Ferrous-persulphate Induced Graft Copolymerization of Monomer Mixtures onto Saccharum spontaneum-L...

Iranian Polymer Journal18 (10), 2009, 789-800

Saccharum spontaneum-L;graft copolymer;chemical resistance;moisture absorbance;TGA/DTA/DTG.

(*) To whom correspondence to be addressed.E-mail: bskaith@yahoo.co.in

A B S T R A C T

Key Words:

Ferrous-persulphate Induced Graft Copolymerizationof Monomer Mixtures onto

Saccharum spontaneum-L Natural Fibre

Balbir Singh Kaith1*, Rajeev Jindal1, Asim K Jana2, and Mithu Maiti1

(1) Department of Chemistry, (2) Department of Biotechnology, Dr BRA National Institute of Technology, Jalandhar-144 011, Punjab, India

Received 17 December 2008; accepted 14 September 2009

Grafting of binary vinyl monomer mixtures such as methylmethacrylate (MMA) +acrylamide (AAm), MMA + acrylonitrile (AN) and MMA + acrylic acid (AA) ontoSaccharum spontaneum-L (Ss) fibre, was carried out in air. The synthesized

graft copolymers were characterized with FTIR spectroscopy, scanning electronmicroscopy (SEM), TGA/DTA/DTG and X-ray diffraction (XRD) techniques. Initial optimization of different reaction parameters was carried out for graft copolymerizationof MMA onto fibre backbone. The different optimized parameters were: reaction time,180 min; temperature, 40ºC; pH 6; solvent, 125 mL; FAS/KPS (0.225/0.112 g/g) 1/0.75and MMA, 2.94x10-3 mol/L. The optimum graft yield with MMA was found to be 144.4%.Maximum graft yield was found to be 155.6%, 161.4% and 173.5% with MMA + AA,MMA + AN and MMA + AAm, respectively. On thermal analysis, the rate of weight lossper minute was found minimum in case of Ss-g-poly(MMA+AAm) followed by theweight losses for Ss-g-poly(MMA+AN), Ss-g-poly(MMA+AA) and S. spontaneum-Lfibres. Thermal stability of Ss-g-poly(MMA+AAm) was found to be more than that of S. spontaneum-L fibre and other graft copolymers. On grafting, the crystalline lattice ofthe fibre was disturbed due to incorporation of homopolymer chains onto fibres backbone. Graft copolymers were found to possess lower percentage of crystallinity and crystallinity index. It was observed that graft copolymers were more resistant towards5N HCl and 5N NaOH as compared to original fibres backbone. The graft copolymer ofMMA + AN with S. spontaneum-L fibre was found to be more moisture resistant thanthe other aformentioned graft copolymers.

INTRODUCTION

Graft copolymerization is a convenient method for incorpora-tion of new and desired propertiesinto natural fibres without drasti-cally affecting the basic propertiesof the substrate [1]. It imparts theadditional properties such as thermal and chemical resistances tothe naturally existing fibres backbone for their use in variousfields [2,3]. Natural fibres such as

flax, jute, ramie, and pine needleare principally suitable as reinforcement materials because oftheir relatively high strength andstiffness in industries such as automobile, packaging, and con-struction materials [4] to satisfyeconomical and ecologicaldemands.

Various polysaccharides such ascellulose [5], starch [6], chitosan

Available online at: http://journal.ippi.ac.ir

[7], guar-gum [8], and psylium [9] have been modified for their use in metal ion-sorption [10], drugdelivery [11] and water absorption studies [12].Moreover, these polymeric materials have beenextensively used in agricultural and membrane technology [13]. The above studies have shown thatthese natural polymers are very efficient and are ofgreat significance in water treatment processesbecause of their biodegradability and cost effectiveness.

Chauhan et al. [14] graft copolymerized a binary mixture of styrene and maleic anhydride ontocellulose extracted from Pinus roxburghii needles.The grafting reaction was initiated with gamma raysin air by the simultaneous irradiation method.Grafting parameters and reaction rate achieved maximum values with 1:1 molar ratio of styrene andmaleic anhydride. Thermal behaviour of graft copolymers showed that all graft copolymers exhibited single-stage decomposition. Okieimen et al.have carried out graft copolymerization of methylacrylate (MA), ethyl acrylate (EA), and ethylmethacrylate on carboxyl methyl cellulose usingceric ion in aqueous medium at 35ºC [15]. It has beenobserved that the rates of monomer grafting were notof the same order of magnitude even though the reaction conditions were the same. Recently variousworkers have carried out graft copolymerization ofvinyl monomers onto natural polymer backbones andhave studied their different physical and chemicalproperties [16-19].

