EFFECT OF SOFT SEGMENT MOLECULAR-WEIGHT AND 3-METHYL SIDE GROUP ON MICROSTRUCTURAL SEPARATION IN POLYURETHANE ELASTOMERS

被引:30
作者
CHEN, WP
FRISCH, KC
KENNEY, DJ
WONG, SW
机构
[1] UNIV DETROIT,DEPT CHEM,DETROIT,MI 48221
[2] DUPONT CO,DEPT CHEM & PIGMENTS,WILMINGTON,DE 19898
[3] UNIV DETROIT,INST POLYMER,DETROIT,MI 48221
来源
JOURNAL OF MACROMOLECULAR SCIENCE-PURE AND APPLIED CHEMISTRY | 1992年 / 29卷 / 07期
关键词
D O I
10.1080/10101329208052183
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The object of this study was to assess the effect of the chain length and of the pendant 3-methyl side group in the soft segment of polyurethane (PU) elastomers. In addition, the effect of annealing-quenching on the degree of microstructural segregation between the hard and soft segments was also investigated. The study employed electron spin resonance (ESR), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Samples for ESR measurements were spin-labeled with the nitroxide probe, 4-hydroxy-2,2',6,6'-piperidine-1-oxyl (TEMPOL), by reaction of an isocyanate group with the hydroxyl group of TEMPOL. The nitroxide label is therefore located at a chain end. The PU's were based on 4,4'-diphenylmethane diisocyanate (MDI), poly(oxytetramethylene) glycols (PTMO), and hydroxyl-terminated random copolymers of tetrahydrofuran and 3-methyl-tetrahydrofuran (THF/Me-THF). Purified 1,4-butanediol (BD) was used as a chain extender. The elastomers made from higher molecular weight (MW) soft segments have better phase segregation than their lower MW counterparts. The 3-methyl side groups on the PTMO backbone have some effect on the arrangements of the two domains. ESR analysis indicated that the increase in the MW of THF/Me-THF decreased the degree of mixing between the hard and soft segments. In PU elastomers made from high MW soft segments, the presence of crystallinity was observed from the DSC measurements. The crystallinity of the soft segments was disrupted by the existence of the 3-methyl side groups.
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页码:567 / 587
页数:21
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