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Progress in Organic Coatings 66 (2009) 59–64

Contents lists available at ScienceDirect

Progress in Organic Coatings

journa l homepage: www.e lsev ier .com/ locate /porgcoat

poxidized Mesua ferrea L. seed oil-based reactive diluent forPA epoxy resin and their green nanocomposites

autam Das, Niranjan Karak ∗

hemical Sciences Department, Tezpur University, Napaam 784028, India

r t i c l e i n f o

rticle history:eceived 20 December 2008eceived in revised form 1 June 2009ccepted 3 June 2009

eywords:poxidized oilesua ferrea L.reen nanocompositeseactive diluent

a b s t r a c t

An epoxidized vegetable oil of Mesua ferrea L. seed was prepared and used as a reactive diluent for com-mercial BPA-based epoxy resin at different compositions for the first time. The prepared epoxidized oil(ENO100) was characterized by determination of physical properties like epoxy equivalent, viscosity,hydroxyl value, saponification value, iodine value, acid value, etc. and FTIR study. The morphology andrheological characteristics of the ENO100 modified commercial epoxy systems have been studied by SEMand rheometer. The performance of poly(amido amine) cured above resin systems have been investigatedby the measurement of drying time, tensile strength, elongation at break, adhesive strength, impact resis-tance, scratch hardness, gloss and chemical resistance studies. The results indicate that the epoxidizedoil not only reduces the viscosity of the BPA-based epoxy resin but it also enhances the performance of

the cured resin. The performance of this system (50 wt.% dilution) was further enhanced by formationof nanocomposites using ex-situ technique with organically modified nanoclay at different dose levels(1–5 wt.%).

The formation of nanocomposites was confirmed by XRD, SEM and FTIR studies. The studies of aboveperformance indicate the enhancement of properties compared to pristine system. As naturally renewablediluent is used in the above studies, so the resultant nanocomposites are green high performance materialswith zero VOC.

. Introduction

Nowadays the use of petroleum-based products in manufactur-ng of different industrial products is facing some serious problems.his is the result of awareness of people to the environmentalssues, such as volatile organic solvent emissions and recyclingr waste disposal problems, spiraling rise in prices and high ratef depletion of the non-renewable stocks [1–3]. Today vegetableil is one of the most important renewable raw materials for thehemical industry and is widely used for the surfactants, cosmeticroducts, and lubricants and also in coatings and paints applica-ion. Some of the most widely applied renewable raw materials inhe chemical industry include plant oils, polysaccharides (mainlyellulose and starch), sugars, wood, and others [4]. Vegetable oilsre also used to prepare different kinds of polymeric resins, such

s epoxy resin [5], polyesteramide [6], polyurethane [7], and oth-rs. This is due to the advantages of vegetable oil in productionf different polymers. These are (i) renewable, (ii) easily availablen large quantity, (iii) environmental friendly, (iv) biodegrad-

∗ Corresponding author. Tel.: +91 3712 267327; fax: +91 3712 267006.E-mail address: karakniranjan@yahoo.com (N. Karak).

300-9440/$ – see front matter © 2009 Elsevier B.V. All rights reserved.oi:10.1016/j.porgcoat.2009.06.001

© 2009 Elsevier B.V. All rights reserved.

able, (v) mostly low cost, (vi) easy to modify and (vii) easy tohandle [8].

A large variety of widely grown plant-based seed oils are avail-able in India. Nahar (Mesua ferrea L.) is such a plant that producesexceptionally high oil content (70–75%) seeds. It is available indifferent parts of India, especially in north-eastern region. The char-acteristics of this oil indicate that it is non-drying oil, comprisingoleic acid (52.3%) and linoleic acid (22.3%) as unsaturated fatty acidsand stearic acid (9.5%) and palmitic acid (15.9%) as saturated fattyacids [9], and hence it can be utilized for the synthesis of differenttypes of resins. There have been a few reports on the utilization ofNahar oil as raw material for coatings and paints from the same lab-oratory [10–13]. So in the present investigation, this oil was utilizedto prepare industrially important epoxy resin, which is not reportedso far.

The vegetable oil-based epoxy resins are generally used asreactive diluent which are low viscous materials and are used inconjunction with the industrial resins for the reduction of viscosity

and to increase the molecular mass of the latter. As the reactive dilu-ent act as a solvent for the used resin system, so it permits to obtainhigh-solid and low VOC coatings [14]. In this report, therefore, lowviscous epoxidized M. ferrea L. seed oil was used as a reactive diluentfor BPA-based commercial epoxy resin.

