| Polyethylene terephthalate(PET)is widely used in food,beverage and many other fields due to its excellent properties.Most PET is discarded after a single usage,and it is difficult to be degraded in nature and sometimes enters the human body along with the food chain,bringing great hidden danger to human environment and health.In this study,1,2-propanediol was used to degrade waste plastic bottles PET,and then the degradation products were used as raw materials to synthesize wateborne photo-curable coatings.In order to further improve the comprehensive properties of photo-curable paint films based on waste PET,degradation products and polyether diol were combined to prepare waterborne photo-curable resin.(1)Use propylene glycol to degrade waste PET.The effects of feed ratio,degradation temperature and degradation time on the color,viscosity,hydroxyl value and average molecular weight of the degradation products have been studied.FT-IR and ~1H-NMR showed that the degradation products contained polyester diols.Gel permeation chromatography showed that the polyester diols in the degradation products were mainly ethylene terephthalate,hydroxyethyl(hydroxypropyl)terephthalate,propylene terephthalate and their dimers,trimers and polymers with a molecular weight of about 20,000.The results showed that the optimum degradation conditions were as follows:the mass ratio of PG to PET was 2:1,the amount of zinc acetate was 1%of the mass of PET,the temperature was 190～200℃and the reaction time was 3h.the degradation product was transparent and yellow,with good color and low viscosity,which was suitable for industrial application.(2)The degradation products of waste PET were used to prepare high-functionality waterborne photo-curable coatings by acetone synthesis method,and the effects of different degradation products,isocyanate types,hydroxyl acrylate functionality,neutralization degree and photoinitiator concentration on the properties of the emulsion and cured film based on the waste PET were discussed.The appearance,particle size and mechanical properties,water absorption and gel rate of the cured film were studied.The thermal stability,glass transition temperature and hydrophilicity of the cured film were studied by TG,DSC and contact angle tests.The hardness of WPUA cured film reaches 3H,up to 6H;WPUA film can be cured in 15 seconds under UV irradiation;the cured WPUA film has high thermal stability,and the particle size of the emulsion is significantly affected by the change of neutralization degree.(3)In order to further improve the comprehensive properties of the waterborne photo-curable resin based on waste PET,the degradation product and polyether diol was used together to prepare photo-curable resin.When the ratio of degradation product and PPG2000 was improved,the flexibility of the paint film got worse from 1mm to2mm,the impact strength decreased,the hardness of cured film increased from 6B to3H,the hardness increased significantly,the water resistance of paint film improved,the gel rate of film increased,the average particle size of emulsion increased.When degradation products and PEG1000 were mixed to prepare photo-curable resin,the hardness of the film was 3H and the water resistance passed the test.When used PEG2000 or PPG2000 instead of PEG1000,the hardness of the film decreased and the water resistance became worse.When the molecular weight of polyether diol increased,the flexibility became better,the impact strength,water absorption and elongation at break of the film increase,but the tensile strength decreased. |
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