natural rubber based adhesive modified with starch and...

AASCIT Journal of Chemistry 2018; 4(1): 1-6

http://www.aascit.org/journal/chemistry

Keywords Adhesive,

Natural Rubber Latex,

Starch,

Reinforcer,

Bonding Strength

Received: October 8, 2017

Accepted: December 8, 2017

Published: January 25, 2018

Natural Rubber Based Adhesive Modified with Starch and Reinforcer

Opara Ifeoma Juliet1, Igwebike-Ossi Clementina Dilim

2,

Okudo Chijioke Okpara3, Onudibia Moses Ejike

4

1Department of Chemical Sciences, Federal University Wukari, Taraba, Nigeria 2Department of Industrial Chemistry, Ebonyi State University, Abakaliki, Nigeria 3Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Nigeria 4Department of Pure and Applied Physics, Federal University Wukari, Taraba, Nigeria

Email address [email protected] (O. I. Juliet)

Citation Opara Ifeoma Juliet, Igwebike-Ossi Clementina Dilim, Okudo Chijioke Okpara, Onudibia Moses

Ejike. Natural Rubber Based Adhesive Modified with Starch and Reinforcer. AASCIT Journal of

Chemistry. Vol. 4, No. 1, 2018, pp. 1-6.

Abstract Adhesives are used to join materials together by surface attachment. The natural rubber

adhesive formulated was good, although its bonding strength was improved by

incorporating starch and reinforcer into it. Cassava starch was modified chemically into

hydrolyzed, dextrinized and oxidized starch and added to natural rubber blend which

increased its adhesiveness. The reinforcer (ZnO) added to natural rubber increased its

bonding strength on paper, wood and bottle label. The reinforced natural rubber adhesive

and the three modified starch adhesive incorporated into rubber showed good bonding

strength compared to natural rubber. Hydrolyzed starch with natural rubber blend and

natural rubber with reinforcer adhesive showed exceptional good bonding strength.

1. Introduction

Natural Rubber (Hevea brasiliensis) is a plant grown in tropical and sub- tropical

regions. In Nigeria, rubber plant is grown in large quantity in Emeabiam in Imo State,

Sapele in Delta State, Warri and Ughelli also in Delta State, Arochukwu in Abia State

and many other places in the southern region. This singular factor (availability) makes it

a cheap raw material for adhesive production.

Natural rubber latex is a colloid system having the rubber particles dispersed in water.

Latex particle size is varying approximately from 0.05 to 3µm [1]. It is obtained from the

trunk of rubber tree through a systematic” tapping “process. Latex (white fluid) is tacky

in nature, after collection, the latex is stabilized with NH3 and transported from the

plantation to where it will be processed. The synthetic latex is prepared from raw

materials based on Petroleum and/or coal which are non-renewable and, therefore, must

be used with economy [2].

The primary unique characteristics of natural rubber latex include high strength,

flexibility and elasticity [3]. This makes it suitable for various products, e.g., tires, under

the bonnet products, gloves, balloons, rubber bands, condoms, adhesives, etc. Natural

rubber latex which is a renewable resource can also be used as a water-based contact

adhesive. However, due to its unsaturated backbone chain nature, natural rubber adhesive

is not quite stable and is brittle when left for a period of time. On the other hand, natural

rubber adhesives show good resistance to water, but poor resistance to oils, organic

solvents, and chemical oxidizing agents [4]. Thus, it is necessary to add antioxidants and

stabilizer into the natural rubber latex adhesive [5]. The improved products from natural

rubber have potentially wide applications as a result of reinforcing with fillers such as

2 Opara Ifeoma Juliet et al.: Natural Rubber Based Adhesive Modified with Starch and Reinforcer

carbon black or silica, as well as physical blends with other

polymer particles or chemical modification, thus enabling

these materials to compete with synthetic rubbers [6].

1.1. Statement of Problem

Natural rubber is a renewable resource used in formulation

of adhesive but often the adhesive formulated using natural

rubber is not stable and is brittle when left for a period of

time due to its unsaturated back bone chain. Thus, structural

modification is required to improve its bonding strength

using starch and reinforcer.

