Why use heat-curing adhesive to bond silicone to other materials?

Silicone heat-vulcanization bonding agents play a crucial role in the process of bonding silicone to other materials (such as plastics, metals, and glass) via heat vulcanization; their core functions can be summarized as follows:

1. Enhance bond strength

①Chemical bonding: Silicone heat-vulcanization primers form chemical bonds between the silicone and the substrate surface through chemical reactions, significantly enhancing bond strength. For instance, active ingredients in the primer can react with silicon-hydrogen bonds in the silicone or polar groups on the substrate surface to form robust covalent bonds.
②Mechanical interlocking: The primer can penetrate the micropores or surface irregularities of the substrate; upon curing, it forms a mechanical interlocking structure that further strengthens the bond.

2. Improve surface compatibility

①Surface activation: Silicone and certain materials (such as non-polar plastics like PP and PE) possess low surface energy, making direct bonding difficult. Treatment agents enhance compatibility between the silicone and the substrate by altering surface polarity or increasing surface roughness.
②Removal of contaminants: Treatment agents clean the material surface, removing impurities such as oil and dust to ensure a clean bonding interface and prevent bond failure caused by contaminants.

3. Promote the vulcanization reaction

①Catalytic function: Some treatment agents contain vulcanization catalysts (such as platinum catalysts) that accelerate the silicone vulcanization reaction, shorten curing time, and enhance production efficiency.
②Vulcanization rate control: Adjusting the treatment agent formulation allows for control over the vulcanization rate, preventing bonding defects (such as bubbles or cracking) caused by the process proceeding too quickly or too slowly.

4. Improve weather resistance and chemical resistance.

①Temperature Resistance: The treatment agent enhances the high-temperature resistance of the bonded area, ensuring stable adhesion for silicone composite products even in high-temperature environments; for instance, certain agents enable the bond to withstand temperatures exceeding 200°C.
②Chemical Resistance: The treatment agent improves the chemical resistance of the bonding interface, protecting against corrosion from substances such as acids, alkalis, and solvents, thereby extending the product's service life.

5. Optimize process performance

①Leveling properties: The treatment agent improves the leveling of the silicone coating, ensuring uniform coverage on the substrate surface and reducing defects such as flow marks and orange peel.
Self-deaeration: Some treatment agents feature self-deaerating capabilities, automatically expelling air bubbles during the curing process to prevent a reduction in bond strength caused by trapped air.
②Processability: The treatment agent can adjust the viscosity of the silicone, making it easier to apply or injection-mold and enhancing production flexibility.

When bonding materials, it is essential to choose the right adhesive.