Polyurethane Paint Replacement Film for Automotive Wrapping
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Solution Overview
Problem
Existing paint replacement films for vehicles lack the necessary combination of chemical resistance, weatherability, and stretchability, with top-coats in PVC-based films often cracking due to their non-stretchable nature, and other films being limited to application during component manufacturing rather than post-manufacture surface application.
Innovation Solution
A paint replacement film comprising a polyurethane layer produced from a formulation with blocked isocyanates and multiple polyols, having a glass transition temperature below 42°C, which is stretchable and conformable, and includes a microstructured adhesive layer for self-adhesive properties, allowing for post-manufacture application and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hard top-coat is applied to improve chemical resistance and weatherability, then durability is improved, but the film loses stretchability and may crack after exterior exposure
Solution Approach 1:
The patent uses a composite polymer layer comprising both rigid polyurethane particles (providing chemical resistance and weatherability) and flexible polyol matrix (providing stretchability). This composite structure allows the film to simultaneously achieve durability and flexibility, resolving the contradiction between hard top-coat protection and stretchability.
Solution Approach 2:
The patent modifies the glass transition temperature (Tg) of the polyol matrix to be below 42°C, ensuring the material remains flexible at service temperatures. By controlling the Tg parameter of the polymer layer, the film maintains stretchability while incorporating rigid polyurethane for durability, thus resolving the contradiction between hardness and flexibility.
2Ease of manufacture
If conventional paint replacement films are used, then application during manufacture is feasible, but post-manufacture surface application is not possible
Solution Approach 1:
The patent incorporates a self-adhesive layer that enables the film to bond to vehicle surfaces without requiring complex manufacturing integration. The self-adhesive property allows the film to be applied independently after vehicle manufacture, giving end-users the ability to re-wrap vehicles and providing flexibility in application timing and location.
3Reliability
If PVC-based films with top-coat are used, then chemical resistance and weatherability are improved, but environmental concerns require reduction of PVC content
Solution Approach 1:
The patent replaces PVC-based materials with polyurethane-polyol composites that have comparable or superior weatherability and chemical resistance. By changing the material composition parameters and controlling the glass transition temperature of the polyol matrix, the film achieves the required durability without relying on environmentally problematic PVC materials.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film achieves chemical resistance and weatherability comparable to paint, with enhanced stretchability and conformability, enabling effective coverage of vehicle surfaces without wrinkling and maintaining adhesion over time.
Implementation Method 1
the polyurethane has a glass transition temperature (Tg) according to ASTM E 1640-09 standard below 42°C
Implementation Method 2
the paint replacement film further comprises an adhesive layer
Data Source
AI summary
A paint replacement film is disclosed comprising a polymer layer comprising a polyurethane produced from a formulation comprising at least one blocked isocyanate. The paint replacement film comprises a liner layer and the formulation comprises at least two polyols in OH weight equivalent ratio in the range 4.5:1 to 1:4.5. The formulation may comprise a colourant and the polyurethane may have a glass transition temperature (Tg) below 42°C. Also disclosed is a method of producing a paint replacement film, by providing a backing layer, providing the liquid formulation, cast-coating the backing layer with the liquid formulation, and gelling the liquid formulation, thereby forming a polymer layer comprising polyurethane. The paint replacement films are useful for replacing paint on surfaces especially in automotive applications.