加成型液体硅橡胶的流动性及结构性能的研究

采用两种二氧化硅粒子填充α,ω-双乙烯基聚二甲基硅氧烷,以含氢聚硅氧烷作为交联剂,在铂催化剂作用下固化得到了加成型液体硅橡胶材料,对其流动性和力学性能进行了研究。结果发现,液体硅橡胶的粘度随着双乙烯基聚二甲基硅氧烷分子量增大而逐渐增加,在超过临界分子量时粘度迅速升高,液体硅橡胶的力学强度在分子量28000~35000时出现极大值。随着动态扫描频率的升高,液体硅橡胶的动态粘度减小,储能模量和损耗模量增加。疏水气相法二氧化硅对聚二甲基硅氧烷的增稠效应大于沉淀法二氧化硅,粘度对温度的敏感性要小,在硅橡胶中的分散较为均匀、补强效果优于沉淀法二氧化硅,但可填充体积分数小。含氢硅油交联剂的含氢量在0.4%~0.8%,A 值(Si-H/Si-CH=CH 2比)接近1.1时,液体硅橡胶的力学性能较优。

Study of the Rheology and Structure Properties of Addition-cured Liquid Silicone Rubber

α,ω-divinyl polydimethylsiloxane was filled by two kinds of silica,and was subsequently cured by ac-tive hydrogen-containing polysiloxane,catalyzed by the platinum complexes.And then the vulcanized LSR materials were obtained.It was found that,with the increase of polydimethylsiloxane molecule weight,the viscosity of liquid silicone rubber grew gradually,and then was shot up while above the critical MW.The mechanical properties reached to maximum point in the MW 28000-35000.With the increase of frequency of dynamic rheological measurement,its storage and loss modulus increased while its viscosity decreased.In contrast to the precipitated silica,the hydrophobic fumed silica had greater thickening effects on liquid polydimethylsiloxane,smaller thermal sensitivity to viscosity,bet-ter dispersion and stronger enforcing effect,but less permitted volume fraction for loading.While the active-hydrogen mass percentage was between 0.4-0.8,and the A value (i.e.SiH/Si-CH=CH 2 ratio)was near 1.1,the mechanical properties of the addition-curable liquid rubber performed well.