Plastic ABS can also be said to be a modification of polystyrene. It has higher impact strength and better mechanical strength than HIPS, and has good processing properties. It can be processed by plastic molding equipment such as injection molding machines and extruders including injection molding, extrusion molding, blow molding, calendering, lamination, foaming, thermal forming, welding, coating, electroplating and machining. The water absorption of ABS is relatively high. The ABS plastic needs to be dried before processing. The drying temperature is 70 to 85℃ and the drying time is 2 to 6h. ABS products are prone to internal stress during processing. If the stress is too large and the product will crack, then annealing treatment should be carried out, and the parts should be placed in a hot air circulating drying box of 70 to 80℃ for 2 to 4h, and then cooled to room temperature.
Plastic ABS can be made into pipes, plates, sheets, and profiles and other products. Pipes can be used for various water pipes, air pipes, and delivery pipes for lubricants and fuel oil; plates and sheets can be used for floors, furniture, tanks, filters, wall interlayer and thermal forming or vacuum forming. The screw length-to-diameter ratio of the extruder is usually relatively high, L/D is between 18 to 22, and the compression ratio is (2.5 to 3.0). Extrusion technology in ABS plastic machining should use a gradual screw with torpedo head. The temperature of the barrel is 150 to 160℃ in the hopper, 180 to 190℃ in the front of the barrel, 185 to 195℃ in die head, and 180 to 200℃ in mold and the blow molding temperature can be controlled between 140 to 180℃.
ABS plastic is a terpolymer developed on the basis of polystyrene resin modification. Wherein A represents acrylonitrile, B represents butadiene, and S represents styrene. ABS resin has the comprehensive ABS plastic properties of three components. A can improve oil resistance and chemical resistance, and thus it has a certain surface hardness; B makes ABS rubbery and improves impact toughness; S makes ABS plastic show better fluidity and makes it have the good performance of ABS plastic machining.
ABS plastic products are mainly used to manufacture the shells of instruments, household appliances, telephones, televisions, etc. and ABS plastics for electroplating to give them metallic luster, and ABS is used to replace metal. Among the liners and plastic products of various models of refrigerators produced by our factory, ABS injection molded products account for more than 88% of the total number of refrigerator plastic products.
A screw-type injection molding machine is used to make the plastic in the barrel heated by an electric heating ring and the barrel screw rotate and generate heat by friction so as to pre-plasticize, melt and inject into the cavity, and then the product is ejected after cooling and opening the mold. The plasticizing effect is good, and the molding temperature can be slightly lower than that of other types of equipment. Avoid high temperature damage to the rubber phase. There are some precautions for using the injection molding machine.
(1) Each injection volume should be 50 to 75% of the maximum injection volume of the equipment.
(2) Single-head, equidistant, gradual, full-thread, and non-return screws are used. The length to diameter ratio L/D of screw is 20:1, and the compression ratio is 2 or 2.5:1.3). The nozzle can be an open general nozzle or an extended nozzle, avoiding the use of self-locking nozzles to reduce the injection process or cause material discoloration . In addition, there should be a heating and temperature control device on the nozzle.