Synthesis Of Silicon Propyl Ester Modified Polyester Resin And Its Application In Powder Coatings

As a result of its advantages of no solvent pollution,superior performance and less consumption,powder coatings are widely used in household appliances,pipeline anticorrosion,and automobiles.Among them,polyester powder coatings account for more than half of the powder coatings market.But with the increasingly severe global environment,polyester powder coatings are also exposed to insufficient weather resistance.Acrylic powder coatings have excellent hydrolysis resistance and weather resistance,but poor mechanical properties.In this paper,a modified polyester powder coating with excellent properties was prepared by graft copolymerization of silicon propyl ester and carboxyl-terminated polyester resin.The main research results are as follows:Using neopentyl glycol and terephthalic acid as the main monomers,a carboxyl-terminated polyester resin was synthesized and the synthesis process were studied.The results showed that the alkyd ratio R₁ was 1.105,R₂ was 1.056,and the holding temperature was 230-250?,holding time was 3-5h,evacuation time was 90-120min,the synthesized carboxyl-terminated polyester resin has better performance;The structure and properties of carboxyl-terminated polyester resin were characterized by FT-IR,GPC,DSC,TGA,XRD,the results reveal that the T_g of the carboxyl-terminated polyester resin was58.75°C,and the polyester powder coating will not agglomerate when stored;The synthesized carboxyl-terminated polyester resin only began to degrade when the temperature was 352°C,the maximum degradation temperature was 475°C,and the thermal stability was excellent.The influence of glycol structure on the performance of polyester powder coatings were studied.Using?meth?acrylate monomers and vinyltrimethoxysilane as the main raw materials,a hydroxysilyl acrylate prepolymer was synthesized and its process conditions were studied.The results indicated that the best process were:the reaction temperature was 130°C,the amount of initiator was 3.0%,the amount of chain transfer agent was 1.5%,the amount of solvent xylene was 80%,the amount of vinyltrimethoxysilane monomer was 2.5%,the synthesized silicon propyl ester prepolymer has better performance;The structure and properties of the silicon propyl ester prepolymer were characterized by FT-IR,GPC,DSC,TGA and other test methods.The glass transition temperature of the silicon propyl ester prepolymer was 59.60?,which was basically the same as the carboxyl-terminated polyester resin.,and the synthesized silicon propyl ester prepolymer had basically no thermal degradation before 300?,and 300?-400?was a fast degradation zone,and the thermal stability was excellent.The self-made carboxyl-terminated polyester resin and silicon propyl ester prepolymer were grafted and prepared into powder coatings.The self-made carboxyl-terminated polyester resin,silicone propyl ester modified polyester resin,and cold-splitting resin were compared.The results indicated that the silicone propyl ester modified polyester resin has better weather resistance.The effects of filler dosage,antioxidant dosage,and curing accelerator dosage on the capability of powder coatings were studied.The results showed that when the amount of precipitated barium sulfate was 15%-20%,the antioxidant dosage was 0.24%,and the curing accelerator dosage was 0.04%,the coating has the best performance.The effects of different PE/PA ratios on aging resistance were studied.The results showed that with the PE ratio addition,the weather resistance of the coating plus accordingly.When the PE/PA ratio was 6:1,the coating performance is relatively good..