synthesis of polyurethane prepolymer using …

© 2018 IJRAR December 2018, Volume 5, Issue 04 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138)

IJRAR1944137 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 1142

SYNTHESIS OF POLYURETHANE

PREPOLYMER USING PONGAMIA GLABRA

SEED OIL

Corresponding Author: K. Rathika1* and S. Begila David 2

1 Research scholar, Reg No: 10252 , Scott Christian College, Affliated to

MS university, Abishecpatty, Tirunelveli,

2 Assistant professor, Department of chemistry, Scott Christian College

(Autonomus),

ABSTRACT

Pongamia glabra seeds contain oil which is mainly used in tanning industry for dressing of leather and

to some extent it is used in soap industry. Another interesting outcome of these natural products chemistry

studies is the synthesis of a non-toxic polyester amide from seed oil that has applications as an anticorrosive

coating material. The data of physicochemical properties of Pongamia glabra seed oil, epoxidized resin and

acrylated epoxidized resin are discussed. The representative FTIR and NMR spectra of pongamia glabra seed

oil, epoxidized resin and acrylated epoxidized resins are focused. Pongamia glabra seed oil showed a

maximum absorption at 3008.96 cm-1 due to the higher proportion of linolenic or linoleic acid groups. By the

addition of multifunctional monomer polyurethane prepolymer was synthesized. All the functionalities are

confirmed by the spectral analysis FTIR and NMR respectively.

Key Words : Pongamia glabra Seed oil, FT-IR, NMR, epoxidized resin.

INTRODUCTION

Vegetable oils (VO) have been used in the preparation of paints, varnishes, printing inks, and other

protective/ decorative coatings. After various modifications, they show desired coating properties such as fast

drying, good adhesion and resistance to alkali, acid, and marine environments. Semidrying and non conjugated

drying oils are needed to be mixed with other moieties like styrene, methyl methacrylate, vinyl acetate, poly

vinyl alcohol, and others to obtain better products 1-8. At present, different vegetable oils are used like linseed,

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Soybean, Rubber Seed oil, Jatropha, and Castor and these are modified in terms of different types of polymers

to improve their properties according to their applications 9-11.

Pongamia glabra (PO) is one of the most non edible vegetable oil belonging to the family

Leguminasea. It is a medium-sized tree with a short crooked trunk and broad crown of spreading or drooping

branches. The tree is valued for shade, ornamental purpose, seed oil, fodder, and green manure. The oil content

28–32% has good amount of unsaturation with a higher concentration of oleic acid. The major mono

unsaturated fatty acid was oleic acid (46%) whereas linoleic acid (27.1%) and linolenic acid (6.3%) constitutes

the total polyunsaturated fatty acid. Low molecular weight fatty acids such as lauric and capric acids occur in

very small amount of about 0.1% each. PO is reportedly used in biodiesel as well as in surface coatings 12-14.

Biopolymers produced from renewable and inexpensive natural resources have drawn considerable

attention over the past decade, due to their low cost, ready availability, environmental compatibility, and their

inherent biodegradability 15. Application of these biomaterials has a huge potential market, because of the

current emphasis on sustainable technologies. Many naturally-occurring biopolymers, such as cellulose,

starch, dextran, as well as those derived from proteins, lipids and polyphenols, are widely used for material

applications 16, 17. The exciting new area of bio renewable, which lies on the border of molecular biology and

polymer chemistry, offers many opportunities to expand the range of exciting new bio-based materials.

Particularly promising is the development of new biopolymers from functionalized, low molecular weight

natural substances, like natural oils, utilizing polymerization methods widely used for petroleum-based

polymers. Natural oils represent one of the most promising renewable resources. These molecules possess a

triglyceride structure with fatty acid side chains possessing varying degrees of unsaturation 18,19.

EXPERIMENTAL

Synthesis of Biobased Epoxidized Resin

The epoxidation reaction is carried out in a 1 lit three neck flask equipped with mechanical glass stirrer.

The whole assembly was immersed in a water bath. 200ml of pongamia glabra seed oil was taken in the reactor

and with respect to this calculated amount of CH3COOH and was added to the reactor and the mixture was

stirred for about 30 minutes. Then the required amount of 30 % aqueous H2O2 was added drop wise in such a

way that the addition was completed in half an hour and the reaction was continued further for the required

time duration 20. Samples were taken out intermittently, considering the completion of H2O2 addition as zero

time. The collected samples were filtered and then extracted with diethyl ether in a separating funnel, after

that washed with cold and slightly hot water successively to remove free acid.

