Effect of Chemical Treatment on the Tensile

7/27/2019 Effect of Chemical Treatment on the Tensile

1/11


2/11

Effect of chem ical treatment o n sisal fibre-reinforced LDP E composites. K. Joseph et al.

v a r i o u s w o r k e r s d u e t o t h e e a s y p r o c e s s a b i l i t y a n di mpro vem en t i n m echan i ca l p roper t i es 1 s -28 . Sap i ehae t a l . 19 have r ep o r t ed t ha t t he ad d i t i on o f a smal l amo un to f benzoy l peroxi de o r d i cumyl peroxi de i n t o ce l l u l o sef i b r e - L D P E ( l ow d e n s i ty P E ) s y s t e m s d u r i n g p r o c e s s in gimp rov es thei r tensi le pro per t ies s igni ficantly . Po tass iump e r m a n g a n a t e ( K M n O 4 ) h a s b e e n r e p o r t e d b y T r i p a t h yet al . 29 a n d M o h a r a n a et al . 30 t o be a pow er fu l i n i t i a t o rfo r g raf t i ng o f met hy l met ha cry l a t e on t o ju t e f i bres .Very r ecen t l y , i n t h i s l abo ra t o ry we have success fu l l yi nco rpo ra t ed s i sa l f i b re i n t o e l as t omers and t hermo-plast ics . Sisal i s a h igh cel lulose content leaf f ibreo b t a i n e d f r o m t h e p l a n t A g a v e - v e r a c r u z . I t i sa b u n d a n t l y a v a i la b l e in t h e s o u t h e r n p a r t o f In d i a ,espec i a l l y i n Kera l a and Tami l Nadu. S i nce i t i s ad rough t r es i s t an t p l an t , i t can be cu l t i va t ed i n bar r en o rd r y l a n ds . D u e t o t h e v e r y g o o d p h y s i c a l a n d m e c h a n i c a lp roper t i es o f t hese f i bres ( T a b l e 1 ) , l a rge sca l e p roduc-t i on and cu l t i va t i on wi l l p roduce g rea t changes i n t hena t ura l f i b re indus t ry . C os t e f fec ti ve po l ym er p rodu c t scan be fabr i ca t ed f rom t he compos i t es o f s i sa l f i b re wi t ht h e r m o p l a s t i c a n d t h e r m o s e t t i n g p o l y m e r s . P r o c e s s i n gcharac t e r i s t i cs , mechan i ca l p roper t i es and rheo l og i ca lb e h a v i o u r o f t h e r e su l ti n g c o m p o s i t e s h a v e b e e n r e p o r t e dby ou r r esearch g rou p 31-35 . In t h i s paper , a t t em pt s haveb e e n m a d e t o s t u d y t h e e f f e c t s o f v a r i o u s c h e m i c a lt r e a t m e n t s s u c h a s s o d i u m h y d r o x i d e , C T D I C ( C a r d a n o lder i va t i ve o f t o l uene d i i socyana t e) , peroxi de andp e r m a n g a n a t e o n t h e te n s il e p r o p e r t i e s o f s i s a l - L D P Ecom pos i t es as a func t i on o f vo l um e f r ac t i on , f i b re l eng t hand f i bre o r i en t a t i on .E X P E R I M E N T A LM a t e r i a l s

Si sa l (Agave-veracruz ) f i b re was obt a i ned f rom l oca ls o u r c e s . T h e p h y s i c a l a n d m e c h a n i c a l p r o p e r t i e s o fsisal fibre are given in T a b l e 1 . T h e f i b r e w a s w a s h e dt h o r o u g h l y w i t h w a t e r a n d d r i e d i n a n a i r o v e n a t8 0 C f o r 4 - 6 h , b e f o r e b e i n g c h o p p e d i n t o t h e d e s i r e dl e n g t h f o r f i b r e t r e a t m e n t a n d c o m p o s i t e p r e p a r a t i o n .L D P E ( I n d o t h e n e 1 6 M A 4 0 0 ) , w a s s u p p l i e d b y I n d i a nP e t r o c h e m i c a l s C o r p . , B a r o d a , I n d i a . T h e p h y s i c a la n d m e c h a n i c a l p r o p e r t i e s o f L D P E a r e g i v e n i nT a b l e 2 .C a r d a n o l , t h e p ri n c ip a l c o m p o n e n t o f c a s h e w n u t s h e lll iq u i d ( C N S L ) o b t a i n e d f r o m A n a c a r d i u m o c c id e n t al e L ,i s a p l an t - source r aw mat er i a l abundan t i n t rop i ca l

coun t r i es l i ke Ind i a ( sout hern par t ) and Vi e t nam.C a r d a n o l w a s s u p p l i e d b y S a t y a C h e m i c a l s , M a d r a s .T o l u e n e - 2 , 4 - d i i s o c y a n a t e ( T D I ) w a s o b t a i n e d f r o mF l u k a , S w i t ze r la n d . D i c u m y l p e r o x id e ( D C P ) ( V a r o xD C P - R ) w a s s u p p l ie d b y R . T. V a n d e r b i l t C o . , N o r w a l k ,U S A . B e n z o y l p e r o x i d e ( B P ) w a s o b t a i n e d f r o m B D HC h e m i c a l s , P e e l e , U K . P o t a s s i u m p e r m a n g a n a t e( K M n O 4 ) a n d s o d i u m h y d r o x i d e ( N a O H ) u s e d i n t h ep resen t s t udy were o f chemi ca l l y pure g rade . D i but y l t i nd i l aura t e was obt a i ned f rom Sc i en t i f i c and Indus t r i a lS u p p l i e s C o r p . , B o m b a y .F i b r e t r e a t m e n t

A l k a l i t r e a t m e n t . T h e c h o p p e d f i b re s w e r e ta k e n i n as t a i n less s tee l vesse l. A 10% so l u t i on o f N aO H w asadded i n t o t he vesse l and s t i r r ed wel l . Th i s was kep tfo r 1 h w i t h su bsequ en t s ti rr ing . The f i bres were t henw a s h e d t h o r o u g h l y w i t h w a t e r t o r e m o v e t h e e x c e s s o fN aO H s t i ck ing t o t he f ibres . F i na l wash i ngs were car r i edout wi th d is t i l l ed water contain ing a l i t t l e acid . The f ibreswere t hen a i r d r i ed .

