-3

169


2/15

be used as a possible substitute for petroleum-basedmaterials due to its availability, sustainability, costeffectiveness, and reactive functionalities.

Physically CNSL appears as a reddish brown,viscous fluid found in shells of cashew fruits of Anacardium occidentale (as shown in Fig. 1) cultivatedin a large number of tropical and subtropical countries.The tree is native to Brazil and the coastal areas of

Asia and Africa and is now being grown extensively inIndia, Vietnam, Mozambique, the Malagasy Republic,Tanzania, Philippines, and other tropical countries.11,12

In some of these regions, cashew is a popularplantation product, while some others import cashewnuts for processing. Figure 2 gives world production of cashew nuts showing the increasing trend in theproduction of CNSL from 1960 until now. Amongthe various countries mentioned above, Vietnam,India, Nigeria, Cote d\’Ivoire, and Brazil have becomethe top five cashew nut producing countries all over theworld in 2010 with the production of 1,159,600, 613,000,594,000, 370,000, and 174,300 metric tons (MT),

respectively.

14

Thus considering the increasing produc-tion of cashew nut from 1960 until now, across theworld, we can consider CNSL as a continuous sourceavailable for industrial exploitation without depletionof stocks which proves its sustainability.

Though having worldwide availability, there aresome challenges in CNSL. For example, the cashewtree is usually grown from seeds placed directly in thefield. Seed nuts should be thoroughly dry, clean, andfree from insect or fungal attack. Cashew seeds shouldbe sown or planted during the rainy season. Once therainy season is over, seeds should be stored properlyuntil the next rainy season before they are planted inthe field. If not, they may lose their germination

capacity. As plantation of cashew seeds is seasonal,harvesting is another challenge in ensuring the continuous

production of cashew trees throughout the year. Thereare a number of other challenges like land preparation,spacing, fertilizer use, entomological/pathologicalproblems, etc., that need to be taken care of in orderto have maximum production. Also, during processing,CNSL is difficult to remove from the shell with highyields due to the hard outer shell, the intricatehoneycombed features of the pericarp and the ther-

mally sensitive nature of the CNSL. Methods forremoving CNSL from the shell include roasting, hot-oilbath, steam processing at 270C, quick roasting at300C, cold methods, and the solvent extractionmethod.16–18 Though commercially being used, thesemethods have some constraints like low yield, poly-merization of CNSL at processing temperature em-ployed, long extraction times (22–336 h), largeamounts of solvent, harsh mechanical pretreatment,etc.19 To overcome these issues, supercritical fluids

Cashew apple

(pseudo-fruit)

Spongy

Shell

Almond

Cashew Nutshell Liquid

(CNSL)

Cardanol

Cashew Nut

(fruit)

OH

OH

OH

OH

Fig. 1: Cashew nut shell liquid origin13

1,400,000

1,200,000

1,000,000

800,000

600,000

400,000

200,000

01961 1965 1970 1975 1980 1985 1990 1995 1998 2000

Years

P r o d u c t i o n

( t o n s )

Fig. 2: World production of cashew nuts (from 1961 to2000)15


170


3/15

have been suggested as an attractive alternativemethod by Saito.20 So, with proper agricultural prac-tices and optimization of various process parameterslike extraction pressure, extraction temperature, andmass flow rate of supercritical fluid in the advancedextraction techniques, one can overcome all the chal-lenges related to the production of cashew tree andCNSL extraction.

Besides having processing constraints, CNSL andtheir derivatives possess a number of technical benefitsover other renewable oils. Unlike oils, the extractedCNSL contains a number of useful phenolic derivativeswith meta-substituted long chain saturated/unsaturatedhydrocarbons which makes them suitable for a numberof polymerization reactions through addition as well ascondensation mechanisms. Also, the combination of aromatic ring and long chain hydrocarbon helps tomaintain the good balance between flexibility andhardness properties of the coatings. On this basis theywere used in a number of industrial applications,including brake linings materials, laminating resins,

adhesives, ion-exchange resins, paint and coatingresins, foundry chemicals, lacquers, fine chemicals,hybrid materials, water proofing agents, surface activeagents, synthetic rubber, wax compounding, etc., asshown in Fig. 3.

Due to reactive phenolic hydroxyl, one-step synthe-sis of epoxy resin with 100% conversion can bepossible, unlike epoxies derived from oil. Also,CNSL-based epoxy synthesis does not involve the useof hazardous chemicals like peroxides which are usedin epoxidation of oils. Thus there are no handling orhealth-related issues in CNSL-based resin synthesis.

Also, chemically unmodified CNSL has been reportedto reduce the corrosion rate of carbon steel by over90% due to phenolic hydroxyl which gets adsorbed onmetal surface.24 This inhibitive property cannot beachieved with oils. Due to structural similarity, CNSLand their derivatives can easily replace toxic phenoliccompounds used in resin synthesis, like phenols inphenolic resin synthesis, bisphenol-A in epoxy resin

synthesis with improved properties. In some cases,epoxy resin derived from CNSL can replace conven-tional epoxy resin with equivalent or slightly higherperformance properties. Also, chemically modifiedCNSL can replace hydroxyl functional resins derivedfrom petroleum-based stocks which can be used in anumber of applications like polyurethane synthesis,crosslinkers, etc., with better performance properties.With esterification, CNSL can replace conventionaltoxic plasticizers like di-octylphthalate (DOP)/di-buty-lphalate (DBP)/di-ethylhexylphthalate (DEHP) whichare used in polyvinyl chloride (PVC) processing.Commercially used hindered phenols for antioxidant

purpose can be replaced by chemically modified CNSL.These are all chemical modifications and their perfor-mance against conventional ones are covered in thesubsequent sections.

Chemistry of CNSL and compositionof its extraction

As an agricultural by-product of the cashew nutproduction, CNSL is one of the major economicsources of naturally occurring phenols and is regarded

– Decorative applications

Lacquers & Varnishes

– Protective applications– Insulation Coatings– Buildings, Furnitures, &

Automobiles

Other Applications

– Foundary Chemicals– Brake Lining & Clutch Facing– Laminates– Cement Hardeners– Diesel Oil– Adhesives

– Hybrid Materials– Rubber Compounding

– Age Resistors (Prevent degradation)– Vulcanizing Agent

Paints & Primers

– Anticorrosive

– Heat Insulating– Flame Resistant– Black EnamelsAdditives

– Antioxidants– Corrosion Inhibitors

– Colorants & Dyes– Coupling Agents– Dispersants

– Bactericides– Fungicides– Emulsifying Agents– Stabilizers– Accelerators– Plasticizers

Resin Synthesis

– Alkyd– Polyesters– Epoxy– Polyurethanes– Acrylics– Phenolics– Ion Exchange Resins, etc.

Specialty Polymers & Coatings

– Anti-biofilm Coating– Crosslinked Polymers– Molecularly Imprinted Polymers– Fire Retardant Polymers– Liquid Crystalline Polymers, etc.

Applications of

CNSL

Fig. 3: Potential applications of CNSL and its derivatives21– 23


171


4/15

as a versatile and valuable raw material for polymerproduction. CNSL obtained from unroasted shells wasfirst found by Stadeler to consist chiefly of anacardicacid which on heating decarboxylated to cardanol andcardol. Since then, a number of authors have reportedon the chemistry, method of extraction, refining, andcompositions of the extracted CNSL.25 The physico-chemical properties of CNSL are stated in Table 1.

On thermal distillation, CNSL yields a number of phenolic derivatives like anacardic acid (6-pentadece-nyl salicylic acid), cardol (5-pentadecenyl resorcinol),and 2-methylcardol (2-methyl 5-pentadecenyl resor-cinol) whose main component is cardanol (3-pentade-cenyl phenol); a meta-substituted unsaturatedhydrocarbon chain having a chain length of C-15,27 asshown in Fig. 4.

Possible reactions of CNSL and their derivatives

CNSL and their derivatives can undergo number of chemical reactions, some of them being sulfonation,nitration, esterification, halogenation, etherification,epoxidation, etc.

CNSL was sulfonated28 to yield alkyl aryl sulfonicacid or their metal salts. The reaction was carried outat 108C using concentrated H2SO4. To preventpolymerization during sulfonation, an aryl or alkaligroup was substituted for hydrogen and the doublebonds of the aliphatic side chain were saturated byhydrogenation before treatment with the acid.

Direct nitration of cardanol leads to simultaneousoxidation and polymerization reactions. By nitration of hydrogenated cardanol, 4-nitro and 6-nitro compoundswere obtained.29 Nitro-derivatives of cardanol are veryefficient antioxidants for gasoline, mineral hydrocar-bons, petroleum products, and lubricating oils.

