Study On PET Degradation And Green Modification

With excellent mechanical properties,abrasion resistance,thermal stability and dimensional stability,Polyethylene terephthalate(PET)has been widely used in traditional textile fibers,films and polyester bottles.However,due to the wide range of PET production,the waste of product made of PET also increased year by year.Holding a good thermal stability,the natural state of PET complete degradation takes decades,resulting in a very serious environmental pollution and waste lots of resources.PET molecular structure have many in common with the styrene-butyl acrylate resin(referred to as toner resin)in market.According to the relevant performance requirements of styrene-acrylic resin,study on the modification of waste PET bottles is made in this paper.The degradation of PET was carried out by using zinc acetate-glycerol to reduce its molecular weight.Then,the transesterification reaction was carried out with PBT to destroy the molecular chain regularity.The PMMA was used to carry out transesterification reaction on its molecular chain.The results of the molecular weight,transesterification reaction,crystallization performance and thermal stability of the composites are showed by means of Ubbelohde viscometer,rotary rheometer,differential scanning calorimeter,X-ray diffractometer thermogravimetric analyzer and so on.The result show that:(1)The addition of glycerol resulted in the appearance of the ternary ring ether structure on the PET molecular chain.When the content of glycerol was 2%,the molecular weight of the PET bottle was reduced to 5022,the melt viscosity decreased,the bright spot of the polarized light microscope became small and sparse,and the grain size measured by XRD was decreased significantly.The crystallization decreased to21.48% and the thermal decomposition temperature decreased from 406.6 ℃ to 393.5℃.(2)With the melt blending of PBT and PET,the sample melt viscosity first increase and stabilized after 15 min reaction through the rheological test.When the PBT content is 10%,the melt viscosity of the sample is the highest,the crystallization decreases obviously,the crystallinity measured by DSC decreases to 12.42%,the bright spot of the polarized light microscope is extremely rare,the change of the grain size measured by XRD is not obvious,The thermal decomposition temperature dropped to 390.1℃.(3)The melt viscosity of the sample was gradually increased after the PMMA and PET ester exchange reaction was observed by using a rotary rheometer.It was observed that PMMA was grafted into the PET by transesterification reaction.When the content of PMMA is 10%,the crystal morphology of the sample is extremely sparse under the polarizing microscope,the grain size change is not obvious,the crystallization rate decreases significantly,the crystallinity is 14.18%,and the thermal decomposition temperature is reduced to 385.34 ℃.