P r e p a r a t i o n o f u r e t h a n e d e r i v a ti v e o f c a r d a n o l. T h es y n t h e si s o f a u r e t h a n e d e r i v a ti v e o f c a r d a n o l w a s c a r r i e do u t u s i n g a 1 /1 m o l a r r a t i o o f c a r d a n o l a n d T D I c o n -t a i n i ng a f r ee i socyana t e g roup . Cardano l (a p r i nc i pa lc o m p o n e n t o f C N S L ( 3 0 g , 0 .1 m o l ) ) w a s t a k e n i n ap ressure equa l i z i ng funne l and d i l u t ed wi t h CC14(50ml ) and l ml o f d i but y l t i n d i l aura t e as ca t a l y s t .TD I (17 .4 g , 0 .1 mo l ) was con t a i ne d i n a round b o t t o me df la s k o f c a p a c i t y 5 0 0 m l . T h e c a r d a n o l s o l u t io n w a sa d d e d d r o p w i s e i n t o T D I u n d e r c o n s t a n t s t i r r i n g u n t i lt he add i t i on o f ca rda no l w as compl e t e . The s t i rr i ngw a s c o n t i n u e d f o r o n e m o r e h o u r f o r t h e c o m p l e t i o no f th e r e a c t io n . T h e p r o d u c t f o r m e d c o n t a i n e d o n ef r e e i s o c y a n a t e g r o u p f o r f u r t h e r r e a c t i o n (F igure 1 ) .T h e p r o d u c t o b t a i n e d w a s u s e d a s s u c h f o r f u r t h e rr eac t i on .

T r e a t m e n t o f s i s a l f i b r e w i t h i s o c y a n a te . The alkal i -t r ea t ed d r i ed f i bres were p l aced i n a round bo t t omedf la s k a n d s o a k e d w i t h a n a p p r o p r i a t e v o l u m e o f C C1 4and a l i tt le (1 ml) d ib utyl t in d i lau rate catalys t . Theround bo t t omed f l ask was f i t t ed wi t h a p ressure equa l i z -i ng funne l con t a i n i ng t he ure t hane der i va t i ve . Theure t hane der i va t i ve was added i n t o t he f l ask d ropwi sewi t h suf f i c i en t s t i r r i ng . Af t e r t he compl e t e add i t i on o f

T a b l e 1 Properties of sisal fibreFibre Lignin Cel lulose Tensi le Tensi le Elong at iond i a me t e r c o n t e n t c o n t e n t s t re ng t h mo d u l us a t b re a k( # m) ( % ) ( % ) ( M Pa ) ( GPa ) ( % )100-300 4 5 85 88 400-70 0 9-20 5 14

T a b l e 2 Physica l and mechanica l p ropert ies of low densi ty po lyethylene (LDPE ; Indothene 16 M A 400)Tensi le Vica tM e l t s t r e ng t h E l o n g a t i o n M o d u l us o f so f t e n in g C ry s t a ll i n ef low Densi ty a t break a t break e last ic i ty po in t po in t(g per 10 min) (g ml - ' ) (MPa) (%) (MPa ) (C) ( C)

40 0.916 9 200 140 85 104

5 1 4 0 P O L Y M E R V o lu m e 3 7 N u m b e r 2 3 1 9 9 6


3/11

Ef fect o f ch emica l t rea tment on s isa l f ib re- re in forced LDP E compos i tes: K . Jose ph et a l .

~ g ~ e l

CH3~ N=C=O

+

N : C : O

T o l u e n e 2 , 4 - d i i s o c y a n a t e(TDIC)

CH~

O H

Cardanol

D i b u t y l t i n d i l au r a t e(catalyst)O

N I I oI TM c L _ _ _ / k _ . _ _ / k =H

N=C=OUrethane derivativeof cardanol (CYDIC)The reaction pathway for the preparation of urethane derivative of cardanol

C e l l u l o s e - - O H +

CH3

N = C = O

oN I I oI TM cH

CTDICDibutyl in dilaurate catalyst)

Cel lulose - - 0 HI IO=C-N

CH3N OH

Figure 2 A possible reaction between the free isocyanate groups in CTDIC and cellulosicsisal fibre

urethane, the reaction was allowed to continue for onemore hour (Figure 2). The urethane treated fibreswere purified by refluxing with ace tone fo r 8 h in aSoxhlet apparatus followed by repeated washing withdistilled water. Finally, the fibres were oven dried at80C.Dicumy lperox ide t rea tmen t . The alkali treated fibres(30 g) were soaked with 11 of a 6% solution of DCP inacetone for 30 min. The solution was decanted and thefibres were air dried.Benzo y l pe rox ide t rea tmen t . A similar procedureadopted as in the case of DCP was used here.Permangana te t rea tmen t . The alkali treated fibres(30 g) were soaked with 11 of KMnO4 solution in acetonehaving different concentrations (0.005-0.205%) for

1 min. This was then decanted and the fibres were driedin air.Prepara tion o f LD PE -s i s a l compos it es

The LDPE-sisal composites were prepared by asolution mixing technique followed by extrusion asreported by Joseph et al. 32. In the solution mixingmethod, the fibre was added to a viscous slurry of PEin toluene which was prepared by adding toluene to amelt of the polymer. The mixing was carried outmanually in a stainless steel beaker using a stainlesssteel stirrer for a period of 10min. The temperature ofmixing was maintained at l l0C. The mix was thentransferred into a fiat tray as lumps and kept in avacuum oven at 70C for 2h to remove the solvent.Composites containing 10, 20 and 30wt% of fibrewere prepared using fibres of length in the range2-10mm.

P O L Y M E R V o l u m e 3 7 N u m b e r 2 3 1 9 9 6 5 1 4 1


4/11

E f f e ct o f c h e m i c a l t re a t m e n t o n s i s a l f i b r e - r e i n fo r c e d L D P E c o m p o s i t e s : K . J o s e p h et al.

Preparation of com posite sheetsSisa l-LD PE randomly oriented ibre composites. Sisal-PE composites prepared by solution mixing were usedfor making the randomly oriented fibre composites.Composite specimens of dimensions 120ram x 12.5 mm x3 mm were prepared by injection moulding of the blends

at 115 ~: 5C using a hand operated ram type injectionmoulding machine.Sisal -LD PE oriented ibre composites . The specimensof oriented fibre composites were prepared from theblends obtained by the solution mixing method. Acombination of injection and compression mouldingtechniques was used for making the composite sheets.The blend was first extruded into 4 mm thick cylindricalrods using a hand injection moulding machine.Rectangular specimens of size measuring 120mmx12.5 mm x 3 mm were prepared by closely aligning thecylindrical extrudates (120 mm long and 4m m thick) ina leaky mould and then compression moulding, employ-ing a pressure of about 4MPa and a temperature of

Figure 4 Optical micrograph of (a) the surfaces of unidirectionallyoriented composites and (b) the fracture surfaces of undirectionallyoriented composites

Figure 3 Opticalmicrograph of (a) the surfacesof randomlyorientedcomposites and (b) the fracture surfaces of randomly orientedcomposites

115 i 5C. The mould was cooled below 50C beforeremoving the composite specimens from the mould.The orientation of the random and unidirectionalcomposites were analysed by optical microscopy.Figures 3a and b and 4a and b show the surfacesof the random and oriented composites. The figuresindicate that the processing operation control theorientation. In the case of random composites wecould not find any major difference in the orienta-tions of the skin and the core. The orientation ofthe treated composites was also analysed by micro-scopy. It was found that orientation was unaffectedby treatment.Mech anical testing of composites

Tensile testing of rectangular specimens of size120ram x 12.5mm x 3mm was carried out using anInst ron Universal testing machine model 1190 at across-head speed of 200 mm min -1 and a gauge lengthof 50mm. The tensile modulus and elongation atbreak of the composites were calculated from theload-displacement curve. At least five specimens weretested for each set of samples and the mean valueswere reported.Fracture surface mo rphology

The surfaces of the tensile fractured specimens wereexamined using a Jeol 35 C model scanning electronmicroscope (SEM).