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0 G. Das, N. Karak / Progress in

Epoxy resins are widely used as engineering materials becausef their extraordinary toughness, good mechanical properties, andutstanding chemical and electrical resistance [15]. The broad inter-st in epoxy resins originates from the versatility of the epoxyroup towards wide variety of chemical reactions and their use-ul properties. These resins are easily cured without evolutionf volatiles or by-products by a broad range of chemicals suchs polyamines, polyacids, polythiols, polyphenols, etc. [16]. Epoxyesins are also chemically compatible with other materials andend to wet surfaces easily, making them especially well suitedo composites applications. Thus they are routinely used as adhe-ives, coatings, encapsulating materials, casting materials, pottingompounds, etc. Some of their most interesting applications areound in the aerospace and recreational industries where resinsnd fibers are combined to produce complex composite structure17]. However, the improvement of performance of such conven-ional composites is not significant. Further, the specific gravity ofuch resultant composites is high.

So the improvement of performances by incorporation of theanometer size organo-inorganic particles with a very low load-

ng, generally ≤5 wt.%, is a topic of today’s interest [13,18]. This isecause of the fact that the formation of exfoliated nanocompos-

tes results significant improvement of properties like dimensiontability, strength, heat resistance, gas barrier capacity, biodegrad-bility of a biodegradable polymer without increase of specificravity of the resulted products. Among the different nano rein-orcing agents, nanoclay is still most accepted for preparation ofolymer nanocomposites due to its combination of properties likeigh aspect ratio, relative low cost, easily modified and adequatevailability. The enhancement of desirable properties by the for-ation of nanoclay-based nanocomposite of epoxy resins has beenell studied in literature [19,20]. Hence in this present investiga-

ion the nanoclay nanocomposites of BPA-based epoxy resin in theresence of epoxidized oil-based reactive diluent has been studied.

Authors, therefore, wish to report here the preparation of a newpoxidized vegetable oil, its use as reactive diluent in commer-ial BPA-based epoxy resin and their nanoclay–nanocomposites.he performance of cured resins with different compositions andanocomposites with different nanoclay loadings are also studied.

. Experimental

.1. Materials

Nahar (M. ferrea L.) seeds (Jamugurihat, Assam) were utilized forhe collection of the oil. Hydrogen peroxide (50%), acetic acid (99%),nd sulfuric acid (Merck Limited, Mumbai), and organically modi-ed nanoclay (octadecylamine modified montmorillonite, Aldrich)ere used as received. The bisphenol-A-based epoxy resin (BPA,raldite LY 250) (epoxy equivalent—180–190 g/eq. and density.16 g/cc at 25 ◦C) and poly(amido amine) hardener (HY 840) weresed for this study and were obtained from Ciba Geigy, Mumbai. Allther reagents used in the present investigation are reagent grade.

.2. Methods

.2.1. Extraction and purification of the oilSeeds were collected from the Nahar tree and pre-treated in

series of processes involving cleaning, dehulling, size reduction,ooking and flaking to about 0.3–0.4 mm thickness to rupture the

ell. The resulting material was then utilized for extraction of Nahareed oil (M. ferrea L.) from dried powder seeds by solvent extrac-ion process. Dirt was removed by settling followed by filtration.egumming was done by treatment of extracted oils with waternd aqueous salt solution. By the process of alkali refining free fatty

ic Coatings 66 (2009) 59–64

acids were removed without excessive saponification of the oil andwithout loss of oil by emulsification. The caustic soda solution ofvery low concentration was used in sufficient quantity to neutralizethe free fatty acids.

2.2.2. Epoxidized M. ferrea L. seed oilThe purified oil was epoxidized by using in-situ peracid method

[21,22]. 40 g of the oil was taken in a three necked round bottomflask equipped with a mechanical stirrer and a thermometer. Tothe oil, 4.4 g of CH3COOH and a required amount of H2SO4 (2% ofthe H2O2–CH3COOH mixture) were added and stirred for 30 min,then 13.4 g of 50% aqueous H2O2 was added for about 30 min. Thereaction was then continued with constant stirring for 8 h. The tem-perature was maintained at 55–60 ◦C. The resulted product waswashed with water until it was free from acid. Then the product wasdried under vacuum to a constant weight. This product is coded asENO100.

