Plastic modification is the use of physical, chemical, and mechanical methods to improve or increase the functions of large quantities of general-purpose resins produced by petrochemical companies. It is used in electrical, magnetic, optical, thermal, aging resistance, flame retardant, and mechanical properties. To achieve the functions used under special environmental conditions.

Modified plastics are a field of plastics industry that involves a wide range of high-tech content, and plastic modification technologies-filling, blending, and reinforcement modification are more deeply involved in the raw materials and molding processes of almost all plastic products. From the production of raw resins to modified plastic masterbatches of various specifications and varieties, in order to reduce the cost of plastic products and improve their functionality, plastic modification technology is inseparable.

(1) Fiber reinforcement. Long-fiber reinforced thermoplastic (UCRT) is a new type of lightweight and high-strength engineering structural material. Because of its light weight, low price, and easy recycling and reuse, its application in automobiles has developed rapidly. The use of natural fibers such as flax and sisal reinforced plastics to manufacture body parts has been recognized in the automotive industry. On the one hand, because natural fibers are environmentally friendly materials, on the other hand, plant fibers are 40% lighter than glass fibers, reducing vehicle weight and reducing fuel consumption. Using flax-reinforced PP to make the underbody underbody, the tensile strength of the material is higher than that of steel, the stiffness is not lower than that of glass fiber reinforced material, and the parts are easier to recycle. The transmission shaft made of fiber-reinforced plastic by British GKN Technology Company has a weight reduction of 50%-60%, a torsion resistance 1.0 times greater than steel, and a bending stiffness 1.5 times greater. Plastic springs can significantly reduce weight. The leaf spring made of carbon fiber reinforced plastic (CFRP) is 14kg, which reduces the weight by 76%. In the United States, Japan, and Europe, leaf springs and cylindrical coil springs have been used to achieve fiber-reinforced plastics. In addition to having obvious anti-vibration and noise reduction effects, it also achieves the purpose of lightweight.
(2) Toughening technology. The stiffness (including strength) and toughness of polymer structural materials are the two most important performance indicators that restrict each other. Therefore, the research of enhancing stiffness while enhancing toughness has always been a difficult problem in polymer materials science. A new way of polymer blending and filling reinforcement and toughening by the Institute of Chemistry, Chinese Academy of Sciences. This achievement has achieved an important breakthrough in solving the scientific problem of polymer materials while strengthening and toughening. It is the first domestically to successfully prepare ultra-high toughness polyolefin engineering plastics. The upgrade of a large variety of general-purpose plastics provides a new way for engineering plastics and engineering plastics to further improve their performance. The Supergravity Engineering Technology Research Center of the Ministry of Education successfully developed the national "863" project-"Nano-CaCO3 plastic toughened masterbatch and its preparation technology". This kind of masterbatch can make PVC toughened and modified. It is mainly used in the production of PVC doors and windows profiled materials, but also in the production of PVC pipes, plates and other hard products. From the perspective of development trends, PVC plastic doors and windows have the potential to completely replace steel windows and wooden doors and windows. At present, the domestic annual production capacity of PVC door and window profiles is 1 million tons, and it is on the rise. The use of nano-CaCO3 plastic toughened masterbatch to produce PVC door and window profiles can not only improve product performance, but also reduce the cost of profile materials by more than 100 yuan per ton. At the same time, its application fields will also expand to PP, ABS and other plastic materials. The use of nano-CaCO3 to toughen PVC is a non-elastomeric toughening plastic technology (inorganic rigid particle toughening plastic technology) developed in recent years, and it is still in the research stage in China. Direct addition of nano-CaCO3 will cause two major problems: one is that the nano-particles will coalesce in the plastic matrix, so that the dispersion is uneven, which affects the toughening effect; the second is that the nano-CaCO3 particles are small, which easily generates dust and affects the environment. The successful development of nano-CaCO3 plastic toughening masterbatch and its preparation technology have effectively solved the two major problems faced by the same research field at home and abroad.
(3) Filling modification (powder filling). Since the plastic filling modification was put on the market in the early 1980s, due to its low price, excellent product performance, and improved certain physical properties of plastic products, it can replace synthetic resins, and its production process is simple, the investment is small, and the Significant economic and social benefits. The surface modifiers of the inorganic powder materials modified by weekly filling range from stearic acid to coupling agents, and have received certain effects. The coupling agents include silane, titanate, aluminate, borate, phosphate, etc. Varieties have emerged one after another.

