Vegetable oil is readily available and inexpensive, can be used to synthesise various types of polymers. In our present study, epoxidised punnal oil has been synthesised from punnal oil via peroxy acetic acid generated ‘insitu’ by treating acetic acid with hydrogen peroxide as oxygen donor. The epoxidation is catalysed by using sulphuric acid. The epoxidation is confirmed by iodine value, oxirane oxygen analysis, fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and thin layer chromatography (TLC) analysis.Natural fibers such as jute, sisal, banana, rice husk etc are locally available in abundance and have excellent physical and mechanical properties and can be used more effectively in the development of composite materials for various applications. Epoxy composite samples are prepared from the natural fiber with different ratios using triethylamine hardener and pthaleic anhydride. The mechanical properties viz. tensile strength and the physical properties observed are discussed in detai

Retna, Dr A Malar

Samuel, Robin Kumar

Sasikala, T.J.

English

Gyandhara International Academic Publication (GIAP): Journals

Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 33 
 
SYNTHESIS AND CHARACTERISATION OF COIR FIBER REINFORCED EPOXY 
COMPOSITES FROM PUNNAL OIL 
T.J.Sasikala, Robin Kumar Samuel*, A.MalarRetna** 
*Caledonian College of Engineering, Sultanate of Oman. 
**Department of Chemistry, Scott Christian College (Autonomous), Nagercoil-3, Tamilnadu, India. 
sasikaladhar34@gmail.com  
Article History: 22
nd
 July, Revised on 25
th
 September, Published on 05
th
 November 2015 
Abstract 
Vegetable oil is readily available and inexpensive, can be used to synthesise various types of polymers. In our present study, epoxidised 
punnal oil has been synthesised from punnal oil via peroxy acetic acid generated ‘insitu’ by treating acetic acid with hydrogen peroxide as 
oxygen donor. The epoxidation is catalysed by using sulphuric acid. The epoxidation is confirmed by iodine value, oxirane oxygen analysis, 
fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and thin layer chromatography (TLC) analysis. 
Natural fibers such as jute, sisal, banana, rice husk etc are locally available in abundance and have excellent physical and mechanical 
properties and can be used more effectively in the development of composite materials for various applications. Epoxy composite samples 
are prepared from the natural fiber with different ratios using triethylamine hardener and pthaleic anhydride. The mechanical properties 
viz. tensile strength and the physical properties observed are discussed in detail.  
Keywords:  Punnal oil,  Epoxidised punnal oil, Epoxy composites, Coir fiber, Chemical resistance
INTRODUCTION 
Epoxidised vegetable oils can be used as plasticisers, stabilisers and lubricants in the polymer industry. As energy demands increase, 
there is utilization of renewable resources instead of petroleum based polymers. Vegetable oils are quite abundant in nature. Soybeen 
oil, castor oil, rape seed oil, palm oil etc are different examples of vegetable oils. Vegetable oils are triglycerides which contain 
different fatty acids such as oleic acid, linolenic acid, linolic acid, stearic acid and palmitic acid. These oils are readily available and 
inexpensive, can be used to synthesise various types of polymers [1]. Punnal oil which are obtained from punnal tree is rich in 
unsaturated fatty acids which are used for the conversion to polymeric material. 
 
Figure 1: Punnal seeds 
Epoxidation of fatty acids is a reaction of a carbon – carbon double bond with active oxygen, which results in the addition of an 
oxygen atom, converting the original double bond into a three membered epoxide (oxirane) ring. A composite material is made by 
combining two or more materials to give a unique combination of properties, one of which is made up of stiff, long fibers and the 
other, a binder or 'matrix' which holds the fibers in place.  
Coir fibers are found between the hard, internal shell and the outer coat of a coconut. The individual fiber cells are narrow and hollow, 
with thick walls made of cellulose. They are pale when immature but later become hardened and yellowed as a layer of lignin is 
deposited on their walls. The coir fiber is relatively waterproof and is one of the few natural fibers resistant to damage by salt water. 
The increase of treated fiber content resulted in a significant increase in tensile strength of composites. Alkali treatment increased the 
strength of natural fiber composites. A strong sodium hydroxide treatment removed lignin, hemicellulose and other alkali soluble 
compounds from the surface of the fibers to increase the numbers of reactive hydroxyl groups on the fiber surface available for 
chemical bonding. The removal of these substances enhanced the surface roughness. Therefore, mechanical interlocking at the 
interface could be improved. Keeping this in view, the present work has been under taken to develop a polymer epoxy composites 
using treated coir fiber as reinforcement. 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 34 
 
