Study On Structure-Property Relationship Of Polyether Grafted Polysiloxane

Polyether grafted polyhydrosiloxane is widely used as defoaming agents, lubricants, softening agents, spinning oil, cosmetic materials and stabilizers for polyurethane foams because of its supreme emulsifying and softening property, wettability, and low surface tension. To investigate the effect of its structure on the performance is of great commercial importance.Firstly, a parameter distribution degree was defined to characterize the microscopic structure of polyhydrosiloxane which is the unit of DH distribution on the polymer chain. Polyhydrosiloxanes were synthesized and the influences of temperature, agitation speed and amount of catalyst on the distribution degree and proportions of polyhydrosiloxane were investigated. Results showed that the process consists of polymerization-equilibrium and distribution-equilibrium of DH and D where the former showed a faster rate. The polymerization equilibrium is achieved in 2-3h while distribution equilibrium is obtained in 6-8h or longer. Distribution degree of DH can be as high as 0.95 which implied nearly random distribution.Secondly, the effects of temperature, amount of catalyst and reaction time on the conversion and graft ratio were studied and the catalytic difference between Speier and Karstedt was studied. Karstedt exhibited a superior catalytic ability over Speier and the optimal conditions were the reaction temperature being 70℃-80℃, the dosage of Karstedt being lOppm and the reaction time being 1h, the conversion of Si-H bond or graft ratio was higher than 96%.Besides, the effect of polyether grafted polyhydrosiloxane structure and composition on surface tension and cloud point was studied. Results showed that crosslinks increased as the polyhydrosiloxane had more Si-H bonds. As the amount of Si-H bond and number of links increased, the surface tension first increased and then decreased. The ability to lower surface tension was crosslinks> grafted products> residual polyethers; the surface tension increased as the distribution degree of polyhydrosiloxane and the graft ratio increased. As the proportion of polyether with higher molecular mass increased, the graft ratio decreased while the cloud point increased.