What is the reason for the poor adhesion between TPE thermoplastic elastomer and PC?

In the diversified application scenarios of plastic products, the composite use of TPE thermoplastic elastomer and PC is becoming more and more common, such as electronic product shells with soft touch and high strength, automotive interior parts, etc. However, in actual production, TPE and PC often delaminate and debond, which not only affects the appearance of the product, but also affects its functionality and service life. So do you know what the reason is? Let's explore it with Huizhou Zhongsuwang editor.

I. The main reason for the poor adhesion between TPE thermoplastic elastomer and PC

1. Chemical structure difference: PC molecules contain polar carbonate groups and have high surface energy; while TPE thermoplastic elastomers such as SEBS are mostly non-polar or low-polar structures, and it is difficult for the two to form chemical bonds.

2. Surface energy mismatch: TPE thermoplastic elastomer has low surface energy, and cannot be fully spread on the PC surface after melting. There are gaps in the interface, resulting in low bonding strength.

3. Processing technology issues: PC processing temperature is high, TPE material has poor heat resistance, and the temperature difference during co-injection is prone to thermal stress; PC surface release agent residue will also affect the combination of the two.

4. Different crystallization behavior: Some TPE thermoplastic elastomers have microcrystalline structures, while PC is an amorphous polymer. The two have poor thermodynamic compatibility and are prone to stress concentration.

II. Methods to improve the poor adhesion between TPE thermoplastic elastomer and PC polycarbonate

1. Surface treatment

Chemical treatment: Use weak acid solution or organic solvent to wipe the PC surface to remove release agent and oil stains and increase surface energy.

Physical treatment: Use plasma or corona treatment to increase the polar groups on the PC surface and enhance the chemical bonding with TPE thermoplastic elastomer.

2. Adhesive selection

Special adhesive: Select adhesives containing polar groups, such as acrylates and polyurethanes, to form strong bonding through chemical reactions.

Blending compatibilizer: Add 5%-10% SEBS-g-MAH maleic anhydride grafted SEBS to TPE thermoplastic elastomer to improve compatibility with PC.

3. Process optimization

In-mold injection molding: Inject TPE material immediately after PC injection molding, and use the residual heat on the PC surface to promote intermolecular diffusion.

Hot melt welding: Use hot plate welding or ultrasonic welding to melt and combine the two materials at the interface.

4. Material modification

PC modification: Add 1%-3% of compatibilizer, ethylene-acrylic acid copolymer can improve the surface activity of PC.

TPE formula adjustment: Increase the styrene content to 30%-40% to enhance the interface bonding strength between TPE thermoplastic elastomer and PC.

To solve this problem, it is necessary to start with chemical modification, surface treatment and process optimization, and fill the gap in material properties by increasing interface polarity matching or physical anchoring. Only by specifically breaking through the compatibility bottleneck can TPE thermoplastic elastomer and PC achieve stable bonding, thus expanding the space for composite material applications.