1.2. Composition of Latex

The table below shows the various constituents of natural

rubber

Table 1. Composition of latex.

Constituents % Composition

Rubber particles (cis-1, poly isoprene) 30.0-40.0

Protein 2.0-3.0

Water 55.0-65.0

Steryl glycosides 0.1-0.5

Resins 1.5-3.5

Ash 0.5-1.0

Sugars 1.0-2.0

Changes in season, soil, tapping methods, weather etc.;

exhibits wide variation in the composition of the natural latex

[7]. Recently, several proteins in natural rubber were found to

cause type I allergic responses that led to life-threatening

anaphylactic reactions. In 1991, the FDA stipulated that rubber

products made from natural rubber latex (e.g., gloves and

condoms) should be treated to remove extractable protein [8].

An adhesive is defined by the American Society for testing

and materials (ASTM) as substance capable of holding

materials together by surface attachment [9]. Adhesives

accomplish this goal by transmitting stresses from one

member to another in a manner that distributes the stresses

much more uniformly than can be achieved with mechanical

fasteners [10].

1.3. Structure of Natural Rubber

Rubber is a polymer of the diene hydrocarbon isoprene.

The isoprene has a molecular formula (C5H8)n. The isoprene

units are linked “head to tail” as residual double bond

occurring in the middle of each segment and within the main

backbone. In the polyisoprene molecule cis-isomerism occur

when all methyl group lie on the same side of the chain,

trans-isomerism occur when all methyl group alternate from

one side to the other. The two quite distinct forms of the

polymeric hydrocarbon as cis 1, 4-poly isoprene and trans-1,

4-poly isoprene are represented below.

Figure 1. Cis-1, 4-Polyisoprene.

Figure 2. Trans-1, 4 Poly isoprene natural rubbers.

Aim of the Research

The aim of this research is to formulate a natural rubber

based adhesive and compare its bonding strength with natural

rubber adhesive modified with starch and reinforcer.

2. Materials and Methods

The natural rubber latex used for this research was

obtained from natural rubber plantation in Emeabiam in Imo

state. The reagents used were of analytical grade.

2.1. Rubber Latex

Fresh from the tree, rubber latex is neutral but due to some

enzymatic activities of some bacteria it coagulates resulting

in separation into clots of rubber and clear serum putrefaction

giving off bad odour. This was prevented by storing it in

ammonia solution. 450 ml ammonia solution was added to

1500 ml of latex. Ammonia solution is preferred to other

preservative because it has bactericidal properties and

increases the pH of the system (which has been decreased by

the bacteria), thus making it more stable. Before using the

rubber for formulation the rubber was deammoniated. This

involves the process of removing ammonia by evaporating

the ammonia in air or addition of acid, centrifugation or other

means. For the purpose of this project addition of weak acid

method was used to neutralize the ammonia.

Deammonification of Natural Rubber latex

450 ml of acetic acid was added to the natural latex on

which 450 ml of ammonia was initially added to; it hardened

the rubber latex into a white mass. This white mass was left

under the sun for 24 hours. It was shredded and left under the

sun for another 24hours before been used to formulate

adhesive. It was then dissolved in a suitable solvent (toluene)

to produce the adhesive. Rubber is almost soluble in all

aliphatic solvent. As a polymer, it first swells after absorbing

and dissolves slowly to form a cloudy solution. The softness

or tackiness is promoted by the reaction with oxygen.

AASCIT Journal of Chemistry 2018; 4(1): 1-6 3

2.2. Formulation of Paper Adhesive Using

Natural Rubber Latex Modified with

Hydrolyzed Starch

Rubber latex is used in wide range adhesives, particularly

for porous surfaces. Based on its application, the proportion

of latex may be small to give a degree of flexibility or may

be large as in paper adhesives. A wide range of compounding

ingredients are used, examples include tackifiers, fillers,

starches, plasticizers and reinforcers

Procedure

Shredded rubber was added in a 500 ml beaker and 30 ml

of toluene was added. This was stirred vigorously for 2

hours. Starch 30 g was suspended in 80 ml of water and

stirred vigorously for 30 minutes. NaOH pellets (2g) were

added while stirring until complete gelation of the starch was

achieved, 2 ml HCl (8ml) was added to neutralize the

adhesive. The resulting adhesive was extended with glycerol

(3 ml) and 2 ml of formalin was added as preservative.

