Transparent plastic products materials and molding process
Because the plastic has the advantages of light weight, good toughness, easy molding. Low cost advantages, so in the modern industry and household products, more and more plastic instead of glass, particularly applied to optical instruments and packaging industry, particularly the rapid development of. But because of the requirements of the transparency is better wear resistance, high impact toughness, better, so the plastic components, injection molding the entire process, equipment. Die, make a lot of work, to ensure that these are used instead of glass plastic ( hereinafter referred to as the transparent plastic), good surface quality, so as to achieve the requirements of the use of.
Currently on the market generally use transparent plastic with polymethyl methacrylate ( commonly known as Maria or organic glass, code-named PMMA ), polycarbonate (code PC ). Polyethylene terephthalate (code PET ), transparent nylon. AS ( acrylonitrile styrene copolymer ), polysulfone (code PSF ), in which we have the most contact is PMMA. PC and PET three kinds of plastic, the knitting width limited, following on the three kinds of plastic as an example, discusses the characteristics of transparent plastic and injection molding process.
One, transparent plastic performance
Transparent plastic must first have high transparency, secondly to have a certain strength and abrasion resistance, can impact resistant, good chemical resistance, excellent water absorption rate to, to small, only such ability in use, can satisfy the requirements of transparency and unchanged for a long time, below are listed in Table L, PMMA, PC and compare the performance of PET.
Note: ( 1) for variety, this is averaged, the actual data is different in different varieties. ( 2) PET data ( Mechanical ) by drawing the data.
From the data in Table 1 shows PC is the ideal choice, but in the price of its raw material is expensive and injection process is more difficult, so still use PMMA, ( the general requirements of the products ), and PPT due to the after stretching to get good mechanical properties, so much in the packaging, container using.
In two, a transparent plastic injection molding process should pay attention to the common problems
Due to high light transmittance of transparent plastics, inevitable requirement of plastic product surface quality requirements strictly, cannot have any markings, pores, whitening. Misty, black spots, discoloration, unfavourable luster and other defects, and so the whole process of raw materials, equipment. Die, even product design, to pay great attention to and strictly even special requirements. Secondly, because the transparent plastic for high melting point, poor mobility, so as to ensure the surface quality of the products, often in barrel temperature, injection pressure, injection rate and other parameters for fine adjustment, the plastic injection not only can fill the die, and does not have the internal stress caused by deformation and cracking.