Polyether Modified Polysiloxane Structure Control And Its Structure-activity Relationship Study

Polyether modified polysiloxane is an organosilicone surfactant with excellent performance, so it is widely used in such areas as foam stabilizers for polyurethane foams, cosmetic materials, textiles, antifogging agents, addition agents in plastics, softening agents and so on. Through kinetic experiments about hydrosilylation, the study on the controlling of cross linkage in hydrosilylation and foaming experiment, a systematic research on the mechanism and process in hydrosilylation is studied in this paper, the controlling effect of antioxidants and influence of the structure of the products on foaming abilities are investigated too.The hydrosilylation of polyhydrosiloxane and polyether terminated with ester group is processed with chloroplatinic acid as catalyst and ethyl acetate as solvent to exclude the mass transfer resistance of the system. The kinetic research has been performed by means of Gel Permeation Chromatography (GPC). A kinetic model is built within a certain experimental range, that is,r_p=k₀exp(-Ea/RT)in which, lnk₀=56.52-0.4168 C_cat, Ea= 1.567 ×10⁵-l.285 X10³ C^catThe cross linkage byproduct in hydrosilylation influences the application performance of polyether modified polysiloxane. The paper analyzes the auto-oxidation of polyether and its effect on synthesis of the product. The research is performed by using several antioxidants to pre-treat the polyether and then investigates their effects on controlling the cross linkage. The results show that the effect of propyl gallate (PG) can reduce the content of the cross linkage byproduct remarkably. Also, we obtain the suitable treatment condition of PG: the amount is 2% of polyether (wt), the treatment temperature is 80℃ and the treatment time is lhr.The structure of polyether modified polysiloxane determines its main properties and foaming abilities. The results show the relationship between structure and its performance is as follows: when the molecular weight of polyether is the same, if the value of EO/PO increases, the cloud point increases and when the value of EO/PO is the same, if the molecular weight of polyether increases, the cloud point also increases. When the hydrogen content of hydrogen-contained polysiloxane increases,the cloud point increases. However, the influence of molecular weight is not very obvious. If the molecular weight of hydrogen-contained polysiloxane with the same other factors, its ability in decreasing the surface tension will become poor. The structure of polyether is not very influential on the surface tension. With the same molecular weight of polyether, for the high hydrogen content of polysiloxane, the foaming performance is good when the EO/PO is between 50/50—40/60 and for the low hydrogen content of polysiloxane, the foaming performance is good when the EO/PO is between 50/50—60/40. With the high hydrogen content of polysiloxane (0.2%) and the same EO/PO of polyether, the molecular weight of polyether has little influence on the foaming performance. With the low hydrogen content of polysiloxane (0.1%), taking the EO/PO being 60/40 for example, only polyether of low molecular weight (about 1000), foams better than the others. In general, the higher the hydrogen content of polysiloxane is, better the foaming results are. However, the hydrogen content should be below 0.3%.