IMPROVEMENT IN WEATHERABILITY OF TRANSPARENT PLASTICS BY SOL-GEL COATING WITH UV ABSORBER AND HALS

摘要

Almost UV-protective coating films have been prepared by simple addition of UV absorber (UVA) into the sol-gel network, which results in the blooming of UVA and lowers mechanical properties of films. In this study, to prohibit the blooming of UVA, we introduced siloxane bonds between modified benzophenone (MBP) obtained from the urethane reaction of 2, 2, 4, 4-tetrahydroxy benzophenone (THBP) with isocyanato propyl triethoxy silane and silane precursors into sol-gel network by hydrolysis and condensation reaction. Also, to improve UV absorption ability, we introduced hindered amine light stabilizers (HALS) as radical scavenger. Silica-gel coating films were prepared by methyl triethoxy silane (MTES), colloidal silica, and UV stabilizers. They were deposited on polycarbonate (PC) substrates by the sol-gel method for preventing their photodegradation. The combination of two different UV stabilizers improved UV stabilization ability. The UVA lifetime was related to not only the quantity of HALS but also the degree of chemical bonding and compatibility between sol-gel network and UV stabilizers.