2.2.3. Mixing of epoxidized oil with BPA-based epoxyEpoxidized oil and bisphenol-A-based commercial epoxy

(Araldite LY 250) resins were mixed by mechanical stirring for10 min at ambient temperature. The hardener was added in eachcase by maintaining the ratio of epoxy to hardener 2:1. The mix-tures were prepared by addition of epoxidized oil (ENO100) withcommercial BPA-based epoxy (ENO0) in the ratio of 75:25, 50:50and 25:75 (w/w) for ENO75, ENO50 and ENO25 respectively.

2.2.4. Preparation of nanocompositesThe nanocomposites were prepared by ex-situ technique [23]

taking the mixed resin system, ENO50. Organically modified claywas added to the blend at 80 ◦C and mixed by a mechanical stirrerfor about 2 h. Then the mixture was sonicated for 30 min followedby degassing for 15 min under vacuum. The prepared nanocompos-ites are coded as ECN1, ECN2.5 and ECN5 for clay loadings of 1, 2.5and 5 wt.%, respectively.

2.2.5. Curing of the resins and nanocompositesA homogenous mixture of each resin and nanocomposite sys-

tem with 50 phr (parts per hundred grams of resin) of poly(amidoamine) hardener was prepared in a glass beaker at room tem-perature by constant stirring for 10 min. Then the mixtureswere uniformly spread on mild steel plates (150 mm × 50 mm ×1.60 mm), tin plates (150 mm × 50 mm × 0.40 mm.) and glass plates(75 mm × 25 mm × 1.75 mm) for impact resistance, gloss and chem-ical resistance tests. The plates were cured at 100 ◦C for specifiedperiod of time.

2.3. Instruments and methods

FTIR spectra of oil and resin were recorded in FTIR spectroscopy(Impact-410, Nicolet, USA) using KBr pellet. The viscosities of theoil and the resin systems were measured using rheometer (ModelCVO100, Malvern, UK). The relationship between viscosity and timeat constant stress (100 Pa) under isothermal condition (at 25 ◦C),viscosity with temperature gradient at constant stress (100 Pa) ofthe resins and blends were determined by using the above instru-ment. The physical properties such as acid value, iodine value,saponification value, solubility and viscosity of the resin were deter-mined by the standard methods. The surface morphology of thesamples was done by a JEOL scanning electron microscope of model

JSM-6390LV SEM after platinum coating on the surface.

The mechanical properties such as tensile strength, elongationat break and adhesion (using the lap shear adhesion method andby taking plywood as the substrate) were measured with the helpof Universal Testing Machine of model Zwick Z010, Germany. The

G. Das, N. Karak / Progress in Organic Coatings 66 (2009) 59–64 61

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The formation of clay/epoxy nanocomposite is first understoodfrom the XRD studies. The XRD patterns of the nanocomposites withdifferent clay loading and pure nanoclay are shown in Fig. 3. Thepure organically modified nanoclay shows sharp peak at 4.2◦ (cor-

Scheme 1. Prepar

cratch hardness by using Scratch hardness tester (Sheen instru-ent Ltd., UK) and impact resistance by Impact tester (S.C. Dey Co.,

olkata) of the cured films were measured. The gloss characteristicsf the cured films were found out by using mini gloss meter (Sheennstrument Ltd., UK) over resin coated mild steel plate at an anglef incidence of 60◦. The chemical resistance of the cured films waserformed in different chemical environments. Glass plates coatedlms were kept in 250 mL beakers containing 150 mL of differenthemicals for 30 days and then visually observed for any change onhe films.

. Results and discussions

.1. Preparation and physical properties of epoxidized oil

The epoxidation of the oil (M. ferrea L.) was directly carried outy in-situ epoxidation reaction using hydrogen peroxide with aceticcid at about (55–60) ◦C for a specified period of time in a single steprocess without using any solvent (Scheme 1). As it is a bulk reactiono it avoids the limitations associated with solvents like removal,ealth hazards, flammability, etc. The hydroxylation reaction of thepoxy group occurs with the increase of reaction time but less thanh reaction is not possible to obtain desired product, so the reactionas carried up to 8 h for this study. The resin was formed with

easonable time with relatively good yield (80–90%) may be due tohe use of sulfuric acid as catalyst in the resinification reaction.

