Polyolefin Foam Sheet Cell Size Control
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Solution Overview
Problem
Thin polyolefin resin foam sheets used in electronic equipment require enhanced impact-absorbing properties and impact resistance while maintaining withstand voltage properties, which existing technologies fail to achieve by simply adjusting expansion ratio and crosslinking degree.
Innovation Solution
A polyolefin resin foam sheet with controlled average and maximum cell sizes in specific dimensions, along with adjusted strength ratios and crosslinking, and an adhesive tape with a pressure-sensitive adhesive layer, to ensure both impact resistance and withstand voltage properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the expansion ratio is increased to improve flexibility and impact-absorbing properties, then the impact-absorbing properties are improved, but the withstand voltage properties deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the average cell sizes (150 μm or less in both MD and TD directions) and maximum cell sizes (500 μm or less), along with controlling the expansion ratio within specific ranges. This optimization of cellular structure parameters enables the foam sheet to achieve both high impact-absorbing properties and satisfactory withstand voltage properties, resolving the contradiction between these two requirements.
2Strength
If the degree of crosslinking is increased to increase rigidity, then the rigidity is improved, but the flexibility deteriorates
Solution Approach 1:
The patent optimizes the degree of crosslinking within specific ranges (gel fraction: 10-60%, preferably 20-50%) to achieve the desired balance between rigidity and flexibility. By controlling crosslinking parameters along with cell size parameters, the foam sheet attains appropriate mechanical properties for impact absorption while maintaining necessary flexibility.
3Length of moving object
If the thickness is reduced for miniaturization, then the device size is reduced, but the impact-absorbing properties deteriorate
Solution Approach 1:
The patent applies local quality by creating a uniform distribution of fine cells throughout the foam sheet structure. The controlled average cell size of 150 μm or less and maximum cell size of 500 μm or less, combined with specific expansion ratios, ensures that even in thin configurations, the foam sheet maintains high impact-absorbing properties through optimized local cellular structure rather than relying on increased thickness.
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 solution provides a thin polyolefin resin foam sheet with improved impact-absorbing properties, impact resistance, and withstand voltage properties, suitable for use in electronic equipment, including as an adhesive tape to prevent damage from impacts and environmental factors.
Implementation Method 1
a polyolefin resin foam sheet having a plurality of cells which is formed by foaming a polyolefin resin
Data Source
AI summary
There is provided a polyolefin resin foam sheet having a plurality of cells which is formed by foaming a polyolefin resin, wherein, in the polyolefin resin foam sheet, the average cell sizes and the maximum cell sizes in the MD direction and the TD direction are each a predetermined value, and a ratio [TD strength at break/MD average cell size] and a ratio [MD strength at break/TD average cell size] are both 80 kPa/µm or more.