Polyolefin Foam Sheet Resin Composition for Dimensional Stability
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Solution Overview
Problem
Conventional polyolefin resin foam sheets and laminates face challenges with insufficient formability due to heat shrinkage and poor appearance resulting from wrinkles during formation processing, which affects their dimensional stability and surface quality.
Innovation Solution
A polyolefin resin foam sheet with a resin mixture comprising 0-30% polyethylene resin, 30-80% polypropylene resin, and 20-40% polyolefin elastomer, optimized to achieve minimal dimensional changes and improved mechanical properties, including a specific compressive strength-to-density ratio and gel fraction, ensuring excellent flexibility and formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polyolefin resin foam sheet uses conventional resin compositions (e.g., polyethylene resin, polypropylene resin, and polyolefin elastomer resin), then flexibility can be improved, but formability deteriorates due to heat shrinkage and wrinkles during formation processing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of polyethylene resin (5-30 mass%), polypropylene resin (40-70 mass%), and polyolefin elastomer resin (20-40 mass%), along with controlling gel fraction (20-70%) and density (25-250 kg/m3). These parameter optimizations resolve the contradiction by achieving both flexibility and formability through compositional tuning rather than structural modification.
2Productivity
If the machine direction stretch ratio is increased to prevent sagging and wrinkling during foaming, then productivity is improved, but dimensional stability deteriorates due to heat shrinkage
Solution Approach 1:
The patent resolves this contradiction through parameter changes in resin composition and gel fraction control. By optimizing the balance between polyethylene, polypropylene, and polyolefin elastomer content, along with controlling gel fraction within 20-70%, the foam sheet achieves dimensional stability even at high stretch ratios required for productive foaming processes.
Solution Approach 2:
The patent employs composite materials by combining three distinct polyolefin resin types with specific functional properties. The composite structure of polyethylene resin (providing flexibility), polypropylene resin (providing structural stability), and polyolefin elastomer resin (providing elasticity) works synergistically to maintain dimensional stability during high-speed foaming while ensuring post-formation dimensional accuracy.
3Ease of operation
If polyolefin elastomer resin is contained in the foam sheet, then flexibility is improved, but the sheet sticks to rolls during processing requiring high stretch ratio
Solution Approach 1:
The patent applies parameter changes by controlling the polyolefin elastomer resin content within 20-40 mass% and optimizing the overall gel fraction to 20-70%. This parameter optimization reduces excessive adhesion to rolls during processing while preserving the flexibility benefits of the elastomer component.
Solution Approach 2:
The patent applies local quality by differentiating the functional roles of each resin component: polyethylene resin (5-30 mass%) provides flexibility, polypropylene resin (40-70 mass%) provides structural integrity and reduced adhesion, and polyolefin elastomer resin (20-40 mass%) provides elasticity. This localized functional assignment resolves the adhesion issue while maintaining flexibility.
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 optimized polyolefin resin foam sheets exhibit reduced shrinkage and improved formability, maintaining dimensional stability and surface quality, thus addressing the limitations of conventional materials.
Implementation Method 1
dimensional changes obtained under heating for 10 minutes at a temperature 20° C. higher than a maximum melting point
Implementation Method 2
maximum melting point that is the highest melting peak in a differential scanning calorimetry
Data Source
AI summary
A polyolefin resin foam sheet includes a resin mixture as a base resin, the resin mixture including 0% by mass or more and 30% by mass or less of polyethylene resin, 30% by mass or more and 80% by mass or less of polypropylene resin, and 20% by mass or more and 40% by mass or less of a polyolefin elastomer, the polyolefin resin foam sheet fulfilling a range of −35% or more and 0% or less for dimensional changes in machine and transverse directions under heating for 10 minutes at a temperature 20° C. higher than a maximum melting point that is a highest melting peak in a differential scanning calorimetry.