EXPERIMENTAL 
Materials  
The punnal oil used in this study is obtained from the local company. Glaciel acetic acid, hydrogen peroxide (30wt %), sulphuric acid, 
95 – 98wt% were obtained from merck. The coir fiber is collected locally. The hardener triethylamine is obtained from Merck, 
pthaleic anhydride and anhydrous isopropyl alcohol from the Sigma-Aldrich. 
Epoxidation of punnal oil 
A calculated amount of punnal oil (1M) is placed in a 500ml three neck flask equipped with reflux condenser containing the required 
amount of acetic acid (0.5M). Then a calculated amount of 30% hydrogen peroxide is added dropwise with continuous stirring for 
about 1hr. Thereafter, the temperature of the reaction mixture is raised to 60
o
C and maintained at this temperature for a period of 8hrs. 
Two different molar ratios of C=C bonds to hydrogen peroxide are used. (1:1.3 and 1:1.5). The product is cooled and decanted to 
effect a separation of the epoxidised oil from water soluble ones. The epoxidised oil is then washed with warm water to remove 
residual contaminants. The product (EPO) is then analysed to determine its iodine value and oxirane oxygen. 
Alkali treatment 
The coir fibers are cleaned and dried in atmosphere for one day and then kept in oven at 50
o
C to remove the moisture. The coir fibers 
are soaked in 4% NaOH solution for 2 hrs to remove any unwanted material and hemicelluloses, washed thoroughly in distilled water 
and dried under the sun for one week. Then it are weighted according to the percentage needed (5, 10, and 15wt. %). 
Preparation of composites 
The mould cavity is coated with a thin layer of silicone grease. A calculated amount of epoxidised punnal oil (EPO), pthaleic 
anhydride and isopropyl alcohol are dissolved in minimum amount of acetone. The mixture is heated in an oil bath to 120
o
C for 2hrs. 
The hardener triethylamine was added. Different amounts of treated coir fiber (5, 10 and 15%wt) is added separately in the above mix 
and stirred. The final resultant mixture is poured into moulds. The sample is cured in an oven at 150
o
C for 14 hours. 
CHARACTERISATION 
Physico-chemical properties 
Fatty acids of oil are obtained by using a Varian star 1gas chromatography - mass spectrometry (GC-MS) instrument. Fourier 
transform infrared spectroscopy (FTIR) spectra of virgin oils and epoxidised oils are recorded by a Thermo Nicolet AVATAR 320 
FTIR spectrometer coupled with Ezominic software. A thin layer of sample is applied over a NaCl plate and the spectrum was 
recorded in the range 400-4000 cm-1. Nuclear magnetic resonance (NMR) spectra are recorded using BRUCKER AVANCE 500 
NMR spectrophotometer. For NMR experiment frequencies of 500 MHz is used to record 1H spectra. The solutions used are prepared 
in deuterochloroform using tetramethylsilane (TMS) as the reference. Iodine value and oxirane oxygen content of oils and their 
derivatives are determined using standard methods [2]. A standard procedure is used to evaluate saponification values of oils.[3] 
Thin layer chromatographic analysis  
 Silica coated aluminium TLC plates are used for TLC analysis. The solvent used is a mixture of hexane and CH2Cl2 in 3:7 ratio are 
added. Plates are visualized in an iodine chamber. 
Chemical resistance of composites 
A chemical resistance of the composites is studied as per ASTM D 543.87 method. For chemical resistance test, the acids namely 
conc.HCl (1N), conc.HNO3 (1N) and H2SO4 (1N), the alkalis namely aquous solution of NaOH (10%), ammonium hydroxide (10%) 
and sodium carbonate (20%) and the solvents diethyl ether, dimethyl acetamide, chloroform, toluene and water are selected. In each 
case, weighed samples are dipped in the respective chemicals under study for 60days, removed and immediately washed thoroughly 
with distilled water and dried by pressing them on both sides by filter papers. The % of weight loss /gain is determined.  
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 35 
 
