Adhesives from Renewable Resources - American Chemical Society

Chapter 24 Cellulose Graft Copolymers for Potential Adhesive Applications Downloaded by EAST CAROLINA UNIV on January 5, 2018 | http://pubs.acs.org Publication Date: December 31, 1989 | doi: 10.1021/bk-1989-0385.ch024

Bonding of Plastics to Wood R a m a n i N a r a y a n and C h r i s t o p h e r

J.

Biermann

1

Laboratory of Renewable Resources Engineering Purdue University West Lafayette, IN 47907 M i c h a e l O . H u n t and D a v i d P . H o r n Department of Forest and Natural Resources Purdue University West Lafayette, IN 47907 Bonding of hydrophobic plastic materials to wood to create new wood-plastic (polystyrene) materials with improved mechanical and physical properties that incorporate the desirable features of each constituent is difficult to achieve. This is due to poor interfacial adhesion between the wood and polystyrene components because of their inherent incompatibility. New, well-defined, tailored cellulosepolystyrene graft copolymers have recently been prepared using anionic polymerization techniques. Preliminary bonding studies showed that these graft copolymers can function effectively as compatibilizers or interfacial agents to bond hydrophobic plastic (polystyrene) material to wood, evolving into a new class of composites. T h e concept o f c o m b i n i n g t w o o r more u n i q u e p o l y m e r s t o prepare new m a t e r i a l systems w i t h t h e desirable features o f t h e i r constituents is w i d e l y p r a c t i c e d i n t h e p o l y m e r i n d u s t r y (1-5). T h e p r i m a r y issue c o n f r o n t i n g t h e design o f such p o l y m e r systems involves g u a r a n t e e i n g g o o d stress transfer between a l l components o f the m u l t i c o m p o n e n t s y s t e m . T h i s is the o n l y way t o ensure t h a t the c o m p o n e n t s ' i n d i v i d u a l p h y s i c a l properties are efficiently u t i l i z e d t o p r o d u c e m i x t u r e s w i t h the desired performance characteristics. O b t a i n i n g g o o d stress transfer is possible i n systems where the m i x t u r e forms a m i s c i b l e a m o r p h o u s phase (where interphase stress transfer i s n o t a n issue); 1

C u r r e n t address:

Assistant

Professor, D e p a r t m e n t

of Forest P r o d u c t s , O r e g o n

U n i v e r s i t y , C o r v a l l i s , O R 97331

0097-6156/89A)385-0337$06.00A) ·

1989 American Chemical Society

Hemingway et al.; Adhesives from Renewable Resources ACS Symposium Series; American Chemical Society: Washington, DC, 1989.

State

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Downloaded by EAST CAROLINA UNIV on January 5, 2018 | http://pubs.acs.org Publication Date: December 31, 1989 | doi: 10.1021/bk-1989-0385.ch024

