As the plastic has a light weight, Clear Corrugated Plastic Sheets good toughness, easy molding. Low cost advantages, so in modern industrial and household products, Clear Corrugated Plastic Sheets more and more use of plastic instead of glass, especially for optical instruments and packaging industry, the development is particularly rapid. However, due to the requirements of its transparency is good, Clear Corrugated Plastic Sheets high wear resistance, impact toughness is better, so the composition of plastic, plastic injection of the entire process, equipment, mold, etc., have to make a lot of work to ensure that these are used to replace the glass Plastic (hereinafter referred to as transparent plastic), the surface quality is good, so as to achieve the requirements of use. Currently on the market generally use transparent plastic polymethyl methacrylate (commonly known as acrylic or plexiglass, code pmma), Clear Corrugated Plastic Sheets polycarbonate (code pc). Polyethylene terephthalate (code pet), transparent nylon. Asp (styrene-styrene-styrene copolymer), polysulfone (code psf), etc., Clear Corrugated Plastic Sheets which we have the most contact is pmma, pc and pet three kinds of plastic, due to limited space, the following three kinds of plastic as an example to discuss Transparent plastic properties and injection molding process.
Transparent plastic must first have a high degree of transparency, followed by a certain degree of strength and wear resistance, to impact resistance, Clear Corrugated Plastic Sheets heat resistance is better, chemical resistance is excellent, water absorption is small, Clear Corrugated Plastic Sheets only in order to use, to meet the transparency Requirements and long-term change, the following list of Table 1, compare the performance of pmma, pc and pet.
Transparent plastic due to high transmittance, plastic products must be required to meet the quality of surface quality, can not have any markings, stomata, whitening. Fog halo, black spots, discoloration, poor gloss and other defects, and thus in the entire injection process on raw materials, Clear Corrugated Plastic Sheets equipment. Mold, and even product design, should be very careful and put forward strict or even special requirements. Second, because the transparent plastic is mostly high melting point, poor mobility, so in order to ensure the product's surface quality, often in the machine high temperature, injection pressure, Clear Corrugated Plastic Sheets injection speed and other technical parameters for minor adjustments, so that when the injection molding material is full of mold, Will produce internal stress caused by product deformation and cracking.
Pc viscosity, high melting temperature, poor mobility, Clear Corrugated Plastic Sheets it must be a higher temperature injection (270-320 ℃ between), relatively narrow range of temperature adjustment, the process is not as good as pmma. Injection pressure on the mobility of small, but because of the viscosity, still larger injection pressure, the corresponding in order to prevent the internal stress, Clear Corrugated Plastic Sheets the holding time to be as short as possible. Shrinkage, large size, but the product stress, easy to crack, it is appropriate to improve the temperature rather than pressure to improve the mobility, and from the mold temperature, improve the mold structure and post-processing to reduce the possibility of cracking. Clear Corrugated Plastic Sheets When the injection speed is low, the gate prone to ripple and other defects, radiation nozzle temperature to separate control, Clear Corrugated Plastic Sheets mold temperature should be high, the flow channel, gate resistance to small.
Pet molding temperature is high, and the temperature adjustment range is narrow (260-300 ℃), but after melting, good liquidity, so the process is poor, and often in the nozzle to increase the anti-flow device. Mechanical strength and performance after injection is not high, Clear Corrugated Plastic Sheets must be through the drawing process and modification in order to improve performance. Mold temperature control, is to prevent warping, deformation of the important element, back to the proposed hot runner mold. Clear Corrugated Plastic Sheets Mold temperature is high, otherwise it will cause the surface gloss difference and stripping difficult.
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