2.2.1. Formulation of Paper Adhesive Using

Natural Rubber Latex Modified with

Dextrinized Starch

Procedure

1.3 g of shredded rubber was put in a 500 ml beaker and 35

ml of toluene was added. This was stirred vigorously for 2

hours. 40 g of starch was mixed with 5 ml of 0.1 M HCl and

then roasted for 30 minutes. The roasted starch was then ground

into powder form. This was then poured into 150 ml of warm

water heated to 70°C and thoroughly stirred with a mechanical

stirrer. 2M solution of caustic soda was added to increase the

viscosity. The rubber solution was added and stirred vigorously.

2 ml of formalin was added as a preservative. Also 0.2 g of

Borax was added to increase the drying speed.

2.2.2. Formulation of Adhesive Using Natural

Rubber Latex Modified with Oxidized

Starch

Procedure

2g of Shredded Rubber was put in a 250ml beaker and

50ml of toluene was added. This was stirred vigorously for 2

hours. 60 g of starch was mixed with 2g of Na2CO3 and 16

ml of H2O2 in a 500ml beaker and the mixture stirred

vigorously for 30 minutes. 100ml of water was then used to

suspend the starch. 4g of NaOH pellets were added while

stirring until complete gelling of starch occurred. 12 ml of

2M of HCl was added. The scrubber solution was added as a

tackifier. The adhesive was extended with 10 ml glycerol and

2ml of formalin was added as a preservative.

2.2.3. Formulation of Natural Rubber Latex

Adhesive

Procedure

The shredded rubber (6 g) was added in a 500 ml beaker

and 150 ml of toluene was added. This was stirred

continuously for 2 hours to obtain a viscous solution (A). The

toluene is indeed a good solvent and acts as a plasticizers and

functions to improve the film-forming ability of the adhesive

without imparting undue softness in the final solution. The

slurry of dispersion B which contains water, casein

(stabilizer), CaCO3 (filler), glycerol (extender/plasticizer),

NH4Cl (accelerator), NaOH pellets (tackifier), gum Arabic,

CH3COONa (corrosion retarder), C6H5COONa (preservative)

was prepared with hot water (95°C). It was then stirred into

rubber solution. A mixture of A and B was obtained.

A+B→AB

2.2.4. Formulation of Natural Rubber Latex

Adhesive Modified with Reinforcer

The procedure is the same as stated above. This was prepared

to see the effect of reinforcer (ZnO) on adhesive formulation.

3. Result and Discussion

The results and performance test of natural rubber

modified with starch are illustrated below

3.1. Natural Rubber Adhesive Modified with

Hydrolyzed Starch

Observation

A physical appearance milky paste was obtained with a pH

of 11. The adhesive was found to be perfect for labeling,

since it adhered strongly. This shows the effect of rubber

latex being a good tackifier and gel property of starch

produce a good adhesive with enhanced adhesiveness.

Performance test

a) Paper to paper bonding

Time taken to observe the fiber tearing bond is 80s after

temper time of 30 seconds.

b) Bottle labeling

Time taken to observe tearing bond is 240 s after temper

time of 60 seconds.

3.2. Paper Adhesive Using Natural Rubber

Modified with Dextrinized Starch

Observation

A light brown paste was obtained with a pH of 8

The adhesive adhered strongly on paper. Performance test

a) Paper to paper labeling

Time taken to observe the fibre tearing bond is 60 s after

temper time of 30 s

b) Bottle labeling


temper time of 60 s

3.3. Natural Rubber Modified with Oxidized

Starch Adhesive

Observation

A white paste was obtained with a pH of 11.

