Preparation And Properties Of PVC/(SMA-NH₂) Blend Film

Polyvinyl chloride（PVC）is an excellent film material with excellent physical and chemical properties and low price,but in water treatment applications,due to its strong hydrophobicity will lead to serious membrane pollution,resulting in low separation efficiency,short service life and other problems,so it is necessary to modify the PVC film hydrophilic to improve its anti-pollution performance.Styrene-maleic anhydride copolymer（SMA）is one of the most commonly used amphiphilic polymers for hydrophilic modification of polymer membrane materials.The research group has done a lot of studies on SMA and its functional modification in the early stage,and found that the opening degree of SMA can be adjusted by alkali treatment technology,so as to improve the compatibility of the casting liquid,improve the hydrophilicity of the matrix,and optimize the properties of the film.However,the current research on SMA amine treatment technology by our research group and other scholars mainly focuses on the modification and grafting of surfactant groups after blending,while there are few reports on the effect of SMA-NH₂obtained by SMA amine treatment technology on the liquid system of casting film and film properties.Therefore,on the basis of the research group,two different molecular weights of amine monomers PEA and TEA were selected first,and a new amphiphilic polymer SMA-NH₂was prepared by the ring-opening reaction of the acid anhydride of SMA,and then PVC/（SMA-NH₂）blended film was prepared by one-step blending method.By adjusting the degree of SMA amine treatment and the amount of SMA-NH₂,the separation membrane with uniform pore structure was prepared,and the PVC blend membrane was given excellent permeability and selectivity.The new separation layer constructed by SMA-NH₂on the surface of PVC membrane has high permeability,high dye retention,low salt retention and high pollution resistance during dye/salt retention,which shows great application potential in textile wastewater treatment,and also provides a new idea for the functional modification of PVC separation membrane and SMA functional modification.The specific research content and main conclusions of this paper are as follows:（1）Preparation of SMA-g-PEA and its effect on the structure and pollution resistance of PVC blend film.Firstly,the purified SMA-g-PEA was prepared by solution grafting,and the effects of the grafting rate of PEA and the amount of SMA-g-PEA on the compatibility,microstructure and properties of the cast film were studied.It was found that with the increase of PEA grafting rate,the compatibility of the cast film solution became worse.Only when a few PEA segments were grafted on SMA,the cast film solution could have better compatibility.When the grafting rate of PEA is low,the surface of the blend film has a uniform circular pore structure,and SMA-g-PEA can play the role of pore-inducing agent.When the mass fraction of PEA was 4.8 wt%and the grafting rate was 10%,the permeability,selectivity and anti-pollution properties of PVC/（SMA-g-PEA）blend films were the best.The addition amount of SMA-g-PEA（4.8 wt%）was adjusted to further optimize the membrane structure and properties.It was found that when the amount of SMA-g-PEA was more than 1.5 wt%,the compatibility of the system was significantly deteriorated,and the number of defect holes on the membrane surface increased,which led to the decrease of contact Angle,the increase of permeation flux and the decrease of anti-pollution index.When the amount of SMA-g-PEA was 1 wt%,the pure water flux of the blended film was 136.36 L·m^-2·h^-1·bar^-1,the BSA retention was 95.68%,the contact Angle was 46.3°,and the FRR was 72%.（2）Preparation of SMA-g-TEA and its effect on the structure and anti-pollution properties of PVC blend film.SMA-g-TEA solution was prepared by ring-opening of highly reactive MA groups in SMA,and then PVC/（SMA-g-TEA）blends were prepared by NIPS method.The effects of different mass fraction ratio of SMA to TEA and different amount of SMA-g-TEA on the compatibility,microstructure and properties of the cast film were investigated.It was found that with the increase of TEA mass fraction,the liquid system of the cast film began to become unstable.The surface structure of the blended film was all round small holes,and the pore size decreased with the increase of TEA mass fraction proportion,but it was still higher than that of pure PVC film.This is because when the proportion of TEA mass fraction is high,excess TEA is deposited on the surface of the film.When SMA:TEA=1:1,the permeability and pollution resistance of PVC/（SMA-g-TEA）blend film are balanced.After determining the optimal ratio,the performance was optimized by adjusting the amount of SMA-g-TEA added.It was found that the higher the additive amount,the more defect holes on the surface of the film,and the film performance decreased.When the addition amount is 1.2 wt%,the pure water flux is 267.27L·m^-2·h^-1·bar^-1,the BSA retention is 95.22%,the contact Angle is 58.1°,and the FRR is 75.51%.（3）The separation performance of two different PVC/（SMA-NH₂）membranes was evaluated by dye/salt system.The addition of SMA-g-PEA significantly improved the permeability and retention performance of PVC/（SMA-g-PEA）loose nanofiltration membrane.The flux of the membrane during dye retention was≥165 L·m^-2·h^-1·bar^-1,and the retention rate was 69.43%～97.28%,with low salt retention efficiency.Although the addition of SMA-g-TEA significantly improved the permeability,with fluxes≥237.27 L·m^-2·h^-1·bar^-1,the retention performance was not improved much,ranging from 55.86%to 87.38%.Both membranes showed good properties of loose nanofiltration membranes,Among them,PVC/（SMA-g-PEA）loose nanofiltration membrane has better separation performance because SMA-g-PEA shows zphozionic potential under acidic conditions and creates a new separation layer through self-crosslinking,which shows great potential in the treatment of textile wastewater.