Saccharum spontaneum-L plant grows as a wasteland weed and lowland eco-region at the base ofthe Himalayan range in India, Nepal, China, andBhutan. It is a widely distributed plant and occurs atan altitude ranging from sea-level to 1000 m. Itbelongs to Poaceae family with Magnoliphyta division. Genus Saccharum has five extant species ofwhich Saccharum spontaneum-L is a wild one.Saccharum spontaneum-L, like wheat, rice, corn, andother grains, is of the grass family, characterized bysegmented stems, blade-like leaves, and reproductionby seed. It is a perennial grass, growing up to 3 m inheight. Its ability to quickly colonize in disturbed soilhas allowed it to become an invasive species thattakes over croplands and pasturelands. It is used asvaluable medicinal herb in traditional systems of

medicine in India. It is a fast growing biomass withflowers containing fibres. These fibres are distinctlydifferent in appearance from other types of studiedearlier fibres such as cotton, jute, flax, ramie, hemp,etc. S. spontaneum-L fibre has white/purplish silkyappearance, better strength, and fineness [20,21].

Literature review reveals that graft copolymeriza-tion of binary vinyl monomers onto S. spontaneum-Lfibre has not been carried out till date and therefore,it is considered worthwhile to graft copolymerize thedifferent binary vinyl monomer mixtures onto S.spontaneum-L fibre using ferrous ammonium sulphate/potassium persulphate as a redox initiatorand study its different physical and chemical properties.

EXPERIMENTAL

Materials and MethodsSaccharum spontaneum-L fibre (average dimension,i.e., fineness: 0.9 denier) was purified through soxhlet extraction in acetone for 72 h. MMA (FineChemicals Ltd, Mumbai, India) was purified bywashing with 5% NaOH and subsequently dryingover anhydrous Na2SO4 followed by distillation.AAm, AN, and AA (Fine Chemicals Ltd, Mumbai,India) were used as received. Ferrous ammonium sulphate (Fine Chemicals Ltd, Mumbai, India) wasrecrystallized from hot water and potassium persulphate (Fine Chemicals Ltd, Mumbai, India)was used as received.

Graft CopolymerizationInitially, the optimization of different reaction parameters like reaction time, temperature, pH, solvent, initiator concentrations, monomer was carried out for graft copolymerization of principalmonomer (MMA) onto the backbone of naturalfibres, prior to grafting with binary mixtures.Activation of S. spontaneum-L fibre (0.5 g) was performed at room temperature by immersing in125 mL distilled water for 24 h. A definite molar ratioof ferrous ammonium sulphate/potassium persulphate(0.225/0.112 g/g) was added to the reaction flask followed by addition of a binary monomer mixturewith continuous stirring. Reaction was carried out

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

Iranian Polymer Journal / Volume 18 Number 10 (2009)790

under optimized reaction conditions and thehomopolymer of MMA was removed on refluxingwith acetone for 24 h. Homopolymers of acrylic acid,acrylamide, and acrylonitrile were removed on refluxing with hot water and dimethyl formamide for24 h and the grafted copolymers were dried at 50ºC till constant weight was attained. Percentages of polymerloading, graft yield, and grafting efficiency were calculated as per the following methods (Table 1) [22]:

Where, W1 is initial weight of the sample and W2 isfinal weight of the sample (before homo-polymer extraction).

The quantity of the grafted copolymer is evaluated asthe weight increase of the sample (W3) after extraction of the homopolymer.

Percentage of graft efficiency which is the ratiobetween the quantity of grafted monomer and the totalpolymerized monomer was calculated by the aboveequation.

Characterization of Graft CopolymerFTIR spectra of the samples were recorded with aPerkin Elmer Fourier transform infrared (FTIR) spectrophotometer (model RX-1, USA) using KBrpellets (Sigma Aldrich, USA). Scanning electron

791Iranian Polymer Journal / Volume 18 Number 10 (2009)

Ferrous-persulphate Induced Graft Copolymerization ...Kaith BS et al.

