Chemical name: acrylonitrile butadiene styrene polymer English name: acrylonitrile butadiene styrene
Specific gravity 1.05g /cm3, molding shrinkage: 0.4 ~ 0.7%.
ABS resin is a mixture of acrylonitrile-butadiene-styrene, and its general ratio is 20:30:50 (melting point is 175℃). Its characteristics are controlled by the proportion of the three components and the chemical structure and physical form of each component. The characteristics of acrylonitrile component in ABS are heat resistance, chemical resistance, rigidity and tensile strength, butadiene is impact strength, and styrene is processing fluidity and luster. The combination and complementary advantages of these three components make ABS resin have excellent comprehensive properties. As long as the ratio, polymerization method and particle size are changed, a series of varieties with different impact strength and fluidity can be produced. If the component of butadiene is increased, the impact strength will increase, but the hardness and fluidity will decrease, and the strength and heat resistance will also become worse. ABS has good rigidity, high impact strength, heat resistance, low temperature resistance, excellent chemical resistance, mechanical strength and electrical properties, easy processing, good dimensional stability and surface gloss, easy painting and coloring, and can also be used for secondary processing such as metal spraying, electroplating, welding and bonding.
ABS is a kind of resin with excellent comprehensive properties, which is non-toxic and yellowish. It has high impact strength in a wide temperature range, higher thermal deformation temperature and good dimensional stability than PVC. The shrinkage rate is in the range of 0.4% ~ 0.8%, which can be reduced to 0.2% ~ 0.4% if reinforced with glass fiber, and it rarely shrinks after plasticization.
Second, the characteristics of ABS:
1, good comprehensive performance, high impact strength, good chemical stability and electrical properties.
2. It has good weldability with 372 plexiglass, can be made into two-color plastic parts, and the surface can be chrome-plated and painted.
3, high impact resistance, high heat resistance, flame retardant, reinforced and transparent.
4. the fluidity is a little worse than HIPS, better than PMMA and PC, and the flexibility is good.
Third, the synthesis method of ABS
There are many production methods of ABS resin. At present, emulsion grafting method and continuous bulk method are widely used in international industrial plants.
1. emulsion graft blending process;
Emulsion grafting blending method is developed on the basis of traditional ABS resin grafting method. According to the different SAN polymerization processes, it can be divided into three types: emulsion graft emulsion SAN blending, emulsion graft suspension SAN blending and emulsion graft bulk SAN blending, of which the latter two are widely used in industrial plants at present. These three emulsion graft blending processes all include the following intermediate steps: preparation of butadiene latex, synthesis of graft polymer, synthesis of SAN polymer, blending and post-treatment.
(1) Synthesis of butadiene latex: The synthesis of butadiene latex is a major unit in ABS production, which is generally produced by emulsion polymerization process. At present, this production technology is relatively mature. By controlling the total solid content in latex (generally, the higher the total solid content, the lower the production cost) and the particle size of rubber particles, the particle size is bimodal in the range of 0.05-0.6μm, preferably 0. 1-0.4μm, so that ABS resin products have excellent surface properties and toughness.
⑵ Synthesis of graft polymer: Grafting of polybutadiene with styrene and acrylonitrile is the core unit in ABS production. Polybutadiene latex with bimodal particle size distribution was continuously fed into emulsion grafting reactor for graft polymerization with styrene and acrylonitrile monomer mixture. With the increase of the ratio of monomer to polybutadiene, the molecular weight and grafting degree of graft polymer and SAN*** polymer increase, and the internal grafting rate generally increases with the increase of rubber particle size and the decrease of rubber crosslinking density. When the particle size and rubber crosslinking density are fixed, the grafting degree and grafting density are the factors that determine the properties of ABS products.
Synthesis of SAN * * * polymers: There are three methods to synthesize styrene and acrylonitrile * * * polymers: emulsion method, suspension method and bulk method. The bulk method adopts thermal initiation continuous polymerization, and the product is pure, high quality and less pollution. In SAN synthesis, especially in large ABS production plants, it is replacing suspension method. The suspension method uses initiator, and the product of batch polymerization is not as pure as that of bulk method, which causes environmental pollution, but the process is simple, the flow is short, the investment is low, and the polymerization heat is easy to escape, so the suspension method is more economical for small and medium-sized devices. Emulsion process has a long technological process and backward technology, which has been basically eliminated in developed countries.
⑷ Blending and post-treatment: Finally, the obtained ABS graft polymer and SAN*** polymer are blended in different proportions to obtain a variety of ABS resin products, and the blending mode makes the products have great flexibility.
There are two methods in the post-treatment process of blending SAN with graft polymer: in the "wet method", a large amount of water is removed from the grafted rubber solution, and the obtained rubber particles or blocks are sent to a special extruder for drying, mixing and granulation together with SAN particles. In the "dry method", a large amount of water in the grafted rubber solution is removed by a centrifuge, then dried by nitrogen and oxygen, and the dried grafted rubber particles are mixed with SAN particles, extruded and dried. Both processes are continuous production, and the equipment details are patented technology.
2. Continuous bulk technology:
In recent years, the continuous ABS process has been further improved and gradually established its position as the main ABS production process. From the perspective of environmental protection and investment, this paper examines ontology.
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