硅灰石增韧聚合物的界面粘接判据

CRITERION OF INTERFACIAL ADHESION FOR FILLER TOUGHENING POLYOLEFIN COMPOSITES

运用不同的偶联剂处理硅灰石表面，研究界面粘接状况对ＨＤＰＥ／硅灰石复合体系力学性能的影响。得到了超韧的ＨＤＰＥ／硅灰石复合物，缺口冲击强度可达４８０Ｊ／ｍ。引入界面相互作用参数Ｂ对复合体系界面粘接状况进行定量化表征。结果表明，Ｂ值愈大，复合体系的界面粘接愈强，增强效果愈好。并且，与通常认为的增加界面粘接对增韧有利的观点不同，过强的界面粘接对增韧有破坏性的影响，适当的界面粘接才能增韧。这是因为适当的界面粘接可以使复合材料形成高能量吸收的损伤机制。由此，首次给出刚性粒子增韧聚合物的界面条件判据：存在一临界Ｂｃ值，当Ｂ＜Ｂｃ时，复合体系才可能增韧，直至发生脆韧转变，只有同时满足形态条件和界面粘接条件判据，ＨＤＰＥ／硅灰石复合体系才可能同时增强增韧。

HDPE/Wollastonite composites with different coupling agents were prepared by melt blending process, the yielding stress σ yc , fracture strength σ bc , Young′s modulus E c and notched impact strength S Ic of the composites with different volume fraction of filler V f were measured respectively. It has been shown that, for rubber toughened polymers, morphology factors such as dispersed particle size, volume fraction should meet a critical value. As for filler toughening polymers, the interfacial adhesion also plays an important role. Turcsanyi proposed a equation to calculate the interfacial interaction with different surface treatment of fillers, Q = σ yc / σ ym [(1+2.5 V f)/(1- V f)], where σ ym is yielding stress for matrix. By plotting ln Q vs. V f, slopes of these plots determine the interaction parameter B . The results indicated that larger the B value, the stronger interfacial adhesion, and the σ yc , σ bc and E c as well. On the other hand, a suitable B value can achieve the toughening effect, It is obviously that the parameter B could be used as a criterion for evaluation the toughening effect of filled polymers. There is a critical value of B for interface adhesion in composites. When B is smaller than a critical value B c, the S Ic is much higher than that of matrix. On the contrary, when B > B c, the S Ic is much lower than of matrix.