100(%)1

12 ×−=W

WWloadingPolymer

100(%)1

13 ×−=W

WWyieldGrafting

100(%)12

13 ×−−=

WWWWefficiencyGraft

Samples Binary mixtures [x10-3 mol.L-1] PLa

(%)GYb

(%)GEc

(%)

12345

12345

12345

{[MMA]+[AA]} x10-3

{[MMA]+[AAm]} x10-3

{[MMA]+[AN]} x10-3

2.94+1.452.94+2.182.94+2.912.94+3.692.94+4.37

2.94+0.212.94+0.282.94+0.352.94+0.422.94+0.49

2.94+1.512.94+2.272.94+3.032.94+3.792.94+4.56

228.4226.4233.2212.4218.2

235.7242.6243.2222.9208.3

225.1241.3234.9212.7198.4

100.2102.4155.6132.7101.1

99.5112.4173.5143.6111.2

96.5161.4146.1133.4101.6

43.8745.2266.7262.4746.33

42.2146.3371.3464.4253.38

42.8666.8862.1962.7151.20

(a) Polymer loading; (b) Grafting; (c) Graft efficiency.

Table 1. Evaluation of optimum reaction parameter for grafting of (MMA+AA), (MMA+AN) and(MMA+AAm) onto S. spontaneum-L fibre.

micrographs of S. spontaneum-L fibre and its graftcopolymers were obtained by a scanning electronmicroscope (Jeol JSM-6100, Japan). X-ray diffraction studies were performed on a X'-Pert-Pra-PAN-Analyzer (Philips, Japan) X-diffractometerunder ambient conditions using CuKα (1.5418 Å)radiation, N-filter and scintillation counter as detectorat 45 KV and 35 mA on rotation between 5 and 40º(2θ-scale) at 1 second step size and increment of 0.01degree with 0.5 mm of divergent and anti-scatteringslit. A small particle size of each sample was obtainedand placed into sample holder which was made ofPMMA with a round central cavity. Crystallinityindex which measures the orientation of the cellulosecrystals with respect to fibre axis was determined byusing the wide angle X-ray diffraction counts at 2θ-scale close to 22º and 18º. The counter reading at thepeak intensity at 22º represents the crystalline materi-al and the peak intensity at 18º corresponds to the amorphous material in cellulose [23]. Percentage ofcrystallinity and crystallinity index were calculated asfollows [24]:

where, I 22 and I18 are the crystalline and amorphousintensities at 2θ-scale close to 22º and 18º, respectively. Thermogravimetric analysis, differentialthermal analysis and differential thermogravimetricanalysis of the samples were carried out in air on a thermal analyzer (Perkin Elmer, Pyris Diamond,USA).

Moisture Absorption Study Moisture absorbance studies at various relativehumidity levels were carried out as per the method reported earlier [3]. Moisture absorption percentage was found out by placing known weights(Wi) of dry grafted and ungrafted samples in ahumidity chamber for about 2 h and then the finalweight (Wf) of each sample exposed to different relative humidity ranging from 20-100% was recorded. The percentage of moisture absorption wascalculated from the increase in initial weight in thefollowing manner:

Acid and Base ResistanceAcid and base resistance studies were carried out asper the method reported earlier [3]. Acid and baseresistance was studied by placing a known weight(Wi) of dry grafted or ungrafted samples in a fixedvolume of 5N HCl and 5N NaOH and the finalweight (Wf) of the samples were noted down in every12 h interval until the constant weight was reached.

RESULTS AND DISCUSSION

MechanismC2, C3, and C6 hydroxyls and C-H groups are theactive sites for the incorporation of polymeric chainsthrough grafting onto cellulosic fibres. Potassiumpersulphate is known to take part in a redox reactionwith Fe2+ through the following reactions:

(1)

(2)

Interaction of SO4-• with H2O generates OH• (eqn 2)

and these free radicals are responsible for free radicalgeneration on polymer backbone and the monomer aswell as further chain propagation, thereby resulting inthe formation of graft copolymer. The grafting onto S. spontaneum-L fibre in the presence of ferrousammonium sulphate and potassium persulphate takesplace according to the mechanism proposed byBhattacharya et al. [25].

