(Polymethylmethacrylate, referred to as PMMA, English Acrylic), also known as acrylic or plexiglass, is called Aga Lijiao in Hong Kong。 Its casting plate polymer has a number average molecular weight of 2。2104 and a relative density of 1。19~1。20。 Acrylic plastics have a shrinkage of 0。6% in plastic molds, a refractive index of 1。482 to 1。521, a moisture absorption of 0。5% or less, and a glass transition temperature of 105 °C。 It has the advantages of high transparency, low price and easy machining。 It is a glass substitute material that is often used frequently。
Acrylic material properties durability:
The product has good protection for the built-in light source and prolongs the service life of the light source。 Rationality: rational design, rain and moisture proof; open structure for easy maintenance. Impact resistance: 200 times that of glass products, there is almost no risk of breakage。 Transmittance: up to 93%, excellent light transmission, soft light, dazzling。 (Light transmittance is higher than Polycarbonate plastic products) Flame resistance: It is flame retardant and can continue to burn after being fired。 Aesthetics: exquisite craftsmanship, full font with mirror effect, no wrinkles on the base, no seams, all riveting is not exposed. Energy-saving: good light transmission performance, correspondingly reduce light source products, save electricity, and reduce the cost of use. Weather resistance: the panel is coated with high-concentration UV absorber, and the metal base is sprayed with imported automotive paint, which can last for a long time and never fade。 The service life is 5-8 years。
Acrylic injection molding focus
(1) In Acrylic injection molding, we must pay attention to the weight of Acrylic finished product, which must be formed below 70% of the material capacity of the material. If it exceeds the machine that needs to be replaced by a large one, the hardness of the material is high, the viscosity is high, and the hydraulic motor usually needs to be added. A large drive torque is enough.
(2) The resistance of the raw material flowing in the material pipe is small, and the pressure loss is small. The tube set can be plated with 0.03-0.04mm, which increases the hardness and smoothness to obtain a smaller resistance.
(3) Its fluidity is not as good as abs, and it is necessary to increase the injection pressure and speed to form, and it is easy to form depressions and internal bubbles.
(4) The melting speed can be slowed down by 40%-50% to increase the heat of fusion. The melt pressure gauge is more suitable between 70~90kg/cm2, so that the temperature of the material can be adjusted.
(5) When there is shrinkage or vacuum bubble, if other conditions cannot be solved, back pressure can be added, which can be solved between 5kg/cm2~20kg/cm2。 If the back pressure is too high, it will cause overheating and driving difficulty。
(6) If it stays in the heated material tube for too long, it is easy to generate too much gas, and sometimes the screw is not easy to drive due to the resistance of the gas, and the continuous injection and retreat can be used to remove the gas.
(7) If the finished product of the meat is not deformed by cooling, it can be cooled by warm water soaking, and the temperature difference between the skin and the center is not too large, so that the shrinkage vacuum bubble can be prevented.
(8) When there is residual stress in the finished product, the strength of the finished product is reduced when it comes into contact with the solvent. In order to eliminate the internal stress, the hot mold can be used. The temperature of the material is increased, and the injection pressure can be lowered. For example, the internal stress is almost non-existent by compression molding.
(9) If the finished product has been produced a lot, in order not to be scrapped due to too high internal stress, annealing treatment can be performed, which can alleviate the tension of the outer surface and alleviate the internal stress.
(10) The secondary material recovery is the best raw material for cleaning the material pipe, and is set to about 240C.
(11) If the temperature is high in the rear part of the material tube, the screw will not produce sharp and abnormal sound.
Acrylic plastic injection molding applications
Acrylic is widely used as a transparent material with excellent properties in the following aspects:
1. Lamps, lighting equipment, such as various household lamps, fluorescent lampshades, car taillights, signal lights, road signs.
2. Optical glass, for example, manufactures various lenses, mirrors, prisms, television screens, Fresnel lenses, camera translucent lenses.
3。 Preparation of various instrumentation dials, covers, dials。
4。 Preparation of optical fibers。
5。 Product advertisement window, billboard。
6. Bulletproof glass for aircraft cockpit glass, aircraft and automobiles (with intermediate sandwich material).
7. A variety of medical, military, architectural glass.
The difference between Acrylic and Polycarbonate
Acrylic: Excellent transparency, excellent UV resistance; general impact strength and low flame retardancy. Maximum operating temperature: 70 ° C -80 ° C. Polycarbonate (polycarbonate): good transparency, excellent flame retardancy, excellent impact resistance, UV resistance. The highest working temperature: 115 ° C.
For most lighting products, the choice of Acrylic material for the lampshade is correct. Because the choice of suitable materials for the diffuse reflector of the lamp, good UV resistance, that is, the lamp shade is not the yellow when the lamp is in use is the most important consideration. In general, Polycarbonate plastics are commonly used in outdoor lighting fixtures, especially where impact requirements or flame retardant requirements are high. Polycarbonate materials should be selected for architectural lighting systems such as stations, terminals, schools, and government departments with high traffic.
Tips Acrylic plastic molds are usually made of highly transparent products. It is not suitable to use Thimble ejection on the top of the product. Usually, the stop pin runner is used around the product. After molding, it is cut off and polished. Acrylic materials have higher hardness and are usually polished with S136H quenching material or NAK80 material due to their stricter optical requirements. At the same time, the mold temperature requirement is relatively high in injection molding. To achieve better optical effect, it is recommended to take oil temp injection molding.