Moisture content test 
Initially each specimen are weighed and then the specimen is dried in ventilated oven at a temperature of 80
o
C until the mass became 
constant to ±0.2% between two successive weighing made at an interval of 1hrs. 
Moisture content = 100

o
fo
m
mm
 
Where mo and mf are initial and final mass respectively. 
Soil buriel degradation 
Specimens of each composite are placed in a series of boxes containing moisturised soil. The specimens (30 X 10 mm) are buried 100 
mm beneath the surface of soil which is regularly moistened with distilled water. At predetermined time points the samples are 
removed, carefully washed with distilled water in order to ensure the stop of the degradation, dried at room temperature to a constant 
weight and then are stored in darkness. 
Weight loss = 100

o
to
W
WW
 
Where Wo is the initial mass and Wt is the remaining mass at any given time, t.  
Tensile test 
Tensile strength, Young’s Modulus and Elongation at break are measured according to the ASTM D638 standard using universal 
testing at a crosshead speed of 5mm/min. 5 Specimens of each sample are tested and tensile strength, youngs modulus and elongation 
at break are expressed as, 
Tensile strength (MPa) =
bh
P
 
Young’s Modulus(MPa) =


 
Where, P = pulling force (N), B= Specimen width (m), H= Specimen thickness (m),   = stress (N/m2),  = strain 
RESULTS AND DISCUSSION 
Physico - chemical properties of the punnal oil 
Table 1: Physico-chemical properties of oil and EPO 
Properties Punnal  oil EPO (1:0.5:1.3) EPO (1:0.5:1.5) 
Colour Dark green Pale yellow Pale yellow 
Specific gravity 0.91 0.99 1.19 
Acid value 35   
Saponification value 182 - - 
Iodine value 71 52 48 
Oxirane Oxygen - 2.5 2.8 
Moisture content - 0.3% 0.56% 
The iodine value and the oxirane oxygen content are important properties in the characterization of epoxidised vegetable oils. While 
the iodine value indicates the remaining unsaturation after the epoxidation reaction, the oxirane oxygen content indicates the epoxy 
groups present in the products. In the preparation of polymers, epoxy resin with a lower iodine value and higher oxirane oxygen 
content are desired. In the present study, the reduction in iodine value indicates the consumption of unsaturation during epoxidation. 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 36 
 
Thin layer chromatography 
Table 2: TLC for oil and EPO 
Solvent used = Benzene : chloroform (7 : 3) 
Rf value for oil 0.56 
Rf value for EPO (1:0.5:1.3) 0.68 
Rf value for EPO (1:0.5:1.5) 0.72 
Thin layer chromatographic study of the resin showed a distinct single spot, indicating the purity of the sample. Rf value for resin is 
different from that of oil indicating the formation of the product.(see table 2) 
Fatty acid composition of punnal oil 
The unsaturated fatty acids present in punnal oil are oleic acid and linoleic acid containing one and two double bonds between two 
carbon atoms respectively. The functionality present in punnal oil is in terms of double bonds thus the C=C acts as a reaction site for 
chemical modification in punnal oil. 
Table 3: Fatty acid composition of punnal oil 
Fatty Acid Composition % 
Palmitic acid C16H32O2 14.5 
Stearic acid C18H36O2 12.9 
Oleic acid C18H34O2 41.4 
Linoleic acid C18H32O2 29.7 
Linolenic acid C18H30O2 0.2 
The possible triglyceride is, 
 
