Polymethyl methacrylate (PMMA) is plexiglass, commonly known as "Acrylic", which is a non-crystalline plastic.

    The uses of polymethyl methacrylate are as follows:

    Mainly used in the production of decorations, sunglasses lenses, stationery, surfaces, instrument cases, lampshades, and billboards.

    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 deform, and good light guide.

    3. The impact resistance and surface hardness are slightly poor, and it is easy to scratch, so the packaging requirements are higher.

    4. It is not resistant to alcohols, ketones, and strong alkalis, and can be dissolved in aromatic hydrocarbons and chlorinated hydrocarbons (trichloroethane can be used as a bonding agent).

    5. The molding shrinkage rate is small (0.2-0.8%), usually 0.5-0.6%. Easy to form and stable in size. Commonly used inner mold material S136H, (because ordinary steel material can not save high finish, mirror steel must be used)

    The molding process knowledge of polymethyl methacrylate is as follows:

    1. The mold surface is kept smooth and chrome-plated to resist corrosion. In order not to affect the transparency and color of the production, it is advisable to increase the angle of mold release to facilitate the release of the mold by using as little release agent as possible.

    2. High mold temperature, high transparency of the product, and reduce poor welding, especially to reduce the internal stress of the product, and it is easy to fill the cavity, the mold temperature is generally 70-90 ¡æ

    3. Acrylic has high transparency, plastic defects, bubbles, flow lines, impurities, black spots, silver filaments, etc. are obviously exposed, so the molding difficulty is high, and the production rate is low.

    4. The raw materials are fully dried. Insufficient drying will cause silver wire and air bubbles. Drying time: 6HRS, the material housing, layer thickness does not exceed 30mm, and the cavity is sufficiently filled, the temperature should not be too high to reduce discoloration, silver wire and other defects. Temperature parameters: the temperature of the front barrel is 200-230¡ãC, the temperature of the middle barrel is 215-235¡ãC, and the temperature of the rear barrel is 140-160¡ãC.

    5. The design runner of the mold should be simple, smooth, and generally made into an S-shape to improve the defects such as flowing clouds and gas lines on the surface of the product. Wide gate is good for forming. Various forms of feed inlets. When the wall thickness of the product is less than 4mm, the size of the flow channel is 0�16.0-�0�18.0mm. When the wall thickness of the product is greater than 4mm, the size of the flow channel is 0�18.0-�0�112.0mm. The size of the exhaust slot is 0.05-0.07mmX1.5mmX6.0mm. Gate size 0.7-0.9tX2t.

    6. Reduce internal stress. The heat treatment temperature is 70-80¡æ (the time for slow cooling with hot air or hot water depends on the wall thickness of the product, generally 4HRS).

    7. Reduce beer black spots:

    1) Ensure that the raw materials are clean (clean environment)

    2) Clean the mold (regularly)

    3) Machine cleaning (cleaning the front end of the barrel, screw, nozzle, etc.).