5 1 4 2 P O L Y M E R V o l u m e 3 7 N u m b e r 2 3 1 9 9 6


5/11

Table 3 Variation of tensile properties of alkali treated sisal fibre-LDP E comp osites with fibre content (fibre length 5.8 mm; the values given inparentheses are the properties of untreated com posites)F i b r econtent(wt %)

Tensile strength (MPa ) Mod ulus (MP a)Unidirect iona l SD R a n d o m S D U n i d i re c t io n a l D R a n d o m SD

Elongation at break (%)Unidirect iona l SD R a n d o m SD

0.10100.1335(o.1218)o.1414

(o.1313)o.1515

(o. 1465)

0 9.2 0.1212 9.2 0.1818 140 0.1010 140 0 .1 8 1 8 200 0.1010 20010 17.67 0.21 13.2 8 0 .2 6 1 6 1700 0.2010 482 0.2 116 5 0.1115 28(15.61) (0.2212) (1 0.8 ) (0.43 10) (1429) (0.1985) (3 2 4) (0.3616) (4) (0.1010) (27)20 24.24 0.1735 16.5 0.281 8 232 6 0.1985 926 0.1 81 8 4 0.1330 12

(21.66) (0.1885) (1 2.5 ) (0.3 81 5) (2088) (0.2098) (4 5 3) (0.2515) (3) (0.1200) (10)30 34.27 0.1865 18.8 0.4218 3328 0.1775 1 1 4 0 0.18 18 1 0.1135 10

(31.12) (0.1515) (1 4. 7) (0. 46 20 ) (3086) (0.1909) (7 8 1 ) (0.2705 ) (2) (0.1225) (7)

~i!!~:~

SD = standard deviat ion

R E S U L T S A N D D I S C U S S IO NEffect o f alkali treatment

T e n s i l e p r o p e r t i e s o f l o n g i t u d i n a l ly a n d r a n d o m l yo r i e n t e d ( a l k a l i t r e a t e d a n d u n t r e a t e d ) s i s a l - L D P Ec o m p o s i t e s w i t h d i f f e re n t fi b re l o a d i n g a r e p r e s e n t e d i nTable 3. F r o m t h e s e t a b le s i t is c l e a r t h a t i n b o t h c a s e s( r a n d o m l y o r i e n t e d a n d u n i d i r e c t i o n a l l y o r i e n t e dc o m p o s i t e s ), t e n s il e s tr e n g t h a n d m o d u l u s i n c r e as e w i t hf i b r e l o a d i n g . H o w e v e r , i t i s s e e n t h a t t h e a l k a l i t r e a t e dc o m p o s i t e s s h o w e d s u p e r i o r t e n s i l e p r o p e r t i e s t h a nu n t r e a t e d c o m p o s i t e s . T h i s i s d u e t o t h e f a c t t h a ta l k a l i t r e a t m e n t i m p r o v e s t h e f i b r e s u r f a c e a d h e s i v ec h a r a c t e r i s t i c s b y r e m o v i n g n a t u r a l a n d a r t i f i c i a li m p u r i ti e s , t h e r e b y p r o d u c i n g a r o u g h s u r f a cet o p o g r a p h y 4. Figures 5a a n d b a r e t h e S E M p h o t o m i c r o g r a p h s o f t h e s u r f a c e o f u n t r e a t e d a n d a l k a lit r e a t e d s i s a l f i b r e , r e s p e c t i v e l y . T h e t r e a t e d f i b r e h a s ar o u g h s u r f a c e t o p o g r a p h y . I n a d d i t i o n , a l k a l i t r e a t m e n tl e a d s t o f i b r e f ib r i l la t i o n , i .e . b r e a k i n g d o w n o f t h ec o m p o s i t e f i b r e b u n d l e i n t o s m a l l e r f i b re s . T h i s i n c r e a s e st h e e f f e c ti v e s u r f a c e a r e a a v a i l a b le f o r c o n t a c t w i t h t h em a t r i x 4 . I n o t h e r w o r d s , a l k a li t r e a t m e n t r e d u c e s f i b red i a m e t e r a n d t h e r e b y i n c r e a s es t h e a s p e c t r a ti o .T h e r e f o r e , th e d e v e l o p m e n t o f a r o u g h s u rf a c e to p o -g r a p h y a n d e n h a n c e m e n t i n a s p e c t r a t i o o f f e r b e t t e rf i b r e - m a t r i x i n t e r f a c e a d h e s i o n a n d a n i n c r e a s e i nm e c h a n i c a l p r o p e r t i e s . Figure 6 i s t h e f r a c t u r e s u r f a c em o r p h o l o g y o f th e a l ka l i t r e a te d s i s a l - L D P E c o m -p o s i te s . T h e b e t t e r f i b r e - m a t r i x a d h e s i o n c a n b er e a d i l y s e e n f r o m t h e f i g u re . T h e e x i s te n c e o f P Ep a r t i c l e s a d h e r e d o n t h e f i b r e s u r f a c e c a n b e o b s e r v e di n a l k a l i t r e a t e d f i b r e c o m p o s i t e s . H o w e v e r , t h eu n t r e a t e d f i b r e s u r f a c e i s s m o o t h (Figure 7) w i t h o u ta n y P E p a r t i c l e s .Table 4 s h o w s t h e t e n s il e p r o p e r t i e s o f l o n g i tu d i n a l l ya n d r a n d o m l y o r i e n t e d s i s a l - L D P E c o m p o s i t e s ( b o t hu n t r e a t e d a n d a l k a l i t r e a t e d ) w i t h d i f f e r e n t f i b r e l e n g t h s .I t i s i n t e r e s t i n g t o n o t e t h a t a l k a l i t r e a t e d s i s a l - L D P Ec o m p o s i t e s s h o w e d s u p e r i o r t e n s i l e p r o p e r t i e s t h a nu n t r e a t e d c o m p o s i t e s a t a l l f i b r e l e n g t h s . T h e s t r e n g t ha n d m o d u l u s o f t h e c o m p o s i t e s s h o w a n e n h a n c e m e n t int h e i r v a l u e s b y i n c r e a s i n g t h e a v e r a g e f ib r e l e n g t h f r o m2 .1 t o 5 .8 m m f o l l o w e d b y a d e c r e a s e i n p r o p e r t i e s w h e n af i br e l e n g t h o f 9. 2 m m i s e m p l o y e d . O b s e r v a t i o n o f t h ec o m p o s i t e s p e c i m e n s h a s s h o w n t h a t l o n g f i b r e s t e n d t ob e n d o r c u r l d u r i n g m o u l d i n g . T h i s c a u s e s r e d u c t i o n i nt h e e f f e c ti v e l e n g t h o f t h e f i br e b e l o w t h e o p t i m u m l e n g t hi n a p a r t i c u l a r d i r e c t i o n , w h i c h r e s u l t s i n a d e c r e a s e o fp r o p e r t i e s . T h e r e s u l t s i n d i c a t e t h a t t h e r e e x i s t s a n