Figure 2: Triglyceride structure of punnal oil 
Generally, oil consists basically of triacylglycerols with different degrees of unsaturation and different distribution and properties of 
fatty acid acyl chains. The high content of unsaturated fatty acids of about 72% in punnal oil gave rise to the high iodine value of 71g 
I2/100g. These properties show that punnal oil is a suitable starting material for epoxidation. 
FT –IR analysis 
The IR spectrum of punnal oil also supports the presence of both saturated and unsaturated acyl groups. The conversion of double 
bonds to epoxy is confirmed by the FT-IR spectra. The epoxidised oil reveals that  disappearance of 3009cm-1 band shows C=C has 
been used up and appearance of the band around 910cm-1 which is not in oils, is characteristic of the epoxide and it can be assigned to 
ring vibrations of the epoxy ring in cis-epoxides.[4] 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 37 
 
 
Figure 3: FT–IR spectrum of (a) Punnal oil; (b) EPO (1:0.5:1.3), (c) EPO (1:0.5:1.5), (d) Epoxy composite 
NMR analysis 
 
Figure 4: Proton NMR spectra of oil 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
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Figure 5: Proton NMR spectra of EPO(1:0.5:1.3) 
 
Figure 6: Proton NMR spectra of EPO (1:0.5:1.5) 
The conversion of olefinic group to epoxy group is clearly indicated by the spectra. The spectra of oil, the olefinic proton is observed 
in 5.3 – 5.5 ppm. In the spectra for epoxidised oil, the peak has almost disappeared. This fact suggest that the C=C undergoes 
complete epoxidation. 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 39 
 
Scheme of epoxidation 
Scheme: I 
 
Scheme: II 
 
Figure 7: Scheme of epoxidation 
Chemical resistance of composites  
The coir reinforced composites seem to exhibit higher weight loss than the neat epoxy composites. Furthermore, the weight loss 
slightly increases with increasing time of exposure to the environment for all the specimens. 
Table 4: Stability of composites to the acidic environment 
Specimen Weight loss(%) 
Conc.HCl (1N) Conc.HNO3 (1N) Conc.H2SO4 
(1N) 
Neat Epoxy(EC) (1:0.5:1.3) 0 0 0 
EC + 5% coir  -0.2 -0.2 0.14 
EC +10% coir  -0.2 -0.2 -0.7 
EC +15% coir  -0.2 -0.2 -0.7 
Neat Epoxy(EC)  (1:0.5:1.5) -0.2 0 0 
EC +5% coir -0.2 0 -0.5 
EC +10% coir  -0.2 -0.2 -0.3 
EC +15% coir  -0.2 -0.2 0 
Table 5: Stability of composites to the basic environment 
Specimen Weight loss(%) 
NaOH (10%) NH4OH (10%) Na2CO3 (20%) 
Neat Epoxy(EC) (1:0.5:1.3) 1.4 0 0 
EC + 5% coir  1.4 0 -0.1 
EC +10% coir  0.9 -0.1 -0.5 
EC +15% coir  0.5 0.5 -0.5 
Neat Epoxy(EC) (1:0.5:1.5) -0.5 -0.5 0 
EC +5% coir -0.1 -0.29 -0.5 
EC +10% coir  -0.5 -0.5 -0.29 
EC +15% coir  -0.29 -0.29 -0.29 
 Punnal oil + CH3COOH + H2O2 + H2SO4 
    Epoxidised Punnal oil 
 Epoxidised Punnal oil +Pthaleic anhydride       +  Triethyl amine +  Coir fiber   
    Epoxy composite 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 40 
 
 
Table 6: Stability of composites to the solvent 
Specimen Weight loss (%) 
Ethanol DMA CHCl3 Toluene Water 
Neat Epoxy(EC) (1:0.5:1.3) 0 0 -0.4 0 0 
EC + 5% coir  -0.2 0 -1.7 0.3 -0.3 
EC +10% coir  0.3 0 -1.7 0.33 -0.3 
EC +15% coir  0.14 0 -1.7 0.14 0.6 
NeatEpoxy(EC)  (1:0.5:1.5) 0 0 -2.3 0 0 
EC +5% coir 0 0 -2.2 0 0.3 
EC +10% coir  0.13 0 -2.2 0.14 0.3 
EC +15% coir  -0.2 0 -3 0 0.3 
 
