一步法(将EVA、EVM、oMMT、过氧化物等各组分熔融共混一步动态硫化)制备的热塑性弹性体(TPV)复合材料中橡胶相(EVM相)相区尺寸为1~2 m
蒙脱土选择性的分散在橡胶相中
但剥离程度较低;与此对应
两步法(即先将EVA/EVM进行动态硫化制备热塑性弹性体
再将该动态硫化胶与oMMT熔融共混)制备的复合材料中蒙脱土在橡胶相中高度剥离
且含有蒙脱土的橡胶相尺寸仅为几百纳米.材料性能研究表明
两步法制备所得TPV复合材料具有更高的拉伸强度、拉伸模量和断裂伸长率.此外
两步法制备的复合材料还具有优异的热稳定性和显著提高的阻燃性能.
Abstract
The composites based on the EVA/EVM thermoplastic vulcanizates and organoclay have been fabricated by two different strategies:(1) One-step fabrication by directly dynamically vulcanizing the EVA/EVM blends with organoclay using a peroxide; (2) Two-step fabrication by first preparing the TPV by dynamic vulcanization followed by melt mixing with organoclay. The structure and properties of the composites have been investigated. Organoclay was selectively located in the crosslinked EVM phase for all the samples by the two strategies. However
it was found that the composites fabricated by the two-step strategy have much smaller phase size and the organocaly shows much higher exfoliation efficiency than those fabricated by one-step strategy. It was further found that the composites fabricated by the two-step strategy exhibit much better physical properties than those by one-step strategy. The tensile strength and elongation at break are 15. 5 MPa and 856% for the two-step fabricated sample with 5% organoclay
respectively
as compared with 9. 1 MPa and 423% for the one-step fabricated sample. Moreover
the limit oxygen index (LOI) of the two-step fabricated samples is also higher than that of the one-step fabricated sample.