E f f e c t o f c h e m i c a l tr e a t m e n t o n s i s a l f i b r e - r e i n f o r c e d L D P E c o m p o s i t e s : K. J o s e p h et al.

bF i g u r e 5 SEM photomicrographof (a) the surface of untreated s i s a lfibre and (b) the surface of alkali treated sisal fibreo p t i m u m f ib r e l e n g t h b e t w e e n 5 . 8 a n d 9 m m a t w h i c h am a x i m u m i m p r o v e m e n t i n th e p r o p e r t ie s o f th ec o m p o s i t e s c a n b e a c h i ev e d .Effect o f isocyanate treatment

I t h a s a l r e a d y b e e n r e p o r t e d t h a t p o l y [ m e t h y l e n ep o l y ( p h e n y l i so c y a n a te ) ] ( P M P P I C ) t r e a t e d c e l lu l os e f i b r e -p o l y m e r c o m p o s i t e s e x h i b i t s u p e r i o r m e c h a n i c a l13 36 37p r o p e r t i e s a n d d i m e n s i o n a l s t a b il i ty ' ' . T h e f u n c -t io n a l g r o u p - N = C - O i n P M P P I C is h i g h ly re a c ti v e t o

PO L YM ER Vo lu me 3 7 Nu mb e r 2 3 1 9 9 6 5 1 4 3


6/11

E f f e c t o f c h e m i c a l t re a t m e n t o n s i s a l f i b r e - r e i n f o r c e d L D P E c o m p o s i t e s : K . J o s e p h et al.

Table 4 Variation of tensile properties of alkali treated sisal fibre-LDP E comp osites with fibre length (fibre content 30 %; the values given inparentheses are the properties of untreated compositesFibrelength(ran)

Tensile strength (MPa)Unidirect ional SD R a n d o m SD

Modulus (MPa) Elongation at break (% )Unidirect ional SD R a n d o m S D U n id i r ec t io n a lS D R a n d o m SD

0 9.2 0.1212 9.2 0.1212 140 0.1818 140 0.18 18 200 0.10 10 2002.1 21.57 0.1345 1 3 .5 2 0 .1 3 1 8 1812 0.2835 526 0.1415 4 0.1125 14

(20.5) (0.1212) (11.3 8) (0.1765) (1687) (0.3010) (2 8 3 ) (0.1215) (4) (0.1020) (12)5.8 34.27 0.186 5 18.8 0.421 8 3328 0.1775 1140 0.1818 1 0.1135 10

(31.12) (0.1515) (1 2. 5) (0.4 60 0) (3086) (0.1919) (4 5 3 ) (0.2715) (2) (0.1225) (7)9.2 28.17 0.2015 2212 0.3112 4 0.1225

(25.9) (0.1535) (1716) (0.3242) (4) (0.1135)

0.10100.1675

(0.2010)0.1515

(0.1465)

SD = standard deviation

Figure 6 SEM photom icrograph of the tensile fracture surface of thealkali treated sisal fibre-LDPE comp ositesshowing PE penetrated intothe fibre

Figure 7 SEM photom icrograph of the tensile fracture surface of theuntreated sisal fibre composites showing poor interaction betwee n PEand fibre

t h e - O H g r o u p s o f c e l l u l o s e a n d l i g n i n 36. T h i s l e a d s t ot h e d e v e l o p m e n t o f a u r e t h a n e l i n k a g e a s s h o w n b e l o w :H O

I I I- N = C = O + H O ---, - N - C - O - (1 )

C a r d a n o l , t h e p r in c i p a l c o m p o n e n t o f C N S L f r o mAnacardium occidentale, i s a p l a n t - s o u r c e r a w m a t e r i a la b u n d a n t i n t r o p i c a l c o u n t r ie s l i ke I n d i a ( s o u t h e r n p a r t ) a n dV ie tn am 37 , 38. Th i s l i qu id p rep o ly m er co n ta in s a m ix tu re o fp h e n o l s p o s s e s s i n g l o n g s a t u r a t e d a n d u n s a t u r a t e d h y d r o -c a r b o n c h a i n s a t t h e meta-posi t ion 37. T h e r e a c t i o n p a t hw a y f o r t h e p r e p a r a t i o n o f u r e th a n e d e r i va t i v e o fc a r d a n o l i s g i v e n i n Figure 1. T h e d e t a i ls o f th ep r e p a r a t i o n o f th e u r e t h a n e d e r i va t i v e o f c a r d a n o l w a sg i v e n i n th e E x p e r i m e n t a l s e c t i o n . T h e i . r. s p e c t r u m o ft h e c o m p o u n d C T D I C e x h i b i t e d t h e c h a r a c t e r i s t i cu r e t h a n e p e a k s a t 3 3 5 0 c m - I f o r - N H a n d 1 7 2 0 c m - 1f o r - C = O s t r e tc h i n g v ib r a t io n s . T h e i n t r o d u c t io n o f t h ec a r d a n o l m o i e t y w a s i n d i c a t ed b y t h e p r e s e nc e o f a- C = C p e a k a t 1 62 0 c m - -1 , - C H a r o m a t i c a t 3 0 2 0 c m - 1a n d - C - H a l i p h a ti c a t 2 9 8 0 c m - ~. T h e i. r. s p e c t r u m o ft h e C T D I C a l s o s h o w e d p e a k s a t 1 44 0 a n d 1 5 9 0 c m - 1d u e t o t h e C = C a r o m a t i c r i n g s t r e t c h in g .T h e c e l l u lo s e h y d r o x y l g r o u p s i n t h e f i b r e a r e r e l a t iv e l yu n r e a c t i v e , s i n c e t h e y f o r m s t r o n g h y d r o g e n b o n d s .A l k a l i tr e a t m e n t m a y d e s t r o y t h e h y d r o g e n b o n d i n g i nc e l l u l o s i c h y d r o x y l g r o u p s , t h e r e b y m a k i n g t h e mm o r e r e a c t i v e 4 '3 9. T h e p o s s i b l e r e a c t i o n b e t w e e n t h ef r e e i s o c y a n a t e g r o u p s i n C T D I C a n d c e l l u l os e isi l l u s t r a t e d i n Figure 2. T h e l i n k in g o f is o c y a n a t e w i t ht h e fi b r e w a s b y t h e f o r m a t i o n o f a c h a i n o f c o v a l e n tc h e m i c a l b o n d s .Table 5 s h o w s t h e t e n si l e p r o p e r t i e s o f C T D I C t r e a t e d ,a l k a li t r e a te d a n d u n t r e a t e d s i s a l - P E c o m p o s i t e s h a v i n g3 0 % f i b re l o a d i n g . T h e f i b re l e n g th u s e d w a s 5 . S m m .I n b o t h c a s es (l o n g it u d in a l a n d r a n d o m ) C T D I Ct r e a t e d f i b r e c o m p o s i t e s s h o w s u p e r i o r t e n s i l e s t r e n g t ha n d m o d u l u s t h a n a l k a l i t r e a t e d a n d u n t r e a t e dc o m p o s i t e s . A s m e n t i o n e d e a r l i e r, o n e o f t h e m a j o rd r a w b a c k s a s s o c i a t e d w i t h c e l l u lo s i c fi b r e s a s r e i n f o r c e -m e n t i n p o l y o l e f in m a t r i c e s i s t h e d i v e r g e n t b e h a v i o u ri n p o l a r i t i e s o f b o t h t h e p h a s e s , i . e . t h e h y d r o p h i l i cn a t u r e o f c e ll u lo s e a n d t h e h y d r o p h o b i c n a t u r e o fp o l y o l e f i n s . B y t r e a t i n g t h e c e l l u l o s e f i b r e s u r f a c e w i t hC T D I C , t h e h y d r o p h i li c n a t u r e c a n b e r e d u c e d. T h el o n g c h a i n s t r u c t u r e o f C T D I C l i n k e d t o th e c e l lu l o si cf i b r e m a k e s t h e f i b r e h y d r o p h o b i c , c o m p a t i b l e a n dh i g h l y d i s p e r s i b l e i n t h e P E m a t r i x . T h i s w i l l r e s u l t i na s t r o n g i n t e r f a c i a l b o n d b e t w e e n t h e f i b r e a n d t h eP E m a t r i x . T h i s c a n b e f u r t h e r u n d e r s t o o d f r o mFigures 8a a n d b , w h i c h s h o w t h a t P E i s h i g h l yb o n d e d t o t h e f i b r e s u r f a c e . T h i s f a c i l i t a t e s e f f e c t i v es t r e ss t r a n s f e r b e t w e e n t h e fi b r e a n d P E m a t r i x . Ap o s s i b l e h y p o t h e t i c a l c h e m i c a l s t r u c t u r e o f ce l l ul o s e

