Macrowave Depolymerization Of Polyethylene Terephthalate In Pure Water-A Study On Method

Recently with the rapid incresing of the PET polyester consumption in the world, fibreand waste plastic were continuously increasing. It is the key technology for polyesterindustry continuance development that developping on polyester recovery technology anddisposalling of polyester abandoned.. At present, the methods used to recovery PET polyesterare hydrolyzation, alcoholysis and amination, etc. However, only hydrolyzation of PET canrealize recycling utilization of resource and keep developing forever.We have researched on the hydrolyzation of PET using microwave as heat source. Theeffects of reaction condition on the depolymerization rate of PET were studied. At the sametime, the kinetics of depolymerization reaction was investigated. The surface and sectionmorphology of undepolymerized PET residues were pictured with Polarized Microscopy(POM) and Scanning Electronic Microscopy (SEM). The results indicate the process andmechanism of the depolymerization reaction. The following results were obtained:1. (1) The effective degree of factors on the depolymerization reaction is ordered inreaction time, pressure, water and microwave power. Reaction time and pressure were themajor factors. The best reaction conditions are that: reaction time is 150 min, pressure is 19bar, mass rate of water and PET is 6, microwave power is 500 W. (2) Dipotassium oxalate,Potassium acetate and Zinc acetate all have catalysis on the depolymerization reaction of PET.The order is oxalate> acetate> zinc acetate. Dipotassium oxalate has the best effect on thedepolymerization reaction and the depolymerization rate can reach 88.5% when the loading ofcatalyst is 1%. The depolymerization rate can exceed 85% when the loading of Potassiumacetate is 0.5%. The quantity of Zinc acetate makes no difference to .depolymerization rate,and the depolymerization rate can reach 60%. The optimal quantity of catalyst is 0.5~2%. (3)With the increasing of particle size of PET, the rate of depolymerization decreased. (4) Therate of PET depolymerization decreased slightly with the increasing of crystallinity of PET,This indicated that the crystallinity of PET has a little effect on the reaction, and thehydrolysis was not preferentially occurred on the amorphous phase of PET resin.2. The reaction order is close to unity by drawing when the depolymerization rate isbetween 5.06% and 35.81%, which is different from that by calculation. Hydrolyzationreaction of PET under microwave radiation is a combined process of rulelessdepolymerization and ruly depolymerization.3. At the beginning of the reaction, the shape of PET resin was not changed but the resinbecame fragile. This proved that some changes happened inside the PET resin. It can be alsoobserved that big blocks of PET were diffused into water, which showed that the hydrolysisreacted not only outside the PET resin, but also inside the PET resin.