Views: 0 Author: Site Editor Publish Time: 2025-07-17 Origin: Site
Common Causes and Typical Defects in TPE/TPR Injection Molding
TPE (Thermoplastic Elastomer) and TPR (Thermoplastic Rubber) often face injection molding defects—especially when producing thin-walled, slender, multi-gate, or complex-shaped products such as toothbrush handles, medical device grips, stationery accessories, and precision sealing gaskets.
The root cause: low melt strength and weak molecular chain entanglement. During injection molding, TPE and TPR melts can’t easily withstand shear forces and cooling shrinkage stress, leading to defects like flow marks, sink marks, and gate breakage, resulting in poor dimensional stability.
Boosting Melt Strength with TPV Modification
A practical solution is to add 5%–15% TPV (Thermoplastic Vulcanizate) into TPE or TPR compounds to enhance melt strength.
Key benefits of TPV modification:
Core mechanism: The crosslinked rubber phase in TPV increases intermolecular interactions, improving resistance to stretching and shearing forces while keeping thermoplastic processing characteristics.
Performance improvements:
Significantly reduce flow marks, sink marks, and gate breakage.
Achieve better dimensional accuracy and smoother product surfaces.
Slight increase in hardness (typically 1–3 Shore A); using low-hardness TPV grades can minimize impact on soft touch feel.
Improve weather resistance and aging performance, extending product lifespan.
Cost-effective TPE/TPR Base Materials and Applications
For balanced performance and cost, it’s recommended to choose TPE/TPR base resins with good compatibility with TPV:
| Base Material | Recommended Grades | Advantages | Suitable Applications |
| SEBS | YH-503T, 533, 602T | Excellent weather resistance, dry touch feel, great TPV compatibility | Medical grips, food-contact parts |
| SBS | YH-792E, 815E, 188E, 988 | Lower cost, moderate elasticity, good flowability | Stationery, standard gaskets, toy components |
Practical Tips for Implementation
1.Blending method: Mix TPV thoroughly with the base resin during pelletizing using a twin-screw extruder at 170–200°C for uniform dispersion.
2.Ratio adjustment:
Thin-walled or complex products: add 10%–15% TPV.
Thicker products: 5%–10% TPV is usually sufficient to balance cost and effect.
3.Process optimization: After TPV modification, the melt viscosity may slightly increase. Adjust injection temperature (+5–10°C) and hold pressure time to ensure complete mold filling.
By starting with proper pelletizing and TPV modification, manufacturers can effectively reduce injection molding defects in TPE and TPR products, improve production efficiency, and enhance product quality—achieving better results and higher profitability in the competitive plastics market.
NANJING HAISI is professional manufacturer of Plastic Extruder Machine, we supply Twin Screw Extruder, Single Screw Extruder, Plastic Recycling Extruder, Two Stage Extruder, Lab Scale Extruder, Mixing and Feeding Machine, Cooling and Pelletizing Machine, Crushing Machine and so on.
