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SynopsisPowdered beech wood (Fagus crenatu) copolymerized with acrolein by using the xanthate method of grafting is examined in a scanning electron microscope. Homopolymer was observed as spherical-shaped particules deposited on the surface of cell walls. Coral-and spongelike shaped graft polyacrolein made its appearance after the removal of the homopolymer by the extraction with the pyridine-water mixture. Wrinkles which were observed in the noncopolymerized sample were interpreted as a result of the formation of voids by dissolving the oxidatively degraded cell wall materials in the pyridine-water and the subsequent collapse of the voids and shrinkage of the cell walls on drying. The wrinkle formation was minimized in the case of the copolymerized samples because of the restriction of the shrinkage of the cell wall by the presence of graft polymer in the cell wall. INTRODUCTIONChemical process of solid wood and lignocellulosic materials causes some alterations in the cells. In the process, chemicals adhere or bind to surfaces, fill voids, and in some cases degrade components of the wood cell wall. These alterations are induced typically by graft polymerization of those materials with vinyl monomers. In the past, the microscopic investigations of the morphology and structure of so-modified cellulosic fibers or wood have been preferably done by several workers. '-5 The xanthate method of grafting developed by Faessinger and Conte' has been successfully applied to producing the acrolein copolymer with powdered beechThe previous paper7 suggests that some wood components decompose during the process, in which the wood was treated successively with a dilute aqueous alkali, carbon disulfide, a dilute aqueous Mohr's salt, an aqueous hydrogen peroxide solution, and acrolein monomer. The decomposition resulted in the weight loss on the extraction with the pyridine-water mixture.Furthermore, the behavior of the graft polyacrolein onto wood to hydroxylamine supports the interpretation that the graft polyacrolein extends from the transient capillaries formed by the swelling action of water to the microscopically visible macropores.'Journal of Applied Polymer Science, Vol. 37, 2283Vol. 37, -2294Vol. 37, (1989 HIRABAYASHIT r e a t m e n t w i t h 3% NaOH, CS2 0 . 0 1 8 2 % M o h r ' s s a l t , a n d 4.5%This paper now relates the morphological and structural changes of cell walls in the grafting process using this method and the behavior of graft and homopolyacrolein as revealed microscopically.T r e a t m e n t w i t h 3% N a O H , C S z 0 . 0 1 8 2 % M o h r ' s s a l t , a n d 5 . 5 % EXPERIMENTAL MaterialsWood meal used in this work was prepared from beech wood (Fagus crenata ). The powdered beech wood (40-60 mesh) was extracted successively with hot water for 5 h, and the ethanol-benzene mixture for 48 h before the copolymerization procedure was applied. CopolymerizationThe details of the copolymerization procedure have been described in a previous paper.7 The wood powder extracted successively with hot water and ...
SynopsisPowdered beech wood (Fagus crenatu) copolymerized with acrolein by using the xanthate method of grafting is examined in a scanning electron microscope. Homopolymer was observed as spherical-shaped particules deposited on the surface of cell walls. Coral-and spongelike shaped graft polyacrolein made its appearance after the removal of the homopolymer by the extraction with the pyridine-water mixture. Wrinkles which were observed in the noncopolymerized sample were interpreted as a result of the formation of voids by dissolving the oxidatively degraded cell wall materials in the pyridine-water and the subsequent collapse of the voids and shrinkage of the cell walls on drying. The wrinkle formation was minimized in the case of the copolymerized samples because of the restriction of the shrinkage of the cell wall by the presence of graft polymer in the cell wall. INTRODUCTIONChemical process of solid wood and lignocellulosic materials causes some alterations in the cells. In the process, chemicals adhere or bind to surfaces, fill voids, and in some cases degrade components of the wood cell wall. These alterations are induced typically by graft polymerization of those materials with vinyl monomers. In the past, the microscopic investigations of the morphology and structure of so-modified cellulosic fibers or wood have been preferably done by several workers. '-5 The xanthate method of grafting developed by Faessinger and Conte' has been successfully applied to producing the acrolein copolymer with powdered beechThe previous paper7 suggests that some wood components decompose during the process, in which the wood was treated successively with a dilute aqueous alkali, carbon disulfide, a dilute aqueous Mohr's salt, an aqueous hydrogen peroxide solution, and acrolein monomer. The decomposition resulted in the weight loss on the extraction with the pyridine-water mixture.Furthermore, the behavior of the graft polyacrolein onto wood to hydroxylamine supports the interpretation that the graft polyacrolein extends from the transient capillaries formed by the swelling action of water to the microscopically visible macropores.'Journal of Applied Polymer Science, Vol. 37, 2283Vol. 37, -2294Vol. 37, (1989 HIRABAYASHIT r e a t m e n t w i t h 3% NaOH, CS2 0 . 0 1 8 2 % M o h r ' s s a l t , a n d 4.5%This paper now relates the morphological and structural changes of cell walls in the grafting process using this method and the behavior of graft and homopolyacrolein as revealed microscopically.T r e a t m e n t w i t h 3% N a O H , C S z 0 . 0 1 8 2 % M o h r ' s s a l t , a n d 5 . 5 % EXPERIMENTAL MaterialsWood meal used in this work was prepared from beech wood (Fagus crenata ). The powdered beech wood (40-60 mesh) was extracted successively with hot water for 5 h, and the ethanol-benzene mixture for 48 h before the copolymerization procedure was applied. CopolymerizationThe details of the copolymerization procedure have been described in a previous paper.7 The wood powder extracted successively with hot water and ...
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