however, o b t a i n i n g a m i s c i b l e phase o f two c h e m i c a l l y i n c o m p a t i b l e c o m p o n e n t s is difficult t o achieve. P r e p a r i n g new m a t e r i a l s b y m i x i n g t w o i n c o m p a t i b l e p o l y m e r s results i n p r o d u c t s w i t h reduced p h y s i c a l properties (6-9). S t r e n g t h a n d toughness values are m i n i m a l a n d are lower for the m i x t u r e t h a n for any of the pure c o m p o n e n t s (10). T h i s c o n d i t i o n is due t o p o o r i n t e r f a c i a l a d h e s i o n between the i n d i v i d u a l components because o f the inherent i n c o m p a t i b i l i t y . O n e p o t e n t i a l s o l u t i o n t o t h i s i n c o m p a t i b l i t y p r o b l e m t h a t is c u r r e n t l y p r a c t i c e d i n the p o l y m e r i n d u s t r y uses b l o c k or graft p o l y m e r s o f the f o r m A - B as c o m p a t i b i l i z e r s or i n t e r f a c i a l agents t o i m p r o v e adhesion between i m m i s c i b l e Α-rich a n d B - r i c h phases. T h e p h y s i c a l affinity of the A p o r t i o n o f the graft p o l y m e r for the A phase a n d the Β p o r t i o n for the Β phase serves to locate the graft p o l y m e r at the interface a n d p h y s i c a l l y connect the t w o phases t h r o u g h covalent b o n d s t o the graft p o l y m e r b a c k b o n e . T h e net result of t h i s i m p r o v e d adhesion is a finer d i s p e r s i o n o f the m i n o r c o m p o n e n t t h a t provides significant i m p r o v e m e n t s i n the m e c h a n i c a l properties o f e l o n g a t i o n a n d tensile s t r e n g t h (11-15). T h i s chapter r e p o r t s successful i n i t i a l efforts t o b o n d w o o d i n the presence o f h y d r o p h o b i c p l a s t i c m a t e r i a l [polystyrene (PS)] u s i n g well-defined a n d t a i l o r e d cellulose-polystyrene graft p o l y m e r s as c o m p a t i b i l i z e r s or i n t e r f a c i a l agents. T h e synthesis o f these t a i l o r e d cellulose graft p o l y m e r s is also presented. A s p r e v i o u s l y s t a t e d , the m a j o r p r o b l e m c o n f r o n t i n g the development of new c o m p o s i t e systems f r o m w o o d a n d p l a s t i c p o l y m e r s is the inherent i n c o m p a t i b i l i t y o f the c o m p o n e n t s : h y d r o p h o b i c p o l y s t y r e n e a n d the p o l a r wood-adhesive m a t r i x . I n order t o create new m a t e r i a l s w i t h i m p r o v e d m e c h a n i c a l a n d p h y s i c a l p r o p e r t i e s , i t is i m p e r a t i v e t o e m p l o y a n i n t e r f a c i a l agent like well-defined cellulose-polystyrene graft p o l y m e r s . T h e cellulose b a c k b o n e o f the graft p o l y m e r is a v a i l a b l e for b o n d i n g t o the w o o d w i t h e x i s t i n g c o m m e r c i a l resins, w h i l e the heat e m p l o y e d t o cure the resin causes the p o l y s t y r e n e side chains t o m e l t a n d flow i n t o the p o l y s t y r e n e c o m p o n e n t of the m i x t u r e . U p o n c o o l i n g , the p o l y s t y r e n e solidifies, c r e a t i n g a s t r o n g b o n d between the i n c o m p a t i b l e w o o d a n d p o l y s t y r e n e c o m p o n e n t s , w h i c h are j o i n e d v i a the direct p o l y s t y r e n e t o cellulose linkage w i t h i n the graft p o l y m e r ( F i g u r e 1). It m a y also be possible t o e v e n t u a l l y e x t e n d t h i s b o n d i n g concept t o the p r e p a r a t i o n o f flakeboards a n d other wood-base c o m p o s i t e m a t e r i a l s . If p l a s tics like p o l y s t y r e n e are i n c o r p o r a t e d i n t o the c o m p o s i t e m a t r i x , a n d successful b o n d i n g between the w o o d a n d p l a s t i c is developed t h r o u g h the graft p o l y m e r s , the t h r e e - d i m e n s i o n a l network of p l a s t i c m a t e r i a l t h r o u g h o u t the c o m p o s i t e m a t r i x m a y l e a d t o enhanced p h y s i c a l a n d m e c h a n i c a l properties as w e l l as i m p r o v e m e n t s i n d i m e n s i o n a l s t a b i l i t y ( F i g u r e 2).



24.

NARAYAN E T AL.

IflSflt I

Cellulose Graft Copolymers

339

Cellulose phase of GP

I Polystyrene phase of GP

F i g u r e 1. E x p l o d e d v i e w o f the use o f graft p o l y m e r s ( G P ) t o c o m p a t i b i l i z e the l i n k i n g of wood ( W ) a n d polystyrene ( P S ) materials. Reprinted with permission from ref. 27. Copyright 1988 Humana Press.



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F i g u r e 2. C o n t i n u o u s t h r e e - d i m e n s i o n a l network o f p l a s t i c (polystyrene) l i n k e d t o w o o d v i a a cellulose-polysytrene graft c o p o l y m e r . Reprinted with permission from ref. 27. Copyright 1988 Humana Press.


24.

