Plasma graft polymerization improves the bonding properties of polymer materials

With the deepening and development of scientific research, the use and the amount of polymer materials (plastics, fibers, etc.) have been rapidly expanded, such as food packaging bags, electrical insulators, photoresists, and composites with excellent properties. Polymer materials are widely used in the fields of electronics, aerospace, agriculture, industry, and medicine based on their properties such as thermal stability, thermal expansion coefficient, roughness, dielectric constant, solvent adsorption, and chemical resistance. Some of the polymer materials, such as polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), etc. due to their own characteristics, it is difficult to bond with the same material or other materials, so that the polymer material Use in some special areas is limited. In order to improve the adhesive properties of polymer materials, the most effective way is to improve or change its surface properties. There are many methods for surface activation, such as chemical etching, ion bombardment, light irradiation, plasma treatment, and surface graft polymerization. Among these surface modification methods, the wet chemical etching method not only changes the characteristics of the surface of the polymer material but also affects the characteristics of the substrate. Plasma treatment surface modification range from several to hundreds of nanometers will not affect the characteristics of the matrix, nor will it cause environmental pollution. It is a green surface modification method. Plasma treatment of polymer materials may introduce polar groups on the surface, but the modification effect will decline over time. It is plasma treatment of polymer materials, and the use of surface fund projects: Shaanxi Provincial Natural Science Foundation Research Project (2001H18) Chen Yaxuan et al.: Plasma radical polymerization of grafted polymerization on the improvement of the bonding properties of polymer materials caused by reactive free radicals to initiate functional grafting of monomers on the surface of the material. The methods of plasma graft polymerization include: (1) gas phase method: gas-phase graft polymerization of the surface of the material after contact with the monomer after plasma treatment; (2) degassing liquid-phase method: the surface of the material is plasma-treated and then placed directly. Into the liquid monomer for graft polymerization; (3) atmospheric pressure liquid method: the surface of the material after plasma treatment exposure to the atmosphere, the formation of peroxides, and then into the liquid monomer, initiated by peroxide graft polymerization; ( 4) Simultaneous irradiation: The monomer is adsorbed on the surface of the material and exposed to plasma for graft polymerization. In recent years, the most studied polymer materials are PE, PP, PTFE, PANI, etc. The monomers are acrylic acid (AAC), acrylamide (AAM), vinylimidazole (VIDZ), glycidyl methacrylate (GMA), Hydroxyethyl acrylate (HEMA), methyl methacrylate (pan), etc. There are few domestic reports on plasma graft polymerization to improve the bonding properties of polymer materials. There are many reports abroad. MaZ.H. et al.13 treated polyaniline (PANI) emeraldine base (EB) film with Ar plasma and thermally induced graft polymerization of VIDZ and AAC. The results show that the EB/AAC/PTFE assembly maximum shear The shear strength can reach 200N/cm2, the maximum shear strength of EB/VIDZ/Cu assembly can reach 640N/cm2. Han 2.2 plasma treatment power Gupta, etc., and the improvement of the surface wettability of the material is to improve the surface adhesive properties of the material. The necessary conditions, but not sufficient conditions.

In plasma graft polymerization, olefin monomers are mostly used. After the polymer material is treated with a plasma material, free radicals are generated on the surface of the material. These radicals initiate the opening of the olefin bond to initiate grafting, which causes the free radical-containing atoms on the surface of the material to bond with carbon atoms in the olefinic bond, resulting in a graft polymer The covalent bond is fixed on the surface of the material, which is beneficial to the improvement of the adhesive properties of the surface of the polymer material. Plasma graft polymerization can introduce a COOH, an NH2, an epoxy group, etc. on the surface of the material. These groups can form an electron transfer complex with the metal, so that the bonding material can be more firmly bonded, thereby promoting the polymer material and Metal bonding. ZouX.P et al. studied adhesion of PTFE and copper after N2,2,H2 plasma treatment. The experimental results show that the improvement of the adhesion between PTFE and copper is due to the formation of oxygen and nitrogen on the surface of Cu and PTFE. Crosslinking of Cu resin occurred. K. Yamada et al.22 studied the adhesion of carbon fiber and epoxy resin after plasma graft polymerization. It was found that carbon fiber graft polymerized acrylamide and had strong bonding strength with epoxy resin, and the bonding strength was proved by experiments. The increase is due to the formation of covalent bonds between the grafted acrylamide and the epoxy resin.

In summary, due to the difference in the objects to be bonded, the surface of the grafted polymer material and the adherent substance will undergo different chemical reactions. If the adherent substance is a metal, a coordination reaction occurs and the grafting occurs. A coordinate bond is formed between the polymer and the metal; if the adherent substance is an organic substance, cross-linking occurs, and a covalent bond is formed between the grafted polymer and the bonded organic substance, and the formation of these chemical bonds effectively improves the polymer Material surface adhesion.

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