ABS (acrylonitrile - butadiene - styrene terpolymer) resin is a kind of polymer material with high demand and rapid development between engineering plastics and general-purpose plastics.ABS sheet (plate) thermoforming products are more commonly used in automobile manufacturing industry, such as dashboards, decorative panels, etc.; in the electronic and electrical appliances, the main common products are manufactured in the inner liner of refrigerators, televisions, washing machines, shells, decorative panels and other products. ABS is used in thermoforming technology.
ABS extrusion board (sheet) material to implement the Ministry of Light Industry standard SG397-1984, the main technical requirements are as follows:
1. Appearance. The surface of the board (sheet) should be smooth and even, not allowing obvious ripples and traces of loss of material, uniform colour, no bubbles and scrapes. The surface is not allowed to have more than 1mm impurity or black spot, and the impurity or black spot below 1mm shall not be more than 5 per square metre.
2. Physical properties. Tensile strength (longitudinal/horizontal) Greater than or equal to 38.2MPa; impact strength (longitudinal/horizontal) Greater than or equal to 0.13kJ/m; heat distortion temperature Greater than or equal to 80 degree .
1.Process flow
Batching I> drying I> extrusion I> head shaping I> three-roller calendering I> bridge cooling I> trimming I> haul-off I> cutting I>
2. Main equipment and characteristics
1) Dryer. The drying equipment for ABS raw material for extruding plate (sheet) is preferably a counter-current dehumidifying dryer, with a general drying capacity of 2 tonnes.
2) Extruder. ABS board (sheet) materials used in general for single-screw extruder, screw type for the single-lead, full screw, equal pitch of the two-stage feed, its length and diameter ratio of (25:1) ~ (35:1). The compression ratio of the first feeding section of the screw is 2.5:1, the compression ratio of the second feeding section is 2:1, and the thread rise angle is 17.7 degree .
The main advantage of two-stage screw is that exhaust equipment can be used to help drying, volatile gases are discharged in the exhaust section in the middle of the two screws, which shows obvious advantages over the ordinary screw under the same situation, and the exhaust measures are very important for the production of high-quality boards (sheets).
The screw should be driven by stepless speed regulation motor, the barrel must have a more sensitive cooling device, easy to control the temperature, the error range of the temperature of a single zone should be between -3~3C.
3) Three-roll calender. Three-roll calender consists of three independently driven high finish rollers. The introductory roll is to take the molten plate (sheet) blank moulded by the head, and pull and press it to the required thickness by the pressure applied between the two rolls. The centre roll also serves to polish or finish and cool the plate (sheet) surface. The three rolls can be heated by steam, oil or water. In addition, the speed fluctuation of each roll should be within 1% during normal production.
4 ) Traction device. Usually consists of two rubber rollers of the same diameter and do rotate in opposite directions. The traction speed is slightly greater than the three-roll calender.