Cardanol esters can be synthesized by reactingcardanol with acid chlorides in the presence of alkalis.Thus benzoyl chloride gives benzoyl cardanol. Variousother esters of industrial importance have also beenreported.30

Epoxidation of the phenolic group can be accom-plished by the reaction of CNSL with epichlorohy-drin.31 The chemical changes during this reaction aresimilar to those of conventional epoxy synthesis. In thisregard, Unnikrishnan et al. have studied the use of cardanol in place of a phenol or diphenol, in thesynthesis of epoxy system and compared with theconventional epoxy. Further, the combination of card-anol and bisphenol-A have also been studied and it wasobserved that introduction of 20 mol% cardanol into

bisphenol-A resulted in a resin having reduced tensile,impact, and compressive strengths upon curing by apolyamine hardener but considerable improvement inelongation-at-break without much decrease in energyabsorption. All possible reactions are shown in Fig. 5.

CNSL and its derivative-based polymers, resins,and functional chemicals

CNSL, a naturally available material, undergoes similarkinds of reactions as those of phenols due to its phenolicstructures. In addition, the presence of long chainunsaturated hydrocarbon chain provide additionalreacting site. Therefore, a diverse range of resins/polymers can be synthesized using CNSL. It includesepoxy, alkyd, polyurethane, phenolic resin, vinyl,acrylic, etc. Further, these synthesized resins can beformulated for different types of coatings like modifiedalkyd-based coatings, epoxy coatings, waterborne coat-ings, UV-curable coatings, modified polyurethane coat-ings, phenolic coatings, etc. (as shown in Fig. 6).Numerous authors have reported on the differentreaction conditions, number of reaction catalyst, andvarious process parameters to polymerized CNSL.32–35

OH

COOH

C15H31• C15H31

•

C15H31•

C15H31•

C15H31•

(a)

OH

HO

(c)

H3C

(b)

OH

HO

(d)

OH

(1)

(2)

(3)

(4)11'

11'14'8'

8'

8'=

Fig. 4: Chemical composition of CNSL: (a) anacardic acid,(b) cardanol, (c) cardol, (d) 2-methylcardol

Table 1: Physicochemical characteristics of Cashew

Nut Shell Liquid (CNSL)26

Parameter Observation

Appearance and nature Reddish brown viscous liquid

Refractive index 1.693–1.686

Specific gravity 0.941–0.924

Viscosity (30

C) (centripore) 41–56Moisture (%) 3.9–6

Ash (%) 1.2

Saponification value

(mgKOH/g)

47–58

Iodine value (mg/100 g) 215–235

Acid value (mgKOH/g) 12.1–15.4

Free fatty acid (mgKOH/g) 6.1–7.8


172


5/15

Epoxy resins

Aggarwal et al.36 have developed an epoxy-cardanolresin with better properties as compared to BPA-basedepoxy resin in terms of an increase in tensile strength(31%), elongation (129%), and bond with steel (28%)and reduced water vapor transmission of the film.Further the synthesized resin was formulated for ananticorrosive paint and cured with an aromatic poly-amine adduct hardener. The formulated paint wastested for physico-mechanical properties, chemicalresistance and corrosion protection efficiency and

compared with conventional epoxy resin-based anti-corrosive paint. It was found that the modified resin-based paints exhibit about 25% higher tensile strengthand 15% more elongation than the paints made withunmodified resin. Finally, authors have concluded thatthe developed resin performed better as binder mediafor the formulation of anticorrosion paints than theunmodified epoxy resin.

Huang et al.37 have synthesized a light color card-anol-based epoxy curing agent from cardanol butylether, formaldehyde, and diethylenetriamine and

compared to phenalkamine with a similar structure.It was observed that etherification of phenolic hydroxylof cardanol improved the color stability and loweredthe viscosity. However, etherified cardanol was foundto be less reactive due to absences of phenolic hydroxylgroup as compared to phenalkamine.

Kim et al.38 have successfully synthesized an epoxide-containing polycardanol by enzymatic route using twodifferent enzymes, viz. lipase and peroxidase. Lipasecatalysis was used for the epoxidation of the unsatu-rated alkyl chains of both cardanol and polycardanol,and peroxidase catalysis was used for the polymeriza-

tion of both cardanol and epoxide-containing cardanol.The product was synthesized by two different routesincluding synthesis of epoxide-containing cardanol inpresence of lipase, followed by the polymerization of the phenolic functional groups of cardanol usingperoxidase. Another route involved a synthesis of polymerized cardanol from cardanol in the presenceof peroxidase and, subsequently, the epoxide-contain-ing polycardanol from polycardanol in the presence of lipase. The curing of the resulting polymers proceededthermally at 150C, and yielded a transparent polymeric

Sulphonation

H2SO4, Zn, Ca –H2O

RCl –HCl

E s t e r i f i c a t i o n

NaCl

E C H N a O H

C 6 H 5

C O C I

A l k a

l i

H N O 3 – H

2 O – H

2 S O

4 R 2 S O

4

NO2

N i t r a

t i o n

O2N

HCI

E t h e r i f i c a t i o n

E p o x i d a t i o n

OR

C15H31

C15H31

C15H31

C15H31

C15H31C15H31C15H31

C15H31

OH

OH OH

OCOC6H5

OR

O

O

OR

SO3M

+

–

+

+

+

Fig. 5: Possible reactions of CNSL and their derivatives


173


6/15

film. The pencil scratch hardness of the films wasimproved compared with that of polycardanol. Owingto the epoxide content in the polymerized cardanol, thefilm cured with phenalkamine showed a higher hardnessvalue after a relatively short curing time.

Longo and co-workers39 have synthesized two dif-ferent novolac resins, named Nov-I and Nov-II, con-taining an amount of unreacted cardanol of 35 and 20wt%, respectively, by the condensation reaction of cardanol and para formaldehyde using oxalic acid ascatalyst. The cardanol-based novolacs were tested as

curing agents for diglycidyl ether of bisphenol-A epoxyresin employing 2-ethyl-4-methyl-imidazole as catalyst.Differential scanning calorimeter (DSC) and thermo-gravimetric studies were performed to identify thethermal properties of the cured resins. In addition, theepoxy resins cured with the synthesized novolacs wereevaluated for tensile tests and synthesized novolacsand were shown to be worthy of consideration aseffective epoxy curing agents.

A new class of phenalkamine (Mannich reactionproduct) from cardanol, formaldehyde, and polyamineswas successfully synthesized by Pathak and Rao.40 Theproduct was characterized by high-pressure liquid chro-matography (HPLC),Fouriertransform infraredspectro-

scopy (FTIR), and nuclear magnetic resonancespectroscopy (1H-NMR). The presence of characteristicmethylene linkages of Mannich bases at d 3.5–4.0 ppmwas observed by 1H-NMR. Further, the synthesizedcuring agent was used to cure diglycidyl ether of bisphe-nol-A at room temperature and the curing times wereoptimized. The cured samples showed good adhesionwith different metal surfaces, in particular, higher valueswere observed with copper due to its high surface energy.Further, the coatings were analyzed for viscoelasticproperties and thermal stability properties by dynamic

mechanical thermal analysis (DMTA) and thermogravi-metry analysis (TGA). The storage modulus (E ¢) wasfound to be on the order of 109 Pa and tan d values werearound 90C. A reduction in storage modulus (E ¢)andanincrease in tan d values on postcuring were observed.TGA showed two-stage degradation above 250C; thefirst stage being the decomposition of the aliphatic chainof the Mannich base and the second stage due to curedepoxy polymer degradation.

Tan and Nieu41 have investigated the thermal,dielectrical, chemical, and mechanical properties of a

newly synthesized carbon fiber composite based ontetrafunctional epoxy resin namely N ,N ,N ,N -tetraglyc-idyl-2,2-bis[4-(4-aminophenoxy)phenyl]propane modi-fied with cardanol. It was observed that the use of cardanol in epoxy resins at cardanol/epoxy molar ratiosless than 0.3/1 improved the chemical resistance as wellas the mechanical properties of the composites, such asflexural strength and modulus, tensile strength andmodulus, and interlaminar shear strength. Highercardanol contents decreased such properties. Themaximum values of all properties of the compositeswere observed with the epoxy-cardanol resin having acardanol/epoxy molar ratio of 0.3/1.