NARAYAN E T A L


Experimental


341

Methodology

P r e p a r a t i o n o f C e l l u l o s e - P o l y s t y r e n e G r a f t C o p o l y m e r s . The polystyry l m o n o - a n d d i - c a r b a n i o n s were p r e p a r e d i n T H F at -78 ° C b y u s i n g n - b u t y l l i t h i u m a n d s o d i u m n a p h t h a l e n e as the i n i t i a t o r s , respectively. T h e c a r b a n ions were reacted w i t h d r y c a r b o n d i o x i d e . T h e p r o d u c t s were p r e c i p i t a t e d i n m e t h a n o l , filtered, washed w i t h water a n d m e t h a n o l , a n d d r i e d . Size e x c l u s i o n c h r o m a t o g r a p h y ( S E C ) established t h a t the m o l e c u l a r weight of the p o l y s t y r y l m o n o c a r b o x y l a t e was 6,200 a n d t h a t o f the p o l y s t y r y l d i - c a r b o x y l a t e 10,2000. T h e m o n o - a n d d i - c a r b o x y l a t e s were reacted w i t h m e s y l a t e d cellulose acetate i n d i m e t h y l f o r m a m i d e at 75 ° C for 20 h t o give the cellulose-polystyrene graft c o p o l y m e r ( G P 1) a n d crosslinked cellulose-polystyrene graft c o p o l y m e r ( G P 2), respectively. B o n d i n g S t u d i e s . Test specimens were c o n s t r u c t e d o f t w o plies o f 1/8" t h i c k yellow p o p l a r veneer. T h e y were c o n d i t i o n e d i n a n A m i n c o c o n d i t i o n i n g c h a m ber at 46 ° C a n d 1 2 % r e l a t i v e h u m i d i t y , w h i c h resulted i n w o o d specimens w i t h a n average m o i s t u r e content of 2.7%. A l l plies used i n t h i s e x p e r i m e n t were c o n d i t i o n e d i n the c h a m b e r for at least 14 days p r i o r t o s a m p l e f a b r i c a t i o n . C a s c o p h e n - 1 6 ( B o r d e n C h e m i c a l , Inc.) was selected as the c o m m e r c i a l oriented s t r a n d b o a r d adhesive t o be used i n the s t u d y . T h e resin was p o u r e d d i r e c t l y i n t o a c o m m e r c i a l p a i n t spray g u n a n d a p p l i e d t o the 1/8" w o o d plies u s i n g a h o m e m a d e s y s t e m developed by the a u t h o r s . T h e s y s t e m consisted of a s m a l l m o t o r i z e d cart capable o f h o l d i n g a c a r t r i d g e o f w o o d plies as t h e y passed t h r o u g h the resin s t r e a m e m i t t e d b y the s t a t i o n a r y s p r a y g u n . T h e a m o u n t o f resin delivered t o each p l y was c o n t r o l l e d b y r e g u l a t i n g the a i r pressure o f the spray g u n a n d the speed o f the m o t o r i z e d c a r t . Test specimens ( c o m p o s e d of two plies) w i t h 0.18 g resin evenly d i s t r i b u t e d across 4 s q . inches of g l u e l i n e were p r e p a r e d w i t h the s y s t e m . P o l y s t y r e n e , graft c o p o l y m e r , a n d p o l y s t y r e n e - g r a f t c o p o l y m e r m i x t u r e s were a d d e d i n powdered f o r m to one p l y f r o m each test s p e c i m e n u s i n g a h o m e m a d e c o l u m n - l o a d i n g s y s t e m . T h i s s y s t e m allowed the delivery o f measured a m o u n t s of evenly d i s t r i b u t e d powders o n t o the test areas. T a b l e I lists the various c o m p o s i t i o n s o f the test specimens a n d the n u m b e r of the test specimens used i n the s t u d y . T h e test specimens (composed of two plies) were l o a d e d onto a l u m i n u m cauls a n d p l a c e d i n the press. E a c h s p e c i m e n was pressed at 50 p s i a n d 149 ° C for 3 m i n . U p o n c o o l i n g , a b a n d saw was e m p l o y e d t o remove 1/2 i n . f r o m each e n d o f the s p e c i m e n (to enable t h e m t o fit i n t o the 4 i n . g r i p s o n the t e s t i n g m a c h i n e ) . A high-speed d r i l l press (12,000 r p m ) fitted w i t h a 1/8 i n . router b i t was t h e n used t o cut the cross grooves i n t o each s p e c i m e n t o isolate the glueline for t e s t i n g . T h e specimens were c o n d i t i o n e d at 21 ° C a n d 5 0 % relative h u m i d i t y for 7 days. P r i o r t o a c t u a l t e s t i n g , a caliper (precision o f ± 0.001 i n . ) was used to measure the glueline area i s o l a t e d for t e s t i n g . T h e specimens were t h e n inserted i n t o the grips o n a R e i h l e s t r i p shear t e s t i n g m a c h i n e a n d l o a d e d


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at a constant rate of 10 l b per sec u n t i l f a i l u r e . T h e u l t i m a t e l o a d at f a i l u r e a n d v i s u a l e s t i m a t e of the a m o u n t of w o o d f a i l u r e were recorded for each s a m p l e .