Talc is often used to fill polypropylene. Talcum powder has the characteristics of flake-like structure in flake configuration, so talc powder with finer particle size can be used as a reinforcing filler for polypropylene. In the modification system of polypropylene, the addition of superfine talc powder masterbatch can not only significantly improve the rigidity, surface hardness, thermal creep resistance, electrical insulation, and dimensional stability of polypropylene products, but also improve polypropylene The impact strength. Adding a small amount of talc powder to polypropylene can also act as a nucleating agent to improve the crystallinity of polypropylene, thereby improving the mechanical properties of polypropylene. As the crystallinity of polypropylene is improved, the crystal grains are refined. , It also improves the transparency of polypropylene. Polypropylene composites filled with 20% and 40% ultrafine talcum powder can significantly improve the rigidity of polypropylene and the creep resistance at high temperatures, no matter at room temperature or high temperature. For polyethylene blown film, the superfine talcum powder masterbatch is better than other fillers, it is easy to form and has good manufacturability.
(4) Blending modification. Plastic blending modification refers to a modification method in which one or more other resins (including plastics and rubber) are mixed into a resin to change the properties of the original resin. Plastic blending modification is a common plastic modification method that goes hand in hand with addition modification. The difference between it and plastic addition modification is that addition modification involves mixing small molecular substances into the resin, while plastic blending modification involves mixing high molecular substances into the resin. Since the blended modified composite system is composed of polymer materials, its compatibility is better than that of the additive system, and at the same time of modification, it has less impact on other properties of the original resin. Plastic blends, also known as polymer alloys, are the most effective way to develop new polymer materials, as well as the main way to achieve high performance and refinement of existing plastic varieties. Almost all required properties of plastics can be obtained by blending modification. For example, PP has the advantages of low density, good transparency, high tensile strength, high hardness, and good heat resistance, but its impact performance is poor and stress cracking resistance is not good. If it is blended with HDPE, it can maintain the original PP. Some of the advantages can also make the blend have the advantages of impact resistance, stress crack resistance and low temperature resistance.
(5) Flame retardant technology. Generally speaking, high polymer flame retardant technology is mainly divided into two types: additive type and reactive type, mainly based on additive type. That is, add the flame retardant matched to the ordinary pellets, mix them thoroughly in the mixer, and then enter the mixing device mainly composed of twin-screw extruders to re-granulate to prepare flame-retardant modified "flame retardant plastics" ". In the past ten years, in the PP flame retardant technology, the intumescent flame retardant pioneered by Professor Camino of the University of Turin in Italy has played a huge role. This type of PN flame retardant has high efficiency, high thermal and light stability, low toxicity, and low toxicity. Smoke, low corrosion, small impact on processing and mechanical properties, and will not cause environmental pollution. Commonly used additives for flame retardants are decabromodiphenyl ether, octabromodiphenyl ether, tetrabromobisphenol A, hexabromocyclododecane, etc., among which decabromodiphenyl ether is the largest. The decomposition temperature of brominated flame retardants is mostly about 200-300℃, which matches the decomposition temperature of various polymers, so it can play a flame retardant effect when the best time is the same as the gas phase and condensation, and the addition amount is small , Good flame retardant effect.
(6) Graft modification. At present, grafted modified plastics are widely used as macromolecular coupling agents, compatibilizers, and toughening agents. At present, the most common grafting monomers are maleic acid, GMA and acrylic acid, GMA and acrylic acid, all of which have the disadvantages of high polymerization tendency, low grafting rate and grafting efficiency, and acrylic acid is very corrosive. The purpose of graft modification of polypropylene is to improve the adhesion or solubilization of polypropylene with metals, polar plastics, and inorganic fillers. The grafting monomers used are generally acrylic acid and its esters, maleic acid and its esters, maleimides and the like. The grafting methods include: ①Solution method, in which peroxide initiator is added to the solvent for copolymerization; ②Radiation method, grafting under high-energy rays; ③Melting mixing method, in the presence of peroxide, in the molten state Mixing and grafting are usually carried out in a twin-screw extruder. The properties of graft-modified polymer materials are related to the physical and chemical properties of the graft, as well as the content of the graft and the length of the graft chain. Its basic performance is similar to that of polypropylene, but it is similar to polar polymer materials. The compatibility of inorganic materials, rubber, etc. can be greatly improved. The crystallinity and melting point of grafted PP decrease with the increase of graft content, but the transparency and low-temperature heat-sealability increase.