Synthesis And Properties Of Silicone Modified Polyester Resin

Polyester resins, which have high mechanical properties and good solvent resistancy, have been found extensive application in many fields. But they exhibit rather poor thermal stability, which restricts their application very seriously. Silicon resin, which has the double property of inorganic and organic compound and differs from other organic resin, is the extremely important category of organic silicon material. Various modified polyester resins, wherein the polyester resin is copolymerized with the silicon resin, are known and have been proposed for certain interesting application. Because the copolymers combining their advantages have much more excellent thermal stability, high mechanical properties and good solvent resistancy. For example, the product of some silicone-modified polyester resins have been employed for coating application.In this paper, we use hydrolysis-polycondensation method from methyl and phenyl siloxanes and get a new kinds of heat-resistant silicone resins. The factors that affluent the hydrolysis process and property of silicon resin are investigated, such as monomer proportion, raw material adding method, hydrolysis temperature, solvent composition, reaction time and stirring speed, finally we get the best condition. IR analysis shows that the silicone resin possesses hydroxyl end group. The effects of different R/Si ratio of silicone resin on adhension strength to metal was discussed, we find that the R/Si ratio of silicone resin below 1.40 has room curing properties.A novel series of branched saturated polyester resins for coating was synthesized by solution polycondensation method of terephthalic acid, isophthalic acid, adipic acid, neopentyl glycol, diglycol and 1,1,1-tri(hydroxymethyl)propane. The silicone-modified polyester resin was synthesized by the silicone intermediate and branched saturated polyester resin made from carefully selected proper monomers in my own laboratory. The structure, morphology and thermal properties of the modified polyester resins have been characterized by IR, XRD, DSC and TG analysis. IR measurement showed that the silicone resin had chemically graft on to polyester by Si-O-C bond. The XRD patterns of the modified polyester resins through copolymerization with 30 wt% silicone resins show the amorphous states. The modified polyester resins showed high thermal stability as increasing the silicone content. It was found that the silicone modified polyester resins through copolymerization increased the thermal stability more obviously than modified polyester resins through blending. From the DSC curve, we can find that the melting point of modified polyester resins through copolymerization with 30 wt% silicone resins is 294.7℃. It was found that the addition of silicone resins changed the melting point of modified polyester resins.We also investigated surface free energy and water resistance of the silicone modified polyester resins. The surface free energy of the copolymer is calculated through measurement of wetting angles of water and glycerin on the copolymer. The influences of composition of copolymer on the surface free energy and water absorption were discussed. It is concluded that the surface free energy and water absorption of the copolymer are decreased with increasing of silicone content. It was found that the addition of 20wt% silicone composition decreased the surface free energy of modified polyester resins most effectively. As compared to the neat polyester, the surface free energy of modified polyester resins was decreased from 57.1 mN/m to 34.7mN/m due to the enrichment of silicone containing polyester in the surface layer, the enrichment would reach a balance when silicone content exceed 20wt%.