The physical properties like acid value, saponification value,odine value, hydroxyl value, and epoxy equivalent of the epoxi-ized oil are given in Table 1. From this table it can be observedhat the iodine value decreases with epoxidation of the oil thoughhe saponification and hydroxy values increase with the same. Theesults indicate that the some amounts of unsaturation are uti-ized for oxirane ring formation which increases molecular weights indicated by the increase in saponification value. High hydroxylalue results from the slight hydrolysis of the oxirane ring duringhe resinification reaction. The epoxy value confirms the forma-ion of oxirane ring, which is also supported by FTIR studies. TheTIR spectra show band at 906 cm−1 for the resin (Fig. 1) whichas not observed for the oil [10]. The other important charac-

eristic bands (cm−1) at 3466–3675, 2852–2923, 1747, 1163–1164nd 1617–1619 for O–H, aliphatic C–H, C O of triglyceride esters,–O–C of ester and C C stretching vibrations respectively were alsobserved in FTIR spectrum for ENO100 before curing. However, after

uring the band at 906 cm−1 again vanishes (Fig. 1, ENO50), whichonfirms the crosslinking reactions. This is also supported by theecrease of intensity of –OH stretching band in the cured spectra,oth for ENO50 and the nanocomposite (ECN2.5). The spectrum ofrganically modified nanoclay shows the presence of bands (cm−1)

able 1hysical property of oil and ENO100.

roperty Pure oil ENO100

cid value (mg KOH/g) 14 12.46odine value (g I2/100 g) 89.28 35.59aponification value (mg KOH/g) 260 279.99ydroxyl value (mg KOH/g) 220 287.35poxy equivalent (g/eq. epoxy group) – 500

of epoxidized oil.

at 3690–3420 for –OH stretching, 2930–2820 for –C–H stretchingof modifying hydrocarbon, 1640 for –OH bending, 1045–980 and538–486 for oxide bands of metals (Al, Mg, Si, etc.) present in theclay, which are agreed well with the reported values. But the inten-sities of these bands particularly for –OH, are reduced drasticallyin the nanocomposite (Fig. 1), which confirmed the participation of–OH of clay in crosslinking of epoxy resin.

The ENO100 is soluble in most of the common organic solventslike DMF, DMAc, DMSO, THF, xylene, toluene, etc.

3.2. Preparation of ENO100 modified BPA-based epoxy

The ability to produce miscible system with improved combi-nation of properties of the individual components depends on thedegree of compatibility of the system [21]. ENO100 show goodcompatibility with the Araldite LY 250 (commercial epoxy resin)without any solvent. The SEM micrographs (Fig. 2) of the cured filmsfor pristine resin as well as nanocomposite systems showed excel-lent dispersion of ENO100 in Araldite LY 250 and nanoclay in thematrix, respectively.

3.3. Formation of nanocomposites

Fig. 1. FTIR spectra for (a) ENO100, (b) cured ENO50, (c) ECN2.5 and (d) pure nan-oclay.

62 G. Das, N. Karak / Progress in Organic Coatings 66 (2009) 59–64

ENO50, (b) ECN1, (c) ECN2.5 and (d) ECN5.

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Table 2aInfluence of ENO amount on drying time and viscosity of ENO100 and ENO100modified commercial epoxy.

Sample code Viscosity at25 ◦C (Pa)

Touch free time(min)

Hard dry time(min)

ENO0 100 30 60

Fig. 2. SEM micrograms for cured (a)

espond to the basal reflection of ‘0 0 1’) along with two small peakst 20.05◦ and 26.5◦, whereas all the nanocomposites exhibit onlyvery broad peak at around 15–28◦ with no sharp peak near 4.2◦.his broad peak may be due to amorphous character of the poly-er and this result is the first sign of exfoliated nanocomposite

ormation. However, it cannot be confirmed from this study only.urther, the participation of nanoclay in the crosslinking reactionf the epoxy in the nanocomposites is already confirmed from FTIRpectra (Fig. 1) and SEM micrographs (Fig. 2) indicate uniform dis-ribution of clay particles in the matrix. Thus nanocomposites areorming by the interaction of nanoclay with epoxy in the presencef reactive diluent epoxidized oil.