T a b l e I. C o m p o s i t i o n of the Test Specimens


Population A Β C D Ε F G H I J

N u m b e r of Test Specimens

Composition

45 10 10 10 48 45 18 46 50 25

C o n t r o l s , P F resin o n l y 0.02 g of P S o n l y (no resin) 0.02 g of G P 1 o n l y (no resin) 0.02 g of G P 2 o n l y (no resin) P F resin a n d 0.02 g of P S P F resin a n d 0.02 g of G P 1 P F resin a n d 0.02 g o f G P 2 P F resin a n d 0.02 g of P S - G P 1 m i x P F resin a n d 0.04 g of P S - G P 1 m i x P F resin a n d 0.02 g of P S - G P 2 m i x

1

1

1

2

2

3

3

3

*In p o p u l a t i o n s B , C , a n d D , no b o n d i n g o c c u r r e d , a n d s a m p l e f a b r i c a t i o n was h a l t e d after 10 specimens. T h e n u m b e r of test specimens was l i m i t e d due t o insufficient supplies of G P 2. T h e P S - G r a f t P o l y m e r ( G P ) m i x t u r e was m a d e u p of 5 0 % b y weight of each c o m p o n e n t . 2

3

Synthesis of Tailor M a d e Cellulose-Polystyrene Graft

Copolymers

P r o b l e m s E n c o u n t e r e d . M o s t of the w o r k done t o date i n p r e p a r a t i o n of cellulosic graft p o l y m e r s has i n v o l v e d free-radical p o l y m e r i z a t i o n m e t h o d s . W i t h these procedures, very few h i g h - m o l e c u l a r - w e i g h t molecules were a c t u a l l y grafted as i l l u s t r a t e d b y l o w levels of graft s u b s t i t u t i o n [only a s m a l l p o r t i o n of the cellulose substrate was grafted (16,17]. T h e m o l e c u l a r weight d i s t r i b u t i o n of the grafted side chains was difficult to c o n t r o l or change, a n d no knowledge of the n a t u r e of the backbone-graft linkage e x i s t e d . S u b s t a n t i a l h o m o p o l y m e r f o r m a t i o n o c c u r r e d ; there was p o o r r e p r o d u c i b i l i t y a n d l i t t l e c o n t r o l over the g r a f t i n g process, graft y i e l d s , r e s u l t i n g properties, a n d other features of the graft p o l y m e r (18). C l e a r l y , these types of i l l - d e f i n e d a n d p o o r l y characterized graft p o l y m e r s w i t h o n l y a few very h i g h m o l e c u l a r weight grafts a n d l o w l e v els of graft s u b s t i t u t i o n s (0.03 to 0.8 p o l y s t y r y l chains per cellulosic c h a i n a n d m o l e c u l a r weights r a n g i n g f r o m 354,000 t o 960,000) w o u l d be p o o r i n t e r f a c i a l c o m p a t i b i l i z e r s . I n fact, the h i g h m o l e c u l a r weights of the grafts a n d the low levels o f graft s u b s t i t u t i o n w o u l d m a k e these m a t e r i a l s behave m o r e like b l e n d s t h a n graft p o l y m e r s .


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N A R A Y A N ET

AL.


