How to Achieve Strong LSR Overmolding on PBT？

Liquid Silicone Rubber (LSR) overmolding has become a key manufacturing technique in automotive, electronics, and medical applications due to its flexibility, chemical resistance, and durability. Polybutylene Terephthalate (PBT), a high-performance engineering plastic, is often chosen as the substrate because of its mechanical strength and heat resistance. However, achieving strong adhesion between LSR and PBT can be challenging due to PBT’s low surface energy and semi-crystalline structure.

This is where CL-26AB-5 primer comes into play — a specially formulated solution designed to ensure reliable LSR-to-PBT bonding.

How CL-26AB-5 Primer Solves the Problem

CL-26AB-5 is two-parts primer engineered specifically for LSR overmolding on engineering plastics like PBT. Its benefits include:

1. Strong interfacial bonding: Forms covalent and hydrogen bonds between PBT and LSR, resulting in durable adhesion.

2. Easy application: Can be applied via spray, dip, or brush, with controlled thickness for consistent results.

3. Improved processing flexibility: Compatible with standard overmolding temperatures and pressures.

4. Long-term reliability: Resists aging, temperature cycling, and chemical exposure, making it ideal for demanding industrial applications.

 Application Guidelines

To achieve optimal results with CL-26AB-5:

1. Clean the PBT surface: Treat the substrates with solvent like industrial to remove dirts and oils.

2. Apply the Primer:  Mix completely the A and B with ratio 1:1 and apply the primer by dipping, brushing, spraying or silk screen printing method. 

3. Dry the Primer: Leave dry in room temp for 30 minutes or baking at 110-140℃ for 10 minutes

4. Proceed with LSR overmolding: Use standard injection molding parameters; the primer ensures strong adhesion even under thermal and mechanical stress.

Backed by a dedicated R&D team specializing in silicone-to-plastic interface technologies, we continuously optimize formulations and processes to ensure reliable adhesion across a wide range of applications. From automotive to electronics and medical devices, we provide tailored solutions that help customers improve product performance, reduce defect rates, and achieve advanced design goals. If you encounter problems with silicone bonding, please feel free to Contact Us.