PET preform mould with gloss and thermal distortion

PET Preform Mould injection molding process is a very important plastic processing technology is one of the PET plastic bottles, the majority of cases, plastic packaging plant will be used to blow molding the way the production process, but the injection molding process is particularly unique Processing advantages, for PET Preform Mould injection molding, the technical staff need to consider many factors, as follows.

PET Preform Mould PET plastic Description: PET chemical called polyethylene terephthalate, also known as polyester. Currently used in the customer is the most GF-PET, mainly to brew the embryo. PET has good rheological properties in the molten state, and the effect of pressure on the viscosity is greater than the temperature. Therefore, the flowability of the melt is mainly changed from the pressure.

PET chemical and physical properties: PET glass transition temperature of 165 ℃, the material crystallization temperature range is 120 ~ 220 ℃. PET has a strong hygroscopicity at high temperatures. For glass fiber reinforced PET materials, bending deformation is very prone to occur at high temperatures. The degree of crystallization of the material can be increased by the addition of a crystallization enhancer. Transparent products processed with PET have gloss and thermal distortion. Special additives such as mica can be added to PET to minimize bending deformation. If a lower mold temperature is used, transparent products can also be obtained using non-filled PET materials.

Injection molding process: The injection molding method is mainly used to enhance the molding of PET. Usually, a screw-type injection machine is used. Screws are generally required to be hardened to avoid abrasion after prolonged use. The length of the injection nozzle hole should be as short as possible, its diameter should be controlled at about 3mm. Enhance the melting point of PET up to 260 ℃, to prevent nozzle clogging, install a larger power heater. In addition, the tip of the nozzle hole is preferably machined into an inverted cone as shown in Fig. 1 so that the molten material in the flow path and the nozzle can be easily cut off.

Injection molding machine: Injection molding is mainly used to enhance the molding of PET. PET under normal circumstances can only use a screw-type injection molding machine. It is best to use the top of the mutant screw with a reverse ring, the surface hardness and wear resistance, length and diameter ratio is not L / D = (15 ~ 20): 1 compression ratio of about 3: 1. L / D too much material in the barrel to stay too long, excessive heat easily leads to degradation, affecting product performance. The compression ratio is too small less shear heat, PET Preform Mold is easy to plastic, poor product performance. The other will make the glass fiber more brittle, mechanical properties. Processing of glass fiber reinforced PET, the barrel wall wears more powerfully, and the use of wear-resistant materials, such as manufacturing or lining with wear-resistant materials. The nozzle is short as well, the inner wall requires polishing, and the aperture is as large as possible. It is better to use a hydraulic brake valve-type nozzle. The nozzle should be kept warm, and the temperature is controlled to ensure that the nozzle does not freeze. But the nozzle temperature can not be too high, otherwise cause salivation. Before the start of molding must use low-pressure PP material, the barrel clean.

PET Preform Mould main injection molding conditions: 1, barrel temperature. The PET molding temperature range is narrow; the level of temperature will directly affect the performance of the products. If the temperature is too low, the plastic is not good, so that plastic parts depression, lack of material, and other defects; on the other hand, if the temperature is too high, it will cause overflow, nozzle salivation, color deepening, and mechanical strength, and even cause degradation. Usually, the cylinder temperature is controlled at 240 ~ 280 ℃, the glass fiber reinforced PET cylinder temperature is 250 ~ 290 ℃, shall not exceed 300 ℃, the nozzle temperature is generally lower than the cylinder temperature by 10 ~ 20 ℃.2, mold temperature. Mold temperature directly affects the melt cooling rate and crystallinity; different crystallinity results in different plastic parts with different performance. Usually, the mold temperature control is in the 100 ~ 140 ℃ range. When forming thin-walled plastic parts, a small value is chosen; when forming thick-walled plastic parts, the choice of larger value is chosen. 3. Injection pressure. PET melt flow is good, easy to shape, usually using medium pressure, the pressure of 80 ~ 140MPa, glass fiber reinforced PET injection pressure of 90 ~ 150MPa. Determination of injection pressure should consider the viscosity of PET, the type and number of fillers, gate location and size, plastic parts shape and size, mold temperature, and injection molding machine type.