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It has been r e p o r t e d t h a t h o m o p o l y m e r blends or r a n d o m c o p o l y m e r s do not show i n t e r f a c i a l a c t i v i t y (19). Therefore, the cellulose graft p o l y m e r s f r o m freer a d i c a l p o l y m e r i z a t i o n processes w o u l d not be effective c o m p a t i b i l i z e r s . P r e ferred m a t e r i a l s w o u l d be precise, well-defined cellulose graft p o l y m e r s w i t h k n o w n backbone-graft linkages developed t h r o u g h procedures t h a t p e r m i t v a r i a t i o n a n d c o n t r o l of m o l e c u l a r weight a n d degree of graft s u b s t i t u t i o n . H i g h e r degrees of s u b s t i t u t i o n t h a n o b t a i n e d i n the free-radical processes w o u l d be required. N e w T e c h n o l o g y . A s the previous section i l l u s t r a t e s , i f cellulosic graft p o l y mers are to be e m p l o y e d i n adhesive a p p l i c a t i o n s , new s y n t h e t i c approaches m u s t be developed. T h e new s y n t h e t i c procedures m u s t allow c o n t r o l of the m o l e c u l a r weight a n d n u m b e r of r e s u l t i n g side c h a i n grafts (degree of graft s u b s t i t u t i o n ) , e l i m i n a t i o n or d r a s t i c r e d u c t i o n o f c o n c u r r e n t h o m o p o l y m e r form a t i o n , a n d exercise of direct knowledge a n d c o n t r o l over the linkage between the cellulosic b a c k b o n e a n d the a t t a c h e d side chains. N e w s y n t h e t i c approaches t o cellulosic graft p o l y m e r s have been developed t h r o u g h use of a n i o n i c p o l y m e r i z a t i o n techniques t h a t allow t h i s t o come a b o u t (20-24). T h u s , the properties of the graft p o l y m e r s c a n be t a i l o r e d b y c o n t r o l of parameters such as the m o l e c u l a r weight of the side c h a i n grafts, e l i m i n a t i o n of concurrent h o m o p o l y m e r f o r m a t i o n , the n u m b e r a n d t y p e of grafted side chains, knowledge of the linkage between the cellulose b a c k b o n e a n d the side c h a i n graft. T h e m e t h o d involves: 1) i n t r o d u c t i o n of e l e c t r o p h i l i c or l e a v i n g groups o n t o the cellulose b a c k b o n e b y c h e m i c a l m o d i f i c a t i o n (i.e., i n t r o d u c t i o n of reactive sites o n t o the cellulose b a c k b o n e ) ; 2) p r e p a r a t i o n of the " l i v i n g " s y n t h e t i c p o l y m e r of desired m o l e c u l a r weight b y a n i o n i c p o l y m e r i z a t i o n techniques; a n d 3) r e a c t i o n of the " l i v i n g " s y n t h e t i c p o l y m e r w i t h the m o d i f i e d cellulose u n d e r h o m o g e n o u s reaction conditions. A n i o n i c p o l y m e r i z a t i o n m e t h o d s p r o v i d e a n extensive a n d unprecedented c o n t r o l m e c h a n i s m over p o l y m e r i z a t i o n processes. T h i s includes p o l y m e r c o m p o s i t i o n , m i c r o s t r u c t u r e , m o l e c u l a r weight a n d m o l e c u l a r weight d i s t r i b u t i o n , a n d m o n o m e r sequence d i s t r i b u t i o n . T h i s is the key to o u r a p p r o a c h because we now have the a b i l i t y to c o n t r o l the essential parameters of the side c h a i n s y n t h e t i c graft t h a t dictates the properties of the graft p o l y m e r . T h r o u g h regu l a t i o n of the r a t i o between the reactive sites o n the cellulose b a c k b o n e a n d the s y n t h e t i c p o l y m e r a n i o n (the " l i v i n g " s y n t h e t i c p o l y m e r ) , the degree of s u b s t i t u t i o n ( D S ) of the graft c a n be c o n t r o l l e d . T h e s y n t h e t i c p o l y m e r a n i o n we have used is generally a c a r b a n i o n (21-23) or a c a r b o x y l a t e a n i o n (24), a n d the reactive sites o n the cellulose b a c k b o n e are g o o d l e a v i n g groups like t o s y l a t e (23) a n d mesylate (24). T h u s , the reaction c h e m i s t r y essentially involves a n SJV2 t y p e n u c l e o p h i l i c displacement r e a c t i o n of the t o s y l a t e or m e s y l a t e group b y t h e s y n t h e t i c p o l y m e r a n i o n . Therefore, there is n o u n c e r t a i n t y i n the n a t u r e of the backbone-graft linkage i n our s y n t h e t i c a p p r o a c h . C o n c u r r e n t h o m o p o l y mer f o r m a t i o n is e l i m i n a t e d , a n d any h o m o p o l y m e r f o r m e d d u r i n g the c o u p l i n g stage is easily e x t r a c t a b l e .


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ADHESIVES F R O M RENEWABLE R E S O U R C E S


