Preparation And Properties Study Of Reinforced And Toughened Polypropylene Composites

Lithium-ion battery flexible packaging film is composed of multi-layer structure,andthe inner layer is polypropylene(PP)layer.It needs to meet certain toughness,strength and barrier properties.However,due to the lack of toughness and strength of pure PP,its application in the inner film of lithium battery flexible packaging was limited,so it needed to be modified..In this paper,the toughness and strength of polypropylene were improved by adding reinforcing fillers and chemical crosslinking.At the same time,the physical barrier and chemical crosslinking of the fillers improved the electrolyte resistance and barrier of the material simultaneously.The main research contents are as follows:(1)Two kinds of silane coupling agents(3-aminopropyl)triethoxy silane(KH550)and N-propyl trimethoxy silane(JH-N313)were used to modify the surface of inorganic filler Si O₂,respectively.PP was used as substrate,polypropylene grafted glycidyl methacrylate(PP-g-GMA)as compatilizer,and 2,4,6-tris(dimethylaminomethyl)phenol(DMP-30)as catalyst.A series of Si O₂/PP composites were prepared.The results showed that KH550 and JH-N313 were successfully grafted onto Si O₂by Infrared spectroscopy,Thermogravimetry and XPS.The effects of coupling agent and filler content on composites properties were studied.The results showed that the modification effect of the coupling agent KH550 was better than that of JH-N313.When the amount of modified Si O₂was 27.5 wt%,the composites had the best comprehensive properties.The impact strength and tensile strength were 4.4 k J/m²and 27.2 MPa,respectively,which were increased by 3.2%and 7.5%compared with PP substrate,and by 23.9%and5%compared with composites prepared with unmodified Si O₂.The solvent resistance of composites samples and film was studied,and the results showed that the maximum mass change of the Si O_2/PP system composites material was 0.13%,which was 77.7%lower than that of PP substrate.Modified by KH550,The maximum mass change of KH550-Si O₂/PP was 0.067%.The surface of Si O₂was connected with amino groups and reacted with epoxy groups in the matrix to form a chemical bond,which improved the interface force,so the strength and barrier properties were improved.(2)A series of BN/PP composites were prepared by the same process when Boron nitride(BN)surface treaded by KH550 and JH-N313 were used as reinforcement filler.The structure and properties of the composites were studied.The results showed that KH550 and JH-N313 were successfully grafted on BN,respectively.And the properties of KH550 modified BN/PP composites were better than those of unmodified BN system and JH-N313 system.When the modified amount of BN was 8.3 wt%,the reaction temperature was 190?,and the reaction time was 100 s,BN/PP composites modified by KH550 had the best comprehensive properties.The impact strength and tensile strength were 7.4 k J/m²and 29.1 MPa,respectively,which were increased by 73.6%and 15%compared with the PP substrate.Compared with the unmodified BN composites material,they were increased by 4%and 2.5%respectively.The chemical bond formed by the reaction between the amino group of KH550 and the epoxy group of the matrix,while the alkyl chain in JH-N313 only improved the interfacial compatibility and had less effect on the improvement of the force between the two phases.Therefore,the strength and toughness were less than that of KH550 modified BN/PP composites.The study of solvent resistance of composites showed that the maximum mass change of the KH550-BN/PP composites was 0.07%,which was much lower than that of the PP substrate(0.582%).The variation of tensile strength of KH550-BN/PP composites films were less than that of the corresponding Si O₂system.Because of the physical barrier of BN and cross-linking with the matrix,KH550-BN/PP composites had better toughness,strength and barrier properties.