TPE injection parts are mostly used in shoes, toys, auto parts, adhesive and other fields. Plastic parts peeling is a common problem, its causes and prevention measures are as follows:

First, skin reasons

1. Insufficient compatibility of each component of the formula:

The compatibility of components in the TPE material formulation is not good, and the phenomenon of peeling delamination is prone to occur during molding, especially at the gate position. The physical and chemical properties of each component are very different, such as molecular weight, melting point, softening point, etc., which may also lead to incompatibility, resulting in skin delamination.

2. Improper mold design:

The size of the gate is too small, resulting in excessive shear of the melt as it passes through the gate, causing the melt to break and thus forming a skin on the surface of the product.

The sudden change of mold cavity design may also affect the flow distribution of melt and lead to peeling phenomenon.

3. The injection speed and pressure are too high:

High injection speed and pressure will increase the shear force generated by the melt at the gate position and the cavity mutation position, thus aggravating the peeling stratification phenomenon.

Injection temperature and mold temperature are too low:

Too low injection temperature and mold temperature will lead to poor material fluidity, and the melt will cure too fast in the mold, resulting in a lack of fusion between the cured and the incomplete cured material, resulting in peeling phenomenon.

4. excessive pressure:

The thermoplastic elastomer is relatively soft, and even after curing, the pressure holding can further push the material into the cavity, resulting in poor integration of the subsequent advancing melt with the already cured material and the formation of skin.

Second. Preventive measures

1. Optimize material selection and matching:

Choose TPE raw materials with better compatibility, or improve the compatibility between different components by adding compatibilizers. If SEBS is compatible with PP and SBS is compatible with PS, graft SEBS should be added when TPU is present in the formula.

Ensure the compatibility between TPE raw materials and compounding agents (such as rheological additives, plasticizers, etc.) to avoid uneven flow and stress concentration caused by mismatches.

2. Improve mold design:

Appropriately increase the size of the gate to avoid excessive shear when the melt passes through the gate.

Optimize the mold cavity design to ensure that the flow distribution of melt in the mold cavity is uniform.

3. adjust the injection molding process parameters:

Appropriately reduce the injection speed and pressure to reduce shear friction and stress concentration.

Adjust the temperature parameters to ensure good flow of the material during injection molding, while avoiding material degradation due to too high temperature or poor flow due to too low temperature.

Appropriately reduce the holding strength to prevent delamination caused by cold and hot melt contact.