Preparation And Properties Of Novel Cyclic Carbonate And PHU Materials

Traditional polyurethane does not meet the requirements of environmental protection because of the use of toxic isocyanate compounds.Cyclic carbonate can react with organic polyamines to form carbamate bonds,which can be used to prepare new isocyanate-free polyurethane materials?PHU?.The present cyclic carbonate preparation usually requires the epoxy groups reaction with carbon dioxide under high pressure,and the process is complex and unsafe.In this paper,a variety of cyclic carbonates and PHU resins were prepared under atmospheric pressure.The structures and properties of the products were characterized,and the regulations of synthesis process on the properties of PHU were studied.?1?Five kinds of difunctional cyclic carbonate were synthesized by the reaction of diisocyanate and glycerol carbonate?GC?under atmospheric pressure.The products were colorless or yellow transparent solids.The purity of the products was higher than 95%determined by ¹H NMR.The optimum reaction conditions were obtained as follows:reaction temperature was 25-35?,catalyst addition was 0.2%,and raw material molar ratio of-OH to-NCO was 1.1:1.PHU coatings were prepared by reaction of difunctional cyclic carbonates with polyamines.The influence factors on the mechanical properties,chemical resistance and thermal stability of PHU were studied.It was found that the longer the chain segment of small molecular diamines was,the lower the hardness and the better the flexibility of the product were.The PHU coatings with high perfermance could be obtained by optimizing the structure of polyamines,which made the glass transition temperature of the coatings higher than 50?,the hardness is high up to 4H,the impact resistance is 95 kg·cm and its flexility is less than 2mm.TGA analysis showed that the PHU coating made by cyclic carbonate and PEI had good thermal stability,and its T_5%ranged from 242 to 276?.?2?Bio-based polycarboxylic acids were prepared by semi-esterification of succinic anhydride with glycerol,erythritol,xylitol and sorbitol,respectively.The optimum reaction conditions were obtained as follows:reaction temperature was 120?,reaction time was 6 h,ethyl acetate as a solvent,0.1%of DMAP as a catalyst.Biobased polyfunctional cyclic carbonate was synthesized by the reaction of bio-based polycarboxylic acid with glycerol carbonate.The optimum reaction conditions were as follows:reaction temperature 140?,catalyst addition was 3%;GC addition was 1.2 times of carboxyl content.The product spectra showed that the high temperature preparation method was feasible.The biobased polyfunctional cyclic carbonate was reacted with organic amines to prepare PHU material.It was found that the HMDA-cured PHU material had good performance.The hardness of HMDA-cured PHU film was HB,impact resistance was 100 kg·cm and flexibility was grade1.The hardness of IPDA-cured PHU film was high upto 2H.The curing products of four kinds of cyclic carbonate have good chemical resistance,their water absorption was less than20%,and toluene absorption was less than 0.5%.The four kinds of cyclic carbonates coatings also had good thermal stability,and their T_5%was above 235?.