As the plastic has a light weight, good toughness, easy molding. Low cost advantages, Clear Corrugated Plastic Sheets so in modern industrial and household products, 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, high wear resistance, impact toughness is better, Clear Corrugated Plastic Sheets 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), polycarbonate (code pc). Polyethylene terephthalate (code pet), transparent nylon. Asp (styrene-styrene-styrene copolymer), Clear Corrugated Plastic Sheets polysulfone (code psf), etc., 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, heat resistance is better, Clear Corrugated Plastic Sheets chemical resistance is excellent, water absorption is small, only in order to use, to meet the transparency Requirements and long-term change, Clear Corrugated Plastic Sheets 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, equipment. Mold, and even product design, should be very careful and put forward strict or even special requirements. Second, Clear Corrugated Plastic Sheets 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, 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.
Preparation and drying of raw materials As the plastic contains any impurities, may affect the transparency of the product, so in the storage, transportation, feeding process, Clear Corrugated Plastic Sheets we must pay attention to seal to ensure that raw materials clean. In particular, the raw materials containing water, heating will cause deterioration of raw materials, it must be dry, and in the injection, the use of drying must be hopper. Also note that the drying process, the input air should be filtered, dehumidified, Clear Corrugated Plastic Sheets in order to ensure that will not pollute the raw materials.
In order to prevent the contamination of raw materials and the presence of old materials or impurities in the depressions of the screw and accessories, the resin with special thermal stability is present. Therefore, Clear Corrugated Plastic Sheets before the use, the cleaning agent is cleaned with the screw cleaning agent, Clear Corrugated Plastic Sheets When there is no screw cleaning agent, pe, ps and other resin can be used to clean the screw. When the temporary shutdown, in order to prevent the raw material at high temperatures for a long time to stay, causing degradation, the dryer and barrel temperature should be reduced, such as pc, pmma and other barrel temperature should be reduced to 160 ℃ below.
Pc viscosity, high melting temperature, poor mobility, it must be a higher temperature injection (270-320 ℃ between), relatively narrow range of temperature adjustment, Clear Corrugated Plastic Sheets 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. When the injection speed is low, the gate prone to ripple and other defects, radiation nozzle temperature to separate control, mold temperature should be high, the flow channel, Clear Corrugated Plastic Sheets gate resistance to small.
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