TPE Material Development Case: Application Research on the Overmolding of TN60B-DDGJ Handle in the Electric Tools Industry
Time of issue:2026-01-19
I. Customer Needs and Background
The customer is an electric tool manufacturer, and their core requirements are as follows:
- Rubber-coating adhesion It bonds firmly with PA substrates (including glass fiber-reinforced PA, PA6, and PA66) and carries no risk of delamination.
- Hand feel and durability Smooth and delicate surface texture, with a hardness of 60A (Shore A), resistant to oil stains and abrasion.
- Processing adaptability Adapts to a 220℃ injection molding process, with a molding cycle of ≤30 seconds and a yield rate exceeding 95%.
- Cost-controllable Under the premise of ensuring performance, the material cost must be 10% lower than that of similar products on the market.
II. Development Process and Sample Validation
1. First-generation test sample: TN70B-15 (Result: NG)
- Adjust direction ：
- Increase the hardness to 70A (Shore A), with the goal of enhancing the handle's impact resistance.
- Increase the glass fiber filler ratio, with a target tensile strength of 5 MPa.
- Reason for failure ：
- The hardness is too high (measured at 72A), and customers have reported poor comfort when holding the handle, leading to fatigue after prolonged use.
- The melt index has dropped to 6 g/10 min (190℃/5 kg), making injection molding filling difficult and resulting in a yield rate of only 65%.
- Microcracks have appeared at the rubber-coated interface, and the adhesion strength does not meet the standard.
- Conclusion ： NG There is an imbalance between hardness and machinability.
2. Second test sample: TN65A-05 (Result: NG)
- Adjust direction ：
- Reduce the hardness to 65A (Shore A) by using a low-cost plasticizer, with the goal of achieving a 15% cost reduction.
- Optimize fluidity, with a melt index target of 8 g/10 min.
- Reason for failure ：
- The adhesive strength of the rubber-coated bond has decreased (peel strength < 20 N/cm), and the interface between the PA substrate and the TPE is prone to delamination.
- After the oil resistance test (ASTM D471, 24 hours), the surface swelled and felt sticky to the touch.
- Costs were reduced by 12%, but overall performance failed to meet the standard.
- Conclusion ： NG Sacrificing performance for cost advantages is not feasible.
3. Final solution: TN60B-DDGJ (Result: OK)
- Formula Design ：
- TPE matrix + polar modifier to enhance chemical bonding with PA.
- Add nano-talc powder to balance hardness (60A) with a smooth, silky surface feel.
- Performance performance ：
- The peel adhesion of the coated material is greater than 35 N/cm, and it has passed a cold-and-hot cycling test from -40℃ to 80℃ (200 cycles without cracking).
- Melt index: 9 g/10 min (190℃/5 kg); injection molding cycle: 25 seconds; yield rate: 98%.
- Tensile strength: 4 MPa; elongation at break: 500%; tear strength: 24 kN/m; well-balanced overall performance.
- Verification result ：
- Customer mass-production testing: 5,000 units produced continuously, with a 99.2% pass rate for encapsulation and excellent tactile feedback that has received positive feedback from end users.
- Costs are 8% lower than those of competitors, achieving the business goal.
- Conclusion ： OK Passed acceptance testing and has achieved mass supply.
III. Key Issues and Solutions
IV. Case Summary and Value
- Technical Insights ：
- For TPE-coated products, interface adhesion strength should be prioritized, with chemical compatibility taking precedence over individual mechanical properties.
- Matching the melt index with the injection molding process is a key factor in improving yield.
- Commercial value ：
- TN60B- DDGJ After successful importation, the customer’s annual procurement volume increased to 20 tons, and its market share grew by 15%.
- Establish a dedicated formulation library for “PA-coated TPE,” shortening the development cycle of similar projects by 30%.
- Follow-up plan ：
- Develop TN60B- DDGJ The Pro series supports antistatic (surface resistance ≤ 1×10^9 Ω) and flame-retardant (UL94 V-2) features.
- Explore the two-color injection molding process to achieve integrated molding of intricate textures and colors.
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