Polycarbonate (PC) (Laxen) commonly known as "bulletproof glass glue", is an amorphous plastic (actually semi-crystalline), its main uses are as follows:
Is mainly used in machinery, instruments, medical equipment, telecommunications equipment, bulletproof glass, coffee pot, gear, screw, rack, click wheel, spindle, bearings, washers, rivets, pump impeller, carburetor parts, lamp shade, flash lamp shade, throttle valve, lubricating oil pipeline, a variety of shells, containers, refrigeration and cooling equipment parts, electrical wiring board, coil skeleton, acid storage battery And high temperature lens.
Its main properties are as follows:
1, can be reinforced with glass fiber.
2, PC material impact resistance is the best in plastic.
3, poor fatigue strength, sensitive to the notch, poor stress cracking resistance.
4, transparent appearance, rigid with toughness. Slow burn, slow extinguish after leaving the fire.
5, good chemical stability, but not alkali, ketone, aromatic hydrocarbon and other organic solvents.
6, forming shrinkage rate is small (0.5-0.7%), often 0.6%. The finished product has high precision and stable size. Commonly used internal mold S136H, (because ordinary steel can not save to high finish, must use mirror steel)
The molding process of polycarbonate (PC) is as follows:
1, the mold temperature is controlled in 80-100℃ is appropriate, the purpose of controlling the mold temperature is to reduce the difference between mold temperature and material temperature, reduce internal stress.
2, after molding, in order to reduce the internal stress, can use annealing treatment, annealing temperature: 125-135℃. Annealing time 2HRS, naturally cooled to room temperature.
3, poor liquidity, high pressure injection is needed. Overflow edge value 0.06mm. But the injection pressure is too high, will make the product residual large internal stress and easy to crack.
4, injection speed is too fast, easy to appear melt rupture phenomenon, there will be spots around the gate, product surface roughness and other defects, or because of poor exhaust (trapped gas) and make the product burnt.
5, PC at high temperature, that is, to trace water is also very sensitive, so before forming should be fully dry, so that the moisture content reduced to 0.015-0.02% below. Drying conditions: temperature 110-120℃, drying time: 8-12hrs.
6, PC material viscosity is very sensitive to temperature, increase the temperature into, the viscosity has a significant decline. Temperature parameters: front barrel temperature 240-260 ℃, middle barrel temperature 260-280℃, rear barrel temperature 220-230℃. The barrel temperature shall not exceed 310℃. PC material molding after improving the barrel temperature is favorable to plasticizing, and the general plastic processing barrel temperature control is the principle of high and low.
7, the mold design requirements are higher: the mold design as far as possible to make the runner short and thick, less bending parts, with a circular section shunt, careful grinding and polishing. In short, the flow resistance is reduced to suit its high viscosity plastic filling. In addition, the molten material is hard and easy to damage the mold, and the cavity and core should be hardened by heat treatment or hard chromium plating. Various types of inlet. Exhaust groove size 6 0.05mmx1.5mmx6.0mm. Gate size 0.7tX2t.