The adhesive was seen to be good for labeling and

packaging. This is as a result of addition of starch to rubber

latex adhesive which enhanced its bonding strength.

Performance test




temper time of 30 s

b) Bottle labeling


temper time of 60 s

3.4. Natural Rubber Latex Adhesive

Observation

A milky paste was obtained with pH of 11. The result of

this formula was very good in terms of viscosity, tackiness

and bonding strength. It was tested on wood, paper and

leather and adhesive strength was excellent.

Performance test


Time taken to observe the fiber tearing bond is 150 s after

temper time of 30 seconds

b) Bottle labeling


60 s

c) Wood bonding

Time taken to separate two pieces of wood joined by this

adhesive is 30 s after temper time of 30 seconds.

The bonding strength comparison of natural rubber modified

with starch adhesive and unmodified natural rubber adhesive on

paper is represented in table 2 and figure 3 while the comparison

on bottle label is represented in table 3 and figure 4

3.5. Natural Rubber Adhesive Modified with

Reinforcer

Observation

An orange colour adhesive was obtained due to addition of

methyl orange. It has a pH of 8. The adhesive gave a very

good yield and proves excellent for paper and leather works.

This shows that reinforcers improve bonding strength of

natural rubber when incorporated into adhesive formulation.

Reinforcement is a simple method to reduce defects. The

reinforcement of natural rubber depends on reinforcing

agents. It has been reported that Silica-reinforced natural

rubber prepared via a sol-gel process is promising and has

been widely used [11]. Also it has been reported that carbon

particles play important role in reinforcing the rubber and

enhancing the cohesion forces in vulcanized polyisoprene

[12]. Organically modified montmorilonite (OMMT) nano

clay incorporated into the natural rubber showed significant

improvement in tensile strength, elongation and thermal

stability [13].

Performance test

The performance test of the adhesive on paper, wood and

leather are illustrated below.


The time taken to observe the fiber tearing bond is 120 s

after temper time of 30 seconds

b) Wood bonding

Time taken to separate two pieces of wood joined by this

adhesive is 60 s after temper time of 30 s

c) Leather bonding

The time taken to separate two pieces of leather after

bonding is 30 s after temper time of 30 s

The comparison of bonding strength of natural rubber

modified with reinforcer adhesive and unmodified natural

rubber adhesive on paper is represented in table 4 and figure

5 while the comparison on wood is represented in table 5 and

figure 6

Table 2. Comparison of Bonding Strength of Natural Rubber Latex adhesive modified with starch and unmodified Rubber Latex adhesive on Paper.

Adhesive Temper time (s) Time taken to obtain the fiber tearing (bonding strength) (s)

Oxidized Starch and Natural Rubber Adhesive 30 65

Hydrolyzed Starch and Natural Rubber adhesive 30 80

Dextrinized Starch and Natural Rubber Adhesive 30 60

Natural Rubber Latex 30 150

Table 3. Comparison of Bonding Strength of natural rubber latex adhesive modified with starch and unmodified rubber latex adhesive on bottle for label.


Oxidized Starch and Natural Rubber Adhesive 60 280

Hydrolyzed Starch and Natural Rubber adhesive 60 240

Dextrinized Starch and Natural Rubber Adhesive 60 300

Natural Rubber Latex 60 420

Table 4. Comparison of Natural rubber adhesive and natural rubber modified with reinforcers on paper.


Natural rubber latex adhesive 30 150

Natural Rubber adhesive with reinforcer 30 120

Table 5. Comparison of Natural rubber adhesive and natural rubber modified with reinforcer on Wood.

Adhesive Temper time (s) Separation Time of two pieces of wood glued together (s)

Natural rubber latex adhesive 30 30

Natural Rubber adhesive with reinforcer 30 60

AASCIT Journal of Chemistry 2018; 4(1): 1-6 5

Figure 3. Comparison of bonding strength of natural rubber latex modified with starch adhesive and unmodified rubber latex adhesive on paper.

Figure 4. Comparison of bonding strength natural rubber latex adhesive with starch modified and unmodified rubber latex adhesive on bottle for label.

