原位聚合法制备纳米二氧化硅/聚氨酯复合树脂

Preparation of Polyurethane/nanosilica Composites via in situ Polymerization

采用高压剪切分散(HPSH)的方法先将纳米SiO2分散在合成聚氨酯原料中,再应用原位聚合的方法制备了纳米SiO2/聚氨酯复合树脂。用热重分析、动态机械热分析(DMTA)和扫描电子显微镜等测试技术研究了纳米SiO2的用量及其分散方法对聚氨酯树脂的热稳定和力学性能的影响。结果表明,二苯甲基二异氰酸酯(MDI)中的—NCO和纳米SiO2表面的—OH发生了化学反应,SiO2表面的包覆率约为7%;通过高压剪切分散的方法能够使纳米SiO2在聚氨酯基体中均匀的分散开来,粒径为30～40 nm,而超声处理的纳米SiO2会聚集约为200 nm聚集体。当SiO2的添加质量分数为3%时复合树脂(HPSH处理SiO2)的拉伸强度和断裂伸长率均达到最大值,分别为84.3 MPa和438.7%。此外,与纯树脂相比,复合树脂(4%纳米SiO2)的Tg、Td和T-50%分别增加了17.2、9和21℃。

The preparation of nanosilica /polyurethane composites via in situ polymerization is reported.Nanosilica particles were first dispersed into polymer diols by high pressure shearing homogenizer（HPSH）,then polymerization was carried out with the addition of the 4,4＇-diphenylmethane diisocyanate（MDI） and the polymer diols containing ethylene glycol（EG） as the chain extender.Effects of the nanosilica content and dispersion method on the thermal and mechanical properties of nanosilica / polyurethane composites were investigated by thermogravimetric analysis（TGA）,scanning electron microscopy（SEM）,and dynamic mechanical thermal analysis（DMTA）.The results indicated that the —NCO groups in reaction mixture had reacted with the hydroxy on the surface of nanosilica particles during the in situ polymerization,and the chemical encapsulating ratio of the surface for nanosilica was 7%.Nanosilica particles（HPSH treated） in the nanocomposites were homogenously dispersed in the polyurethane matrix at the size of 30 ～ 40 nm,while the nanosilica treated by ultrasonic method aggregated so seriously that the diameter of the agglomerate size reached about 200 nm.Meanwhile,the tensile strength and elongation of the nanocomposites（HPSH treated） increased with increasing the nanosilica mass fraction（ 3%）.When the mass fraction of silica was 3%,the tensile strength and enlongation reached the maximal values,and were 84.3 MPa and 438.7% respectively.Moreover,the polyurethane / nanosilica composites（HPSH treated） obtained by in situ polymerization had better thermal stability than pure polyurethane resins.Compared with the pure PU,the Tg,Td and T-50% of the nanocomposites samples（4% nanosilica） were increased by 17.2,9 and 21 ℃,respectively.