000			01999nam a2200229Ia 4500
008			220216s9999 xx 000 0 und d
100			_aKawahara Seiichi
245		0	_aCrystallization behavior and strength of natural rubber- Skim rubber, deproteinized natural rubber and pale crepe
260			_bAbstracts of Meeting Papers: 155th Meeting (Spring 99) of the Rubber Division American Chemical Society Chicago, Illinois April 13-16, 1999. p785
500			_aSource Year: 1999
520			_aCrystallization behaviour of natural rubber (NR) prepared by different procedures, such as skim rubber, deproteinized natural rubber (DPNR) and pale crepe, was investigated by dilatometry at -25 C. DPNR was fractionated into four fractions by molecular weight. The high molecular weight fractions contained about 1.5 linked fatty acids per rubber molecule, while low molecular weight fraction contained about 5 fatty avids. The overall crystallization rate of the rubber decreased as the molecular weight decreased. Skim rubbers, purified by extraction with acetone, crystallized rapidly compared to acetone-extracted pale crepe, despite the fact that the molecular weight of skim rubbers was about one-half of pale crepe. The quantity of linked fatty acid per rubber molecule of skim rubbers was less than 0.5, while that of pale crepe was 1.6. The difference in the rate of crystallization was presumed to be associated to the level of fatty acids linked to rubber molecule at the terminal and branch points present in pale crepe. The green strength of skim rubbers was significantly smaller than that of untreated pale crepe and DPNR but was comparable to transesterified DPNR which contains no gel fraction and no linked fatty acids.
650			_aCrystallization
650			_aDPNR
650			_aPale crepe
650			_aSkim rubber
700			_aBronjawat Jariya
700			_aKakubo Takashi
700			_aNishiyama Naoyuki
700			_aTanaka Yasuyuki
856			_uRC&T
942			_cJS
999			_c56599 _d56599