Figure 5. Comparison of Natural rubber adhesive and natural rubber modified with reinforcers on paper.


Figure 6. Comparison of Natural rubber adhesive and natural rubber modified with reinforcer on Wood.

4. Conclusion

Natural rubber is a cheap and readily available raw

material for adhesive production. It is tacky in nature but it is

brittle and not stable, this is as a result of the unsaturation of

its back bone and as such there was need for it to be

improved. This research compared the natural rubber starch

and the one incorporated with starch and reinforcers. It was

observed that the one with reinforcer and modified starch had

good bonding strength on paper, wood and bottle labels more

than the unmodified natural rubber latex.

From the findings natural rubber modified with reinforcers

and starch increased its adhesiveness and bonding strength

and can compete with synthetic natural rubber.

Recommendation

This research is based on formulation of adhesive using

natural rubber and comparing its bonding strength with

natural rubber modified with starch and reinforcer. I

recommend that further work should be carried out on natural

rubber using varieties of reinforcers to improve its properties

for commercial production.

References

[1] Leonardo Da Vinci, (2007) Rubber Chemistry. ©Matador Rubber s.r.o

[2] Ochigbo Stephen, Roheem Fatima and Ajai Alexander Ikechukwu (2010). Adhesive formulations with ternary blends using simple lattice design. International Journal of the Physical Sciences Vol. 5 (13), pp. 2098-2103.

[3] J R. Rosin, M. Y. Amir Hashim and P. T. Augurio (2012). Natural Latex Foam. Journal of Engineering Science, Vol. 8, 15–27.

[4] Adhesives.specialchem.com downloaded on 6/10/2017

[5] Pranee Chumsamrong and Oukrit Monprasit (2007). Preparation, adhesive performance and stability of natural rubber latex grafted with n-butyl acrylate (BA) and methyl methacrylate (MMA). Suranaree J. Sci. Technol. 14 (3): 269-276

[6] Wanvimon Arayapranee and Garry L. Rempel (2013). Effects of Polarity on the Filler-Rubber Interaction and Properties of Silica Filled Grafted Natural Rubber Composites. Journal of Polymers http://dx.doi.org/10.1155/2013/279529

[7] M T. Jayanthy, P. E. Sankaranarayanan Sathyabama (2005). Measurement of Dry Rubber Content in Latex Using Microwave Technique. MEASUREMENT SCIENCE REVIEW, Volume 5, Section 3.

[8] Jitladda T. Sakdapipanich and Porntip Rojruthai (2012). Molecular Structure of Natural Rubber and Its Characteristics Based on Recent Evidence, Biotechnology - Molecular Studies and Novel Applications for Improved Quality of Human Life, Prof. Reda Sammour (Ed.), ISBN: 978-953-51-0151-2, In Tech, Available from: http://www.intechopen.com/books/biotechnology-molecular-studies-and-novel-applications-for-improvedquality-of-human-life/molecular-structure-of-natural-rubber-and-its-characteristics-based-on-recent-evidence

[9] Herman. F. Mark, Norman. G. Encyclopedia of polymer Science and Technology. Volume 1, 1964, p. 482.

[10] Adhesives technology handbook 2nd Edition, edited by Sina Ebnesajjad, (2008). William Andrew Inc.

[11] Sirilak Phomrak and Muenduen Phisalaphong 2017) Reinforcement of Natural Rubber with Bacterial Cellulose via Latex Aqueous Microdispersion Process. Hindawi Journal of Nanomaterials. P. 1-9.

[12] Mahmoud Kardan, Robert Ferguson, and Rebecca Seitz (2016) Impact of Carbon Black on Durability of Vulcanized Rubbers. Vernay flow control solutions, P. 1-5.

[13] Benson. U. Da, Abdul Majeed. S. S. Ma*, Rajesh Babub (2016) Natural rubber / OMMT nanocomposites for reinforcement in tyre ply. International Journal of NanoScience and Nanotechnology. Volume 7, Number 1, pp. 41-55.

natural rubber based adhesive modified with starch and...

Documents