Study On Preparation And Plasticization Properties Of Fat Graft Modified PVC

As one of the five general plastics,PVC has the advantages of corrosion resistance,wear resistance,flame retardant,easy processing,good electrical insulation and low production cost.It is widely used in building materials,food packaging,toys,wires and cables,medical devices and et al.However,PVC products usually need to add a lot of plasticizers to improve their performance during processing.Since the plasticizer may have problems of dissolution,migration,and volatilization during long-term use,that will not only decrease the performance of product,but also have a certain toxic effect on the environment and the human body.In recent years,the strategy of covalently connecting the plasticizer to the PVC branch by chemical modification method to avoid the migration of plasticizer has become a research hotspot.This internal plasticized PVC material modified by chemically way is expected to be used in the production of PVC products with good stability and low migration,such as food packaging,toys and medical equipment.This thesis is based on the nucleophilic substitution of chlorine atoms on PVC by long-chain amine compounds,introducing fatty side chains on the PVC molecular chain.The large volume structure of the long branched chain is used to increase the spacing of the PVC chains and reduce the interaction force between molecular chainsmolecular chain,improving the plasticity of PVC materials.The main research contents are as follows:(1)Study on the preparation of octadecylamine plasticized grafted PVC.Single-functional octadecylamine with long fatty chain structure was used to nucleophilically replace the chlorine atom of polyvinyl chloride to prepare octadecylamine modified PVC(PVC-C18)material.Using infrared spectroscopy and DSC to characterize the structure of PVC-C18 obtained with different amounts of octadecylamine,it was found that when the content ratio of octadecylamine added to PVC was 1:30,the obtained PVC-C18 had the lowest Tg of 59.36℃.Mechanical properties test also show that the plasticity of PVC-C18 is significantly improved compared to pure PVC materials.When the content of octadecylamine continues to increase,the long fat chain will form a microcrystalline structure.Compared with pure PVC,Due to the existence of crystallites restricts the movement of PVC molecular chains,the tensile strength and modulus of PVC-C18 containing crystals are decreased.(2)Preparation of modified PVC grafted with alkylamines of different lengths.Different lengths of alkylamines(butylamine,octylamine,dodecylamine)were used to prepare modified PVC(PVC-C4,PVC-C8,PVC-C12)materials respectively.The influence of glass transition temperature and mechanical properties were also compared.Results show that the shorter side chain has less effect on the glass transition temperature of PVC under the set variable range,and the Tg of PVC-C4 is not obvious.The PVC-C4 and PVC-C8 materials generally show a good plastic effect,and the plasticizing effect of octylamine on polyvinyl chloride is better than that of butylamine.The elongation at break of PVC-C12 material at the reaction ratio of 1:50 reached 260.31%,showing a good plastic effect.(3)Preparation of long-chain fatty acid ester graft modified polyvinyl chloride.The long-chain methyl stearate containing flexible ester groups was selected,and propylene diamine was used as the active bridging functional group.The amine-terminated methyl stearate(AMS)was first prepared as a plasticizing modifier and then reused AMS terminal amine group(-NH2)nucleophilically substituted the chlorine of PVC to prepare a long-chain fatty acid ester grafted modified PVC(PVC-AMS).Infrared spectroscopy(FTIR),nuclear magnetic hydrogen spectroscopy(1H-NMR),differential scanning calorimeter(DSC)were used to analyze the structure of AMS,and the optimal reaction ratio of methyl stearate and propylene diamine was determined as 1:1.75.Then,the obtained AMS modifier is reacted with PVC to prepare a series of PVC-AMS with different degrees of grafting.The results show that the glass transition temperature of the prepared internally plasticized PVC-AMS is significantly reduced.When the amount of AMS added is 1:30,the Tg is the lowest,which can be reduced to 42.66℃,and the elongation at break reaches 323.52%.showing a better plastic effect.And the solvent migration test shows that PVC-AMS is basically non-migration.