In the present study, all epoxy composites showed excellent acid, alkali and solvent resistance and no significant change in the 
physical appearance of epoxy samples is seen except CHCl3. In chloroform, the samples became brittle after drying. 
Soil buriel degradation 
Biodegradability depends not only on the origin of the polymer but also on its chemical structure and the environmental degradation. 
In the present study, there is no weight loss observed in the composites even a period of 2 months. Hence these composites are non-
biodegradable. 
Table 7: Soil buriel test for composites 
Specimen Weight(g) 
Initial Final 
Neat Epoxy(EC)  (1:0.5:1.3) 1.54 1.54 
EC + 5% coir  1.67 1.67 
EC +10% coir  1.98 1.98 
EC +15% coir  1.8 1.8 
Neat Epoxy(EC)   (1:0.5:1.5) 1.93 1.93 
EC +5% coir 1.68 1.68 
EC +10% coir  1.89 1.89 
EC +15% coir  1.88 1.99 
Tensile Properties 
Table 8: Tensile strength, elongation at break and youngs modulus of epoxy composites 
Specimen Tensile Strength 
(MPa) 
% of elongation 
at break 
Youngs Modulus 
(MPa) 
Neat Epoxy(EC) (1:0.5:1.3) 1.8 11 16.36 
EC + 5% coir  3.3 12.1 27.5 
EC +10% coir  5.9 12.9 45.7 
EC +15% coir  10.8 14.04 77.14 
Neat Epoxy(EC)  (1:0.5:1.5) 2.5 10.64 23.6 
EC +5% coir 5.4 10.8 50 
EC +10% coir  8.9 11.9 74.8 
EC +15% coir  13.73 12.1 113.47 
The increase in coir fiber content leads to the increase in the tensile strength and the young’s modulus. The elongation at break, 
however, was decreased, which is in line with the changes of mechanical properties of general natural fiber reinforced polymer 
composites. Coir fibers possess good mechanical properties. As the content of the coir fibers increased, more fibers shared the tensile 
Green Chemistry & Technology Letters  
Vol 1, No 1, November 2015, pg 33-41 
DoI: 10.18510/gctl.2015.115 
 
www.greenchemistry.in 41 
 
stress to improve the tensile strength and Young’s modulus greatly. On the other hand, the limit deformation of coir fibers made the 
elongation at break decrease. When the mass fraction of coir fiber above 15%, the fibers could not distribute evenly and the defects of 
the composite increased, which limited the improvement of mechanical properties. 
CONCLUSION 
Punnal oil was epoxidised successfully by peroxy acetic acid generated ‘insitu’ by reacting acetic acid with hydrogen peroxide at the 
temperature range of 60 – 70oC. The epoxidation was confirmed by iodine value, TLC and FT-IR analysis. Further epoxy composites 
are prepared from the treated coir fiber of different composites (5, 10 and 15wt %). As the coir fiber content increases, the tensile 
strength also increases. There is no weight loss observed from the chemical resistance test concluded that these composites are non-
biodegradable. The moisture uptake increases with the increase in percentage of fiber content. 
REFERENCES 
1. Blayo, A.; Gandini, A.; Le Nest, J. F. Chemical and rheological characterization of some vegetable oils derivatives 
commonly used in printing inks; Ind. Crops Prod. 2001, 14, 155 – 167. 
2. Standard methods for the analysis of oils (1994). In: Fats and Derivatives part I, section II, 10.86th edition, pp 66-70,92-94 
3. Standard methods for the analysis of oils (1994). In: Fats and Derivatives part I, section II, 10.86th edition, pp 66-70 
4. Bellamay,13.7 L. J.; (1975): The infrared spectra of complex molecules. In: Ethers, peroxides and ozonides volume I, 
3rdedition., pp. 133-135, Methuen and company Ltd, London, UK.  


SYNTHESIS AND CHARACTERISATION OF COIR FIBER REINFORCED EPOXY COMPOSITES FROM PUNNAL OIL

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