| Poly (ethylene terephthalate) (PET) is one of the versatile engineering plastics, possessing excellent thermal and mechanical properties. It is semi-crystalline, thermo-plastic polyester with high strength, transparency and safety, which is widely used in textile industry, video and audio tapes, X-ray films, and food packing, especially in beverage bottle. However, with the sharp increasement of the global annually PET production and consumption, tremendous quantities of this material becomes waste. PET creates no direct hazard to the environment, but it causes severe environmental pollution due to its substantial fraction by volume in the waste stream and its high resistance to the atmospheric and biological degradation. PET accounts for 8% by mass and 12% by volume of the world's solid wastes. Development of a feasible recycling process of waste PET can reduce the consumption of oil and develop the recycling economy for sustainable development. Generally, degradation and modification of waste PET are the two main approaches for PET recycling.The ease, speed and flexibility of the microwave method make it ideal for laboratory investigations of polymer degradation reactions that are traditionally cumbersome and slow. In the present work, microwave-enhanced degradation of PET in ethanol/dioxane mixture was carried out at low temperature and atmospheric pressure to recover pure terephthalic acid (TPA) and ethylene glycol (EG), the main two monomers in the industrial production of PET. Factors associated with degradation performance, such as solvents, reaction temperature, microwave power and concentration of NaOH were investigated. Results showed that microwave irradiation could lower the activaton energy of degradation reaction and significantly shorten reaction time and the addition of dioxane improved the degradation efficiency. Degradation rate of PET is up to 93.3% under the conditions of reaction time of 10 min at 70℃, microwave power of 600 W, and the volume ratio of ethanol to dioxane of 4?1. The process presented is economically feasible for its mild reaction conditions, short reaction time and simpleness to recover mononers. The chemical compositions of degradation products, chain cleavage mechanism were also discussed and a simple theoretical model was developed to describe the degradation behaver.Inorganic nanoparticles modified Poly (ethylene terephthalate) (PET) have attracted much attention. However, the homogeneous dispersion of nanoparticles in polymer matrix is very difficult because they are prone to agglomerate and have poor compatibility with polymer. TiO2 was equably dispersed to recycled PET to improve the properties of recycled PET. Results indicated there was a strong hydrogen bond between nano-TiO2 and PET molecular chain. However, the chemical structure of PET did not change. Factors influencing on the intrinsic viscosity of the composite following the content of nano- TiO2, the concentration of PET and the volume ratio of ethanol to water were also investigated.DTA and TGA were used to study the thermal properties of the composite. It revealed that, compared with recycled PET, PET/TiO2 composite exhibited higher glass transition temperature (Tg), quicker crystallization rate, a little lower melting point, and better thermostability. This newly-developed mixing method has the advantages of energy-effcient, simple and efficiency and requires further investigation.
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