Synthesis of elastomeric polyester and physical properties of polyester coating for automotive pre-primed system

摘要

An automotive pre-primed system has been investigated to remove wash and pre-treatment processes using a roll coating application for environmental regulations. However, automotive pre-primed sheets must have high flexibility and formability to overcome harsh conditions such as cutting, press and stamping processes. For these reasons, elastomeric polyester resins were designed to improve flexibility and formability in terms of high molecular weight, low crosslink density and content of flexible segment. The curing, viscoelastic behavior, flexibility, formability and physical properties of resins were measured to evaluate suitability of the synthesized primers for an automotive pre-primed system. Regarding the curing and viscoelastic behavior, CE-PE-I and III have good stiffness and elasticity due to the high molecular weight and crosslink density comparing CE-PE-II which was designed for low crosslink density. In terms of the tan δ result, T _g of primers was similar to each other, thus surface hardness of CE-PE series was around 120-140 s. For tensile results, CE-PE-I and III have good tensile strength and elongation values. From the result of drawing, no defects were observed at the side of all drawn samples after 48 mm drawing. However, the side of drawn cup was tone, excepting that of CE-PE-I after 57 mm drawing. Consequently, high molecular weight and the content of flexible segment are powerful factors affecting the formability for an automotive pre-primed system.