Polymethyl methacrylate (PMMA), also known as Acrylic, is an amorphous plastic.
The uses of POLYmethyl methacrylate are as follows:
Mainly used for decoration, sunglasses, stationery, surface, instrument watchcase, lampshade, billboard production.
The main properties of POLYmethyl methacrylate are as follows:
1. PMMA is difficult to catch fire and can burn slowly.
2, high transparency, light weight, not easy to deformation, good light conductivity.
3, impact resistance and surface hardness are slightly poor, easy to scratch, so the packaging requirements are higher.
4, not resistant to alcohol, ketone, strong alkali, soluble in aromatic hydrocarbons, chlorinated hydrocarbons (trichloroethane can be used as adhesive).
5, forming shrinkage rate is small (0.2-0.8%), often take 0.5-0.6%. Easy to form, stable size. Commonly used internal mold S136H, (because ordinary steel can not save to high finish, must use mirror steel)
Polymethyl methacrylate molding process knowledge is as follows:
1, the die surface to maintain smooth, chrome plating corrosion resistance. In order not to affect the production transparency, color, use less release agent and should increase the mold Angle, convenient release.
2, high mold temperature products with high transparency, and reduce poor welding, especially can reduce the internal stress of products, and easy to fill the cavity, mold temperature is generally 70-90℃
3, high transparency, beer plastic defects bubble, flow lines, impurities, black spots, silver and other obvious exposure, so the molding difficulty is high, low production rate.
4, raw materials fully dry dry insufficient silver wire, bubble phenomenon. Drying time: 6HRS, material room, layer thickness is not more than 30mm, and with enough cavity under the premise of the temperature should not be too high, in order to reduce discoloration, silver wire and other defects. Temperature parameters: front barrel temperature 200-230℃, middle barrel temperature 215-235℃, rear barrel temperature 140-160℃.
5, the design of the mold runner to be simple, smooth, generally made into S shape to improve the surface of the product cloud, gas lines and other defects, the wide gate for molding. Various types of inlet. When the wall thickness of the product is less than 4mm, the flow channel size is 16.0-18.0mm. When the wall thickness of the product is greater than 4mm, the size of the flow channel is 18.0-112.0mm. Exhaust groove size 0.05-0.07mmx1.5mmx6.0mm. Gate size 0.7-0.9TX2T.
6, reduce the internal stress heat treatment temperature 70-80℃ (hot air or hot water slow cooling treatment time depends on the product wall thickness and general 4HRS).
7, reduce beer plastic black spots:
1) Ensure raw materials clean (clean environment)
2) Clean the mold (regularly)
3) Machine cleaning (cleaning the front end of the barrel, screw, nozzle, etc.).