Reference Table of Molding Temperatures for Common Injection Molding Materials
The injection molding temperature is one of the core process parameters that determine the quality of injection molded products. It is mainly divided into two key dimensions: the melting temperature and the mold temperature. The melting temperature directly affects the melting state, fluidity, and melt strength of the plastic raw material. If the temperature is too low, the raw material will not be fully melted, resulting in defects such as material shortage and obvious weld marks on the product; if the temperature is too high, it is prone to cause material degradation, leading to yellowing of the product and a decline in mechanical properties.
The mold temperature is related to the cooling and solidification process of the plastic melt in the mold cavity, and has a significant impact on the dimensional stability, surface finish, and internal stress distribution of the product. To help injection molding technicians quickly match the temperature parameters of different materials and improve production efficiency and product qualification rate, this article has compiled a reference table of molding temperatures for common injection molding materials, along with key application instructions.
| Material Name | Abbreviation | Melt Temp Range (℃) | Mold Temp Range (℃) | Key Molding Notes |
|---|---|---|---|---|
| Low Density Polyethylene | LDPE | 160-200 | 30-60 | Good flowability, easy to mold; avoid high pressure/speed to prevent deformation |
| High Density Polyethylene | HDPE | 180-220 | 40-70 | High crystallinity; uniform cooling required to maintain toughness |
| Polypropylene | PP | 170-220 | 20-80 | Brittle at low temp, prone to degradation at high temp; GF reinforced grade needs +10-20℃ melt temp |
| Rigid Polyvinyl Chloride | PVC-U | 160-190 | 30-60 | Poor thermal stability; decomposes above 200℃ (releases HCl); use dedicated screw machine |
| Flexible Polyvinyl Chloride | PVC-P | 140-170 | 20-50 | Contains plasticizer (good flow); strict temp control to prevent plasticizer migration |
| Acrylonitrile Butadiene Styrene | ABS | 200-240 | 50-80 | Amorphous, moderate flow; prone to yellowing at high temp; higher mold temp for electroplating grade |
| Polycarbonate | PC | 240-300 | 70-120 | High hygroscopicity; dry fully (120℃, 4-6h); high melt viscosity, need high injection pressure |
| Polymethyl Methacrylate | PMMA | 210-260 | 40-80 | Transparent; prone to silver streaks; control injection speed to avoid melt fracture |
| Polyamide 6 | PA6 | 220-270 | 40-90 | High hygroscopicity (dry before molding); mold temp affects crystallinity (higher temp improves toughness) |
| Polyamide 66 | PA66 | 260-300 | 60-100 | Higher melting point than PA6; GF reinforced grade needs enhanced mold cooling |
| Polystyrene | PS | 180-220 | 20-60 | Good flow; prone to stress cracking at low temp; annealing required for finished parts |
| Polyoxymethylene | POM | 180-220 | 60-120 | Crystalline, narrow melt range; prone to decomposition; control screw speed/back pressure |
In the actual injection molding production process, the above-mentioned temperature parameters are only reference values for conventional material grades. When applying them, specific adjustments need to be made based on the type of material modification, the structural characteristics of the product, and the performance of the equipment.
For modified materials such as glass fiber reinforced, flame retardant, and impact resistant, due to the addition of fillers which alters the melting characteristics of the material, the melting temperature usually needs to be increased by 10-30℃ to ensure that the melt has sufficient fluidity to fill the mold cavity. The setting of mold temperature should take into account both product quality and production efficiency.
High mold temperature can reduce internal stress in the product and improve surface quality, but it will prolong the cooling time and reduce production efficiency; low mold temperature can accelerate the molding process, but it may cause uneven shrinkage and warping deformation of the product. In addition, factors such as the type of screw in the injection molding machine, the size of the clamping force, the wall thickness and complexity of the product, will also have an impact on the final setting of the molding temperature.
In conclusion, properly controlling the injection molding temperature is a crucial step in achieving high-quality and efficient production. Technicians should base their work on the reference table and optimize the parameters according to the actual production conditions. Through mold testing and verification, they should continuously adjust until they determine the suitable temperature scheme.
