3.2 添加
填料
PU膠中添加合適的填料可以降低
收縮應(yīng)力和熱應(yīng)力，從而提高其耐熱性。由于聚氨酯中有機(jī)和無機(jī)部分相互作用形成獨(dú)特的界面效應(yīng)和協(xié)同作用，使得這種材料具有更高的熱和氧穩(wěn)定性。按有機(jī)相和無機(jī)相的相互作用關(guān)系可[30]將混合聚氨酯分為2類 ：第1類是有機(jī)與無機(jī)相通過弱鍵如氫鍵、范德華力和靜電力相互作用，另一類則是有機(jī)相和無機(jī)相通過共價(jià)鍵結(jié)合。常用的填料有
纖維（如
玻璃纖維、
云母等）、粉末（如纖維素、二氧化硅、三氧化二
鋁等）、片狀材料（如滑石）、塊狀材料（如重晶石）及納米粒子或功能納米粒子。[31]
Sebastian Clauβ等 在單組分PU膠中加入體積分?jǐn)?shù)30%的白堊，膠接接頭的熱穩(wěn)定性明顯提高。B. S. Kim等[32]分別用疏水和
親水性基團(tuán)改性的2種納米二氧化硅增強(qiáng)UV固化聚氨酯乳液，發(fā)現(xiàn)隨著納米二氧化硅加入量的增[33]加，聚氨酯降解溫度尤其是硬段降解溫度增加。Lee等 研究了水性聚氨酯/粘土納米復(fù)合材料，也發(fā)現(xiàn)體系中含有粘土越多其耐熱性就越高。
4 結(jié)束語
在聚氨酯膠粘劑的制備和使用過程中應(yīng)充分了解其結(jié)構(gòu)與性能的關(guān)系，根據(jù)使用的目的和要求合理進(jìn)行設(shè)計(jì)。目前，開發(fā)新型耐熱聚氨酯膠粘劑，研發(fā)新的合成技術(shù)、新的添加材料以及相應(yīng)機(jī)理研究已成為聚氨酯研究的重點(diǎn)。
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