.4. Rheological behavior of ENO100, ENO100 modifiedPA-based epoxy and nanocomposites

The variation of viscosities of the resins with time for ENO100,

NO50 and ECN2.5 shows that the resin and the nanocomposite sys-ems before curing exhibit a Newtonian fluid like behavior (Fig. 4).he viscosity of the BPA-based epoxy drastically decreases with theddition of ENO100 (Table 2a), which supports the fact that thepoxidized oil can act as a reactive diluent for BPA-based epoxy.

Fig. 3. XRD micrograms for pure nanoclay and nanocomposites.

ENO25 33.09 15 35ENO50 27.36 20 45ENO75 25.96 60 180ENO100 2.04 600 700

Fig. 5 shows that all the above systems exhibit constant viscosityafter temperature of about 55–60 ◦C though the viscosity tends todecrease with the increase of temperature before reaching 60 ◦C.Under the influence of temperature, this decrease may be due to theincrease in the molecular mobility of the chains as kinetic energyof the system increases.

3.5. Curing of ENO100, ENO100 modified BPA-based epoxy andnanocomposites

It has been found that with the increase of Araldite LY 250 in themixture of epoxidized oil with commercial epoxy, the drying time

Fig. 4. Variation of viscosity against time at constant stress (100 Pa) under isother-mal condition (25 ◦C) for (a) ENO100, (b) ENO50 and (c) ECN2.5.

G. Das, N. Karak / Progress in Organic Coatings 66 (2009) 59–64 63

Fig. 5. Variation of viscosity against temperature under constant stress (100 Pa) for(a) ENO100, (b) ENO50 and (c) ECN2.5.

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Table 3Performance characteristics of the ENO100 modified BPA-based epoxy.

Sample code ENO0 ENO25 ENO50 ENO75 ENO100

Tensile strength (N/mm2) 6.9 7.04 7.16 4.55 –Elongation at break (%) 1.23 6 16.21 19.29 –Impact resistance (cm) >100 >100 >100 6 12

is almost double even at dose level of 2.5 wt.% of nanoclay, which isa significant achievement from this study. Further more the elonga-

ig. 6. Influence of amount of ENO on drying time and viscosity of ENO modifiedpoxy.

ecreases (Table 2a and Fig. 6). This may be due to the increase ofpoxy functionality in the matrix, i.e., due to higher epoxy contentf commercial epoxy than the epoxidized oil. The long drying timef 100% ENO100 is due very low epoxy value. However, decrease ofuring time by the addition of ENO100 may be explained by theact that because of much lower viscosity of ENO100 than BPA-ased epoxy (Table 2a and Fig. 6), the dispersion and diffusion of theardener is much better for crosslinking reactions. But again whenhe amount of ENO100 increases the curing time also increases asverall epoxy equivalent decreases. The long drying time of ENO100ndicates that M. ferrea L. seed oil-based epoxy cannot be used asole epoxy resin.

The incorporation of nanoclay in the 50:50 mixture of ENO100ith BPA-based epoxy resin further enhances the cure rate, though

he effect is not so significant (Table 2b). This may be due to theresence of hydroxyl groups in the clay that may take part in

able 2bnfluence of clay amount on drying time and viscosity of nanocomposites.

ample code Viscosity at25 ◦C (Pa)

Touch free time(min)

Hard dry time(min)

CN1 30.02 18 45CN2.5 32.20 16 40CN5 36.34 15 35

Gloss (60◦) 50.2 64.7 62.0 54.3 41.2Adhesion (N/m) 684.26 1138.48 800.42 730.30 –Scratch hardness (kg) 1.0 0.6 2.5 0.1 0.5

crosslinking reactions. This is supported by FTIR and SEM studies(Figs. 1 and 2).