Alkyd resins

Madhusudhan and Murthy42 have synthesized a poly-functional compound from cardanol by reacting withmaleic anhydride under various experimental condi-tions to yield up to 70% conversion. Further, theproducts were evaluated as intermediates for preparingwater-soluble binders and as alkyd resin modifiers. Itwas concluded that the modification improved resis-tance to water and chemicals and showed high scratch

Polyurethane

Coatings

MDI

DBTDL

ModifiedPolyol

Water SolubleBinder

Pd, Co

Driers

Water Borne

Coatings

N e u t r

a l i z a

t i o n

D i e t h a n

o l a m

i n e

Pd, Co

DriersModified Alkyd

Modified Alkyd

Resin

Modified AcrylicCoating

based Coatings

P h t h a l i c a n h y d r i d e ,

L i n s e e d O i l ,

G l y c e r o l

Photoinitiator

Diluent

UV-CurableCoating Material

Modified PhenolicResin

Epoxy-Phenolic

Coating

Epoxy Coating

High Mol.Wt

Epoxy, 180°C

NaOh, Reflux Chlorohydrin

I P D I , H y d r o x y e t h y l

m e t h a c r y l a t e

HCHO

H+

ECH NaOH

Malenization

180-200°C

H y d r

o l y s i s

P o l y a m i n e

A d d u c t

OH

OCH2CHCH

2OH

OCH2CHCH

2OH

C15

H31

C15

H31

C15

H31

C15

H31

C15

H31

C15

H31

C15

H31

OH

OH

OH

O H

HO

OO

OH OH HO

OH HO

O O

OO

Fig. 6: Coatings based on CNSL and its derivatives


174


7/15

hardness values (1900 g for water-soluble binder and1100 g for modified alkyd compared to 800 g of neatalkyd).

Polyurethanes

Tan et al.43 have investigated the synthesis of carda-

nol–glycols (CGs) and polyurethane (CGPU) filmsthereof. The films were characterized for FTIR and 1H-NMR spectroscopy, swelling test and DSC studies. Thecontent of cardanol in CGPUs was found to beinversely proportional to the molecular weight of glycols and affected the crosslinking density of thefilms. The reduced crosslinking density stronglyaffected the swelling property and glass transitiontemperature. Further, the crosslinking of CGPUs wasimproved by autooxidation–autopolymerizationthrough the double bonds of the cardanol side chain,catalyzed by cobalt salt.

A class of tough and crosslinked polyurethanes was

successfully synthesized from a derivative of CNSL byGopalakrishnan and co-workers.44 A three-stage syn-thesis of hydroxyl functional resins for polyurethaneinvolved a synthesis of novolac resin using cardanol andformaldehydein three different molar ratios followed byepoxidation and subsequent hydrolysis to obtain hy-droxyalkylated cardanol–formaldehyde resin. The syn-thesized hydroxyl functional resin along with acommercial polyol (PPG-2000) was used to cure diph-enylmethane diisocyanate (MDI). Polyurethane pre-pared using a higher mole ratio of cardanol/formaldehyde of hydroxyalkylated cardanol–formalde-hyde resin was found to possess better thermal andmechanical properties than the polyurethane prepared

from a lower molar ratio.Asha and co-workers45 have established a one-pot

synthetic step to prepare UV-curable urethane–meth-acrylate crosslinkers from cardanol. The methodologyinvolved an endcapping of isophorone diisocyanate withone equivalent of hydroxyethyl methacrylate followedby condensation with cardanol. The structures of theresins were characterized by FTIR, 1H-NMR, 13C-NMR, matrix-assisted laser desorption/ionization timeof flight (MALDI-TOF) spectroscopies, and size exclu-sion chromatography (SEC). Further, the synthesizedacrylate oligomer was formulated for UV-curable coat-ings. The experimental results revealed that the hydro-gen bonded crosslinkers based on cardanol and itsderivatives had higher double bond conversion whencompared to a nonhydrogen bonding standard such ashexanediol diacrylate (HDDA) under identical condi-tions. The temperature effects on the hydrogen bondingand thereof on the curing process werealso investigated.

Phenolic resins

CNSL has potential industrial applications such as forresins, friction lining materials, and surface coatings.

Especially in the field of polymers, CNSL has primarilybeen studied as a modifier of phenol–formaldehyde(PF) resins due to its structural similarity with phenol.CNSL reacts with formaldehyde under a variety of conditions, yielding both resole and novolac resinsdepending on the catalyst used. Figure 7 shows thepossible structure of crosslinked CNSL–formaldehyderesin where R represents the side chain.

The phenolic nature of the constituents of CNSLalong with varying degrees of unsaturation in the sidechain makes it a highly polymerizable substanceamenable to a variety of polymerization reactions.The most obvious and common method of obtainingpolymeric materials from CNSL is the condensationreaction with formaldehyde.

Mahanwar and Kale46 experimentally investigatedthe effect of process condition during replacement of phenol with CNSL on the properties of novolac andresole resins. The addition of CNSL into phenol seemsto increase reaction times for the preparation of phenolic resins. This increase in reaction time can be

due to the low reactivity of the CNSL, arising from thestearic hindrance caused by the side chain. Experi-mental results revealed that an acid value of CNSLplayed an important role in resin synthesis. WhenCNSL with acid value more than 10 was used, only aviscous fluid with very low resin content was obtained.Finally, the authors concluded that only CNSL with anacid value less than 10 was suitable for resin prepara-tion; the addition of CNSL leads to a decrease intensile strength but an improvement in the impactstrength and electrical properties of the resole resins.

Similarly, the effect of partial replacement of phenolby CNSL in PF resin has studied by Papadopoulou andChrissafis.47 Further, the synthesized resin was com-

pared with a conventional petroleum-based PF resin.The resins were characterized for physicochemical andthermal properties. Wood panels impregnated withthese resins were also evaluated for thermal propertiesby DSC from an end application point of view. TheDSC measurements revealed that the wood reducesthe curing temperature of both resins, but it has greater

OHOH

H2 H2

R

H

HO R

H2C

CH

R

C

C

C

Fig. 7: Crosslinked structure of CNSL-formaldehyde resin


175


8/15

effect on the CNSL-modified PF resin (PCF) where itbrings a reduction of 7C. In the case of the PFstandard resin this reduction corresponds to only 3.6C.It was proven that, although the neat PCF cured atlonger time and higher temperature than a conven-tional PF resin, wood affects it more significantly,resulting in the equalizing of their curing performance.Further, the adhesion strength of synthesized resins

was investigated by their application in plywoodproduction. The plywood panels were tested for theirshear strength and wood failure performance whiletheir free formaldehyde emissions were determinedwith the desiccator method. This was a novel findingthat manifests the possibility of replacing a conven-tional PF resin with a CNSL-modified one in theplywood production, without changing any of theirproduction conditions and with improvement to theiroverall properties.

The various reaction parameters like reaction kinet-ics, reaction mechanism, composition of resin for acidas well as alkali catalyzed cardanol-based phenolic

resins have been extensively studied by a number of authors.48–52

Eswaran and co-workers53 have demonstrated anovel methodology for the synthesis of a new series of CNSL/cardanol-based ‘‘high ortho’’ novolac copoly-mers, used as photoresists for microlithography. Theauthors have used gel permeation chromatography(GPC) and both 1-D and 2-D NMR spectroscopictechniques to elucidate the exact microstructure of synthesized copolymer and to calculate the percentageincorporation of different monomers in the polymermicrostructure. The lithographic performance of pho-toresists using novolac resins based on cardanol (frac-tionated CNSL) and diazonaphthoquinone ester was

also evaluated.A novel phenolic type of thermoset resin with

improved mechanical and toughness properties wassuccessfully synthesized by Cardona et al.54 Themodification involved a copolymerization of phenolwith cardanol at different weight ratios. The modifiedphenolic resins (CPF) were prepared at various molarratios of total phenol (phenol with cardanol) toformaldehyde. CPF resins with maximum content of 40 wt% of cardanol were synthesized and used. Bothresins (CPF/PF) were mixed in different proportions,and their thermal and mechanical properties were thenestablished. An increase in the content of cardanolresulted in a proportional increase of the flexuralstrength and fracture toughness together. The resultsobtained by the DMA analysis of the post cured resinCPF/PF blends revealed a decrease in the crosslinkdensity and T g values with increasing cardanol contentand also with the decreasing total phenol/formalde-hyde molar ratio. This could be due to the flexibilityenhancement by introduction of cardanol inside thephenolic molecular network.

