Precautions for TPV Injection Molding

TPV is a thermoplastic vulcanizate combining rubber elasticity and plastic processability, widely used in seals, damping parts, automotive components, and overmolded products. However, its high viscosity, slow cooling, and easy sticking require strict process control to avoid defects such as sinking, bubbles, flow marks, delamination, and deformation.

Raw Material Drying and Handling

Although TPV has low moisture absorption, it should be dried at 60–80°C for 1–2 hours before production. Over-drying must be avoided to prevent hardening and yellowing. TPV should not be mixed with other plastics. The screw and barrel must be thoroughly cleaned. The recycled ratio should be limited to 10–20% to maintain mechanical properties.

Mold Structure and Conditions

Runners and gates should be short and large to reduce shear resistance. Cooling systems must be uniform and sufficient to control shrinkage and warping. Draft angle should be at least 1.5°–2°, and cavity surfaces should be polished. Ejection should be large-area and balanced to avoid deformation and tearing. For overmolding, the substrate surface must be clean to ensure bonding.

Injection Molding Parameter Control

TPV processing follows the principles of medium-low temperature, medium-low speed, moderate pressure, and sufficient cooling. Barrel temperature is generally 170–210°C. Mold temperature is 30–50°C. High temperatures cause sticking and degradation. Injection speed should be moderate to avoid over-shearing. Pressure and holding time should be minimized to prevent stress and deformation. Sufficient cooling time is critical for stable dimensions.

Operational and Product Handling

Clean the barrel before starting production. Check appearance regularly for sinking, bubbles, sticking, and delamination. Ejected parts should cool naturally before packing to avoid deformation. Excessive release agent must be avoided. During long pauses, lower the barrel temperature to prevent degradation.

Mold Cleaning and Maintenance

TPV may produce small amounts of deposits, so regular cleaning is necessary. Use soft cloths and air guns to keep the cavity clean. Avoid sharp tools that may scratch the mold. After production, clean the barrel, close cooling water, and apply rust protection.

Conclusion

Stable TPV production relies on controlled temperature, speed, cooling, ejection, and cleanliness. Comprehensive management of materials, mold, processing, and operation effectively reduces defects. Standardized processing and maintenance help achieve efficient, stable, and high-quality TPV injection molding.