Injection molding process of transparent plastic
Due to the advantages of light weight, good toughness, easy molding, and high cost, plastic is increasingly being used instead of glass in modern industry and daily products, especially in the fields of optical instruments and packaging industry, with rapid development. However, due to the requirements for good transparency, high wear resistance, and good impact resistance, the composition of the plastic, the entire injection molding process, configuration, mold, etc. should be examined. We must undertake a significant mission to ensure that the plastic used to replace glass (hereinafter referred to as transparent plastic) has excellent surface quality and meets the requirements for use. Compared to reinforced nylon.
At present, the commonly used transparent plastics in the market include polymethyl methacrylate (PMMA, commonly known as acrylic or organic glass), polycarbonate (PC), polyethylene terephthalate (PET), transparent nylon, acrylonitrile styrene copolymer (AS), polysulfone (PSF), etc. Among them, the three plastics that we come into contact with the most are PMMA, PC, and PET. Taking these three plastics as examples, we will discuss the characteristics and injection molding process of transparent plastics.
Performance of transparent plastics
Transparent plastic must first have high transparency, which mainly has certain strength and wear resistance, can resist impact, have good heat resistance, and enhance nylon. Good chemical resistance and low water absorption are necessary to meet the requirements of transparency and remain unchanged for a long time during use.
Injection molding process of transparent plastic
The process characteristics of PC include high viscosity, high melting temperature, and poor flowability. Therefore, injection molding must be carried out at a higher temperature (between 270-320T). Relatively speaking, the range of material temperature adjustment is narrower, and the processability is not as good as PMMA. The injection pressure has a relatively small impact on fluidity, but due to its high viscosity, a larger injection pressure is still required. To prevent internal stress, nylon is reinforced accordingly. The holding time should be as short as possible.
The process characteristics of PET are high molding temperature and narrow material temperature adjustment range (260-300 ℃), but after melting, the flowability is good, so the processability is poor, and anti flow devices are often added in the nozzle. The mechanical strength and performance are not high after injection, in fact, it enhances nylon. Performance can only be improved through stretching and modification processes. Accurate control of mold temperature is to prevent warping. Due to its important role in deformation, it is recommended to use hot runner molds. The mold temperature is high, otherwise it will cause poor surface gloss and difficulty in demolding.