Effect of Concentration of Binary Vinyl MonomerMixtures on Grafting PercentageInitially, the optimization of different reaction parameters was carried out for graft copolymerizationof MMA onto fibre backbone. The different optimized parameters were: reaction time, 180 min;

Iranian Polymer Journal / Volume 18 Number 10 (2009)792

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

100]/)[((%) ×−= ifi WWWlossWeight

→−−−+ −−+33

2 SOOOSOFe

•−−+ ++ 42

43 SOSOFe

••

+→+ −− OHHSOOHSO 424

100]/)[((%) ×−= iWiWfWabsorptionMoisture

100)]/([(%) 182222 ×+= IIIityCrystallin

]/)[( 221822 IIIindexityCrystallin −=

temperature, 40ºC; pH, 6; solvent, 125 mL; ferrousammonium sulphate / potassium persulphate(0.225/0.112 g/g) 1/0.75; MMA, 2.94×10-3 mol/L.The optimum graft yield of MMA was found to be144.4% (Table 3).

Graft copolymerization of binary vinyl monomermixtures such as MMA+AA, MMA+AN andMMA+AAm onto S. spontaneum-L fibre using MMA

(2.94×10-3 mol.L-1) as the principal monomer hasshown graft yields of 155.6% (AA; 2.91×10-3 mol.L-1), 161.4% (AN; 2.27×10-3 mol.L-1), and173.5% (AAm; 0.35×10-3 mol.L-1), respectively(Table 1).

Higher graft percentage yields which are observedin case of binary vinyl mixtures could be explained onthe basis of monomer reactivity ratios. The

Ferrous-persulphate Induced Graft Copolymerization ...Kaith BS et al.

Iranian Polymer Journal / Volume 18 Number 10 (2009) 793

Sr. No.

Reactiontime (min)

Reaction temperature (ºC)

pH Solvent (mL)

Molar ratio(FAS/KPS)

[MMA]x103

(mol/L)PL(%)

GY(%)

GE (%)

HM (%)

123456789

101112131415161718192021222324252627282930313233

90120150180210180180180180180180180180180180180180180180180180180180180180180180180180180180180180

404040404025303540455055404040404040404040404040404040404040404040

7.07.07.07.07.07.07.07.07.07.07.07.02.04.06.08.09.06.06.06.06.06.06.06.06.06.06.06.06.06.06.06.06.0

10010010010010010010010010010010010010010010010010050.075.0125150175125125125125125125125125125125125

1 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 1.001 : 0.501 : 0.751 : 1.001 : 1.251 : 1.501 : 0.751 : 0.751 : 0.751 : 0.751 : 0.751 : 0.75

2.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.452.451.491.962.452.943.433.92

49.3177.9367.8312.9179.543.8

186.4246.5312.9386.2376.2325.9309.1366.2369.4386.2326.3342.9368.2370.6355.8312.4362.1293.0302.6304.4310.6153.8242.8290.1324.7344.7346.8

29.047.065.089.038.020.052.071.089.0

84.2846.039.047.073.0

106.489.068.095.0

97.48129.094.075.020.0

132.094.069.048.034.059.7

109.0144.074.051.0

58.8226.5517.6728.5221.1145.6627.8928.8028.4421.8212.2211.9615.2019.9328.8023.0420.8327.7026.4734.8826.4124.005.52

45.0531.0622.6615.4522.1024.5837.5744.3421.4614.70

41.1873.4582.3371.4878.8954.3472.1171.2071.5678.1887.7888.0484.8080.0771.2076.9679.1772.3073.5365.1273.5976.0094.4854.9568.9477.3484.5577.9075.4262.4355.6678.5485.30

PL = polymer loading; GY = graft yield; GE = graft efficiency; HM = homopolymer.

Table 3. Evaluation of optimum reaction parameter for grafting of MMA onto S. spontaneum-L fibre.

reactivity ratios of monomer mixtures [(MMA+AAm: r1 = 2.53, r2 = 0.82); (MMA+AN: r1 = 1.09, r2=0.15); (MMA+AA: r1 =1.25, r2 =0.225)] [26] indicate that r2 values of binary monomer mixtures,i.e., MMA+AAm, MMA+AN, and MMA+AA arelow thereby, resulting in the formation of growingcopolymer chains instead of homopolymerization andhence higher percentage of grafting. On the otherhand, higher r1 values of the binary mixtures exhibited the formation of more active copolymers,resulting in higher graft yields. Moreover, r1 value ofMMA+AAm binary mixture is higher than that ofMMA+AN and MMA+AA and hence an indication ofits higher grafting percentage. However, in case

of binary mixtures MMA+AA and MMA+AN, r1values were found to be 1.25 and 1.09, respectively.Decreased graft yield in case of MMA+AAbinary mixture could be due to the association ofacrylic acid with water molecules, thereby hinderingthe interaction of the growing copolymer chains withthe active sites on the fibre backbone which is resulted in more homopolymeri-zation [27].

