Synthesis And Properties Of The Unsaturated Polyester Polyurethane With Lateral Double Bonds

Unsaturated polyester polyurethane coating has been widely used in automobile industry, chemical equipment protection, decoration construction and other fields for the high wearability, excellent corrosion resistance, high decorative property. Single polyurethane coatings exist the problems of tide foaming, paint film pulverization, and so on. Meanwhile, containing btex makes the coating yellow.The low viscosity of unsaturated polyesters are the advantages of easy processing and preparation, and easily biodegradable polymer, so the synthesis of unsaturated polyester was applied to PU, in order to enhance the mechanical properties of the polyurethane, chemical resistance, heat resistance, et al.Polyester-poly(butyene itaconate)(PBI) was prepared using itaconic acid as raw material by a new method; This was to introduce the unsaturated polyester of PBI to polyurethane, and synthesis of new polyurethane molecular chains contained unsaturated polyester links. Moreover, the preparation process of the unsaturated polyurethane was studied. Preparation of polyurethane coatings combined the advantages of the unsaturated polyester and polyurethane that could improve the polyurethane coatings of hardness, adhesion, impact strength, heat resistance and other properties.The traditional way of PBI synthesis was method one(direct esterificationpolycondensation). Based on itaconic acid, a new method synthesis of PBI – method two was studied in this paper. Synthesis of PBI by mehod one and method two were characterized using FT-IR, GPC to analyze the individual product of chemical structure.Acid value, intrinsic viscosity, relative molecular mass and distribution were estimated to determine the best synthesis method. Results showed that:The acid value of PBI in the two methods of synthesis all decreased, but the acid value of method two of synthetic products was 39.61 mgKOH/g, and the hydroxylvalue of method two was 116.48 mgKOH/g. With method two in intrinsic viscosity field, intrinsic viscosity of polyester product was [η]= 6.6973 mL/g, which intrinsic viscosity of the synthesis of PBI product was of low viscosity, more easy to dissolve in the solvent. In terms of molecular weight and molecular weight distribution, method two of synthetic products ’molecular weight were Mn = 2559, which molecular weight distribution coefficient is 1.568, so method two of synthesis of PBI were more concentrated distribution of molecular weight. In conclusion, the preparation of PBI is the best way to method two.Prepolymer as the synthesis of two-component polyurethane was one of the most important components of polyurethane. Study the TDI-TMP prepolymers synthesis conditions, such as the performed reaction temperature, reaction time and catalyst, and how these factors effect on the NCO content and the reaction of the performed,combining with FT-IR characterization of TDI-TMP prepolymers. Results showed that:under the condition of nitrogen, with DBTDL as a catalyst and catalyst dosage of 0.8%,the reaction best temperature in 70 ℃for 2 h, the synthesis of TDI- TMP polyurethane pre polymers of free NCO content was to 4.54% in the system.TDI-TMP prepolymers with unsaturated polyester glycol were mixed that using PBI as polyurethane soft segment, TDI-TMP prepolymers as hard segment, which proportionally mixed to preparation of the unsaturated polyester polyurethane. The paper used FT-IR to characterize the films of un-curing chemical structure, analyzed the effect of content of itaconic acid, the dosage of PBI, dosage of initiator and different polyols on the properties of curing coating. And the characteristic method of DSC analyzed the cured coating thermal property. Results showed that:The PBI of being the application in polyurethane, were prepared by itaconic acid and when the mass of IA accounting for the percentage of mixed acid(IA and SA)was100%, the synthesis of unsaturated polyester polyurethane’s properties such as hardness, adhesion and impact strength were optimum. In TDI- TMP pre polymers mixing with PBI,when the mixture ratio was 0.5, and benzoyl peroxide initiator dosage was 0.8%, the pencil hardness of the coatings was at 6H + 1750 g and adhesion was A grade. With impact strength up to 50 cm, the glass transition temperature was Tg= 134.9 ℃ in heat resistance.