5 1 4 4 P O L Y M E R V o lu m e 3 7 N u m b e r 2 3 1 9 9 6


7/11

Ef fect o f che mica l t rea tment on s isa l f ib re- re in forced LD PE com posi tes: K . Joseph et al.

Table 5 Va r ia t ion o f t e ns i l e prope r t i e s of longi tudina l ly or i e n te d LD PE -s i s a l c ompos i t e s w i th f ibre t r e a tme nts ( fib re l e ngth 5 .8 r a m; f ib re c onte n t30%; the va lue s g ive n in pa re nthe se s a re the va lue s of r a ndo mly o r ie n te d compos it e s)

Compos i t e sTe ns i l e E longa t ions t r e ngth Mod ulus a t b re a k(MPa ) SD (MPa ) SD (%) SD

Un trea ted 31.12 0.1515 3086 0.1919 2 0.1225(14.7) (0.4620) (781 ) (0.2715) (7) (0.1465)Al kali 34.27 0.1865 3328 0.1775 1 0.1135

treated (18.8) (0.4218) (1140) (0.1818) (10) (0.1515)lsocy anate 41.5 0.1939 4066 0.1798 4 0.1212treated (19.5) (0.2115) (1230) (0.1818) (10) (0.1020)SD = s ta nd a rd de via t ion

Figure 8 SEM p hoto micro graph of (a) tensi le frac ture surface ofi~c ya na te (CTD IC) t r e a te d s i s a l -LD PE c ompos i t e s a nd (b ) themagnified view of isocyanate (CTDIC) trea ted s isa l f ibre-LDPEcomp osite showing PE grafted to f ibre surface

f i b r e - C T D I C - P E i n t h e i n t e r f a c i a l a r e a i s g i v e n i nFigure 9.E f f ec t o f perox ide t r ea tment

T h e e f f ec t o f p e r o x i d e D C P a n d B P c o n c e n t r a t i o n o nt h e te n s il e st r e n g th o f s i s a l - L D P E c o m p o s i t e ( b o t hu n i d i re c t i o n a l a n d r a n d o m ) a t 3 0 % f ib r e l o a d i n g iss h o w n i n Figure 10. I t i s o b v i o u s f r o m Figure 10 t ha t t het ens i l e s t r eng t h va l ues o f t he compos i t es i ncrease wi t hi ncrease i n conc en t r a t i o n o f perox i de up t o a ce r t a i n l eve l

( 4 % f o r D C P a n d 6 % f o r B P ) a n d t h e n r e m a i n sc o n s t a n t . T h i s c o n c e n t r a t i o n m a y b e d e f i n e d h e r e a scr i t i ca l peroxi de concen t r a t i on a t wh i ch t he t ens i l es t r eng t h r ea ches m axi m um fo r a g i ven f i bre con t en t 19.The ex i s t ence o f a c r i t i ca l concen t r a t i on o f peroxi desugges t s t ha t t he g raf t i ng r eac t i ons t e rmi na t e when t hef i b r e s a r e c o v e r e d w i t h g r a f t e d P E . E x c e s s o f p e r o x i d ec a u s e s s o m e c r o s s l i n k i n g o f t h e P E a n d t h i s h a s o n l y am i n o r e f fe c t o n t h e o v e r a l l m e c h a n i c a l p r o p e r t i e s o f th ecompos i t es . I t i s c l ear f rom t he above f i gure t ha t DCP i smo re e f fec t ive t han BP a t a l l leve l s o f peroxi de add i t i on .Th i s may be due t o t he d i f fe r ence i n t he r e l a t i ve r a t es o fp e r o x i d e d e c o m p o s i t i o n . I t i s r e p o r t e d t h a t D C P h a s a19l o w e r d e c o m p o s i t i o n r a t e t h a n B P a n d e n su r e s b e t t e rd i sper s i on i n the po l y me r mat r i x . T herefo re , t h i s i s mo reef f ic i en tl y u t i li zed fo r t he g raf t i ng r ea c t i on be t we enLDPE and ce l l u l o se , wh i ch i s d i scussed l a t e r .Table 6 show s the t ens i le p roper t i es o f peroxi de t r ea t edr a n d o m l y a n d u n i d i r e c t i o n a l l y o r i e n t e d s i s a l - L D P Ecompos i t es , r espec t i ve l y , a t 30% f i bre l oad i ng . I t i si n te r e s ti n g t o n o t e t h a t p e r o x i d e t r e a t m e n t i m p r o v e s t h et ens i l e p roper t i es s i gn i f i can t l y . Fo r exampl e , t he t ens i l es t r e n g th o f D C P t r e a t e d r a n d o m l y o r i e n t e d f ib r ec o m p o s i t e s i s 2 1 . 8 M P a . T h i s i s a p p r o x i m a t e l y 5 0 %m o r e t h a n t h e t en s il e s tr e n g t h o f t h e u n t r e a t e d c o m -pos i t es (14 .7 MP a) . B P t r ea t ed com pos i t es a l so show as i mi l a r i ncrease i n t ens il e p roper t ies . T he m odu l us va l ueso f t h e t r e a t e d c o m p o s i t e s a l so s h o w a s i m i la r t r e n d . T h ei ncrease i n t he t ens i l e p roper t i es o f fe red by t he peroxi det r ea t ed compos i t es i s due t o t he peroxi de i n i t i a t ed f r eer a d ic a l r e a c t i o n b e t w e e n t h e L D P E m a t r i x a n d c e l lu l o sef i bres as shown be l ow:

R O - O R ~ 2 R O"R O " + P E - H ~ R O H + PE "

R O " + C e l l u lo s e - H ~ R O H + C e ll u lo s e "PE" + C el lu l o se" --~ PE -C el l u l o s e

Figures 11 a n d 12 a r e t he S E M p h o t o m i c r o g ra p h s o f th et ens il e f r ac t ure sur faces o f DC P and BP t r ea t ed s i sa l f i b re -LDPE composi tes , respect ively . The above f igures clear lyindicate that PE i s grafted on to the cel lulose surface. As imi la r t ype o f peroxide i nduced P E ~af t i ng on t o ce l lu lo se19f i bre was r epo r t ed by Sap i eha e t a l . . T h e t reated fibresadhere wel l t o t he po l ymer mat r i x and undergo breaki ngand delaminat ion dur ing tensi le fai lure, whereas unt reatedf i bres a r e eas i ly pu l l ed out f rom t he mat r i x dur i ng t ens il ef a il u re . F r o m t h e f r a c tu r e s u r f a c e s o f D C P t r e a te d a n dB P t r e a t e d c o m p o s i t e s , i t c a n b e u n d e r s t o o d t h a t t h ei n t e r fac i a l bond i ng i s s t ronger i n t he DCP sys t em.



8/11

E f fe c t o f c h e m ic a l t r e a tm e n t o n s i s a l f i b re - re i n fo r c e d L D P E c o m p o si te s ." K . J o s e p h et al.

Fig ur e 9

o o o o 0 6I I I I I IR R R R R RI I I I I I

0 0 0 0 0 0

-- CH 2 - CH 2 - CH 2 - CH 2 - CH 2 - CH2 -- CH 2 - CH 2- C H 2---- CH2_LDPE Matrix

.... I . . . . . . _ _ 1IWhereR= C=OIN- - H, o CNCH 3 IH

A possible hypothetical chemical structure of sisal fibr e-C TD IC- PE in the interfacial area

50

40

.~ 31)

20

m Benzoyl peroxide - - Dicumyl peroxide+ Unidirectional x Random

. . . . .

t o I I I I I I0 2 4 6 8 I0

Peroxide concentration (%)Figure 10 Effect of peroxide concentr ation on the tensile strengt h ofsisal LDP E composit e at 30% fibre loading

Effect o f permanganate treatmentFigure 13 s h o w s t h e e f fe c t o f p e r m a n g a n a t e c o n c e n -t r a t i o n o n t h e t e n s i le s t r e n g t h o f r a n d o m l y a n du n i d ir e c ti o n a ll y o r i e n te d s i s a l - L D P E c o m p o s i t e s a t3 0 % f i b re lo a d i n g . I t is s e e n t h a t t e n s i l e s t r e n g t h r e a c h e sa m a x i m u m a t a p e r m a n g a n a t e c o n c e n t r a t io n o f 0 .0 5 5 %a n d t h e n d e c r e a s e s s h a r p l y w i t h f u r t h e r i n c r e a s e i n

c o n c e n t r a t i o n . T h i s m a y b e d u e t o t h e d e g r a d a t i o n o fc e l lu l o si c f ib r e s a t h i g h e r p e r m a n g a n a t e c o n c e n t r a t i o n .S o t h e p e r m a n g a n a t e c o n c e n t r a t i o n i s a c ri ti c a l f a c t o r i nd e t e r m i n i n g t h e t e n s il e p r o p e r t i e s o f p e r m a n g a n a t et r e at e d s i s a l - L D P E c o m p o s i te s .

Figure 11 SEM photo microg raph of the dicumyl perodixe treatedsisal fibr e-LD PE composite showing PE grafted to fibre surface

Table 7 s h o w s t h e t e n s il e p r o p e r t i e s o f p e r m a n g a n a t et r e a t e d ( 0 . 0 5 5 % ) s i s a l - L D P E c o m p o s i t e s . I t is i n te r e s ti n gt o n o t e t h a t t h e t e n s il e p r o p e r t i e s o f p e r m a n g a n a t e t r e a t e dc o m p o s i t e s s h o w e d a s i g n i f i c a n t i m p r o v e m e n t a s c o m -p a r e d t o u n t r e a t e d c o m p o s i t e s . T h e i n c r e a s e i n t e n s i l ep r o p e r t ie s o f p e r m a n g a n a t e t r e a t e d c o m p o s i t e s is d u e t ot h e p e r m a n g a n a t e i n d u c e d g r a f ti n g o f p o l y e th y l e n e o n t os i sa l fi b r e s . T h e h i g h l y r e a c t i v e M n ~ + i o n s a r e r e s p o n s i b l ef o r i n i ti a t in g g r a f t c o p o l y m e r i z a t i o n 3 as s h o w n b e l ow :C e l l u l o s e -H + M n ( l l I ) ~ C e l l u l o s e - H - M n ( I I I ) c o m p le x

C e l l u l o s e - H - M n ( I I I ) ~ C e ll ul os e" + H + + M n ( I I I)T h e S E M p h o t o m i c r o g r a p h s o f th e t en s i le fa i lu r es u rf a c e s o f t h e p e r m a n g a n a t e t r e a t e d c o m p o s i t e s i n d i c a tet h e g r a f t i n g o f P E o n t o c e l lu l o s e f i br e (Figure 14 ).



9/11

E f f e c t o f c h e m i c a l t re a t m e n t o n s i sa l f i b r e - r e i n f o r c e d L D P E c o m p o si te s ." K . J o s e p h et al.