Souza et al.55 have developed cardanol-based pheno-lic resins and blended them in situ with polyaniline(PANi) for pressure-sensitive applications. The final

polymer blend was found to be composed of a soft solidmaterial and insoluble in ordinary solvents. Sampleswere characterized through X-ray scattering, FTIR,electrical conductivity, and pressure sensitivity mea-surements. FTIR results indicated that the insertion of PANi into the blends did not change the chemical natureof the resin. According to wide-angle X-ray scatteringresults, PANi was dispersed homogeneously in the final

polymer samples which improved the sensitivity of theelectrical conductivity to pressure variations. Pressuresensitivity and electromechanical analysis indicated thatthe produced blends could be used as pressure-sensingmaterials. Among the tested materials, the blend con-taining 5 wt% PANi presented a larger variation of conductivity (340%). The increase of the PANi concen-tration led to a decrease in the conductivity variation.This could be related to theincreasing number of contactpoints among the PANi chains.

A number of researchers have reported on thesynthesis of epoxidized cardanol-based novolac typephenolic resins.56–58 Though having several outstand-

ing characteristics, epoxy resins exhibit a low impactresistance in their cured state which limits the appli-cations of epoxy resins. To alleviate this deficiency,epoxy resins were modified by the incorporation of acarboxyl-terminated copolymer of butadiene and acry-lonitrile (CTBN).59–62 In this regard, Yadav et al.63

have tried to produce the modified epoxy matricesbased on cardanol and improved its impact resistanceby physical blending with CTBN. Further, CTBNblended epoxidized novolac resin was cured with astoichiometric amount of polyamine curing agent. Theformation of various products during the synthesis of cardanol-based novolac resin, epoxidized novolacresin, and blending of epoxidized novolac resin with

CTBN has been studied by FTIR analysis. The numberaverage molecular weight was determined by GPCanalysis. The blend sample, having 15 wt% CTBNconcentrations, showed minimum cure time and themost thermally stable system.

Miscellaneous coating materials

ANTIBIOFILM COATINGS: Some species of naturalunsaturated hydrocarbon phenols such as cardanol andsome component of lacquer tree sap (sap extracted fromlacquer tree) have been reported to have an anti-biofouling effect. Kim et al. reported polymerization of cardanol by enzymatic reaction and its potentialapplication as antibiofilm coating material.64

Choi et al.65 have studied an antifouling property of newly synthesized polydimethylsiloxane (PDMS) matri-ces impregnated with natural unsaturated hydrocarbonphenols, i.e., urushiol from the sap of natural lacquertree and a mixture of cardol and cardanol from refinedCNSL. Incorporation of naturally available unsaturatedphenols showed excellent antimicrobial property toboth Escherichia coli and Saccharomyces cerevisiae.


176


9/15

PROCESSABLE AROMATIC DIAMINE: More and co-workers66 have synthesized a processable aromaticdiamine monomer, viz., 4-(4¢-aminophenoxy)-2-pentadecylbenzenamine containing pendant pentadecylchain from CNSL for electronic applications. A series of new polyazomethines containing flexibilizing etherlinkages was synthesized by polycondensation of synthesized diamine monomer with commercially

available aromatic dialdehydes viz., terephthaldehyde(TPA), isophthaldehyde (IPA), and varying mixtures of TPA and IPA. Inherent viscosities and number averagemolecular weights of (co) polyazomethines were in therange 0.50–0.70 dL/g and 10,490–40,800 (GPC,polystyrene standard), respectively, indicating theformation of medium to reasonably high molecularweight polymers. Polyazomethines containing pendantpentadecyl chains were found to be soluble in commonorganic solvents such as chloroform, dichloromethane,tetrahydrofuran, pyridine, m-cresol andcould be cast intotransparent and stretchable films from their solution inchloroform. Polyazomethines exhibited glass transition

temperatures (T g) in the range 21–48C. The observeddepression of T g could be ascribed to the ‘‘internal

plasticization’’ effect of pentadecyl chains. Thetemperature at 10 wt% loss (T10), determined fromTGA in nitrogen atmosphere of polyazomethines was inthe range 434–441C indicating their good thermalstability.

FIRE RETARDANT MATERIAL: The recognition of toxicity and environmental persistence of halogenatedflame retardant (FR) materials has prompted thereduction in their usage across the globe. There is animmediate need for new types of nontoxic andeffective FR produced preferably through sustainableroutes. In this regard, Ravichandran et al.67 havereported the synthesis and characterization of a newpolyphenolic FR material-based cardanol. Cardanolwas polymerized in aqueous media using various typesof oxidants. The thermal properties of the resultingpolymers were investigated. Polycardanol synthesizedusing a specific type of oxidant exhibited good thermalstability and low heat release capacity. Finally, authorsconcluded that the preliminary results obtained fromthe study were quite promising and indicated thepossibility of synthesizing new types of FR materialsfrom bio-based phenols.

CROSSLINKED POLYMER: A novel crosslinked polymerfrom cardanol was synthesized easily by Bai et al.68

through solvent-free polymerization with FeCl3. Themethodology involved grinding of cardanol andanhydrous FeCl3 powder using a glass pestle in amortar at ambient temperature and solvent-freecondition, yielded up to 80% in 5 min. It wasconcluded that the rigid structure of conjugatedcondense rings improved the thermal stability of thepolymer which was in good agreement withthermogravimetric graphs as shown in Fig. 8.

MICROBIAL CATALYZED POLYMER: Kim et al.69 havesuccessfully carried out an oxidative polymerization of cardanol in water–organic solvent mixtures using afungal peroxidase from Coprinus cinereus (CiP). So far,only uneconomic plant peroxidases, such as soybeanperoxidase (SBP), have been used to polymerizecardanol. The fungal peroxidase used was easilyproduced by cultivating C. cinereus, and was purifiedby ultrafiltration and size exclusion chromatography.Microbial CiP-catalyzed the cardanol polymerizationas efficiently as SBP. The effects of reactiontemperature and peroxide concentration on the CiP-catalyzed polymerization of cardanol were investigated

in aqueous 2-propanol. It was found that a low reactiontemperature of 10 and 15C increased the polycardanolyield (to 91%) and the hydrogen peroxide feed ratewas found to affect the initial reaction rate and the finalconversion. Finally it was concluded that the microbialCiP could be more useful for the synthesis of a range of polyphenols from renewable resources than plantperoxidases.

COPOLYMER CURING SYSTEM: Rao et al.70 havedeveloped a new copolymer curing system based onnewly synthesized monofunctional benzoxazine (CBO)and hydroxyl functionalized benzoxazoline monomer

(HBO), 2-(4-hydroxy phenyl)-2-oxazoline fromcardanol derivatives. Further, the curing system wasevaluated for thermal and mechanical properties byvarying proportions of CBO and HBO in copolymersystem. A significant reduction in curing temperaturewas observed from thermal studies and an increase inheat of polymerization value with incorporation of HBO was also noted. The activation energy of cardanol benzoxazine was found to reduce withincorporation of 25 mol% of hydroxy benzoxazolinedue to the catalytic effect of OH group lowering the

100

90

80

70

60

50

40

30

20

10

100 200 300 400 500

a

b

Temperature (°C)

W t %

Fig. 8: TG curves of the polycardanol by solvent-freepolymerization (a) and by liquid-phase polymerization (b)


177


10/15

activation energy. The flexible cardanol benzoxazinepolymer displayed a lower storage modulus of 2.7 9108 (Pa) and a tan d of 104C, with incorporation of rigid hydroxy benzoxazoline monomer in thecopolymers exhibiting significant enhancement of these values. The width of tan d peak of copolymerswas found to increase, suggesting an enhancement of toughness value.

WATER-SOLUBLE MANNICH BASES: Ramasri et al.71

have synthesized water-soluble Mannich bases fromcardbisphenol, a reaction product of distilled cardanoland phenol by Mannich reaction, as shown in Fig. 9.

The effect of electrodeposition parameters on thefilm formation from synthesized binders and from thepigmented composition was studied. It was found thatthe polymers gave uniform coatings with good mechan-ical properties and the pigmented systems exhibitedhigh resistance to organic solvents and excellentcorrosion resistance properties.

POLY(AMIDEIMIDE): A novel class of aromatic diacy-lhydrazide monomer was successfully synthesized fromcardanol by More et al.72 The synthesized monomer wasused to developed a new series of poly(amideimide)scontaining flexibilizing ether linkages andpendant pentadecyl chains by a two-step solution

polycondensation in N ,N -dimethylacetamide. Thesolubility of poly(amideimide)s in N ,N -dimethylacet-amide, 1-methyl-2-pyrrolidinone, pyridine, and m-cresolat room temperature was found to be significantlyimproved by incorporation of pendant pentadecyl chains.In addition,the synthesized polymer was characterized forwide-angle X-ray diffraction, while thermal stability wasdetermined by TGA in nitrogen atmosphere. From the

experimental results, the authors concluded that thethermal stability of poly(amideimide)s was excellent.Also, a glass transition temperature of poly(amideimide)was in the range 162–198C. It was observed that theplasticization effect of attached pentadecyl side chainsinduced the depression of T g.

