At present, there are two main methods to prepare silicone modified polyester resin: physical blending method and chemical copolymerization method. In general, the properties of chemically modified resins are superior to those of physically modified resins.
Physical blending is the physical blending of polyester resin and silicone resin. The physical blending method can be divided into simple blending method and adding the third phase blending method.
Simple blending method is to directly mix polyester resin and silicone resin to improve the heat resistance and weather resistance of polyester resin; However, due to the poor compatibility between silicone resin and polyester resin, the silicone resin will overflow and enrich on the surface, resulting in microphase separation, which affects the hardness, stability and mechanical properties of the modified resin.
To solve the problem of poor compatibility between silicone resin and polyester resin, a third phase can be added. That is, a third compound, such as silane coupling agent, is added to the mixed system of silicone resin and polyester resin. Since the solubility parameters of silane coupling agent are close to those of silicone resin and polyester resin, they can be used as intermediate phase to combine them, thus increasing their compatibility and enhancing the stability of the blend system.
A.Fustin et al. used siloxane prepolymers containing terminated vinyl groups to blend with polybutylene terephthalate in the molten state, and found that they had good compatibility at high temperature, and could be copolymerized in the presence of a catalyst to form silicone/polyester thermoplastic elastomer.