POM (also known as Saigang, Trane). It is obtained by polymerizing formaldehyde and the like. POM-H (polyoxymethylene homopolymer) and POM-K (polyoxymethylene copolymer) are high-density, high-crystallinity thermoplastic engineering plastics. Has good physical, mechanical and chemical properties, especially excellent friction properties.
POM is a crystalline plastic and its melting point is obvious. Once it reaches the melting point, the melt viscosity drops rapidly. When the temperature exceeds a certain limit or the melt is heated for too long, it will cause decomposition.
Copper is a catalyst for POM degradation, and copper and copper materials should be avoided where they come in contact with the POM melt.
1, plastic processing POM water absorption is small, generally 0.2% -0.5%. In general, POM can be processed without drying, but wet raw materials must be dried. Drying temperature above 80 °C, time 2 hours or more, according to the specific supplier should be carried out.
The proportion of recycled materials used is generally not more than 20-30%. But depending on the type of product and the end use, it can reach up to 100%.
2. The selection of POM in addition to the requirement for the screw to have no stagnation area, there is no special requirement for the injection molding machine, and generally injection molding can be used.
3, mold and gate design Common mold temperature control is 80-90 °C, runner diameter 3-6mm, gate length is 0.5mm, gate size depends on the thickness of the glue wall, the diameter of the round gate should be at least The thickness of the product is 0.5-0.6 times, the width of the rectangular gate is usually 2 times or more the thickness, the depth is 0.6 times the wall thickness, and the draft is 40′-1°30′.
Exhaust system POM-H thickness 0.01-0.02mm width 3mm
POM-K thickness 0.04mm width 3mm
4. Melt temperature can be measured by air-ejection method POM-H can be set to 215 °C (190 °C -230 °C)
POM-K can be set to 205°C (190°C-210°C)
5, the injection speed is usually medium speed is too fast, too slow and easy to produce ripple, too fast and easy to produce radiation and shear overheating.
6, the lower the back pressure the better, generally not more than 200bar
7. Residence time POM-H can be retained for 35 minutes at 215°C without POM-H retention. POM-K can be retained at 205°C for 20 minutes without severe decomposition. The melt cannot be retained in the barrel at the injection temperature. 20 minutes. The POM-K can be held at 240°C for 7 minutes. If the machine shuts down, the barrel temperature can be reduced to 150°C. To stop the machine for a long time, the machine must be cleaned and the heater turned off.
8. Stopping the barrel must use PE or PP, turn off the electric heat, push the screw in the front position. The barrel and screw must be kept clean. Impurities or dirt can alter the POM's superheat stability (especially POM-H). Therefore, when the halogen-containing polymer or other acidic polymer is used up, the POM material can be used only after the PE is cleaned, otherwise an explosion will occur. Improper pigments, lubricants, or materials containing GF nylon can cause plastic degradation.
9. Post-treatment For parts that are used at very high temperatures and have high quality requirements, heat treatment is required.
For the annealing treatment, the product can be immersed for 30 minutes in a ** solution with a concentration of 30%, and then visually observed to determine whether there is a residual stress crack.
POM post-treatment process temperature time air bath annealing 140-150 °C for every 5mm increase in the thickness of the wall to increase 40-60 minutes oil bath annealing 140-150 °C for every 5mm increase in wall thickness increases 20-30 minutes
POM is a crystalline plastic and its melting point is obvious. Once it reaches the melting point, the melt viscosity drops rapidly. When the temperature exceeds a certain limit or the melt is heated for too long, it will cause decomposition.
Copper is a catalyst for POM degradation, and copper and copper materials should be avoided where they come in contact with the POM melt.
1, plastic processing POM water absorption is small, generally 0.2% -0.5%. In general, POM can be processed without drying, but wet raw materials must be dried. Drying temperature above 80 °C, time 2 hours or more, according to the specific supplier should be carried out.
The proportion of recycled materials used is generally not more than 20-30%. But depending on the type of product and the end use, it can reach up to 100%.
2. The selection of POM in addition to the requirement for the screw to have no stagnation area, there is no special requirement for the injection molding machine, and generally injection molding can be used.
3, mold and gate design Common mold temperature control is 80-90 °C, runner diameter 3-6mm, gate length is 0.5mm, gate size depends on the thickness of the glue wall, the diameter of the round gate should be at least The thickness of the product is 0.5-0.6 times, the width of the rectangular gate is usually 2 times or more the thickness, the depth is 0.6 times the wall thickness, and the draft is 40′-1°30′.
Exhaust system POM-H thickness 0.01-0.02mm width 3mm
POM-K thickness 0.04mm width 3mm
4. Melt temperature can be measured by air-ejection method POM-H can be set to 215 °C (190 °C -230 °C)
POM-K can be set to 205°C (190°C-210°C)
5, the injection speed is usually medium speed is too fast, too slow and easy to produce ripple, too fast and easy to produce radiation and shear overheating.
6, the lower the back pressure the better, generally not more than 200bar
7. Residence time POM-H can be retained for 35 minutes at 215°C without POM-H retention. POM-K can be retained at 205°C for 20 minutes without severe decomposition. The melt cannot be retained in the barrel at the injection temperature. 20 minutes. The POM-K can be held at 240°C for 7 minutes. If the machine shuts down, the barrel temperature can be reduced to 150°C. To stop the machine for a long time, the machine must be cleaned and the heater turned off.
8. Stopping the barrel must use PE or PP, turn off the electric heat, push the screw in the front position. The barrel and screw must be kept clean. Impurities or dirt can alter the POM's superheat stability (especially POM-H). Therefore, when the halogen-containing polymer or other acidic polymer is used up, the POM material can be used only after the PE is cleaned, otherwise an explosion will occur. Improper pigments, lubricants, or materials containing GF nylon can cause plastic degradation.
9. Post-treatment For parts that are used at very high temperatures and have high quality requirements, heat treatment is required.
For the annealing treatment, the product can be immersed for 30 minutes in a ** solution with a concentration of 30%, and then visually observed to determine whether there is a residual stress crack.
POM post-treatment process temperature time air bath annealing 140-150 °C for every 5mm increase in the thickness of the wall to increase 40-60 minutes oil bath annealing 140-150 °C for every 5mm increase in wall thickness increases 20-30 minutes