MOLECULARLY IMPRINTED POLYMER: Recently, Philipet al.73 have used monomers from CNSL to developmolecularly imprinted polymers. The extracted CNSLwas used to synthesize anacardanyl acrylate (AnAcr)and anacardanyl methacrylate (AnMcr) monomers andwere characterized by FTIR and 1H-NMR. Different

imprinted bulk polymers based on AnAc, AnAcr, andAnMcr functional monomers were separatelycopolymerized in toluene with ethylene glycoldimethacrylate and divinylbenzene as crosslinkers,using racemic propranolol as a model template. Theexperimental results showed that the AnAc-basedpolymer revealed a meager rebinding ability, theimprinted polymers made from AnAcr and AnMcrdisplayed highly specific propranolol binding. At apolymer concentration of 2 mg/mL, AnAcr- andAnMcr-based imprinted polymers were able to bindover 50% of trace propranolol. Under the samecondition propranolol uptake by the two nonimprintedcontrol polymers was less than 20%.

Adhesives

Kim74 developed CNSL–formaldehyde (CF)-basedresin and its alloy with polyvinyl acetate (PVAc) resinfor the maple face of the veneer bonding on plywood.The CF resin was used to replace urea–formaldehyde(UF) resin in the formaldehyde-based resin system inorder to reduce formaldehyde and VOCs emissionsfrom the adhesives used between plywoods and fancyveneers. The use of PVAc was found to introducereactive sites in the CF resin. The green adhesives with

varyingpercentagesof PVAc resins such as 5, 10, 20, and30% were evaluated for surface bonding strength byUniversal Testing Machine (UTM) in the tensile mode,light microscopy, scanning electron microscopy, form-aldehyde emission test, and a VOC analyzer test. TheCF/PVAc resins showed better bonding than the com-mercial natural tannin adhesive with a higher level of wood penetration, as shown in Fig. 10.

The bonding strengths of the nontreated (beforeboiling), engineered flooring samples made using CF/PVAc hybrid adhesives were considerably higher than

OH

(CH2)7

(CH2)7

HC (CH2)6CH3

(CH2)6CH3

OH

HO

N

OH

HC

OH

HON

Mannich base

0 to –5°C

Cardbisphenol

2-ethylaminoethanol

HCHO

Fig. 9: Mannich Bases from cardanol for cathodicallyelectrodepositable system


178


11/15

those of the CF resin. With increasing PVAc content,the bonding strength was increased up to 20% of PVAccontent.

Lee et al.75 have studied the properties of greenadhesives based on tannin (a naturally occurringphenolic compound) and CNSL for the replacementof conventional formaldehyde-based toxic and hazard-ous adhesives in indoor environments.

Laminating resins

Sridhar et al.76 have synthesized a series of resoleresins from distilled multivalent phenol obtained dur-ing the carbonization process of a lignite source, alongwith other phenolic derivatives like cardanol. Theyestablished a low cost method for making electrical-grade laminate from the synthesized resin on alaboratory scale. The properties of the resoles wereevaluated and found to be similar to that of purephenol (C6H5OH) resins. The resole varnishes pre-pared were used for making cotton paper phenoliclaminates by hand impregnation and the compressionmolding technique. The paper laminates were evalu-ated for physical, chemical, mechanical, and electrical

properties. The experimental investigations indicatedthat the distillate of multivalent phenol can be a usefulinexpensive substitute for conventionally used phenolsin the manufacture of P3 grade laminates.

Modifying agents for resins and plastics

Although providing excellent application properties,some of the resins like PVC, low molecular weightepoxies, and unsaturated polyesters when cured with

styrene and methyl ethyl ketone peroxide (MEKP)have shown low impact resistance and flexibility in thefinal cured state. In this regard, some of the researchershave reported the use of cardanol derivatives asrenewable plasticizers/flexibilizers to achieve the re-quired properties.

Greco et al.77 have studied two different plasticizersobtained by esterification of the cardanol hydroxyl

group (cardanol acetate) and further epoxidation of the side chain double bonds (epoxidated cardanolacetate). The synthesized renewable plasticizer wascharacterized for DSC to study the miscibility withPVC. The miscibility was correlated to the chemicalstructure of plasticizer by means of the Hansensolubility parameter analysis. Results obtained indi-cated that esterification of cardanol yields a partialmiscibility with PVC, whereas esterification and sub-sequent epoxidation yield a complete miscibility withPVC. Therefore cardanol acetate, obtained by solvent-free esterification of cardanol, was used as a secondaryplasticizer of PVC. Mechanical and rheological anal-

ysis showed that the cardanol acetate can partiallyreplace commercially used di-ethyl-hexyl-phthalate(DEHP) plasticizer in PVC formulation.

Coating additives

ANTIOXIDANT AGENT: Dantas et al.78 have synthesizednovel tert -butyl substituted phenolic compounds fromCNSL at ortho and para position, through simple andlow cost methodology. The electron donor character of the substituent increased the electronic density of thephenolic oxygen atom, and hence, yielded a goodproportion between the captive and the captor radicals

which helped to retard/inhibit the oxidativedegradation as compared to commercially availableadditives.

Additionally, an antioxidant property of newlysynthesized phosphorated cardanol on the mineral oilsNH10 and NH20 was investigated by Facanha et al.79

using TGA. It was found that the addition of 1.2–2.0 wt% of phosphorated cardanol compound to themineral oils improved their thermal oxidative stabilityon 14–18C, respectively. The occurrence of majorthermal degradation events at higher temperatures(T max) on additivated oils confirmed an antioxidantproperty of phosphorated cardanol compound.

Lomonaco et al.

80

reported on the synthesis of phosphorylated compounds derived from cardanol andits application as antioxidants for biodiesel. Thesecompounds were added in biodiesel samples in threedifferent concentrations (500, 1000, and 2000 ppm) andtheir antioxidants activities were tested by TGA byevaluating their integral procedure degradation tem-peratures (IPDTs). The results showed that the addi-tion of new antioxidants increased the thermal stabilityof biodiesel, making this biofuel more resistant to thethermo-oxidative process.

20

15

10

5

0 5 10 15 20 25 30

PVAc content in CNSL–formaldehyde/PVAc green adhesive

B o n d i n g s t r e

n g t h ( k g f / c m

2 )

Non-treated

After bonding

Fig. 10: Bonding strength between the face of the fancyveneer and plywood substrate in engineered flooring:CNSL–formaldehyde (CF) resin and CF/PVAc green adhe-sives


179


12/15

COLORANTS AND DYES: CNSL and its derivatives havebeen found to be excellent raw materials for thepreparation of colorants and dyes. A number of azocompound-modified cardanol-based dyes have beenwell reported as a colorant for polymer/plastic andcoatings.81,82

Similarly, Thamyongkit and co-workers83 success-fully synthesized a novel bis (azo) dye from the

coupling of cardanol with a series of diazotizedaromatic amines and diamines. The dyes were highlysoluble in a variety of common organic solvents andgasoline as a consequence of the cardanol unit. Basedon the colorimetric analysis, the practical concentra-tion of the synthesized dye that gives the most similargasoline color compared to that of the commercial onewas 6 or 18 ppm. Further from experimental results of stability and solubility of synthesized dye in gasoline91, authors concluded that the synthesized dye can besuccessfully used as a coloring agent in gasoline 91.

CORROSION INHIBITOR: Philip et al.84 have reported a

mechanism of interaction of CNSL with metallicsubstrate and their effect on the dissolution rate of SAE 1008 carbon steel in CO2 saturated NaClsolution. It was observed that CNSL acts as ananionic inhibitor at higher solution pH (i.e., a basictype inhibitor). The phenoxide ions, R–C6H4–O

, of the CNSL inhibitor was adsorbed on SAE 1008 carbonsteel surface in aqueous CO2 saturated 3% NaClsolution by electrostatic interaction as shown inFig. 11.

DISPERSANT: The principal reasons for applyingpigmented coating to paper and paperboard are to

improve printability and appearance. The simplestform of coatings contains a pigment and a binder tobind the pigment particles both to one another and tothe base sheet of paper. It is very important that thepigment be fully dispersed to ensure satisfactoryperformance and to fully contribute to the propertiesof the coated paper. A number of systems are used forpigment dispersion, all of which involve the addition of chemical dispersant and the use of mixing equipment.

