What solutions exist for poor adhesion in TPR materials?

Poor adhesion is a common issue in TPR material applications. Whether bonding to substrates like metal or plastic, or achieving interlayer adhesion within the material itself, insufficient bonding strength can lead to delamination, detachment, and seal failure. This is particularly problematic in applications such as coated products, seals, and toy components, directly impacting product quality and lifespan. Resolving this issue requires multi-dimensional optimization across materials, processes, and surface treatments. Here are specific solutions from the Zhongsu Wang editorial team:

I. Optimizing the TPR Material Formulation

The composition of TPR forms the foundation for adhesion. Bond strength can be enhanced through three adjustments:

First, appropriately increasing the proportion of polar components—such as introducing small amounts of polar resins into non-polar systems—to improve compatibility with polar substrates. Second, controlling plasticizer dosage—excessive amounts may migrate and form weak interface layers, so reduce usage or select low-migration types; Third, adding specialized adhesion promoters like silane coupling agents or maleic anhydride graft copolymers to form chemical bonds at the interface, thereby enhancing bond strength.

II. Improving the Surface Condition of Substrates

The cleanliness and roughness of substrate surfaces directly affect adhesion effectiveness: First, thoroughly remove surface contaminants like oil, dust, and release agents using alcohol wipes, plasma cleaning, or alkaline washing. Second, roughen surfaces through sanding or sandblasting to increase contact area and enhance mechanical interlocking. For low-polarity substrates (e.g., certain plastics, metals), activate surfaces via plasma etching or chemical etching to boost polarity and reactivity.

III. Adjusting Molding and Bonding Process Parameters

Process conditions must align with bonding requirements: During molding, carefully control temperature—too low reduces TPR flowability and prevents adequate substrate wetting, while too high may cause degradation. Simultaneously optimize pressure and holding time by moderately increasing pressure and extending holding duration to minimize interfacial voids. For secondary molding (e.g., TPR coated), ensure appropriate preheating of substrates to prevent bonding failure due to excessive temperature differentials.IV. Selecting Complementary Bonding Methods

When foundational adjustments yield limited results, employ supplementary methods: First, select specialized adhesives (e.g., polyurethane-based, neoprene-based) compatible with both TPR and substrates, ensuring even application without bubbles. Second, incorporate mechanical interlocking structures—such as recesses or protrusions in substrates—to embed TPR during molding, achieving dual reinforcement through mechanical interlocking and material adhesion. Third, employ hot-press bonding to promote interfacial molecular diffusion at specific temperatures and pressures, enhancing bond strength.

In summary, addressing poor adhesion in TPR materials requires a comprehensive approach: establish a solid foundation through formulation, eliminate barriers via surface treatment, strengthen bonding through process optimization, and utilize supplementary methods when necessary to enhance stability. In practice, it is recommended to first test solutions in small batches before scaling up to mass production, balancing adhesion strength with cost control.