Table 6 V a r i a t i o n o f t e n s i le p r o p e rt i e s o f s i s a l - L D P E c o m p o s i t e s w i t h p e ro x i d e t r e a t m e n t s ( fi b re c o n t e n t 3 0 % ; f i b r e l e n g t h 5 .8 m m )T e n s i le s t r e n g t h ( M P a ) M o d u l u s ( M P a )

C o m p o s i te s U n i d i re c t i on a l S D R a n d o m S D U n i d i re c t io n a l S D R a n d o m S DE l o n g a t i o n a t b r e a k ( % )

U n i d i r e c t i o n a l S D R a n d o m S DUn tre ate d 31 .12 0 .1575 14 .7 0 .4620 3086 0 .1919 781 0 .2715 1 0 .1212 7 0 .1465BP t rea ted 40 .90 0 .1435 20 .6 0 .1819 4018 0 .1675 132 6 0 .3414 3 0 .3264 9 0 .1010D C Pt re at ed 41 .80 0 .1635 21 .8 0 .7010 4156 0 .1675 144 8 0 .1818 4 0 .2010 10 0 .1212S D = s t a n d a r d d e v i a t io n

Table 7 T e n s i le p r o p e r ti e s o f u n t r e a t e d a n d K M n O 4 t r e a t e d s i s a l - L D P E c o m p o s i t e s (f i br e c o n t e n t 3 0 % ; f i b re l e n g th 5 .8 m m )T e n s i le s t r e n g t h ( M P a ) M o d u l u s ( M P a ) E l o n g a t i o n a t b r e a k ( % )

C o m p o s i t e s U n i d i r e c t i o n a l S D R a n d o m S D U n i d i r e c t i o n a l S D R a n d o m S D U n i d i r e c t i o n a l S D R a n d o m S DU nt re at ed 31.2 0.1575 14.7 0.4620 3086 0.1919 781 0.2715 2 0.1212 7 0.1465K M n O 4 t r e a t e d 3 8 .8 0 0 .1 8 2 5 1 9 . 8 0 . 34 1 4 3 8 16 0 .1 5 1 5 1 2 6 4 0 .2 8 6 5 3 0 . 13 6 3 8 0 .2 1 3 0S D = s t a n d a r d d e v i a t i o n

F i g u re 1 2 S E M p h o t o m i c r o g r a p h o f th e b e n z y oy l p e r o x i d e t r e a t e ds i s a l f i b r e - L D P E c o m p o s i t e s h o w i n g P E g r a f t e d t o t h e f i b r esu r f a c eF i g u r e 1 4 S E M p h o t o m i c r o g r a p h o f t e n si l e f r a c t u r e s u r fa c e o f th ep e r m a n g a n a t e t r e a t e d s i s a l - L D P E c o m p o s i t e s

a: + Unidirectional Random35I " . , .

~- 2o ~

o 0.05 o.i ().is o.2KM n O4 concentration (% )

F i g u r e 1 3 E f f ec t o f p e r m a n g a n a t e c o n c e n t r a t i o n o n t h e t e n s il es t r e n g t h o f s i s a l - L D P E c o m p o s i t e a t 3 0 % f i b re l o a d in g

Eff ic iency o f di f ferent trea tmen tsFina l ly , t he e f f ec ts o f t he d i f f e ren t types o f t r ea tmen t s[ a l k a l i , C T D I C , K M n O 4 ( 0 . 0 5 5 % ) , D C P ( 1 0 % ) a n d B P( 1 0 % ) ] o n t h e t e n s il e m o d u l u s a n d t e n si le s t r e n g t h o f th eu n i d i r e c t i o n a l l y o r i e n t e d c o m p o s i t e s ( a t 3 0 % f i b r e

l o a d i n g ) h a v e b e e n c o m p a r e d i n Figures 15 a n d 16,re spec t ive ly . From the above f igu res i t i s i n t e re s t ing ton o t e t h a t d i c u m y l p er o x id e t r e at e d a n d C T D I C t r e a te dc o m p o s i t e s s h o w s u p e r i o r t e n s i l e p r o p e r t i e s t h a n o t h e rchem ica l ly t r ea t ed s i sa l f ib re comp osi t e s . The p rop e r tyi n c r e a s e u p o n v a r i o u s t r e a t m e n t s v a r i e s i n t h e o r d e rD C P > C T D I C > B P > K M n O 4 > a l k a l i .H o w e v e r , s im p l e a l ka l i t r e a t m e n t is m o r e e c o n o m i c a l ,t h o u g h t h e t r e a t m e n t b y D C P o r p e r m a n g a n a t e i s n o tv e r y e x p e n s i v e b e c a u s e t h e a m o u n t r e q u i r e d i s v e r ys m a l l . S i m i l a r l y , C T D I C t r e a t m e n t i s a l s o n o t v e r yexpens ive , due to the e asy ava i l ab i l i ty o f t he inexpens iven a t u r a l p r e p o l y m e r c ar d a n o l , o b t a in e d f r o m C N S Lres in . In Ind ia , e spec ia l ly in Kera l a , ca rd ano l is a ve ryc h e a p m a t e r i a l. A g a i n , f o r t h e p r e p a r a t i o n o f C T D I C ,t h e T D I r e q u i r e d i s o n l y a v e r y s m a ll q u a n t i ty . H o w e v e r ,i t i s i m p o r t a n t t o m e n t i o n t h a t C T D I C t r e a t e d c o m -pos i t e s show ed be t t e r r e t en t ion in t ens i l e p rop e r t i e s a f t e ra g e i n g t h a n a n y o t h e r t r e a t m e n t s 41.



10/11

Ef fec t o f che mica l t rea tm en t on s isa l f ib re - re in fo rced LDP E compos ites . " K . Jose ph et al.

%-0 .

J

oE

#

10

+ D C P x C T D I C X B P K M n O 4 Alkal i Unt rea ted

L I I L I I I0 5 10 15 20 25 30

F i b r e c o n t e n t ( % )F i g u r e 1 5 E f f e c t o f d if f e r e n t t y p e s o f c h e m i c a l t r e a t m e n t o n t h e t e n s i lem o d u l u s o f u n i di r e ct i on a l ly o r i e n t e d s i s a l - L D P E c o m p o s i t e a t 3 0 %f i b r e l o a d i n g

45

35

ca

#15

+ DCP x CTDIC ~( BP

I ~ I I I I5 I0 15 20 25 3(1

F i b r e c o n t e n t ( % )F i g u r e 1 6 E f f e ct o f d if f e r e n t t y p e s o f c h e m i c a l t r e a t m e n t o n t h e t e n s i les t r e n g t h o f u n i d i r e c t io n a l l y o r ie n t e d s i s a l - L D P E c o m p o s i t e a t 3 0 %f i b r e l o a d i n g

F i g u r e 1 8 P h o t o g r a p h o f th e s u r fa c e s o f r a n d o m l y o r i e n t e d s i s a l -L D P E c o m p o s i t e s

Surface finish of s is al-P E compositesThe surface finish of the composites has been analysedto check if they exhibit wood like appearance. Figures 17and 18 show the photographs of the surfaces of thelongitudinal and random composites. It is interesting tonote that they exhibit wood like surface characteristics.The texture of the oriented composite is similar to Indianteak wood. Therefore, these composites have potential

application as a substitute for wood.CONCLUSIONSThe effects of different fibre treatments such as alkali,isocyanate, permanganate and peroxide on the tensileproperties of sisal-LDPE composites were investigatedas a function of fibre loading, fibre length and orienta-tion. Alkali treated fibre composites showed bettertensile properties than untreated composites due totheir rough surface topography and increased aspectratio. It has been seen that CTDIC treated compositesexhibit superior mechanical properties. This may be dueto the fact that the long chain structure of CTDIC linkedto the cellulosic fibres makes the fibre hydrophobic,compatible and highly dispersible in the PE matrix. TheSEM photomicrographs also support the strong fibre-matrix adhesion in sisal-LDPE composites. Peroxidetreated composites showed an enhancement in tensileproperties due to the peroxide induced grafting.Permanganate treated composites also showed a similartrend due to the permanganate induced grafting. Amongthe various types of treatments, CTDIC and DCPtreatments showed the maximum properties. Finally,it is worth mentioning that these composites havewood like appearance and can be used as a substitutefor wood.