Synthesis of Acrylated Epoxidized Resin




EPOA was successfully synthesized by an esterification reaction between epoxidized pongamia glabra

seed oil product (EPOP) and acrylic acid in the presence of triethylamine (TEA) as a catalyst. The epoxy

groups (oxirane rings) reacted with the carboxylic acid groups in the acrylic acid to form a hydroxy acrylate

resin 21.

Synthesis of Polyurethane Prepolymer

A three–necked round–bottomed flask, equipped with a mechanical stirrer, thermometer and nitrogen

gas inlet, was used for preparation of the polyurethane. The reaction vessel was flushed with nitrogen and

charged with Acrylated epoxy resin and TDI, in order to maintain NCO/OH ratio 1.6 and stannous octoate

was stirred for 1 hr at 45°c.The polymer mixture resulted a viscous solution 22.

Determination of Physicochemical properties

Determination of Specific Gravity

The specific gravity bottle was used to determine the specific gravity of all triglyceride oils. The

specific gravity bottle was filled with pure oil until it overflows by inserting the stopper. Then it was immersed

in the water bath (maintained at 30° C±0.20° C) and held for 30 minutes. The capillary opening was thoroughly

wiped off, cooled to room temperature and weighed 23. The process was then repeated with distilled water

.Then using formula the specific gravity of oil was calculated,

Specific gravity (g/cc at 30/300° C) = (A-B) / (C-B)

Determination of Hydroxyl Value and Number of Hydroxyl Groups

Hydroxyl value was determined by acetylation method as per the method of Goodman. About one

gram of oil was mixed with 10 ml of a mixture of dry pyridine and acetic anhydride in 3:1 volume ratio in an

Erlen Meyer flask. Then it was refluxed on a water bath for 40-50 minutes using an air condenser with

occasional swirling. After this process 10 ml of distilled water was added through the air condenser carefully

and heated for another 5 minutes. The entire mixture was cooled and washed down the sides of the flask with

10 ml of n butyl alcohol. One ml of phenolphthalein was added and titrated against 1 N sodium hydroxide to

a slightly pink end point. A blank titration was performed. Using the equations, hydroxyl number and Number

of hydroxyl groups were calculated 24.

Hydroxyl number = (B-S) N 56.1/W

Determination of Iodine Value

Wij's method was used to determine the Iodine value of the oil (As per the standard IS: 840-1964).

About 50 g of oil was taken in a 250 ml beaker and heated slowly to 205 ± 50 ֯ C on an electric hot plate with

continuous stirring. The content was cooled and filtered through a filter paper to remove any impurities. 0.1 g

of the filtered sample was weighed in a clean dry 250 ml iodine flask to which 25ml of carbon tetra chloride

was added to dissolve the content. 25ml of the Wij's solution was added and replaced the glass stopper after

wetting with potassium iodide solution. The entire content was swirled for intimate mixing and allowed to




stand in the dark for one hour. Then 15 ml of potassium iodide solution was added. The liberated iodine was

titrated immediately with standard sodium thiosulphate solution using starch indicator. A blank test was carried

out simultaneously under similar experimental condition 25. Using the formula Iodine value was calculated,

Iodine value = 12.69(B-S) N / W

Determination of Saponification Value

A one gram (1 g) sample of the oil was weighed into a 250 ml glass conical flask, and then 10 ml of

ethanolether mixture (2:1) was added to the same flask followed by 25 ml of 0.5 N ethanolic potassium

hydroxide. The flask was then fitted to a reflux condenser and refluxed using a boiling water bath for 30 min

with occasional shaking. To the warm solution were added 3 - 4 drops of phenolphthalein indicator and the

warm solution was titrated against 0.5 M HCl to the end point 26. The same procedure was used for other

samples and blank. The expression for saponification value (S.V) is given by equation.

Viscosity

A clean, dried Ostwald viscometer with a flow time above 200 seconds for the fluid to be tested was

elected. The sample was filtered through a sintered glass (fine mesh screen) to eliminate dust and other solid

materials in the liquid sample. The viscosity meter was charged with the sample by inverting the tube’s thinner

arm into the liquid sample and suction force drawn up to the upper timing mark of the viscometer, after which

the instrument was turned to its normal vertical position. The viscometer was placed into a holder and inserted

to a constant temperature bath set at 29˚C. The oil was kept for approximately 10 minutes for it to come to the

bath temperature of 29˚C. The suction force was then applied to the thinner arm to draw the sample slightly

above the upper timing mark. The afflux time was recorded by timing the flow of the sample as it flowed

freely from the upper timing mark to the lower timing mark. Three recordings were taken and using water as

a standard, a viscosity for each sample was recorded 27.

