PU Primers: An Essential Solution for Bonding Footwear Materials

    TPU and PU are widely used in athletic and casual footwear, each offering different performance advantages. To achieve reliable bonding between these materials, PU Primers play a critical role. Below is a brief overview of the differences between TPU and PU, and the key PU primer categories.

Differences Between TPU and PU

    1. PU (Polyurethane)

        * Commonly used in foamed midsoles and outsoles

        * Lightweight, cushioned, abrasion-resistant

        * Focuses on comfort and shock absorption

    2. TPU (Thermoplastic Polyurethane)

        * Thermoplastic, strong and elastic

        * Excellent abrasion and tear resistance

        * Used for shanks, upper frames, air-cushion shells, and ETPU popcorn soles

    PU = comfort; TPU = strength and functionality.

What Is a PU Primer?

    A PU Primer is a surface treatment liquid applied before bonding PU or TPU materials.

    Main functions:

        * Increase surface energy for better adhesive wetting

        * Promote strong chemical and physical adhesion

        * Solve issues caused by material inertness or plasticizers

        * Enhance long-term durability under heat, humidity, and flexing

    Using a primer is essential for preventing debonding and ensuring reliable bonding performance.

PU Primer Product Categories

    1. PU Popcorn Primer Series (for ETPU)

    Features:

        * Ready-to-use

        * Excellent yellowing resistance

        * Designed for aromatic and aliphatic ETPU pellets

    Applications:

        * ETPU foam soles

        * High-elasticity sports shoe midsoles

    2. PU Primer Series (Single / Two-Component)

    1) Single-Component Primer

        * Easy to use

        * Fast drying

        * Suitable for most TPU and PU substrates

    2) Two-Component Primer

        * Higher bonding strength

        * Better heat and hydrolysis resistance

        * Ideal for outdoor and performance footwear

    Applications:

        * PU soles

        * TPU shanks and upper parts

Conclusion

    PU Primers significantly improve the bonding performance of TPU and PU materials. Choosing the right primer helps reduce adhesive failures, enhance product quality, and ensure stable footwear manufacturing.