Chemical dispersant serves to aid in the wetting of thepigment particles, adjust the surface charges of thepigment particle to prevent flocculation, and reducethe viscosity. In this regard, Suryanarayan et al.85 havestudied the sodium salt of sulfonated CNSL as adispersant for china clay and calcium carbonate andcompared it with the conventional dispersant(polyacrylate) used in paper mills. Finally, the

properties of coated papers were studied and it wasfound that the bio-based dispersant gave better resultscompared to conventional one at an optimum dose of 0.8%.

COUPLING AGENT: The term coupling agent generallyapplies to silicon-containing species capable of formingchemical linkages between dissimilar materials. Thematerials to be linked are often organic polymers andinorganic fillers, as in pigmented coatings, althoughsilane coupling agents can also be useful with otherkinds of fillers and polymers. Small amounts of silanecoupling agents, used at an interface, can greatly

improve the mechanical properties of the coating.Silane coupling agents are found in a broad range of applications as varied as metal coatings, dentalmaterials, and contact lenses.86

In this regards, Tanaka et al.87 have developed acardanol-modified silane coupling agent, by reactingcardanol or a derivative thereof with an epoxy silanecoupling agent (3-glycidoxypropyl trimethoxy silane)or an isocyanate silane coupling agent (c-isocyanato-propyl trimethoxy silane/c-isocyanatopropyl triethoxysilane/c-isocyanatopropyl methyl diethoxy silane/c-iso-cyanatopropyl methyl dimethoxy silane) which canimprove strength and toughness by improving adhesionat an interface between a filler and a cellulose resinwhen being used as an surface treatment agent

Conclusion

CNSL, one of the major sustainable resources, mainlyextracted by hot-oil and roasting process, containsnumber of useful phenolic derivatives like cardol,cardanol, 2-methyl cardol, and anacardic acid withmeta-substituted unsaturated hydrocarbon chain(chain length of C15). The combination of reactivephenolic structure and unsaturated hydrocarbon chainmakes CNSL a suitable starting material to synthesize

various resins like epoxy, alkyd, polyurethanes, acryl-ics, phenolic resins, etc. In addition, a number of otheruseful products, such as modifiers like flexibilizer andreactive diluents, adhesives, laminating resins, antiox-idants, colorants and dyes, etc., have also beendeveloped from CNSL and its derivatives. So, consid-ering the high depletion rate of petroleum-basedstocks and the range of possible applications, CNSLcan be accepted as a greener and sustainableapproach for future expansion in the modern coatingindustry.

R R R

Metal

- - -

+++

0 0 0

Fig. 11: Electrostatic adsorption of the anionic corrosioninhibiting CNSL to positively charged SAE 1008 carbonsteel surface


180


13/15

Future trends

Due to availability of unsaturation in the long chainand reactive phenolic hydroxyl group of CNSL andtheir derivatives, a number of functional groups likecarboxyl, hydroxyl, epoxy, amines, isocyanate, etc., canbe incorporated via Diels–alder reaction mechanismand addition mechanism, respectively, to yield chem-

ically modified CNSL (CMCn). This modified CNSLcan be further modified or utilized as such for coatingapplications. This functionality can be utilized forsynthesizing hyperbranch polymers followed by theirapplication in coatings as wetting and dispersing agentor crosslinker, etc. Also, CMCn can be used in highsolid coating formulations as it can act as a reactivediluent maintaining the viscosity of the formulationand later on becoming part of the film. CMCn can beutilized in UV-curable coating formulation as such orwith little modifications. A number of water-basedcoatings can be synthesized with CMCn. Today, sol–gel-derived organic inorganic hybrid coatings are

widely used in the coating industry due to a numberof advantages they possess, including eco-friendlytechnology, room temperature synthesis, chemicalinertness, high oxidation and abrasion resistance,excellent thermal stability, very low health hazard,etc. In this regards, CMCn can be further modified withorganofunctional silane like 3-glycidoxypropyltri-methoxy silane (GPTMS) or c-isocyanatopropyl tri-methoxy silane or aminopropyltrimethoxy silane(APTMS), etc., to get CNSL-based hybrid precursorwhich can further be hydrolyzed to yield CNSL-basedhybrid coatings. Similarly, CNSL or CMCn can beutilized in a number of coating applications likehyperbranch polymers, water-based coatings, UV-cur-

able coatings, and hybrid materials, etc. The commer-cialization of all these technologies, however, willrequire further research and development for cost-effective solutions.

References

1. Mukherjee, T, Kao, N, ‘‘PLA Based Biopolymer Reinforcedwith Natural Fibre: A Review.’’ J. Polym. Environ., 19 (3)714–725 (2011)

2. Ahmed, T, Marcal, H, Lawless, M, Wanandy, NS, Chiu, A,Foster, LJR, ‘‘Polyhydroxybutyrate and its Copolymer withPolyhydroxyvalerate as Biomaterials: Influence on Progres-sion of Stem Cell Cycle.’’ Biomacromolecules, 11 (10) 2707–2715 (2010)

3. Mohanty, AK, Misra, M, Hinrichsen, G, ‘‘Biofibres, Biode-gradable Polymers and Biocomposites: An Overview.’’Macromol. Mater. Eng., 276/277 1–24 (2000)

4. Zafar, F, Ashraf, SM, Ahmad, S, ‘‘Air Drying Polyestera-mide from a Sustainable Resource.’’ Prog. Org. Coat., 51250–256 (2004)

5. Pan, X, Sengupta, P, Webster, DC, ‘‘High Biobased ContentEpoxy-Anhydride Thermosets from Epoxidized SucroseEsters of Fatty Acids.’’ Biomacromolecules, 12 (6) 2416–2428 (2011)

6. Ferrer, CB, Hablot, E, Garrigos, MC, Bocchini, S, Averous,L, Jimenez, A, ‘‘Relationship Between Morphology, Prop-erties and Degradation Parameters of Novative BiobasedThermoplastic Polyurethanes Obtained from Dimer FattyAcids.’’ Polym. Degrad. Stab., 97 1964–1969 (2012)

7. Oliveira, WD, Glasser, WG, ‘‘Multiphase Materials withLignin. II. Starlike Copolymers with Caprolactone.’’ Macro-molecules, 27 5–11 (1994)

8. Li, Y, Mlynar, J, Sarkanen, S, ‘‘The First 85% Kraft Lignin-

Based Thermoplastics.’’ J. Polym. Sci. B: Polym. Phys., 35(12) 1899–1910 (1997)

9. Cordeiro, N, Aurenty, P, Belgacem, MN, Gandini, A, Neto,CP, ‘‘Surface Properties of Suberin.’’ J. Colloid Interface Sci.,187 498–508 (1997)

10. Dumont, MJ, Kong, X, Narine, SS, ‘‘Polyurethanes fromBenzene Polyols Synthesized from Vegetable Oils: Depen-dence of Physical Properties on Structure.’’ J. Appl. Polym.Sci., 117 3196–3203 (2010)

11. Wilson, RJ, The Market for Cashew Nut Kernels and CashewNut Shell Liquid. Tropical Products Institute, London, 1975

12. Araú jo, BQ, Saffi, J, Richter, MF, ‘‘Antioxidant Propertiesand Chemical Composition of Technical Cashew Nut ShellLiquid (tCNSL).’’ Food Chem., 126 1044–1048 (2011)

13. Lomonaco, D, Maia, FJN, Clemente, CS, Mota, JPF,Mazzetto, SE, ‘‘Thermal Studies of New Biodiesel Antiox-idants Synthesized from a Natural Occurring PhenolicLipid.’’ Fuel , 97 552–559 (2012)

14. Food and Agriculture Organization of the United Nation,FAOSTAT Data, 2012, www.fao.org.

15. Hammed, LA, Anikwe, JC, Adedeji, AR, ‘‘Cashew Nuts andProduction Development in Nigeria.’’ Am. Eurasian J. Sci.Res., 3 (1) 54–61 (2008)

16. Hughes, ER, ‘‘Method of Expelling the Liquid of CashewNut Shells by Heat.’’ US Patent 2,058,456, 1939

17. Rector, TM, ‘‘Extracting Oil from Cashew Nuts.’’ US Patent2,018,091, 1936

18. Caplan, S, ‘‘Cashew Nut Shell liquid and Kernel OilSeparation.’’ US Patent 2,480,221, 1949

19. Tyman, JHP, Johnson, RA, Muir, M, Rokhgar, R, ‘‘Theextraction of natural cashew nut-shell liquid from the cashewnut ( Anacardium occidentale).’’ J. Am. Oil Chem. Soc., 66553–557 (1989)

