Silicone Modified Polyesters Vulcanizable at Room Temperature for Anti-corrosion Coatings on Tinplate

Abstract

Trimethoxysilyl Polyester (TMOS-PET) was prepared via hydrosilylation of trimethylsilane with acryl-terminated polyester. Copolymerization of TMOS-PET with trimethylmethoxysilane, tetramethoxysilane, and/or dimethyldimethoxysilane give silicone modified polyesters (Si-PET) containing =(SiO₂)=, −(CH₃SiO_3/2)=, and/or −((CH₃)₂SiO)- units. Coatings from Si-PET were formed on tinplate surface via room temperature vulcanization with applicable curing time (the quickest tact free time and completely drying time are 2 h and 15 h, respectively). Mechanical properties, thermal stability, chemical resistance, and anti-corrosion of coatings were detected. Although the flexibility of the coatings were lowered by =(SiO₂)= and -(CH₃SiO_3/2)= units, adhesion and thermal stability of coatings were both improved. On the contrary, (CH₃)₂SiO- units seem to improve the flexibility, while decrease the adhesive force for less crosslink points. Generally, the silicone modified polyesters act as an effective shielding for tinplate. According to electrochemical impedance spectroscopy (EIS), the electric resistance of coatings (Rc) were improved about 25 times and open circuit potential (OCP) increased about 0.10 V compared to the control. The chemical resistance and anti-corrosion of the coatings were decreased slightly after =(SiO₂)= and -(CH₃SiO_3/2)= units were added, but they could be greatly improved by -(CH₃SiO_3/2)= units. Specially, after adding -(CH₃SiO_3/2)= units, coatings give doubled Rc, and its OCP is about 0.20 V higher than the control.

Keywords

silicone modified polyester / coatings / electrochemical impedance spectroscopy / mechanical property / thermal stability

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