F i g u r e 17 P h o t o g r a p h o f t h e s u r f a c e s o f l o n g i t u d i n a ll y o r ie n t e d s i s a l -L D P E c o m p o s i t e s

REFERENCESl F o l k e s , M . J . ' S h o r t F i b r e R e i n f o r c e d T h e r m o p l a s t i c s ' , J o h nW i l e y , N e w Y o r k , 1 98 2, C h . 6



11/11

E f f e c t o f c h e m i c a l t re a t m e n t o n s i s a l f i b r e - r e i n f o r c e d L D P E c o m p o s i t e s . K . J o s e p h et a l.

2 Lightsey, G. L. 'Organ ic Fil le rs for Therm oplas t ics ' , Polym . Sci .Techno l . , Vol . 17, Plen um Press , New Yo rk, 19833 Ma lda s , D . a nd Kokta , B . V . J . Comp. Mater . 1991, 25, 3754 Bisanda , E. T. N. and Ansell , M. P. Comp. Sci. Technol. 1991,4 1 , 16 55 Brou tm a n, L . J . a nd Kroc k , R . H . 'Comp os i t e Ma te r i a l s ', Vol .6, Acad emic Press, New Y ork, 19746 Pra sa d , S . V . , Pa vi thra n , C . a nd Roha tg i , P. K. J. Mater. Sci.1983, 18, 14437 Va rma , D . S ., Va rma , M. a nd Va rma , I . K . Text. Res. J. 1984,5 4 , 82 78 Va rma , D . S ., Va rma , M. a nd Va rma , I . K . J . Reinf. Plast.Comp. 1985, 4, 4199 Va rma , D . S . , Va rma , M. a nd Va rma , I. K. J. Polym. Mater.1986, 3, 10110 Va rma , I . K . , Ana ntha kr i sh na n , S . R . a nd Kr i shna mo or thy , S .Text . Res. J. 1988, 58, 48611 Va rma , I , K . , Ana ntha kr i sh na n , S . R . a nd Kr i shna mo or thy , S .Text . Res. J . 1988, 58, 53712 Beshay, A. D. , Ko kta , B. V. and Daneault , C. Polym. Comp.1985, 6, 26113 Raj, R. G. , Ko kta , B. V. and Dane ault , C. J. Adhes. Sci.Technol. 1989, 3, 5514 Zang , Y. H. and Sapieha, S. Po l y m e r 1991, 32, 48915 Ra j , R . G . , Kok ta , B . V . , Grole a u , G . a nd D a ne a u l t , C . Plast.Rubb. Process Appl. 1989, 1 1 , 21 516 Raj, R. G. , Ko kta , B. V. , Maldas , D. and Dane ault , C. J. Appl.Polym. Sci . 1989, 37, 917 Ko kta , B. V. , Malda s , D. , Dan eault , C. and Beland, P. Polym.Plast. Technol. Eng. 1990, 29, 8718 Man rich, S. and Agnell i, J . A. M. J . App/ . Polym. Sci . 1989, 37,177719 Sapieha, S., Allard, P. and Zang, Y. H. J . Appl. Polym. Sci.1990, 41, 203920 Stofko, J . Ph D Disser ta t ion, Unive rs i ty of California , Berkeley,197221 Young , R . A . Wood Fiber 1978, 10, 11222 Sapieha, S., Pup o, J. F. an d Schreiber, H. P. J. Appl. Polym. Sci.1989, 37, 233

23 Co usin , P., Bataille, P., Schreiber, H. P. and Sapieha, S. J. Appl.Polym. Sci. 1989, 37, 305724 Subra m a nia n , R . V . a nd H offma nn , R . J . Polym. Sci . , Polym.Chem. Edn 1983, 12, 10525 Mon te , S . J . a nd Suge rma n, G . Polym. Plast. Technol. Eng.1981, 17, 9526 Kalins ki , R. , Galeski , A. and Kryszewski , M. J . Appl . Polym.Sci. 1981, 26, 404727 Flink, P. , Rigda hl , M. and Stenberg, B. J. Appl. Polym. Sci.1988, 35, 215528 Ta ne da , K . , Ka w a ka m i , H . a nd H a se gaw a , I. J. Jpn Wood. Res.Soc. 1972, 18, 39329 Tripa th y, S. S. , Jena , S., Misra , S. B. , Padhi , N. P. and Singh, B.C. J. Appl. Polym. Sci. 1985, 30, 139930 Mo haran a , S. , Mishra , S. B. and Tripa th y, S. S. J. Appl. Polym.Sci. 1990, 40, 34531 Joseph, K. , Pavith ran, C. and Thom as, S. Mater. Left . 1992, 15,22 432 Joseph, K. , Thom as, S. , Pav ithran , C. and Brahmak uma r, M. J .Appl. Polym. Sci. 1993, 47, 173133 Joseph, K. , Pav ithran , C. and Thom as, S. , Kuriako se , B. andPremala tha , C. K. Plast. Rubb. Comp. Process. Appl. 1994, 21,23 734 Joseph, K. , Pavith ran, C. and Thom as, S. J . Reinf. Plast. Comp.1993, 12, 13935 Varughese , S. , Kuriako se , B. and Thom as, S. Ind ian J. N at .Rubb. Res. (in press)36 Maldas , D. , Ko kta , B. V. , Raj, R. G. and Daneault , C. Po l y m e r1988, 29, 125537 Pil lot , J . P. , Duno gues , J . , Gerval , J . , The , M. D. and Than h, M.V. Eur. Polym. J. 1989, 25, 28538 Pil la i , C. K. S., Me non , A. R. R. , Pav ithran, C. andD a m o d a r a n , A . D . Metals, Mater. Processes 1989, 1, 15539 Varghese , S. , Kuriako se , B. , Thom as, S. and Koshy , A. T.Indian. J. Nat. Rubb. Res. 1991, 4, 5540 Misra , B. N. , Meh ta , I . K. and Kh etarpa l , R. C., J. Polym. Sci.,Polym. Chem. Edn 1984, 22, 276741 Joseph, K. , Tho mas, S. and Pav ithran , C. Comp. Sci. Technol.1995, 53, 99

Documents

Effect of Chemical Treatment on the Tensile