纳米二氧化硅诱导聚氨酯弹性体结晶行为的研究

Nano-silica Induced Crystallization in Polyurethane Elastomers

使用溶剂共混法制备了热塑性聚氨酯弹性体/纳米二氧化硅复合材料,采用多种实验技术阐明了纳米二氧化硅诱导聚氨酯弹性体中软段结晶的微观机理.TEM表明纳米二氧化硅在聚氨酯弹性体中有很好的分散性,DSC实验发现高温退火后等温结晶处理的聚氨酯纳米复合材料中软段的结晶性和玻璃化转变温度显著提高,纳米二氧化硅的加入量影响玻璃化转变温度和熔融焓最终的平衡值以及它们的增长速率.固体NMR实验发现退火后复合材料中的软段分子运动受到限制,而硬段的链运动明显提高.上述实验结果表明硬段链间的氢键在高温下被破坏,在退火过程中纳米二氧化硅与硬段间的相互作用使得硬段链运动增强,进而促进了与硬段相连的软段结晶能力的提高.基于实验结果建立了聚氨酯/无机纳米复合材料在高温退火和低温等温结晶处理下微观结构和动力学演化的物理模型.

Polyurethane/silica nanocomposites were prepared by solution mixing procedure, and the effect of nano-siliea on the crystalline behavior in these nanocomposites was investigated by a variety of techniques. TEM results indicate that nano-silica is well dispersed in the polyurethane matrix. It is found from the DSC experiments that the crystallization of soft segments are obviously enhanced after annealing at high temperature and subsequent isothermal crystallization at 10 ~C ,the addition of nano-siliea affects the final glass transition temperature and the crystallinity of soft segments, as well as the rate of increment. Solid-state NMR analyses reveal that the mobility of soft segments is is restricted after annealing, while the mobility of hard segments obviously enhanced. The above results reveal that the interehain hydrogen bonding among hard segments is broken at high temperatures, and the increased interaction of hard segments and nano-silica results in the high mobility of hard segments, thus promoting the crystalline ability of the soft segments connected with hard segments. On the basis of the above results, a suggested model concerning the evolution of structure and dynamics in polyurethane nanoeomposites under high-temperature annealing and subsequent isothermal crystallization is proposed.