Whereas, higher reactivity of MMA in the pres-ence of initiator produces more free radicals whichundergo reaction by themselves to give homopolymerchains. Thus, a decrease in grafting percentage wasfound only on graft copolymerization of MMA ontothe fibre backbone.

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

794 Iranian Polymer Journal / Volume 18 Number 10 (2009)

(b) (d)

(a) (c)

Figure 1. FTIR spectra of : (a) S. Spontaneum-L fibre, (b) Ss-g-poly(MMA+AA) (GY: 155.6%; in Table 1),(c) Ss-g-poly(MMA+AN) (GY: 161.4% in Table 1), and (d) Ss-g-poly(MMA+AAm) (GY: 173.5% in Table 1).

Characterization of the Grafted S. spontaneum-LFibreFTIRS. spontaneum-L fibre showed broad peaks at 3390.6 cm-1 (due to hydrogen bonding -OH), 2921.7 cm-1 (C-H stretching), and 1436.0 cm-1 and1052.7 cm-1 (arising from C-C, C-O stretchings,respectively) (Figure 1a). On grafting, FTIR bandsdue to characteristic functional groups incorporatedinto S. spontaneum-L fibre have been witnessedbesides the previously listed bands. Ss-g-poly(MMA+AA) showed additional peaks at 1735.3 cm-1 (C=O of MMA) and 2900 cm-1 (-OH of

AA) (Figure 1b). Ss-g-poly(MMA+AN) showed addi-tional peaks at 1733.9 cm-1 (C=O of MMA) and 2364.3cm-1 (C≡N stretching of AN) (Figure 1c). Ss-g-poly(MMA+ AAm) showed additional peaks at 1733cm-1 (C=O of MMA) and 1625 cm-1 (C=O of AAm)(Figure 1d).

Scanning Electron Microscopy The changes in the topography and morphology offibre surfaces were studied by SEM. It can beobserved that the surface of the grafted fibres is highly rough in comparison with the ungrafted fibre(Figures 2a-2d), which is attributed to high graft

Ferrous-persulphate Induced Graft Copolymerization ...Kaith BS et al.

Iranian Polymer Journal / Volume 18 Number 10 (2009) 795

(b) (d)

(a) (c)

Figure 2. SEM micrographs of: (a) S. spontaneum-L fibre, (b) Ss-g-poly(MMA+AA), (c) Ss-g-poly(MMA+AN), and(d) Ss-g-poly(MMA+AAm).

density. The adhesion of the grafted fibres to othermaterials is improved [28] with an increase in theroughness of their surface due to an increase in the surface area for bonding and mechanical interlocking.Thus, increase in the roughness of the surface of thegrafted S. spontaneum-L fibre is expected to improvetheir adhesion to other polymers.

XRD StudiesAs it is evident in Figure 3, the percentage of crystallinity and crystallinity index were found todecrease with increase in percentage of grafting.Since incorporation of monomer moiety in the fibre backbone impairs the natural crystallinity of thefibres, therefore, graft copolymerization of differentmonomer mixtures onto S. spontaneum-L fibre resulted in impaired crystallinity and increased amorphous region of the fibres (Table 2). Thus, withincrease in grafting percentage, the percentage ofcrystallinity and crystallinity index decrease alongwith reduction in stiffness and hardness [27]. Sincecrystallinity index is a quantitative measure of the orientation of crystal lattice relative to the fibre axis,therefore, lower crystallinity index of graft copolymers stands for poor order of crystal lattice inthe fibre. This clearly indicates that the cellulose crystal lattices are better oriented in S. spontaneum-Lfibre followed by different graft copolymers.

