Synergistic Compatibility Analysis of PET Decorative Film and PUR Hot Melt Gule: Mechanism, Advantages, and Application Prospects

1. Complementary Material Properties: The Physicochemical Basis of Compatibility

PET (polyethylene terephthalate) decorative film possesses high surface hardness, excellent weather resistance, rich color expression, and environmentally friendly characteristics. However, its low surface energy and chemical inertness result in insufficient interfacial bonding strength with traditional adhesives. PUR (polyurethane reactive) hot-melt adhesive contains highly reactive isocyanate groups in its molecular structure, which can form a cross-linked network structure with the substrate under moisture catalysis, combining the processing convenience of hot-melt adhesives with the ultimate bonding strength of reactive adhesives. When combined, the high mechanical strength of the PET film and the flexible cross-linked network of the PUR Hot Melt Gule form a "rigid-flexible" composite system, maintaining interfacial stability even under thermal stress.

2. Interfacial Bonding Mechanism: From Physical Adsorption to Chemical Anchoring

Traditional bonding relies on van der Waals forces and mechanical interlocking, while the PET/PUR system achieves strong interfacial bonding through a triple synergy:

• Surface Energy Matching: Plasma treatment increases the surface energy of PET from ~40 mN/m to ≥50 mN/m, forming good wetting with the PUR Hot Melt Gule;

• Chemical Bond Construction: Hydroxyl and carboxyl groups grafted onto the PET surface react with the -NCO groups in PUR Hot Melt Gule to form polyurethane/urea bonds, increasing the peel strength to 8-12 N/25mm (ISO 8510-2 standard);

• Shrinkage Rate Coupling: The thermal shrinkage rate of modified PUR Hot Melt Gule (0.3%, ASTM D1204) is highly matched with that of the PET film (≤0.5%), eliminating the risk of delamination.

3. Process Adaptability: Technical Support for Precision Manufacturing

• Low-Temperature Activation Characteristics: The activation temperature of  PUR Hot Melt Gule (110-130℃) is significantly lower than the glass transition temperature of PET film (~78℃), avoiding thermal deformation of the substrate;

• Rheological Optimization: Thixotropic PUR Hot Melt Gule maintains zero adhesive penetration at a coating thickness of 0.1-0.3mm (EN 12701 standard);

• Stress Dissipation Design: After curing, PUR Hot Melt Gule forms an elastomer phase (storage modulus E’≈5 MPa), which can absorb the 0.4% linear expansion of the PET film caused by temperature changes.

4. Performance Verification: Durability Performance in Extreme Environments

After 1000 hours of double 85 testing (85℃/85% RH), the adhesion strength retention rate of the PET/PUR Hot Melt Gule system is >85%, superior to the traditional EVA system (<60%). In -40℃~120℃ thermal cycling, there is no cracking at the interface (compliant with IATF 16949 automotive interior standards), and its hydrolysis resistance (ASTM D3137) meets the 25-year weather resistance requirements for outdoor building materials.

5. Industrialization Value: From Cost Optimization to Technological Iteration

Currently, the mass production cost of domestically produced PET/PUR composite film is 18-25% lower than imported products, and it supports customized spectral reflectivity (adjustable in the 380-780nm band). In the automotive interior field, this system passes VOC emission tests (≤50μg C/g) and meets the FMVSS 302 flame retardant standard, marking the evolution of polymer interface engineering from "adhesion" to "functional integration".

Conclusion: Adaptability-Driven Industrial Chain Upgrade

The compatibility of PET film and PUR Hot Melt Gule is essentially a systematic integration of surface and interface science, polymer rheology, and precision process control. This system not only solves the long-standing "film-substrate separation" problem in the decorative industry but also provides a transferable technological paradigm for flexible electronic packaging, new energy battery insulation, and other fields through the targeted design of material genomics. With the popularization of domestically produced high-speed PUR coating equipment (120 m/min) and online plasma treatment modules, PET/PUR composite materials are expected to exceed a market size of 20 billion yuan by 2028, becoming one of the material foundations for high-end manufacturing in China.