Preparation And Properties Of Polyvinyl Chloride-based Graft Copolymer Membranes

Membrane separation technology with energy-saving,environmentally friendly and efficient has become a new type of separation technology and is widely used in many industrial fields,such as biology,food and waste water treatment.However,the membrane fouling is still an important problem for the development of membrane separation technology.According to the membrane fouling mechanism and industrial production cost,the membrane material modification,improving the membrane hydrophilic property,is one of the core ways to solve the membrane fouling problem.In order to improve the hydrophilicity of polyvinyl chloride(PVC)membrane,the synthesis of hydrophilic and low surface energy PVC based membrane materials and the preparation of PVC based graft copolymer membranes and their antifouling properties were studied.The PVC-g-PPEGMA-g-PTFEMA graft copolymer was prepared by free radical polymerization with polyethylene glycol methacrylate(PEGMA)as hydrophilic material,trifluorobutyl methacrylate(TFEMA)as low surface energy material and PVC as the main chain.The quality amount of the PEGMA was chosen by XPS?FTIR and GPC.For the PVC-g-PPEGMA graft copolymer,the content of PPEGMA segment was higher when the added mass ratio of DPVC and PEGMA was 10: 1.Then the PVC based graft copolymer was optimally selected as the membrane material to prepare the PVC based graft copolymer membrane via the nonsolvent induced phase separation method(NIPS).The surface properties and permeability of PVC based graft copolymer membranes were further adjusted and optimized by forced surface segregation.The effect of the heat treatment condition on the structure and properties of PVC based graft copolymer membranes were investigated.The obtained PVC based graft copolymer membranes exhibited typical asymmetric structure.When the heat treatment condition was 50? and 12 h,the water contact angle of the PVC-g-PPEGMA graft copolymer membrane surface was the smallest,showing that the PVC-g-PPEGMA graft copolymer membrane obtained the good hydrophilic property.At the same time,the membrane pore size,porosity,zeta potential and pure water flux all obtained significant improvement.Compared with the PVC-g-PPEGMA graft copolymer membrane,the water contact angle of the PVC-g-PPEGMA-g-PTFEMA graft copolymer membrane slightly increased thanks to the presence of the hydrophobic PTFEMA segment under the same heat treatment condition,but the pore size,porosity and pure water flux of the PVC-g-PPEGMA-g-PTFEMA graft copolymer membrane all increased.The PVC-gPPEGMA-g-PTFEMA graft copolymer membrane antifouling performance was effectively improved due to the synergy between the hydrophilic PPEGMA segment and low surface energy PTFEMA segment and obtained the long-term hydrophilic stability.The PVC-g-PPEGMA-g-PTFEMA graft copolymer with the different amount of the PTFEMA segment was used as the membrane material to prepare the PVC-gPPEGMA-g-PTFEMA graft copolymer membrane via NIPS and forced surface segregation process.The effect of PTFEMA segment content on the structure and performance of PVC-g-PPEGMA-g-PTFEMA graft copolymer membrane was studied by controlling the amount mass of TFEMA monomer.The obtained PVC-g-PPEGMAg-PTFEMA graft copolymer membrane exhibited typical asymmetric structure and the cross section was consisted of the dense separation layer,the finger-like pore layer and sponge-like pore.Compared with the PVC membrane,the pore size and porosity of the PVC-g-PPEGMA-g-PTFEMA graft copolymer membranes increased significantly.As the content of PTFEMA segment increased,the pore diameter of the PVC-g-PPEGMAg-PTFEMA graft copolymer membranes gradually decreased,and the porosity and pure water flux increased firstly and then decreased.When the mass ratio of DPVC and TFEMA was 10:4,the PVC-g-PPEGMA-g-PTFEMA graft copolymer membrane exhibited the best permeability and antifouling property.