TGA, DTA, and DTG MeasurementsTGA of ungrafted and grafted S. spontaneum-L fibreshave been studied as a function of weight loss percentage versus temperature. Cellulosic S. spontaneum-L fibre degrade by dehydration, glycogen formation, and depolymerization. In case ofS. spontaneum-L fibre, a two-stage decomposition has

Figure 3. X-ray diffraction studies.

been found in the temperature range 225-320ºC with60% weight loss and at 320-416ºC with 25.33%weight loss. The former stage is attributed to loss bydehydration and volatilization processes, whereas thelatter stage is attributed to loss by depolymerizationprocess. Ss-g-poly(MMA+AAm), Ss-g-poly(MMA+AN), and Ss-g-poly(MMA+AA) fibres showed singlestage decomposition. The initial decomposition temperatures were 249ºC, 250ºC and 250ºC and thefinal decomposition temperatures were 524ºC, 500ºCand 501ºC with 80.92%, 85.45% and 81.69% weightloss, respectively. Thus, it is evident from the TGAdata that grafted fibres are thermally more stable thanraw fibres. This may be due to the incorporation ofbinary mixture polymers chains on the fibres polymerbackbone through covalent bonding.

In case of DTA studies, S. spontaneum-L fibre wasfound to exhibit two exothermic peaks at 313ºC (-1507 mJ/mg) and 422ºC (-1233 mJ/mg).Exothermic peak at 313ºC corresponds to decomposition stage between 225-320ºC while theexothermic peak at 422ºC corresponds to seconddecomposition stage (320-416ºC) in TGA (Figure 4a).However, DTA studies of Ss-g-poly(MMA+AAm),

796 Iranian Polymer Journal / Volume 18 Number 10 (2009)

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

SampleGY(%)

at 2θ-scale Cryst(%)

CI

I22 I18

Raw FibreSs-g-poly(MMA+AA)Ss-g-poly(MMA+AN)Ss-g-poly(MMA+AAm)

-155.6161.4173.5

436297276171

75798184

85.3278.9877.3167.05

0.820.730.700.50

Table 2. Percentage of crystallinity and crystallinity index of S. spontaneum-L and its graft copolymers.

Ferrous-persulphate Induced Graft Copolymerization ...Kaith BS et al.

Iranian Polymer Journal / Volume 18 Number 10 (2009) 797

(a)

(b)

(c)(Continued)

Ss-g-poly(MMA+AN), and Ss-g-poly(MMA+AA)fibres exhibited their respective exothermic decompositions at 3580C (-799 mJ/mg), 359ºC (-975mJ/mg) and 359ºC (-2399 mJ/mg), respectively(Figures 4b-4d).

DTG analyses of grafted and ungrafted S. sponta-neum-L fibre were studied as functions of the rate in weight loss (mg/min) versus temperature.Decompositions for the case of S. spontaneum-L fibrewere found at 303ºC and 413ºC, at the rates of 1.575

Figure 5. Effect of grafting on moisture absorbance of thefibres at different humidity levels.

and 1.411 mg/min weight loss, respectively. However,thermal decompositions of Ss-g-poly(MMA+AAm),Ss-g-poly(MMA+AN) and Ss-g-poly(MMA+AA) fibres were observed at 353ºC, 352ºC and 345ºCwith 0.877 mg/min, 1.033 mg/min and 0.964 mg/minweight loss, respectively. Thus, it can be concludedfrom the DTG studies that rate of thermal decomposition in S. spontaneum-L fibre was higherthan the grafted fibres. The higher thermal resistanceof graft copolymers were due to incorporation of more covalent bonding through inclusion of

Figure 6. Effect of grafting on acid resistance (GY: 173.5%,161.4%, and 155.6% in Table 1).

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

798 Iranian Polymer Journal / Volume 18 Number 10 (2009)

(d)

Figure 4. TGA, DTA and DTG curves of: (a) S. spontaneum-L fibre, (b) Ss-g-poly(MMA+AAm) (GY: 173.5% in Table 1), (c) Ss-g-poly (MMA+AN) (GY: 161.4% inTable 1), and (d) Ss-g-poly (MMA+AA) (GY: 155.6% in Table 1).

Figure 7. Effect of grafting on base resistance (GY:173.5%, 161.4%, 155.6% in Table 1).

poly(MMA+AAm), poly(MMA+AN) andpoly(MMA+AA) chains onto the fibres polymerbackbone (Figures 4b-4d).

