Preparation of five-membered bis(cyclic carbonate)s at atmospheric pressure for polyhydroxyurethane coatings

Cyclic carbonates reacted with diamines or polyamines have been proposed as a greener and safer method to prepare free isocyanate polyurethane coatings. Here, five kinds of bis(cyclic carbonate)s (TDC: toluene bis(cyclic carbonate), MDC: 4,4 '-diphenylmethane bis(cyclic carbonate), IPDC: isophorone bis(cyclic carbonate), HMDC: 4,4 '-methylenebis(cyclohexyl cyclic carbonate), HDC: hexamethylene bis(cyclic carbonate)) were prepared by reacting glycerol carbonate with diisocyanate under atmospheric pressure. Their structures were verified by H-1-NMR and C-13-NMR. These difunctional cyclic carbonates were then reacted with several amines to prepare new polyhydroxyurethane (PHU) coatings, and the film properties were tested. It was found that PHUs based on aromatic and alicyclic structures including TDC, MDC, IPDC, and HMDC displayed high hardness but had poor flexibility and impact resistance, whereas PHUs based on aliphatic structures such as HDC exhibited good flexibility and impact resistance and low hardness. When the length of the alkyl groups in the amine curing agents increased, the impact resistance and flexibility of the PHUs increased, but their pencil hardness decreased. PHUs from TDC, MDC, and IPDC had excellent chemical resistance, but the PHUs from HMDC and HDC had less chemical resistance. Some films displayed excellent properties including 4H pencil hardness, 100 cm kg impact resistance, and excellent flexibility. Some PHUs exhibited good thermal stability, with T-5% values all above 242 degrees C. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47957.