3.6. Performance of the ENO100 modified BPA-based epoxy andnanocomposites

The performance characteristics such as impact resistance,scratch resistance, gloss, tensile strength and adhesive strength ofthe cured resins are given in Table 3. From this table it has beenfound that with the increase of the epoxy content in the mixture ofepoxidized oil with commercial BPA-based epoxy resin the impactstrength increases. The impact resistance is the ability to absorbexternal instant applied energy. Thus it is the combined effect ofstrength (tensile strength) and flexibility (elongation at break) ofthe system. So even though the flexibility of the system increaseswith the increase of ENO but the strength decreases with the sameand hence the impact strength should be resultant of those twoproperties. Thus the observed impact resistance is low at high ENOcontent. The tensile strength has been found to marginally increasewith the amount of the BPA-based epoxy in the modified epoxyresins up to 50% dilution but at 75% dilution the strength prop-erty decreases a little due to low crosslinking density, as the epoxyequivalent of ENO100 is low. The increase in the tensile propertiesand the hardness can be explained from the fact that ENO100 helpsin diffusion and uniform crosslinking by the hardener of the films.The modified epoxy shows good adhesive characteristics with theincorporation of ENO100 may be due to polar functional groups,which promote the binding to the cellulosic plywood substrate. Alsodiffusion increases with ENO100 content in the materials whichincreases mechanical interlocking with the substrate. The gloss ofthe modified resin shows an improvement over the pristine resin.These improvements may be due to the better compatibility ofthe two components, higher crosslinking and smoothness of thesurface.

The improvement of performance characteristics is observedwith the formation of nanocomposites compared to the pristineENO50. The optimum level of properties was obtained in case of2.5 wt.% loading of nanoclay (Table 4). The improvement of prop-erties may be explained from significant interaction of nanoclayparticles with epoxy resin and this is facilitated by the presence ofreactive diluent epoxidized oil. The improvement of tensile strength

tion at break and impact resistance were also improved significantlywhich are rare to achieve. This may be due to better diffusion of

Table 4Performance characteristics of nanocomposites.

Property ECN1 ECN2.5 ECN5 ENO50

Tensile strength (N/mm2) 10.73 11.18 11.4 7.16Elongation at break (%) 64.12 59.26 96.40 16.21Impact resistance (cm) >100 >100 >100 >100Gloss (60◦) 65.1 74.3 72.0 62.0Adhesion (N/m) 629.76 757.79 425.50 800.42Scratch resistance (kg) 3 4 5.5 2.5

64 G. Das, N. Karak / Progress in Organic Coatings 66 (2009) 59–64

Table 5aThe Influence of amount of ENO on chemical resistance of ENO100 and ENO100 modified commercial epoxy.

Sample code Aq. NaOH (0.5%) Aq. HCl (10%) Aq. NaCl (10%) Distilled water Ethanol (20%)

ENO0 Fair Excellent Excellent Excellent ExcellentENO25 Poor Excellent Excellent Excellent ExcellentENO50 Poor Excellent Excellent Excellent ExcellentENO75 Peeled off Fair Good Fair GoodENO100 Very poor Peeled off Good Good Peeled off

Table 5bThe influence of amount of clay on chemical resistance of nanocomposites.

Sample code Aq. NaOH (0.5%) Aq. HCl (10%) Aq. NaCl (10%) Distilled water Ethanol (20%)

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[21] F.E. Okieimen, I.O. Bakare, C.O. Okieimen, Ind. Crop Prod. 15 (2002) 139–144.

[22] V.V. Goud, A.V. Patwardhan, N.C. Pradhan, Bioresour. Technol. 97 (2006)

CN1 Peeled off ExcellentCN2.5 Excellent ExcellentCN5 Excellent Excellent

poxy in the gallery of nanoclay by the presence flexible diluentpoxidized oil. This is also supported by adhesion strength value,here the increment is also significant.

.7. Chemical resistance test

The chemical resistance of all the samples excluding ENO100nd ENO75 are very good in all the tested media except in alkaliedium (Table 5a). The poor alkali resistance is due to the pres-

nce of hydrolyzable ester group of the fatty acids in the reactiveiluent. However, the improvement of chemical resistance throughhe formation of nanocomposite is excellent for ECN2.5 and ECN5Table 5b). The poor alkali resistance of ECN1 indicates that 1 wt.%anoclay loading is insufficient to achieve the desired alkali resis-ance properties. Thus the overall chemical resistance of the curedesins and the nanocomposite are very good.

. Conclusion

From this study it can be concluded that a non-edible vegetableil is utilized to produce a value added product. M. ferrea L. seedil is used for the first time to prepare epoxidized oil, which isuccessfully utilized as reactive diluent for BPA-based epoxy resin.he incorporation of nanoclay even at low level of loading signifi-antly improved many desired properties of the epoxy resin in theresence of epoxidized oil.

cknowledgement

The authors express their gratitude and thanks to theesearch project assistant given by DRDO, India through grant no.RIP/ER/0403490/M/01/962, dated 14th May 2007.

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