Low-Storage-Modulus Polymeric Sheets for Concave Surfaces
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Solution Overview
Problem
Conventional polymeric sheets struggle to adhere adequately to surfaces with concave topographies due to high storage modulus, leading to undesired lift or separation over time.
Innovation Solution
A polymeric sheet with a polyurethane-based carrier layer having a low storage modulus, formed without chain extenders of 350 grams/mole or less and high molecular weight polyols, is used to improve adhesion to concave surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional polymeric sheets with high storage modulus are used, then the sheet maintains its shape, but it causes undesired lift or separation from concave surfaces over time
Solution Approach 1:
The patent changes the storage modulus parameter of the polymeric sheet from high to low by selecting specific polymer formulations. This parameter change allows the sheet to adapt to concave surface topographies without generating excessive recovery forces that cause lifting, while still maintaining sufficient structural integrity through controlled polymer chain flexibility and crosslinking density.
Solution Approach 2:
The patent employs composite material structures combining multiple polymer layers with different properties. The formulation integrates polymers with varying molecular weights, crosslinking densities, and chemical compositions to achieve a balance between shape stability and adhesion reliability, where each layer contributes specific mechanical characteristics that work synergistically.
2Reliability
If soft polyurethanes with low storage modulus are formulated, then adhesion to concave surfaces improves, but the material becomes tacky and exhibits poor releasability from mold during injection molding
Solution Approach 1:
The patent applies local quality by creating different polymer environments within the sheet structure. The formulation incorporates regions with varying degrees of crosslinking and different polymer chain configurations, allowing the material to exhibit soft, adherent properties where needed while maintaining sufficient mold releasability through controlled local stiffness variations and reduced tackiness in specific zones.
Solution Approach 2:
The patent precisely controls the storage modulus parameter within a specific range (0.01-10 MPa) and adjusts polymer formulation parameters including molecular weight distribution, crosslinking density, and chain extender ratios. These parameter changes enable the material to achieve the desired balance between softness for adhesion and sufficient rigidity for mold releasability during injection molding processing.
3Strength
If high molecular weight macrodiols are used to form softer TPU, then hardness decreases below 80 Shore A, but the resulting product exhibits severe shrinkage and poor processing characteristics
Solution Approach 1:
The patent uses composite material formulations combining high molecular weight macrodiols with carefully selected chain extenders and polyols in specific ratios. This composite approach allows the material to achieve the desired softness and hardness characteristics while the synergistic interaction of components prevents excessive shrinkage by balancing elastic recovery forces with viscous dissipation during processing.
Solution Approach 2:
The patent systematically adjusts formulation parameters including polyol molecular weight, chain extender type and amount, and polyisocyanate stoichiometry to control the hard segment content and polymer chain architecture. These parameter changes enable precise control over hardness (below 80 Shore A) while maintaining dimensional stability by preventing runaway shrinkage through optimized polymerization kinetics and crosslinking density.
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 polymeric sheet effectively maintains adherence to concave surfaces at various temperatures, reducing lift and separation issues.
Implementation Method 1
an outwardly exposed adhesive layer for adherence of the polymeric film to a surface of an article
Implementation Method 2
Energy stored in the polymeric sheet after stretching the same to conform to a complex surface topography is believed to be a force driving return of the polymeric sheet to its normal shape
Data Source
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AI summary
Polymeric sheets of the invention comprise sequential layers as follows: a topcoat layer, a polyurethane-based carrier layer, and an adhesive layer. The polyurethane-based carrier layer is formed using essentially no chain extender having a molecular weight of 350 grams/mole or less, resulting in a relatively low storage modulus polymeric sheet. Such polymeric sheets are particularly useful for application to surfaces having a concave topography.