Study On Preparation And Degradability Of Photodegradable PVC Composite Film

Polyvinyl chloride(PVC)has non-combustibility,corrosion resistance,insulation and good mechanical properties.It is widely used in various fields such as agriculture,daily necessities,construction,aerospace,chemical industry,and electronics.However,the"white pollution"caused by a large number of discarded PVC plastic products has become an urgent environmental problem.Faced with this problem,the development of photodegradable plastics is a feasible solution.In order to improve the photodegradability of PVC and avoid complicated processes,this article prepared a series of excellent photodegradability by doping methylene blue(MB),nano graphite(Nano-G)and rare earth lanthanum ion(La³⁺)in the TiO₂/PVC system Performance MB/TiO₂/PVC,Nano-G/TiO₂/PVC,La³⁺-TiO₂/PVC and Nano-G/MB/La³⁺-TiO₂/PVC composite film.The mechanical properties,thermal stability,light absorption,and photodegradation properties of the composite film were systematically studied,and the photocatalytic oxidation degradation mechanism of the PVC composite film was explored.(1)In order to study the effect of co-doping of MB and TiO₂ on the photodegradability of PVC composite film,a photodegradable MB/TiO₂/PVC film was prepared.The weight loss rates of PVC,TiO₂/PVC,MB/PVC and MB/TiO₂/PVC films after irradiation for 30 h were2.12%,8.94%,15.84%,and 27.55%,respectively.The photodegradable rates of Mw and Mn of MB/TiO₂/PVC were 35.68%and 65.38%,respectively.MB/TiO₂/PVC composite film has high photodegradability,and the optimal doping amount of MB was 2 wt%.On this basis,the photocatalytic degradation mechanism of MB/TiO₂/PVC composite film was discussed.MB enhances the absorption of light by PVC,and TiO₂ realizes effective separation of photogenerated carriers,improves the photocatalytic activity,and accelerates the degradation of PVC plastic.(2)In order to study the effect of Nano-G and TiO₂ co-doping on the photodegradability of PVC composite film,a photodegradable Nano-G/TiO₂/PVC composite film was prepared.The weight loss rates of Nano-G/PVC,TiO₂/PVC and Nano-G/TiO₂/PVC films after 30 h of light irradiation were 7.68%,8.94%and 17.24%respectively,while PVC was only 2.12%,Nano-G/TiO₂/PVC composite film has high photodegradability,and the optimal doping amount of Nano-G was 1 wt%.The photocatalytic degradation mechanism of Nano-G/TiO₂/PVC composite film was discussed.Nano-graphite can store and transfer electrons,can effectively improve the migration and separation of TiO₂ photogenerated electrons,inhibit the conformation of photogenerated carriers,and improve photocatalytic efficiency.(3)In order to study the effect of TiO₂ modified by ball milling with rare earth lanthanum ions on the photodegradability of PVC composite films,a photodegradable La³⁺-TiO₂/PVC composite film was prepared.After 30 h of irradiation,the degradation rate of La³⁺-TiO₂/PVC composite film was 17.78%,which was 8 times of PVC degradation rate and 2 times of TiO₂/PVC degradation rate.Obviously,the photocatalytic degradation activity was increased,and the optimal doping amount of La³⁺-TiO₂ was explored at 1.5 wt%.The photodegradation mechanism of PVC by the interaction of La³⁺and TiO₂ was discussed.La has a special 4f electronic structure,which can become a shallow potential trap for photogenerated carriers,which was conducive to the separation of photogenerated electron-hole pairs.(4)In order to study the effect of MB,Nano-G and La³⁺-TiO₂ co-doping on the photodegradability of PVC composite film,Nano-G/MB/La³⁺-TiO₂/PVC composite film was prepared.The optimal doping ratios of Nano-G,MB and La³⁺-TiO₂ were explored to be 0.1wt%,1 wt%,and 1.5 wt%.Among them,MB has the most significant effect on PVC degradation.Compare the photodegradation performance of the MB/TiO₂/PVC,Nano-G/TiO₂/PVC,La³⁺-TiO₂/PVC and Nano-G/MB/La³⁺-TiO₂/PVC(M-7)composite films selected in the first three chapters.The results show that M-7 film has the best photodegradation effect,with a weight loss rate of 67.00%.Under the combined action of nano graphite,methylene blue and La³⁺-TiO₂,the Nano-G/MB/La³⁺-TiO₂/PVC composite film has a good photodegradation effect.The mechanical properties can be adjusted through different addition amounts to ensure normal usability.In this paper,the prepared photodegradable PVC composite film can provide certain technical and theoretical references for the development and utilization of photodegradable PVC composite film.