| Poly(ethylene terephthalate) is a kind of non-biodegradable polymeric material withexcellent overall performance and large available space. Around the world, the number ofannual consumption of PET is nearly billions of tons and continues to increase to a certainproportion. The resulting pressure of waste on the environment can not be ignored, therefore,waste PET recycling has become one of the focuses of attention of the world. Waste PETrecycling has not only promoted the development of the ecological environment, but alsobrings good economic and social benefits, and has laid a good foundation for the sustainabledevelopment of the PET industry.This paper mainly studied the process conditions that1,4-butanediol depolymerizingwaste PET, purified depolymerization products using distillation under reduced pressure andrecrystallization, analyzed the concrete structures and properties of depolymerization products,and depolymerization products were employed to fabricate polyurethane foam, etc. Thedepolymerization principle is similar to hydrolysis reaction of PET, promotingdepolymerization of the polyester through overheating and numerous hydroxyl groups.According to historical researches, depolymerization catalyst used was zinc acetate,depolymerization process conditions adopted univariate multi-level design optimization. Theoptimum conditions was: the amount of zinc acetate catalyst was0.3%of the mass of PET,depolymerization time was5~6h, depolymerization temperature was190~220℃. And thecomprehensive analysis using liquid chromatography-mass spectrometry (LC-MS), nuclearmagnetic resonance (1HNMR and13CNMR), infrared spectroscopy (FT-IR) demonstrated theproducts were mainly composed of bis(hydroxybutyl) terephthalate with purity of99.12%. Thethermal properties and surface morphologies of products were understood by thermal analysis(DSC and TG). Also, according to the national standard measurement to understand hydroxyland acid value of products. The hydroxyl value measured was358.7mg KOH/g, theoreticalhydroxyl value was361.9mg KOH/g, can be employed to prepare the polyurethane foam bythe products.The depolymerization product that bis(hydroxybutyl) terephthalate possessed thecharacteristics of high hydroxyl value and the low molecular weight. This advantage can beused to prepare the polyurethane foam. According to univariate multi-level optimizationdesign, the effects that using different amounts of stannous octoate catalyst, vesicant waterand polyisocyanate on the properties of polyurethane foam were investigated, respectively.And drawing the best mass ratio: BHBT: polyisocyanate: catalyst: water is9.3~10:10:1.0~1.1:1.0~1.1. Polyisocyanate used in the study was PM200. The structuremorphologies and compression performances of the polyurethane foam were analyzed byinfrared spectroscopy (FT-IR), universal material tester, thermal analysis (DSC and TG), andscanning electron microscopy (SEM). The cell structures of polyurethane foam were nearlycircular, good crosslinked network skeleton, excellent thermal preservation and thermalinsulation performances. Dimensional stability of the foam of resistance to high temperatureand low temperature were both less than1%, which was relatively stable. The density of polyurethane foam was about62.6Kg/m3, the compression strength was400~420KPa,thermal decomposition temperature was258.4℃, both can be applied the generalenvironment.Polyurethane foam is widely used, from the transportation, construction, refrigeration,plumbing, to packaging, acoustic materials and other fields, especially the thermal insulationmaterials for refrigerators, with long service life, and efficient and the obvious advantages ofhighly efficient resource conservation. Polyurethane foam prepared in this study had theadvantages of lightweight, small density, uniformity and good stability of foam, excellentthermal preservation and thermal insulation performances, has a good application prospect. |
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