TPR, usually refers to styrenic thermoplastic elastomer SBS, SEBS and other resins and additives mixed into a dry molecular alloy of elastomers (TPES). As the most commonly used TPE refers to styrene elastomer alloy TPES, and the TPE in China generally refers to TPES elastomer, therefore, the TPE/TPR in this paper is based on SEBS, SBS base material modified materials.
The problem of TPE/TPR injection temperature -
Influencing factors: oil filling rate; SEBS/SBS molecular weight and molecular conformation (linear or star); product thickness; special material formulations and equipment and mold problems, etc.
1. The higher the oil-filling ratio, the lower the injection temperature should be.
2. The injection temperature of SEBS base material is higher than SBS base material, because the thermal stability of SEBS base material is better than SBS base material.
3. SEBS, SBS molecular weight, high injection temperature; star SEBS / SBS system, injection temperature is higher than the linear SEBS SBS system.
4. For special materials, such as TPE with sticky PA, the introduction of high melting point phase components in the formulation makes the injection temperature higher.
5. products with large thickness require higher injection temperature than products with thin thickness.
6. Equipment type or melt capacity, as well as mold design (including runner, inlet design and the number of cavities in a mold, etc.) will have an impact.
In terms of hardness and injection method, the recommended injection temperature range is as follows (the specific temperature is adjusted according to the TPE grade provided by the supplier combined with the actual processing situation).
1.TPE hardness 0C~15A super soft material, injection molding temperature 130~200℃;
2.TPE/TPR hardness 20~110A single material injection material, recommended injection temperature 140~230℃.
3. TPE/TPR covered PP, the recommended secondary injection temperature 170~200℃;
4. TPE/TPR encapsulated ABS,PC, the recommended secondary injection temperature is 180~220℃.
5. TPE/TPR coated PA, the recommended secondary injection temperature is 240~270℃.
6. TPR coated PS (HIPS, GPPS), the recommended secondary injection temperature is 160~190℃.
In short, about the TPE/TPR material injection temperature, the general supplier can only give a reference value according to the material type. It should also be combined with the product structure size, processing equipment and mold design and other factors to consider, and gradually adjust the most appropriate injection molding temperature according to the actual processing conditions.
TPE/TPR shrinkage rate, 1 ~ 3%, low hardness TPE shrinkage rate is larger, other formula system is the same, the filling amount of TPE shrinkage rate is smaller than the filling amount of small TPE.