20. Saito, S, ‘‘Research Activities on Supercritical Fluid Scienceand Technology in Japan—A Review.’’ J. Supercrit. Fluids, 8177–204 (1995)

21. Mele, G, Vasapollo, G, ‘‘Fine Chemicals and New HybridMaterials from Cardanol.’’ Mini. Rev. Chem. Org., 5 243–253(2008)

22. Bhunia, HP, Nando, GB, Basak, A, Lenka, S, Nayak, PL,‘‘Synthesis and Characterization of Polymers from CashewNut Shell Liquid (CNSL), a Renewable Resource III.Synthesis of a Polyether.’’ Eur. Polym. J., 35 (9) 1713–1722(1999)

23. Patel, RN, Bandyopadhyay, S, Ganesh, A, ‘‘EconomicAppraisal of Supercritical Fluid Extraction of RefinedCashew Nut Shell Liquid.’’ J. Chromatogr. A, 1124 (1–2)130–138 (2006)

24. Mutasingwa, J, ‘‘An Assessment of Cashew Nut Shell Liquidas a Corrosion Inhibitor of Mild Steel Alloys in FlowingAqueous System’’, MSc. Thesis, University of Dar Es Salaam,2004

25. Gedam, PH, Sampathkumaran, PS, ‘‘Cashew Nut ShellLiquid: Extraction, Chemistry and Application.’’ Prog. Org.Coat., 14 115–157 (1986)

26. Akinhanmi, TF, Atasie, VN, ‘‘Chemical Composition andPhysicochemical Properties of Cashew Nut ( Anacardium


181

http://www.fao.org/http://www.fao.org/


14/15

occidentale) Oil and Cashew Nut Shell Liquid.’’ J. Agric.Food Environ. Sci., 2 (1) 1–10 (2008)

27. Paramashivappa, R, Kumar, PP, Vithayathil, PJ, Rao, AS,‘‘Novel Method for Isolation of Major Phenolic Constituentsfrom Cashew ( Anacardium occidentale L.) Nut ShellLiquid.’’ J. Agric. Food Chem., 49 2548–2551 (2001)

28. Harvey, MT, ‘‘Sulphonation Process.’’ US Patent 2,324,300,1943

29. Dawson, R, Wassemian, D, ‘‘Nitro-Hydrogenated Cardanols

and Process for Preparing Same.’’ US Patent, 2,502,708, 195030. Shivadasami, HM, ‘‘Production of Alkyd Resins.’’ British

Patent 1,279,257, 197231. Unnikrishnan, KP, Thachil, ET, ‘‘Synthesis and Character-

ization of Cardanol-Based Epoxy Systems.’’ Des. Monom.Polym., 11 (6) 593–607 (2008)

32. Harvey, MT, ‘‘Resin form Cashew Nut Shell Oil.’’ US Patent1,725,791, 1929

33. Harvey, MT, ‘‘Substitute for Shellac and the Like.’’ USPatent 1,725,793, 1929

34. Caplan, S, ‘‘Treatment of Cashew Nut Shell Liquid.’’ USPatent 2,176,059 (1940).

35. Groote, MD, Pettingill, OH, ‘‘Oxyalkylated Drastically-Oxidized Cashew Nut Shell Liquid and Method of MakingSame.’’ US Patent 2,531,502, 1950

36. Aggarwal, LK, Thapliyal, PC, Karade, SR, ‘‘AnticorrosiveProperties of the Epoxy-Cardanol Resin based Paints.’’Prog. Org. Coat., 59 76–80 (2007)

37. Huang, K, Zhang, Y, Li, M, Lian, J, Yang, X, Xia, J,‘‘Preparation of a Light Color Cardanol-Based Curing Agentand Epoxy Resin Composite: Cure-Induced Phase Separa-tion and Its Effect on Properties.’’ Prog. Org. Coat., 74 240–247 (2012)

38. Kim, YH, An, ES, Park, SY, Song, BK, ‘‘EnzymaticEpoxidation and Polymerization of Cardanol obtained froma Renewable Resource and Curing of Epoxide-containingPolycardanol.’’ J. Mol. Catal. B: Enzym., 45 39–44 (2007)

39. Campaner, P, D’Amico, D, Longo, L, Stifani, C, Tarzia, A,‘‘Cardanol-Based Novolac Resins as Curing Agents of Epoxy Resins.’’ J. Appl. Polym. Sci., 114 3585–3591 (2009)

40. Pathak, SK, Rao, BS, ‘‘Structural Effect of Phenalkamineson Adhesive Viscoelastic and Thermal Properties of EpoxyNetworks.’’ J. Appl. Polym. Sci., 102 4741–4748 (2006)

41. Tan, TTM, Nieu, NH, ‘‘Carbon Fiber Cardanol-EpoxyComposites.’’ J. Appl. Polym. Sci., 61 133–137 (1996)

42. Madhusudhan, V, Murthy, BGK, ‘‘Polyfunctional Com-pounds from Cardanol.’’ Prog. Org. Coat., 20 63–71 (1992)

43. Tan, TTM, ‘‘Cardanol–Glycols and Cardanol–Glycol-BasedPolyurethane Films.’’ J. Appl. Polym. Sci., 65 507–510 (1997)

44. Mythili, CV, Retna, AM, Gopalakrishnan, S, ‘‘Physical,Mechanical, and Thermal Properties of Polyurethanes Basedon Hydroxyalkylated Cardanol–Formaldehyde Resins.’’ J. Appl. Polym. Sci., 98 284–288 (2005)

45. Rekha, N, Asha, SK, ‘‘Synthesis and FTIR Spectroscopic

Investigation of the UV Curing Kinetics of TelechelicUrethane Methacrylate Crosslinkers Based on the Renew-able Resource-Cardanol.’’ J. Appl. Polym. Sci., 109 2781–2790 (2008)

46. Mahanwar, PA, Kale, DD, ‘‘Effect of Cashew Nut ShellLiquid (CNSL) on Properties of Phenolic Resins.’’ J. Appl.Polym. Sci., 61 2107–2111 (1996)

47. Papadopoulou, E, Chrissafis, K, ‘‘Thermal Study of Phenol–Formaldehyde Resin Modified with Cashew Nut ShellLiquid.’’ Thermochim. Acta, 512 105–109 (2011)

48. Misra, AK, Pandey, GN, ‘‘Kinetics of Alkaline-CatalyzedCardanol–Formaldehyde Reaction. I.’’ J. Appl. Polym. Sci.,29 361–372 (1984)

49. Misra, AK, Pandey, GN, ‘‘Kinetics of Alkaline-CatalyzedCardanol–Formaldehyde Reaction. II. Mechanism of theReaction.’’ J. Appl. Polym. Sci., 30 969–977 (1985)

50. Misra, AK, Pandey, GN, ‘‘Kinetics of Alkaline-CatalyzedCardanol–Formaldehyde Reaction. I. Determination of Com-position of the Resin.’’ J. Appl. Polym. Sci., 30 979–983 (1985)

51. Sultania, M, Rai, JSP, Srivastava, D, ‘‘A Study on theKinetics of Condensation Reaction of Cardanol and Form-aldehyde, Part I.’’ Int. J. Chem. Kinet., 41 559–572 (2009)

52. Nimuru, N, Miyakoshi, T, ‘‘Structural Characterization of Cashew Resin Film Using Two-Stage Pyrolysis-Gas Chro-matography/Mass Spectrometry.’’ Int. J. Polym. Anal. Cha-ract., 8 47–66 (2003)

53. Roy, D, Basu, PK, Raghunathan, P, Eswaran, SV, ‘‘CashewNut Shell Liquid–based Tailor-Made Novolac Resins: Poly-mer Morphology Quantitation by 1-D and 2-D NMRTechniques and Performance Evaluation.’’ J. Appl. Polym.Sci., 89 1959–1965 (2003)

54. Cardona, F, Tak, ALK, Fedrigo, J, ‘‘Novel Phenolic Resinswith Improved Mechanical and Toughness Properties.’’ J. Appl. Polym. Sci., 123 2131–2139 (2012)

55. Souza, FG, Michel, RC, Pinto, JC, Cosme, T, Oliveira, GE,‘‘Effect of Pressure on the Structure and Electrical Conduc-tivity of Cardanol–Furfural–Polyaniline Blends.’’ J. Appl.Polym. Sci., 119 2666–2673 (2011)

