I. Project Background and Customer Requirements

Target product High-end kitchenware handles (such as scissors and spatulas) must meet the following core requirements:

1. Security Compliant with the EU food contact standards (EU2020/1245), non-toxic and with no risk of migration.
2. Functional : Resistant to kitchen environments (oils, high-temperature steam, and cleaning agents); exhibits strong adhesion to PP/PE substrates, with a peel strength exceeding 3.5 N/mm.
3. Processability Injection molding yield > 95%, with no defects such as mold sticking or color variations.

 

II. Preliminary Material Testing and Problem Identification

1. TPO-TO6700 (Transparent TPO) ：

Advantages: Good demolding performance and excellent chemical resistance.

Problem: When coating with PP/PE, the adhesion is insufficient, and the peel strength is only 1.8 N/mm (the requirement is ≥3.5 N/mm).

Root cause: TPO has low polarity, resulting in poor compatibility at the PP/PE interface and preventing effective bonding between molecular chains.

2. TPU-T7001 (Transparent TPU) ：

Advantages: Bonding performance meets the standard (peel strength of 3.0 N/mm), with high transparency.

Problem: During injection molding, severe sticking to the mold occurs, resulting in a demolding damage rate exceeding 15%, and the material cost is relatively high.

Root cause: The TPU exhibits high viscoelasticity, resulting in significant frictional resistance between the melt and the mold, and the lack of lubrication makes demolding extremely difficult. Customer feedback: Both materials fail to meet the dual requirements of “adhesion + processability,” necessitating the development of a completely new solution.

III. Development Strategies and Key Technological Breakthroughs

1. Material System Reconstruction: TPO/SEBS Blending Modification

• Substrate Selection ：
  • Retain the oil-resistant and weather-resistant advantages of TPO;
  • Introducing SEBS elastomer, which enhances polarity through its styrene segments, thereby improving adhesion to PP/PE.
• Additive Optimization ：
  • Lubricant Add 0.5% silicone-based lubricant to reduce melt viscosity and minimize injection molding friction.
  • Compatibilizer Using maleic anhydride-grafted POE (2% addition rate) to enhance the interfacial adhesion between TPO and the substrate;
  • Dispersion control Replace the externally mixed color powder with pre-mixed color masterbatches to address the issue of uneven color dispersion.

2. Precise control of the injection molding process

• Temperature adjustment The injection molding temperature was reduced from 210℃ to 190℃ for TPU, thereby preventing high-temperature degradation and improving flowability.
• Mold optimization The mold surface is coated with a nano-scale release coating, reducing the demolding force by 40%. The number of ejector pins has been increased to minimize localized stress concentration during demolding.
• Improved Color Powder Process Using a color-dyeing process (pre-mixing with color masterbatches), the color difference ΔE value has been reduced from 1.2 to within 0.5.

3. Performance Validation and Iteration

• Bonding performance The peel strength has been increased from 1.8 N/mm for TPO to 3.8 N/mm (exceeding the customer’s requirements).
• Demolding property The demolding damage rate has decreased from 15% for TPU to less than 2%.
• Compliance Passed the full set of tests under EU2020/1245 (including heavy metal migration and sensory testing, etc.);
• Durability After 1,000 cycles of high-temperature steaming (100℃ steam), there was no cracking or deformation.

IV. Mass Production Results and Customer Value

1. Production performance ：

The injection molding yield has increased from 85% for TPU to 98%, and production efficiency has improved by 20%.

The finished PP handle with rubber coating features no delamination and no color variation, achieving the appearance standards of high-end kitchenware.

2. Cost optimization ：

Material costs are 20% lower than those of imported TPU and only 5% higher than the initial TPO solution.

Reducing the use of mold release agents can save approximately 10,000 yuan in production costs annually.

3. Customer reviews ：

“ EN9508E-JDSB It perfectly solves two major industry challenges: poor adhesion of TPO and poor processability of TPU. Moreover, it has passed our most rigorous durability tests and has fully replaced the original imported materials.

 

V. Summary of Experience and Industry Insights

1. Technical level ：

Polarity-balanced design: By blending TPO and SEBS and adding a compatibilizer, we achieve compatibility between "high adhesion and chemical resistance."

Lubrication-assisted demolding: A synergistic effect between silicone lubricants and mold coatings breaks through the traditional bottlenecks in TPU demolding.

2. Process level ：

Masterbatch pre-mixing process: Effectively addresses the dispersion challenges of externally blended color powders and enhances batch-to-batch consistency.

Low-temperature injection molding strategy: Avoid material degradation while reducing energy consumption.

3. Market value ：

Offer cost-effective, domestically produced solutions for food-contact-grade coated products.

Break the reliance on imports; this can be extended to sectors with high demands for safety and durability, such as small household appliances and maternal and infant products.