ABS plastic is a terpolymer of acrylonitrile (a), butadiene (b) and styrene (s). The relative contents of the three monomers can be changed at will to make various resins.
ABS plastic has the same characteristics as these three components. A makes it resistant to chemical corrosion and heat and has a certain surface hardness. B makes it have high elasticity and toughness. S makes it have the processing and molding characteristics of thermoplastic and improves its electrical properties. Therefore, ABS plastic is a kind of "tough, hard and rigid" material, with easily available raw materials, good comprehensive performance, low price and wide application. ABS plastics have been widely used in machinery, electric power, textiles, automobiles, airplanes, ships and other manufacturing and chemical industries.
key property
Plastic ABS resin is the most widely used polymer with the largest output. It organically unifies all kinds of properties of PB, PAN and PS, and has excellent mechanical properties of toughness, hardness and rigidity in balance. ABS is a terpolymer of acrylonitrile, butadiene and styrene, where A stands for acrylonitrile, B stands for butadiene and S stands for styrene. After practical use, it is found that ABS plastic pipe is not resistant to sulfuric acid corrosion and will be crushed and broken when it meets sulfuric acid.
Because it has three components, it has good performance; Acrylonitrile endows ABS resin with chemical stability, oil resistance, certain stiffness and hardness; Butadiene improves toughness, impact resistance and cold resistance; Styrene makes it have good dielectric properties and good processability.
Most ABS is non-toxic and impermeable to water, but slightly permeable to water vapor, with low water absorption. Soaked in water for one year at room temperature, the water absorption rate is less than 65,438+0%, but the physical properties remain unchanged. The surface of ABS resin products can be polished to obtain high gloss products. The strength is 3-5 times higher than that of ordinary plastics.
ABS has excellent comprehensive physical and mechanical properties and good impact resistance at low temperature. Dimensional stability. Good electrical properties, wear resistance, chemical resistance, dyeability, finished product processability and machinability. ABS resin is resistant to water, inorganic salts, alkali and acid, insoluble in most alcohols and hydrocarbon solvents, but soluble in aldehydes, ketones, esters and some chlorinated hydrocarbons. ABS resin has low thermal deformation temperature and poor heat resistance. The melting temperature is 2 17~237℃, and the thermal decomposition temperature is above 250℃. At present, many modified ABS materials on the market are doped with nozzle materials and recycled materials. Therefore, the performance of customers' molded products is not very stable.
preparation method
There are many production methods of ABS, which can be divided into four categories: blending method, grafting method and grafting-blending method, and there are about eleven preparation processes. Now emulsion method is widely used, and emulsion grafting method is the most promising one at present. By changing the ratio of the three monomers and adopting different polymerization methods, ABS can produce products of various specifications, including graft polymers with elastic backbone and graft polymers with resin backbone. Generally, the proportion of the three monomers ranges from 25% to 35% of acrylonitrile, 25% to 30% of butadiene and 40% to 50% of styrene.
Because PC/ABS is a mixture of two polymers, and PC is the main component, mottling sometimes occurs at the gate when processing products, which is usually caused by the melt expanding into the mold cavity during high-speed injection. Caused by melt fracture. From the aspect of molding technology, measures can be taken to reduce the appearance of PC/ABS products, such as increasing the material temperature, increasing the nozzle temperature and slowing down the injection speed. It can also increase the mold temperature, increase the overflow groove, increase the gate size and modify the gate shape. For example, a fan-shaped gate or an ear-shaped gate can be used for large thin-walled parts, and a Gall-shaped groove is formed at the gate outlet, so that the injection, material flow impact point and residual stress near the gate are concentrated in the ear-shaped groove without affecting the quality of PC/ABS parts. At the same time, weld marks will also appear due to multi-gate injection molding or multi-branching.