Block copolymers composed of poly (oxytetramethylene) glycol (PTMG) and poly (butylene terephthalate) (PBT) were prepared and the effect of PTMG molecular weight on the properties of block copolymer was evaluated. The ability of various antioxidants to provide stabilization of prepared block copolymer against thermooxidative degradation was also investigated.
For the polycondensation reaction the optimum temperature was 250℃ and optimum reaction time was 3 hrs with 0.1% level of magnesium acetate and titanium tetrabutoxide.
Effect of antioxidants on thermo-oxidative degradation was examined by isothermal thermogravimetric method and by ovenaging test. Change in tensile strength and elongation were followed after oven-aging for certain time intervals. Antioxidants of aromatic amine type were found to be most effective among various types of antioxidants such as phosphorous, sulfur and phenol derivatives. Synergistic effect was observed when some phenolic antioxidants were mixed with phosphorous compounds. Very effective stabilization was obtained by combination of preventive antioxidants with chain-breaking antioxidants.
Tensile strength, elongation and melting point were found to increase with the increase in PTMG molecular weight, but glass transition temperature and Young's modulus were rather decreased.