Progress in blending modification technology of th

Progress in blending modification technology of hybrid plastic waste

overview of blending modification technology progress of hybrid plastic waste "Fang Zhengping, Zeng Minfeng, Xu Chengwei (Institute of composite materials, Zhejiang University, Hangzhou, 310027) The main technologies of blending modification and recycling of hybrid plastic waste, namely compatibilization modification, crosslinking modification, powdering and composite technology with other materials, were evaluated, and the possibility of Compatibilization crosslinking synergistic technology applied to the recycling of hybrid plastic waste was discussed. As an important part of polymer materials, plastic products have been widely used in various departments of the national economy because of its low price, light weight, corrosion resistance, easy processing and other advantages. However, with the convenience brought by plastic products to people's lives, its negative effects are also obvious. Because many plastic products are disposable consumer goods, a large number of waste plastic products are discarded at will, forming new environmental problems. Reasonable recycling of plastic waste can not only solve the problem of environmental pollution, but also reuse resources. It is a more positive way to reduce the pressure of plastic waste on the environment. Therefore, in recent years, the research, production and environmental protection departments of polymer materials at home and abroad have attached great importance to this. Although there is still debate about the economy of post consumer plastic recycling, the actual recycling rate of post consumer plastic has been increasing. Plastic waste mainly includes leftover materials in factories and post consumer plastics in garbage. Among them, the leftover materials in the factory are easy to recycle because of their clear composition and high cleanliness. Post consumer plastic is usually a mixture of various plastics, and its main body is a large variety of plastics represented by polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS). These four kinds of plastics, except PE and PP have good compatibility, other plastics are incompatible with each other due to large differences in molecular structure, and the mechanical properties of their blends are very poor. They must be separated and processed, which not only costs a lot of manpower and material resources, but also cannot guarantee the quality of recycled products. Therefore, it is of great social and economic significance to develop the recycling technology of direct blending modification without sorting, so that the product performance is close to or slightly lower than that of new raw materials. So far, this technology can be summarized as the following aspects. Compatibilization modification technology compatibilization is a common method to improve the mechanical properties of incompatible polymer blends. As early as the 1970s, Paul et al. Developed a hydrogenated styrene thermoplastic elastomer (SEBS), whose molecular chain is styrene ethylene and attaches importance to the computer-controlled butene structure of the machine, which is called H-type compatibilizer. In this H-type compatibilizer, reactive functional groups are introduced, which is called M-type compatibilizer. Table 1 shows the compatibility of these two compatibilizers with some common polymers. It can be seen from the data in the table that they have good compatibility with PE, PP, PS, PVC, acrylonitrile butadiene styrene (ABS) and other general-purpose plastics, especially type m, which is expected to be used as a universal compatibilizer for the recycling and regeneration of hybrid plastic wastes. Table 1 compatibility between compatibilizer and resin for waste plastic recycling in shipbuilding market plastic type plastic name compatibility H-type compatibilizer M-type compatibilizer general plastic is good and poor engineering plastic polyamide is poor, polyester is poor, polyphenylene ether is good, polyformaldehyde is poor, polycarbonate is poor, thermosetting plastic is good, epoxy resin is poor, phenolic resin is poor, DAP resin is poor and good note: SMC is sheet molding material, BMC is block molding material. 2. Crosslinking modification technology Vivier et al. Grind waste PVC into powder, and carry out special treatment on the powder, and then extrude and foam the product, which has appropriate density, good impact strength and surface gloss, and can be used as packaging materials and building materials. Because thermosetting plastics cannot melt, their recycling is often used as fillers for other polymers after crushing. Masatshin6 powdered the cured epoxy resin containing silica filler and additives. The powder has good reactivity with polar resins such as epoxy resin and brewed resin. Its impact strength is better when it is used in epoxy resin molding than that of products without the powder, and has been used in the production of electrical parts. 4. Composite technology with other materials. Liao Bing and others used wood fibers treated with coupling agents to strengthen waste PE, PP and PVC, which greatly improved the tensile strength and impact strength of a high-quality product created less than one year ago, and can be used to prepare plastic reels, containers and other products. They also filled waste PVC with calcium carbonate to make PVC calcium plastic materials with good performance. Ninmiya mixes waste plastics, fillers and adhesives to form. Fly ash, sludge, slag, broken glass, broken ceramics, paper scraps, etc. can be used as fillers. The materials made can be used for floors or pavements. Zhejiang Santai board factory uses recycled agricultural film and sawdust to make plastic wood, with a flexural strength of 20.8mpa and a compressive strength of 55.2mpa. This material not only has the same properties as natural wood, such as sawing, planing, nailing, sticking and so on, but also has the advantages of moisture resistance, moth resistance and strong manufacturing flexibility. It can be extruded into plates, profiles, or molded into products at one time. 5 compatibilization crosslinking synergistic technology our research group 241 has carried out in-depth and systematic research on the blending modification of incompatible general-purpose plastics PE, PP, PVC, PS, etc. since 1986, through in-situ crosslinking and its synergy with compatibilization or phase dispersion, the properties of the blends have been greatly improved. Table 4 shows the compatibilization crosslinking synergistic effect of compatibilizer CPE and crosslinker DCP in pvc/hdpe blends. Table 4 composition of Compatibilization and crosslinking on tensile properties of pvc/hdpe blends tensile strength/mpa elongation at break,% through research, it is proved that the core of Compatibilization crosslinking synergy is phase dispersion crosslinking synergy. Although adding phase dispersant alone can improve the degree of two-phase dispersion, the improvement of mechanical properties is limited because the bonding between phases still depends on van der Waals force; The addition of cross-linking agent alone can cause the cross-linking between or within the two components, which plays a certain role in the properties of the blend. However, due to the low degree of two-phase dispersion, the probability of cross-linking agent appearing at the phase interface is small, so there are few cross-linking products and the modification effect is not significant; When the two are added at the same time, the current asset liability ratio has reached 100%. The phase dispersant promotes the mutual dispersion of the two components, increases the mutual contact of the two components, reduces the phase size, and the probability of the cross-linking agent appearing at the two-phase interface is correspondingly increased, resulting in a quantitative amount of cross-linked products between the two components, thus significantly improving the phase interface adhesion. Due to this phase dispersion cross-linking synergy, The mechanical properties of the blends were significantly improved. For systems containing more than two components, preliminary experiments show that the compatibilization crosslinking synergistic technology is still effective. Taking pe/pvc/pp/ps (70/10/10/10) as the simulation system of hybrid plastic waste, several different elastomers and crosslinking agent DCP are used to modify it. Through the synergistic effect of compatibilizer and crosslinking agent, the properties of the blend can be greatly improved (see Table 5)% We believe that the compatibilization crosslinking synergistic technology will play a good role in the recycling of hybrid plastic waste. Table 5 modification effect of Compatibilization crosslinking Synergistic Technology on pe/pvc/pp/ps blends compatibilizer type compatibilizer dosage simply supported beam impact strength (notched>/(JT1) tensile strength/mpa elongation at break,% none