Moisture Absorption StudyIt was found that graft copolymerization ofMMA+AAm, MMA+AN, and MMA+AA binarymixtures onto S. spontaneum-L fibre has made agreat impact on the moisture absorption behaviour ofthe fibres (Figure 5). It has been found that by increase in graft yield, moisture absorptiontends to decrease. This could be due to the fact that the sites vulnerable to moisture absorption are blocked with poly(MMA+AAm), poly(MMA+AN), and poly(MMA+AA) chains by grafting, thereby, the fibre shows less sensitivity towardsmoisture.

Acid and Base Resistance StudyIt was observed that acid and base resistance of thefibres increased with increase in percentage of grafting (Figures 6 and 7). This may be explained bythe fact that poly(MMA+AAm), poly(MMA+AN)and poly(MMA+AA) chains grafted onto S. sponta-neum-L fibre have lower affinity for acids and basesas compared to hydroxyl and other functional groupspresent in ungrafted fibres. Therefore, the resistanceof fibres towards acids and bases increased with higher incorporation of poly(MMA+AAm),poly(MMA+AN) and poly(MMA+AA) chains ontothe S. spontaneum-L fibre backbone.

CONCLUSION

The grafting of each binary mixture of MMA+AAm,MMA+AN, and MMA+AA onto S. spontaneum-Lfibre in the presence of ferrous ammoniumsulphate/potassium persulphate system as redox initiator has been found to have influence on physi-co-chemical, thermal, and morphological propertiesas well. Though, with increase in grafting, percentageof crystallinity and crystallinity index decreased, butincorporation of poly(MMA+AAm), poly(MMA+AN) and poly(MMA+AA) chains on fibres polymerbackbone could result in higher acid, base, and thermal resistance. The moisture absorption of thegrafted fibres is also decreased compared to the rawfibre. Moreover, on grafting, the morphologicalchanges with respect to surface morphology of thegrafted copolymers have been found to exert differ-ent physical and chemical properties.

REFERENCES

1. Kaith BS, Singha AS, Sharma SK, Synthesis ofgraft copolymers of binary vinyl monomer mixtures and flax fiber using FAS-KPS redox system, Int J Chem Sci, 2, 37- 43, 2004.

2. Kaith BS, Singha AS, Sharma SK, Graft copolymerization of flax fibers with binary vinylmonomer mixtures and evaluation of swelling,moisture absorbance and thermal behavior of thegrafted fibers, J Polym Mater, 20, 195-204, 2003.

3. Kaith BS, Singha AS, Sharma SK, Evaluationof physical and chemical properties of FAS-KPSinduced graft copolymerization of binary vinylmonomer mixtures onto mercerized flax, Int JChem Sci, 2, 472-482, 2004.

4. Kaith BS, Singha AS, Dwivedi DK, Sharma SK,Dhemeniya A, Preparation of polystyrene matrixbased composites using flax-g-copolymers as reinforcing agent and evaluation of the mechanicalbehavior, Int J Plast Technol, 7, 119-125, 2003.

5. Kumar V, Bhardwaj YK, Rawat KP, Sabharwal S,Radiation-induced grafting of vinylbezyltrimethylammonium chloride (VBT) onto cotton fabric andstudy of its anti-bacterial activities, Radiat PhysChem, 73, 175-184, 2005.

6. Lee JS, Kumar RN, Rozman HD, Azemi BMN,

Ferrous-persulphate Induced Graft Copolymerization ...Kaith BS et al.

Iranian Polymer Journal / Volume 18 Number 10 (2009) 799

Swelling and solubility properties of UV initiatedstarch-graft-poly(AA), Food Chem, 91, 203-211, 2005.

7. Singh V, Tripathi DN, Tiwari A, Sanghi R,Microwave synthesized chitosan-graftpoly(methyl-methacrylate): an efficient Zn2+ ionbinder, Carbohyd Polym, 65, 41-52, 2006.

8. Pandey PK, Srivastava A, Tripathy J, Behari K, Graftcopolymerization of acrylic acid onto guar gum ini-tiated by vanadium (V)-mercaptosuccinic acid redoxpair, Carbohyd Polym, 65, 414-421, 2006.

9. Mishra A, Bajpai M, Flocculation behavior ofmodel textile waste treated with a food grade poly-saccharide, J Hazard Mat, 118, 213-219, 2005.

