Pet preform is a kind of widely used product. It is mainly made of plastic and has strong insulation. Many chemical plants will use pet preform. Do you know how experts predict the future development prospects of PET Preforms? The following is an introduction to the development trend and related knowledge of pet preforms.
[introduction to pet preform]
Pet chemical name is polyethylene terephthalate, also known as polyester. At present, gf-pet is widely used in customers, mainly for bottle making. The rheological property of pet in melt state is better, and the effect of pressure on viscosity is greater than that of temperature. Therefore, the fluidity of PET melt is mainly changed by pressure.
1. Treatment of plastics
Because pet macromolecules contain fatty groups and have a certain hydrophilicity, the particles are sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of pet decreases during processing, and the products are colored and brittle. The drying temperature is 150 ℃ for more than 4 hours, generally 170 ℃ for 3-4 hours. The air shot method can be used to check whether the material is completely dry. Generally, the proportion of recycled materials should not exceed 25%, and the recycled materials should be dried thoroughly.
2. Selection of injection molding machine
Due to the short stabilization time after the melting point of pet and the high melting point, it is necessary to select an injection system with more temperature control sections and less self friction heat generation during plasticization, and the actual weight of the product (water containing material) should not be less than 2 / 3 of the injection volume of the machine. Based on these requirements, Huameida has developed a series of pet special plasticizing systems in recent years. The clamping force should be greater than 6300 T / m2.
3. Mold and gate design
PET bottle preform is usually molded by hot runner mold. There should be a heat insulation board between the mold and the mold plate of the injection molding machine, with a thickness of about 12 mm, and the heat insulation board must be able to withstand high pressure. The exhaust must be sufficient to avoid local overheating or fragmentation, but the depth of the exhaust port should not exceed 0.03mm, otherwise it is easy to produce flash.
4. Melt temperature
It can be measured by air shooting method. The enhanced gf-pet can be set at 290-315 ℃.
5. Injection speed
Generally, the injection speed should be fast, which can prevent premature solidification during injection. But too fast, high shear rate makes the material fragile. Firing is usually done in 4 seconds.
6. Back pressure
The lower the better, to avoid wear. Generally not more than 100bar. It is usually unnecessary to use.
7. Retention time
Do not use too long residence time to prevent the decrease of molecular weight. Try to avoid the temperature above 300 ℃. If the shutdown time is less than 15 minutes. If it is more than 15 minutes, clean it with viscosity PE and lower the barrel temperature to PE temperature until it is started again.
8. Precautions
(1) the recycled material should not be too large, otherwise it is easy to "bridge" at the blanking place and affect the plasticization.
(2) if the mold temperature is not well controlled or the material temperature is not properly controlled, it is easy to produce "white fog" and opaque. The mold temperature is low and even, the cooling speed is fast, and the product is transparent with less crystallization.
[experts predict that the future development prospect of pet preform is very good]
Compared with the common plastic products, the mould has the inherent characteristics of high precision and low rigidity. The price of a set of mould for PET bottle blank group cavity is even higher than that of the host machine. Therefore, the mold closing mechanism must be able to play a good role in protecting the mold. In order to achieve this function, the clamping mechanism must have enough rigidity, excellent speed characteristics of locking and opening the mold, uniform deformation of the template and good deformation repetition accuracy.
PET bottle injection molding equipment is a high-end equipment, the development idea is different from the development of ordinary injection machine. Some units in China regard the research and development of PET bottle blank injection molding machine as ordinary medium and low-end products, and change the screw barrel as pet injection molding machine. From the beginning, they have taken a wrong route, so they always hover at the low-end level.
First of all, we should correct the development ideas and develop the PET bottle blank injection molding machine as a high-end product, in order to develop a high-performance PET bottle injection molding machine suitable for the market.
With the development of hot runner technology and the development of multi cavity mold, especially the application of PET bottle in geometric progression, the performance requirements of PET bottle blank injection molding machine are higher and higher. In order to adapt to the development of market, the mechanism and structure control of PET bottle blank injection molding machine further reflect the performance characteristics of special injection molding machine, mainly in the aspects of high speed, high efficiency and precision noodles.
The above introduction of "related introduction of pet preform" and "experts predict that the future development prospect of pet preform is very good". I hope you can understand the "development trend and related knowledge introduction of pet preform" to help you.
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