Basic knowledge of poly (methyl methacrylate) (PMMA) introduced
Basic knowledge of poly (methyl methacrylate) (PMMA) introduced
Poly (methyl methacrylate) (PMMA) plexiglass (Acrylic), commonly known as "acrylic" is a non-crystalline plastic.
Polymethyl methacrylate used for the following purposes:
Mainly used for accessories, sunglasses, stationery, surface, instrument case, shade, billboard production.
Polymethyl methacrylate main properties are as follows:
PMMA difficult to fire and slow combustion.
2, high transparency, light weight, easy to deformation, good guide light.
3, the impact resistance and surface hardness are somewhat less easy to scratch, so the higher packaging requirements.
4, intolerant of alcohol, ketone, alkali, can be dissolved in aromatic hydrocarbons, chlorinated hydrocarbons (TCA sticky full agent).
5, the mold shrinkage (0.2-0.8%), often take 0.5-0.6%. Easily molded, dimensional stability. Commonly used within the mold material S136H Province to high-quality finish (for ordinary steel material can not be used mirror steel)
Polymethyl methacrylate molding process knowledge is as follows:
1, the mold surface remains smooth, chrome-plated anti-corrosion. Does not affect the production of transparency, color, and as little as possible with a release agent should increase the mold angle, easy mold release.
2, high transparency of high mold temperature products, and reduce poor welding, especially products can reduce the internal stress, and easily filled cavity, the mold temperature is generally 70-90 ¡ã C
3, Acrylic high transparency, the plastic beer defects vocational bubbles, rhyolite, impurities, black spots, silver and other significant exposure, so forming a high degree of difficulty, the production of Minamata low grid.
4, the raw material is dried thoroughly inadequate drying occurs silver bubble phenomenon. Drying time: 6hrs material houses, thickness no more than 30mm, and with enough under the premise of the filled cavity, the temperature should not be too high, in order to reduce the discoloration, silver, and other defects. Temperature parameters: barrel temperature of 200-230 ¡ã C, in barrel temperature 215-235 ¡ã C, after the barrel temperature of 140-160 ¡ã C.
5, mold design flow channel should be simple, smooth, normally made in the S-shaped in order to improve the product surface, clouds, gas lines and other defects, the width of the gate enabling molding. The various forms of the feed inlet. When the wall thickness is less than 4mm, the flow channel dimensions 016.0-018.0mm. When the wall thickness greater than 4mm, the runner dimensions 018.0-0112.0mm. Exhaust slot size 0.05 the-0.07mmX1.5mmX6.0mm. The gate size 0.7-0.9tX2t.
6 to reduce the internal stress of the heat treatment temperature of 70-80 ¡ã C (slow cooling hot air or hot-water processing time depending on the wall thickness may be general 4hrs).
7 to reduce the the molding black spots:
1) to ensure that the raw materials clean (clean environment)
2) Clean the mold (regular)
3) Clean the machine (clean barrel front-end, screw, nozzle, etc.).