T h u s p o l y s t y r y l c a r b a n i o n s a n d p o l y aery l o n i t rile c a r b a n i o n s p r e p a r e d b y a n i o n i c p o l y m e r i z a t i o n were reacted w i t h cellulose acetate or t o s y l a t e d cellulose acetate i n t e t r a h y d r o f u r a n u n d e r h o m o g e n o u s r e a c t i o n c o n d i t i o n s . T h e c a r b a n ions d i s p l a c e d the acetate groups or the t o s y l a t e groups i n a S JV 2-type n u c l e o p h i l i c d i s p l a c e m e n t r e a c t i o n t o give C A - g - P S a n d C A - g - P A N . M i l d h y d r o l y s i s t o remove the a c e t a t e / t o s y l a t e groups furnishes the pure cellulose-g-polystyrene ( F i g u r e 3). C e l l u l o s e graft p o l y m e r s h a v i n g ester linkages w i t h c o n t r o l over the m o l e c u l a r weight o f the side c h a i n graft (24) have also been p r e p a r e d . I n t h i s synthesis, the p o l y s t y r y l c a r b a n i o n p r e p a r e d b y a n i o n i c p o l y m e r i z a t i o n techniques has been m o d i f i e d b y c a p p i n g w i t h c a r b o n d i o x i d e to generate the p o l y s t y r y l c a r b o x y l a t e a n i o n (1) ( F i g u r e 4). W h i l e t h i s a n i o n is n o t sufficiently reactive t o displace acetate groups f r o m cellulose acetate, i t i s , however, sufficiently n u c l e o p h i l i c t o displace better l e a v i n g groups like the m e s y l a t e g r o u p f r o m a m e s y l a t e d cellulose acetate b a c k b o n e w i t h the c o n c o m i t a n t f o r m a t i o n of a n ester l i n k a g e . A f u r t h e r advantage o f the direct use of p o l y s t y r e n e c a r b o x y l a t e a n i o n s over p o l y s t y r y l c a r b a n i o n is t h a t water does not interefere w i t h the g r a f t i n g r e a c t i o n . T h e r e a c t i o n is essentially c o m p l e t e at 75 ° C after 20 h o u r s . G r a f t i n g y i e l d s appear t o be l i m i t e d by the efficiency o f c a r b o x y l a t i o n o f the p o l y s t y r e n e . W e have, for e x a m p l e , p r e p a r e d a graft p o l y m e r p r o d u c t h a v i n g one p o l y s t y r y l ester c h a i n o f m o l e c u l a r weight 6,200 for every 17 anhydroglucose u n i t s o f the cellulose b a c k b o n e . W i t h t h i s a p p r o a c h , monodisperse p o l y s t y r y l ester chains of any p r e d e t e r m i n e d m o l e c u l a r weight c a n be grafted onto the cellulose b a c k b o n e i n a consistent m a n n e r . A n i o n i c p o l y m e r i z a t i o n of styrene w i t h s o d i u m n a p h t h a l e n e as the i n i t i a t o r gave the d i f u n c t i o n a l p o l y s t y r y l c a r b a n i o n o f desired m o l e c u l a r weight t h a t , o n r e a c t i o n w i t h CO2, f u r n i s h e d the p o l y s t y r y l p o l y s t y r y l d i c a r b o x y l a t e a n i o n (2) ( F i g u r e 5). R e a c t i o n of t h i s a n i o n w i t h m e s y l a t e d cellulose acetate resulted i n the f o r m a t i o n of a s o l i d g e l , i n d i c a t i v e of c r o s s l i n k i n g . C r o s s l i n k i n g is t o be e x p e c t e d , since b o t h ends of the p o l y s t y r e n e c h a i n c o u l d p o t e n t i a l l y react w i t h the m e s y l a t e groups o n the cellulose b a c k b o n e as s h o w n i n F i g u r e 5 (24). W e have p r e p a r e d crosslinked graft p o l y m e r s w i t h p o l y s t y r e n e o f m o l e c u l a r weight 10,000 a n d one p o l y s t y r y l crosslink for every 23 anhydroglucose u n i t s . T h e s e well-defined, t a i l o r - m a d e cellulosic graft p o l y m e r s p r e p a r e d b y the n e w l y developed a n i o n i c p o l y m e r i z a t i o n procedures show p r o m i s e i n s e r v i n g as c o m p a t i b i lizers o f i n t e r f a c i a l agents for d e v e l o p i n g new p o l y m e r blends of w o o d , p h e n o l i c resins, a n d p o l y s t y r e n e . A series of r e l a t i v e l y s i m p l e b o n d i n g e x p e r i m e n t s was designed t o s u p p o r t or reject the a b i l i t y of the new graft p o l y m e r s t o f a c i l i t a t e b o n d i n g between w o o d a n d p l a s t i c m a t e r i a l s . Bonding Studies T h e p o t e n t i a l use of cellulose graft p o l y m e r s to c o m p a t i b i l i z e the l i n k i n g o f a n a t u r a l p o l y m e r ( w o o d ) w i t h a s y n t h e t i c p o l y m e r (polystyrene) is based o n


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Adhesives from Renewable Resources - American Chemical Society

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