A series of bis(oxo/thioxothiazolinyl) aromatic atropisomers with two chiral C(aryl)-N(heterocycle) axes was synthesized. The separation of antiparallel, parallel diastereomers was achieved by chromatography on silica. Conformationalassignment for the bis-thione atropisomers 1a,b-4a,b and bis-one atropisomers 9a,b-12a,b was based on polarimetric results in analytical chiral chromatography on microcrystalline
Postcure treatment for reaction injection molded polyurethanes
申请人:——
公开号:US20010041754A1
公开(公告)日:2001-11-15
A method of treating reaction injection molded polyurethane, polyurethane/urea and polyurea polymers comprising exposing a reaction injection molded polyurethane, polyurethane/urea or polyurea polymer to an amount of infrared energy sufficient to increase the temperature of the polymer to at least 180° C., and then maintaining the temperature of the polymer at or above that temperature, for a time sufficient to increase the Gardner impact property, as measured using ASTMD-3029, when compared to the same polymer which has been heated to the same temperature and maintained thereat for the same time in a convection oven. The invention produces marked improvements in impact, heat sag and heat distortion temperature properties, and thus is particularly suited to rapid preparation of parts using a mass production conveyor and is particularly well-suited to preparation of parts which are to be subjected to later high temperature processes, such as the “E-coat” process.