Studies on Multiple Unsaturated Poly(urethane-ester) Containing Epoxy Residues

Abstract

The epoxy resins are used in a large number of fields, including surface coatings, in adhesives, reinforced with carbon fiber. The polyesters are most widely versatile materials and have broad spectrum of characteristics and wide applications ranging from aerospace to micro electronics. They are also important as laminating resins, molding composites, fibers, films, surface coating resins, fiber cushion. Polyurethanes are widely used in high resiliency flexible foam seating, rigid foam insulation panels, microcellular foam seals and gaskets, durable elastomeric wheels and tires, automotive suspension bushings, electrical potting compounds, high performance adhesives and sealants, Spandex fibers, seals, gaskets, carpet underlay, and hard plastic parts (such as for electronic instruments). Merging of all the four unsaturation, epoxy, ester and urethane segments into one polymer chain has not received attention academically and technically. Certain properties of thermoplastics may also be improved via blending or addition to an unsaturated resin is another possibility. In order to improve certain properties of such reported polymers their blending with commercial vinyl esters (epoxy resin) such as vinyl ester epoxy resin may afford a commercially important material for wide industrial applications. Hence the present report comprises synthesis of poly (urethane-ester) having epoxy residues. Unsaturated polyesters were successfully synthesized using different aromatic diamines and diglycidyether of bisphenols. Unsaturated polyesters, vinyl ester and hexamethylene diisocyanates used for the production of unsaturated poly(urethane-ester). All the produced polymer systems have been characterized by following techniques: The C, H, and N contents were estimated by means of Thermofinagan 1101 flash elemental analyzer (Italy). The IR spectra were recorded in KBr pellets on a Nicollet 760 D spectrometer. The number average weights were estimated by non-aqueous conductometric titration followed by the method reported in the literature. Pyridine was used as a solvent and vi tetra-n-butyl ammonium hydroxide was used as a titrant. Curing of all blends was carried out on a differential scanning calorimeter (DSC) by using benzoyl peroxide as a catalyst. A universal V3 gTA DSC was used for this study. Unreinforced cured samples of blends were subjected to thermogravimetric analysis (TGA) on Du Pont 950 thermo gravimetric analyzer. The Flexural strength, Compressive strength, Impact strength, Rockwell hardness, Electrical strength was measured according to ASTM standards. The values of C, H, N of each of the unsaturated polyesters and acrylated unsaturated polyesters were consistent with their predicted structures. The number average molecular weight of acrylated unsaturated polyesters were estimated by nonaqueous conductometric titration method and vapor pressure osmometric method. The results indicate that the degree of polymerization is about 6. The IR spectra were consistent with the ones expected from the structures of the unsaturated polyesters and poly(urethane-ester)s.The TGA data of all PUEs reveals that decomposition starts around 290C, depending on the nature of the polymers. The rate of decomposition increases by increasing the temperature and it is the fastest between 400 C and 550 C. It was observed that the weight loss is completed beyond 760 C. The results show that composites have good chemical resistant property, good mechanical and electrical strength. The results of these novel poly(Urethane-ester) resins suggest that these resins can be competitors to commercial unsaturated polyester resins.