POM injection molding material characteristics
Polyoxymethylene (POM) is divided into two types: homopolymerization and copolymerization. The copolymerized formaldehyde has good strength in a short period of time and the homopolyformaldehyde has good softness. The copolymer is 10 ° C higher than the homopolymerization softening point, and has a high heat distortion temperature under load, good thermal stability, and a wide molding temperature range. Commonly used in the industry is the copolymerization of formaldehyde. Paraformaldehyde is mostly used in luggage products and zippers. There are differences in the molding process. Asia Billiom Mold and plastic Discussed here is the copolymerization of formaldehyde.
Although the hygroscopicity of POM is smaller than that of PA, it is still dried before processing due to the degree of size and surface quality. Gears and other fine teeth: 100 ~ 120 ° C, 4 ~ 8 hours; general parts: 80 ~ 90 ° C, 3 ~ 4 hours.
The melting point of POM is 163 ° C, above which it melts. In general, most POMs have a processing range of 170 to 230 ° C and are typically used at temperatures ranging from 170 to 200 ° C. POM is a heat-sensitive plastic part that decomposes under heat for a long time, and the decomposed formaldehyde is easily oxidized to formic acid, and the formic acid further accelerates the decomposition of polyoxymethylene. If this is the case, it should be cleaned in time to eliminate decomposition products. Clean available PE.
Since formaldehyde is easily dissolved in water, the cleared POM material can be poured into a bucket of water to reduce smoke. Therefore, the following points should be proposed:
1. Do not heat the POM above 250 °C to avoid pyrolysis;
2. When the temperature of the cylinder exceeds 210 °C, the residence time of the POM melt in the cylinder shall not exceed 30 minutes. The higher the barrel temperature, the shorter the residence time.
3. As long as the machine is turned on, the nozzle temperature must be maintained at a temperature above the POM melting point (163 ° C). Thus, when overheating occurs, the nozzle will not clog.
4. If the machine has just processed PVC, it is necessary to clean the barrel strictly, and it is not allowed to mix PVC particles into the POM particles, otherwise a strong reaction will occur.
5. If it is necessary to stop: short-time stop, adjust the material temperature to near the melting point, remove the plastic in the barrel, the screw should always be in the forward position, turn off the heater. If it is necessary to stop for a long time, the application PE is cleaned according to the normal procedure.
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