56. Prabhakaran, K, Narayan, A, Pvithran, C, ‘‘Cardanol as aDispersant Plasticizer for an Alumina/Toluene Tape CastingSlip.’’ J. Eur Ceram. Soc., 21 2873 (2001)

57. Pillai, C, Prasad, V, Sudha, J, Bera, S, Menon, A, ‘‘PolymericResins from Renewable Resources. II. Synthesis and Char-acterization of Flame-Retardant Prepolymer from Carda-nol.’’ J. Appl. Polym. Sci., 41 2487 (1990)

58. Bhunia, H, Nando, G, Chakib, T, ‘‘Synthesis and Character-ization of Polymers from Cashew Nut Shell Liquid (CNSL),a Renewable Resource II. Synthesis of Polyurethanes.’’ Eur.Polym. J., 35 1381 (1999)

59. Frigone, M, Masica, L, Aciermo, D, ‘‘Oligomeric andPolymeric Modifiers for Toughening of Epoxy Resins.’’Eur. Polym. J , 31 1021 (1995)

60. Tripathi, G, Srivastava, D, ‘‘Effect of Carboxyl-terminatedPoly(butadiene-co-acrylonitrile) (CTBN) Concentration onThermal and Mechanical Properties of Binary Blends of Diglycidyl Ether of Bisphenol-A (DGEBA) Epoxy Resin.’’Mater. Sci. Eng: A, 443 (1–2) 262–269 (2007)

61. Pearson, R, Yee, A, ‘‘Toughening Mechanisms in Elastomer-modified Epoxies—Part 3. The Effect of Cross-link Den-sity.’’ J. Mater. Sci., 24 2571–2580 (1989)

62. May, C, Epoxy Resin—Chemistry and Technology. MarcelDekker, New York (1988)

63. Yadav, R, Srivastava, D, ‘‘Studies on Cardanol-based Epox-idized Novolac Resin and Its Blends.’’ Chem. Chem. Tech-nol., 2 (3) 173–184 (2008)

64. Kim, DS, Kim, YH, An, ES, Song, BK, Chelikani, R,

‘‘Polymerization of Cardanol using Soybean Peroxidase andits Potential Application as Anti-bio Film Coating Material.’’Biotechnol. Lett., 25 (18) 1521 (2003)

65. Choi, YH, Kim, JC, Ahn, JK, Ko, SY, Kim, DH, Lee, TY,‘‘Anti-biofouling Behaviour of Natural Unsaturated Hydro-carbon Phenols Impregnated in PDMS Matrix.’’ J. Ind. Eng.Chem., 14 292–296 (2008)

66. More, AS, Sane, PS, Patil, AS, Wadgaonkar, PP, ‘‘Synthesisand Characterization of Aromatic Polyazomethines BearingPendant Pentadecyl Chains.’’ Polym. Degrad. Stab., 95 1727–1735 (2010)

67. Ravichandran, S, Bouldin, RM, Kumar, J, Nagarajan, R,‘‘A Renewable Waste Material for the Synthesis of a Novel


182


15/15

Non-Halogenated Flame Retardant Polymer.’’ J CleanProd., 19 454–458 (2011)

68. Bai, W, Xiao, X, Chen, Q, Xu, Y, Zheng, S, Lin, J, ‘‘Synthesisand Characterization of Cross-linked Polymer from Carda-nol by Solvent-Free Grinding Polymerization.’’ Prog. Org.Coat., 75 184–189 (2012)

69. Kim, YH, Won, K, Kwon, JM, Jeong, HS, Park, SY, An, ES,Song, BK, ‘‘Synthesis of Polycardanol from a RenewableResource Using a Fungal Peroxidase from Coprinus cinere-

us.’’ J. Mol. Catal. B: Enzym., 34 33–38 (2005)70. Rao, BS, Palanisamy, A, ‘‘A New Thermoset System Based

on Cardanol Benzoxazine and Hydroxy Benzoxazoline withLower Cure Temperature.’’ Prog. Org. Coat., 74 427–434(2012)

71. Ramasri, M, Rao, GSS, Sampathkumaran, PS, Shirsalkar,MM, ‘‘Synthesis and Characterization of Mannich Basesfrom Cardbisphenol.’’ J. Appl. Polym. Sci., 39 1993–2004(1990)

72. More, AS, Patil, AS, Wadgaonkar, PP, ‘‘Poly(amideimide)sContaining Pendant Pentadecyl Chains: Synthesis and Char-acterization.’’ Polym. Degrad. Stab., 95 837–844 (2010)

73. Philip, JYN, Buchweishaija, J, Mkayula, LL, Ye, L, ‘‘Prep-aration of Molecularly Imprinted Polymers Using AnacardicAcid Monomers Derived from Cashew Nut Shell Liquid.’’ J. Agric. Food Chem., 55 (22) 8870–8876 (2007)

74. Kim, S, ‘‘The Reduction of Formaldehyde and VOCsEmission from Wood-Based Flooring by Green Adhesiveusing Cashew Nut Shell Liquid (CNSL).’’ J. Hazard. Mater.,182 919–922 (2010)

75. Lee, JH, Jeon, J, Kim, S, ‘‘Green Adhesives Using TanninandCashew Nut Shell Liquid for Environment-Friendly FurnitureMaterials.’’ J. Korea Furnit. Soc., 22 (3) 219–229 (2011)

76. Sridhar, S, Cadlince, P, Ratra, MC, ‘‘Laminating ResolVarnishes Made with Crude Multivalent Phenol.’’ J. Appl.Polym. Sci., 47 797–804 (1993)

77. Greco, A, Brunetti, D, Renna, G, Mele, G, Maffezzoli, A,‘‘Plasticizer for Poly(vinyl chloride) from Cardanol as a

Renewable Resource Material.’’ Polym. Degrad. Stab., 952169–2174 (2010)

78. Dantas, TNC, Dantas, MSG, Neto, AAD, D’Ornellas, CV,Queiroza, LR, ‘‘Novel Antioxidants from Cashew Nut ShellLiquid Applied to Gasoline Stabilization.’’ Fuel , 82 1465–1469 (2003)

79. Facanha, MAR, Mazzetto, SE, Carioca, JOB, De Barros,GG, ‘‘Evaluation of Antioxidant Properties of a Phosphor-ated Cardanol Compound on Mineral Oils (NH10 and

NH20).’’ Fuel , 86 2416–2421 (2007)80. Lomonaco, D, Maia, FJN, Clemente, CS, Mota, JPF,

Mazzetto, SE, ‘‘Plasticizer for Poly(vinyl chloride) fromCardanol as a Renewable Resource Material.’’ Fuel , 97 552–559 (2012)

81. Achary, PGR, Mohanty, N, Guru, BN, Pal, NC, ‘‘Synthesisand Thermal Degradation Study of Polymer blends fromPolyurethanes of Linseed Oil and Cardanol Based Dyes withAminophenols.’’ J. Chem. Pharm. Res., 4 (3) 1475–1485 (2012)

82. Gopalakrishnan, S, Nevaditha, NT, Mythili, CV, ‘‘ThermalDegradation and XRD Studies of Diazotised- p-SulphanilicAcid Dye Based Resins Synthesized from RenewableResource.’’ Arch. Appl. Sci. Res., 4 (2) 1091–1099 (2012)

83. Paebumrung, P, Petsom, A, Thamyongkit, P, ‘‘Cardanol-Based Bis(azo) Dyes as a Gasoline 91 Colorant.’’ J. Am. Oil.Chem. Soc., 89 321–328 (2012)

84. Philip, JYN, Buchweishaija, J, Mkayula, LL, ‘‘Cashew NutShell Liquid as an Alternative Corrosion Inhibitor forCarbon Steels.’’ Tanzan. J. Sci., 28 (2) 9–19 (2002)

85. Suryanarayan, SS, Satish, N, Anita, N, ‘‘Study of Sodium Saltof Cashew Nut Shell Liquid (CNSL) as an Alternate Disper-sant in Coating of Paper.’’ IPPTA, 24 (2) 119–122 (2012)

86. Mark, HF, ‘‘Silane Coupling Agents.’’ In: Rogers, ME, Long,TE, (eds.) Encyclopedia of Polymer Science and Technology,3rd ed., Vol. 8, pp. 38–49. Wiley, New York, 2004

87. Tanaka, S, Iji, M, ‘‘Cardanol-Modified Silane CouplingAgent, Cardanol-Modified Filler, and Cellulose Resin Com-position.’’ US Patent 0036940 A1, 2013


183

csnl an environment friendly alternative

Documents