Determination of epoxy content by titration method

The epoxy content and epoxy equivalent were determined by pyridinium hydrochloride titration

method. 0.5 – 1 g of resin was refluxed for 20 minutes with 50 ml of pyridinium hydrochloride solution. The

pyridinium hydrochloride solution was prepared by taking 16 ml of concentrated hydrochloric acid and diluted

to 1 litre with pyridine. After refluxing, the mixture was cooled and titrated with 0.1 N sodium hydroxide

(NaOH) using phenolphthalein as indicator.

SPECTRAL ANALYSIS

Infrared spectra




For chemical characterization FT-IR was used as a key technique to verify the path of synthesis.The

related spectra were collected by Shimadzu FTIR 4200 series spectrophotometer. The scanning region was

4000 cm-1 to 500 cm-1. Samples were analyzed by applying with the help of KBr powder.

1HNMR Spectroscopic Analysis

1H-NMR (Nuclear Magnetic Resonance) of the purified novolac resin was recorded using Jeol-LA 500

NMR spectrophotometer. About 20 mg of the sample, in 10 mm diameter sample tube, was dissolved in about

5ml of chloroform-d1 (CDCl3) which was used a solvent along with tetramethylsilane (TMS) as internal

standard. Finally, the spectra were recorded on computer.

RESULT AND DISCUSSION

Physicochemical Properties

The data of physicochemical properties of Pongamia glabra seed oil, epoxidized resin and acrylated

epoxidized resin are shown in table.

Table 1 Physicochemical Properties

Property Pongamia glabra

seed oil

Epoxidized resin Acrylated

Epoxidized resin

Colour Yellowish red Yellow Brown

Odour Unpleasant odour - -

Specific gravity

(gm/c.c)

.935 1.05 1.114

Viscosity at 30 ֯c 56.4 194 48.2

Iodine Value 86.5 14 11.57

Saponification Value 184 115 94

Epoxy content - 520 -

Hydroxyl Value - - 12.4

Molecular weight

calculated

886 918 1062

From the data of physicochemical properties of pongamia glabra seed oil represents the degree of

unsaturation in the triglyceride units. The saponification index is used for the determination of the size,average




molecular weight of the fatty acid and to estimate the non fatty impurities present. The epoxidized resin and

acrylated epoxidized resin showed that the changes in all physicochemical properties such as Saponification

Value and Iodine Value are decreased in comparision with corresponding parent oil due to the consumption

of unsaturation during the specified reactions.

SPECTRAL ANALYSIS

FTIR SPECTRAL ANALYSIS

Pongamia Glabra Seed Oil

The FTIR spectroscopy is a rapid, non-destructive technique that has been widley applied in the

characterization of different functional groups with characteristic absorption bands in infrared region of the

electromagnetic spectrum. The representative FTIR spectra of pongamia glabra seed oil, epoxidized resin and

acrylated epoxidized resins are shown in figures. Pongamia glabra seed oil showed a maximum absorption at

3008.96 cm-1 due to the higher proportion of linolenic or linoleic acid groups . The band at 2924.09 cm-1 is

attributed to the symmetric strectching vibration of the aliphatic CH2 groups. The band at 2864.65 cm-1 is

attributed to the C-H stretching of a alkane. A very strong and sharp absorption band at 1743.65 cm-1 due to

C=O stretching of esters.

Figure 1 IR-Spectrum of pongamia glabra seed oil




Biobased Epoxide resin of Pongamia Glabra Seed Oil

The IR spectra of epoxy resin shows the disappearance of the band at 3008.96 cm-1 which indicates

C=C has been used up and the presence of the absorption bands at 1240-1250 cm-1 and 910-950 cm-1which

are attributed to the oxirane ring. The epoxy groups gave the bands at 1250 cm-1 and 950 cm-1 because of the

symmetric and asymmetric ring strectching. The other peaks observed were methyl and methylene groups at

2900-3000cm-1, olefinic double bond at 1635cm-1, ester group of oil at 1735.93 cm-1.

