Injection molding characteristics of polyethylene terephthalate
Publisher: Administrator Date：2021-08-02
Polyethylene terephthalate is abbreviated as PET. Typical application range of PET: There are structural devices such as mirror boxes in the automotive industry. Electrical components such as headlight reflectors, etc. In addition, electrical components include motor housings, electrical couplings, relays, switches, and internal components of microwave ovens. In terms of industrial applications again, there are pump housings, hand-operated instruments and so on. PET is applied to a wide variety of products.
Injection molding process conditions: First drying treatment: Drying treatment before processing is necessary, because PET is highly hygroscopic. The recommended drying condition is 120~165C, 4 hours of drying treatment. Secondly, the humidity should be less than 0.02%. Melting temperature: for non-filled type: 265~280C; for glass filled type: 275~290C. Mold temperature of re-injected parts: 80~120C. Injection pressure: 300~1300bar. The approximate range values of these parameters are like this.
There is also injection speed: higher injection speeds can be used without causing embrittlement. As well as runners and gates: all conventional types of gates can be used. Under normal circumstances, the gate size should be 50-100% of the thickness of the plastic part.
The chemical and physical properties of PET: The glass transition temperature of PET is about 165C, and the crystallization temperature of the material ranges from 120 to 220C. We know that PET has strong hygroscopicity at high temperature. For glass fiber reinforced PET materials, bending deformation is very easy to occur at high temperatures. This situation can be circumvented. The answer given here is that the crystallinity of the material can be improved by adding a crystallization enhancer.
Transparent products processed with PET have gloss and heat distortion temperature. Special additives such as mica can be added to PET to minimize bending deformation. This effect is very obvious. According to experience, it can be known that if a lower mold temperature of injection molded parts is used, transparent products can also be obtained using non-filled PET materials. Transparent products made of PET materials are also very rare.
The process conditions of PET are drying treatment first, melting temperature second, reaching an ideal value, and then mold temperature and injection pressure reaching an ideal value. PET also requires injection speed, and the gate should be half or double the thickness of the plastic part. PET also has the conversion temperature and crystallization temperature, which can increase the crystallinity of the material by adding a crystallization enhancer. PET processing transparent products also have experience to follow, adding special additives can reduce its bending deformation.