端乙烯基硅油的制备及流变特性研究

Preparation and Rheology Characterization of Vinyl-ended Polydimethylsiloxane

以八甲基环四硅氧烷(D4)、二乙烯基四甲基二硅氧烷(亦称乙烯基双封头)为原料,氢氧化钾碱胶为催化剂,采用开环聚合反应制备端乙烯基硅油。考察了聚合温度、聚合时间、物料配比等对单体转化率的影响。结果表明,聚合温度和时间对D4转化率的影响不显著,但对乙烯基双封头的转化率影响显著,随着温度由130℃提高到150℃,乙烯基双封头的转化率由54.62%升高至86.73%;随着聚合时间由3 h延长至6 h,乙烯基双封头的转化率由52.87%升高至86.02%。最佳聚合温度为150℃、聚合时间为6 h。采用旋转黏度计研究端乙烯硅油的黏度随剪切速率的变化。端乙烯基硅油为胀流性流体,其流动规律满足通式ηa=Krn-1。

The vinyl-ended polydimethylsiloxane was synthesized by ring-opening polymerization with oc- tamethylcyclotetrasiloxane （D4 ） as raw material and 1,3-divinyhetramethylsiloxane as the capping agent and potassium hydroxide as the catalyst. The effect of the polymerization temperature and duration, the ratio of raw materials on the reaction of the monomers were investigated. The results showed that the temperature and duration had no significant effect on the conversion rate of the D4 but they had strong impact on the conversion rate of 1, 3-divinyhetramethylsiloxane. The conversion rate of divinyhetramethylsiloxane increased from 54.62% to 86. 73% with the temperature rising from 130℃ to 150℃. The conversion rate of divinyhetramethylsiloxane increased from 52. 87% to 86.02% as the polymerization time was extended from 3 hours to 6 hours. The optimal polymerization conditions were 6 hours at 150 o C. The rheology characterization of the vinyl-ended polydimethylsiloxane was tested by a digital rotational viscometer. The vinyl-ended polydimethylsiloxane was a dilatant fluid and its rheology characterization matched with the general formula ηa= Krn-1.