Figure 2 Spectrum of Epoxidized Pongamia glabra seed oil resin

Acrylated Epoxidized Resin

The FTIR spectrum of acrylated epoxidized resins shows that the epoxide group is successfully

converted to the acrylated functionality. This is indicated the presence of hydroxyl functionality of resin at

absorption band of 3448.72cm-1, associated with hydrogen band of –OH. The peak of esteric C= O stretching

vibrations are observed at 1728.22cm-1which confirms the presence of ester linkages in the acrylated products,

a new band appeared at 1627 cm-1 which may be attributed to the acrylate group (CH2=CH-COO-). Such as

the absorption band at 848 cm-1, which is attributed to the out-of-plane deformation of the C=C of the vinyl

moieties of the acrylate groups, besides, the band at 1618.41 cm-1.




Figure 3 IR-Spectrum of Acrylated Epoxidized Pongamia glabra seed oil resin

Polyurethane Prepolymer (TPOPU)

It was observed that the prepolymer possess the following characteristic absorption bands, urethane

NH stretching at 3294.42cm-1, bending at 1550 .77cm-1, methylene or alkyl group at 2924.09 cm-1, carbonyl

group at 1728.22 cm-1 and C-O-C stretching at 1026.13 cm-1. All the above-mentioned peaks indicate

formation of isocyanate terminated polyurethane prepolymer. It confirms the formation of prepolymer through

the FT-IR data.




Figure 4 IR-Spectrum of polyurethane prepolymer based on Pongamia glabra seed oil

NMR SPECTRAL ANALYSIS

Pongamia Glabra Seed Oil

The peak at 0.885 ppm corresponds to the hydrogens of the terminal methyl groups (CH3-(CH)n-).The peak

at ∂ = 2.062 ppm corrresponds to allyl hydrogens (CH2-CH=CH-).

Figure 5 H-NMR Spectrum of pongamia glabra seed oil

Biobased Epoxide resin of Pongamia Glabra Seed Oil




1H-NMR spectra of POE shows proton of terminal methyl group at =.87-.9 ppm, methylene group

attached to carbonyl at ∂ = 2.1-2.3 ppm, the peaks at ∂=2.062 were disappeared in the epoxy resin showing

that the double bond is replaced by the epoxy group. The peak at ∂ = 1.44 ppm corresponds to –CH- hydrogens

adjacent to epoxy group. Proton of glyceryl methylene group at ∂=3.5-3.7 ppm, proton attached to olefinic

double bond at ∂ =4.8 ppm.

Figure 6 1H-NMR Spectrum of Epoxidized Pongamia glabra seed oil resin

Acrylated Epoxidized Resin

The esterification takes place between the epoxidized pongamia glabra seed oil and acrylic acid in the

presence of trimethylamine. Epoxide resins react with carboxylic acid to form esters.This reaction occurs by

the opening of the oxirane rings and grafting of the acrylate moieties on the triglyceride backbone, besides,

the formation of hydroxyl groups. This was confirmed by 1H-NMR spectrum .Figure shows the 1H-NMR

spectrum of Acrylated Epoxidized Resin, where in addition to the characteristic signal of the triglyceride

backbone, the spectrum shows the NMR signals assigned to the acrylate groups. The NMR signal with the

chemical shift at δ 3.59–3.65 ppm can be assigned to the methine protons in the α position of the –OH groups

(-CH-OH), and the other methine protons α to the oxygen atom of the acrylate groups –CH-CH-O-C=O<,

show signals at δ 4.14–4.17 ppm.




Figure 7 H-NMR Spectrum of Acrylated Epoxidized Pongamia glabra seed oil resin

Polyurethane Prepolymer

1H NMR spectra of the polyurethanes indicated the presence of urethane linkage, and TDI moieties. In

1H NMR, the protons of allylic - CH2 , -CH2 adjacent to oxygen atom of urethane group and CH3 of TDI

showed peaks at ∂ = 1.62 ppm, ∂ = 2.3 ppm and ∂ = 2.66 ppm respectively. Protons attached to C= C appeared

at at ∂ = 5.8 ppm. The peaks correspond to aromatic protons of TDI were appeared at 6.43. Protons attached

in aromatic group between two urethane linkages were found at ∂ = 4.45 ppm.




Figure 8 1H-NMR Spectrum of polyurethane prepolymer based on Pongamia glabra seed oil

CONCLUSION

Plant oil based products are used rapidly in polymeric material because of the depletion of non

renewable resources. The non edible pongamia glabra seed oil is utilized to produce a valuable product, epoxy

resin. Epoxy resin was used to prepare acrylated epoxy resin. By the addition of multifunctional monomer

polyurethane prepolymer was synthesized. All the functionalities are confirmed by the spectral analysis FTIR

and NMR respectively.




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