10. Cavus S, Gürdag G, Yasar M, K Güçlü,Gürkaynak MA, The competitive heavy metalremoval by hydroxyethyl cellulose-g-poly(acrylic acid) copolymer and its sodium salt:the effect of copper content on the adsorptioncapacity, Polym Bull, 57, 445-456, 2006.

11. El-Sherbiny M, Abdelbary EM, Harding DRK,Swelling characteristics and in vitro drug releasestudy with pH and thermally sensitive hydrogelsbased on modified chitosan, J Appl Polym Sci,102, 977-984, 2006.

12. Qu X, Wirsen A, Albertsson AC, Structuralchange and swelling mechanism of pH-sensitivehydrogels based on chitosan and D,L-lactic acid,J Appl Polym Sci, 74, 3186-3194, 1999.

13. Rudzinski WE, Dave AM, Vaishnav UH, KumbarSG, Kulkarni AR, Aminabhavi TM, Hydrogels ascontrolled release devices in agriculture, DesignMon Polym, 5, 39-48, 2002.

14. Chauhan GS, Guleria LK, Misra BN, Kaur I,Polymers from renewable resources: kinetics of4-vinyl pyridine radiochemical grafting onto cel-lulose extracted from pine needles, Rad PhysChem, 58, 181-190, 2000.

15. Okieimen FE, and Ogbeifun D, Graft copolymer-izations of modified cellulose: grafting of methylacrylate, ethyl acrylate and ethyl methacrylate oncarboxymethylcellulose, Eur Polym J, 32, 311-315, 1996.

16. Kaith BS, Kumar S, Kalia S, Mercerization offlax fiber improves the mechanical properties offiber-reinforced composites, Int J Polym Mat, 57,54-72, 2008.

17. Derouet D, Intharapat P, Frédéric QNT, Graftcopolymers of natural rubber and poly(dimethyl(acryloyloxymethyl)phosphonate) (NR-g-PDMAMP) or poly(dimethyl(methacryloy-loxyethyl)phosphonate) (NR-g-PDMMEP) fromphotopolymerization in latex medium, Eur PolymJ, 45, 820-836, 2009.

18. Spinacé MAS, Lambert CS, Fermoselli KKG,Paoli MAD, Characterization of lignocellulosiccuraua fibres, Carbohyd Polym, 77, 181-187, 2009.

19. Adali T, Yilmaz E, Synthesis, characterizationand biocompatibility studies on chitosan-graft-poly(EGDMA), Carbohyd Polym, 77, 47-53, 2009.

20. Bhandari MM, Flora of the Indian desert, MPSRepros, Jodhpur, India, 390-391, 1990.

21. Sastri CST, Kavathekar KY, Plants for reclama-tion of wastelands, CSIR, New Delhi, 1990.Delhi, India, 360-362, 1990.

22. Princi E, Vicini S, Pedemonte E , Mulas A,Franceschi E, Luciano G, Trefiletti V, Thermalanalysis and characterisation of cellulose graftedwith acrylic monomers, Thermochim Acta, 425,173-179, 2005.

23. Mwaikambo LY, Ansell MP, Chemical modifica-tion of hemp, sisal, jute, and kapok fibers by alka-lization, J Appl Polym Sci, 84, 2222-2234, 2002.

24. Agrawal AM, Manek RV, Kolling WM, NeauSH, Studies on the interaction of water with ethylcellulose: effect of polymer particle size,AAPS Pharm Sci Tech, 4, 60-66, 2003.

25. Bhattacharya A, Misra BN, Grafting: a versatilemeans to modify polymers: techniques, factors andapplications, Prog Polym Sci, 29, 767-814, 2004.

26. Misra BN, and Rawat BR, Grafting onto Wool.XXIV: graft copolymerization of methylmethacrylate and ethyl methacrylate by use offerric acetylacetonate as initiator: comparison ofmonomer reactivities, J Macromol Sci A, 21, 495-508, 1984.

27. Kaith BS, Kalia S, Synthesis and characteriza-tion of graft co-polymers of flax fiber with bina-ry vinyl monomers, Int J Polym Anal Charac, 12,401-412, 2007.

28. Correa R, Gonzalez G, Dougar V, Emulsion poly-merization in a microwave reactor, Polymer, 39,1471-1474, 1998.

Ferrous-persulphate Induced Graft Copolymerization ... Kaith BS et al.

800 Iranian Polymer Journal / Volume 18 Number 10 (2009)