Polyurethane Urea Coating Adhesion to Expanded TPU
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Solution Overview
Problem
Expanded thermoplastic polyurethane (TPU) substrates face challenges with adhesion of coatings due to the presence of lubricants, which lead to poor processability and reproducibility, and existing solutions either require washing to remove additives or result in coatings that crack and peel when the substrate is flexed.
Innovation Solution
A polyurethane urea solution with polycarbonate structural units and organic solvents is used to coat expanded TPU substrates, providing sufficient adhesion even in the presence of lubricants and maintaining adhesion when the substrate is bent, without the need for washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lubricants are added to expanded TPU particles to prevent adhesion during transport, then the processability and flowability are improved, but the adhesion of subsequent coatings to the substrate is significantly reduced
Solution Approach 1:
A silane coupling agent is applied as an intermediary layer between the lubricant-coated expanded TPU substrate and the subsequent coating. This coupling agent chemically bonds to both the substrate surface (including lubricants) and the coating material, creating a bridge that ensures strong adhesion despite the presence of lubricants. The silane coupling agent effectively mediates the interaction between the substrate and coating, resolving the adhesion problem caused by lubricant interference.
2Reliability
If washing is performed to remove lubricants from expanded TPU particles before coating, then coating adhesion is improved, but additional process steps and harsh chemicals are required
Solution Approach 1:
Instead of removing lubricants through washing, the invention extracts and neutralizes the harmful effect of lubricants by applying a silane coupling agent that is specifically designed to work in the presence of these additives. The coupling agent selectively bonds to the substrate surface while being compatible with the lubricant layer, effectively extracting the adhesion problem without requiring lubricant removal.
3Object-affected harmful factors
If rigid surface coatings are applied to expanded TPU substrates to improve resistance properties, then chemical resistance and scratch resistance are enhanced, but the coatings crack and peel when the flexible substrate is bent
Solution Approach 1:
The invention changes the key parameter of coating flexibility by using a polymeric coating material with appropriate elastic properties that can accommodate the bending and flexing of the expanded TPU substrate. The coating formulation is adjusted to achieve optimal balance between resistance properties and flexibility, allowing the coating to maintain integrity during substrate deformation while still providing the required chemical and scratch resistance.
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 coating adheres stably to expanded TPU substrates, enhancing water resistance, chemical resistance, scratch resistance, and durability while maintaining the mechanical properties of the substrate, and can be applied without removing surface additives.
Implementation Method 1
A coating which is obtained by curing a polyurethane urea solution comprising at least one organic solvent... the coating adheres stably to expanded TPU substrates
Implementation Method 2
a polyurethane urea solution comprising at least one organic solvent
Data Source
AI summary
The present invention relates to an article comprising expanded thermoplastic polyurethane as a substrate and a specific polyurethane urea coating on said substrate, as well as footwear, a process for producing the article and a use of a polyurethane urea solution. It has been found that a polyurethane urea coating comprising polycarbonate structural units strongly binds to expanded TPU substrates and maintains the intrinsic properties of the expanded TPU.