Cross-linked Polypropylene Foam for Vacuum Forming
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Solution Overview
Problem
Cross-linked polyolefin resin foams used in vehicle interiors face challenges in maintaining formability and preventing rupture when forming temperatures exceed the melting point of polypropylene, leading to difficulties in accurately transferring complex patterns onto sheet materials during vacuum forming.
Innovation Solution
Controlling the cross-linking degree within a specified range and optimizing the composition of homopolypropylene, random polypropylene, and linear low-density polyethylene to achieve specific elongation and modulus values at 160°C, thereby preventing foam rupture and enhancing formability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the forming temperature is elevated to 160°C or higher to accurately transfer projection and depression pattern on the mold to the sheet material, then the manufacturing precision is improved, but the foam causes rupture during vacuum forming because the temperature exceeds the melting point of polypropylene
Solution Approach 1:
The patent changes the chemical structure parameters of the polypropylene resin by controlling the molecular weight distribution (specifically setting the weight average molecular weight to 200,000 or more) and the composition ratios of propylene and comonomer (ethylene content of 5-20 mass%). These parameter changes enable the resin to maintain its shape and mechanical properties at forming temperatures of 160°C or higher, preventing foam rupture while allowing accurate pattern transfer.
Solution Approach 2:
The patent uses a composite resin system consisting of polypropylene as the base resin combined with specific amounts of comonomers (ethylene, propylene, or butylene) in controlled ratios. This composite structure provides both the high-temperature stability needed to prevent rupture and the necessary formability for accurate vacuum forming at elevated temperatures.
2Adaptability or versatility
If the cross-linked polyolefin resin foam is used for vehicle interior materials requiring high designability, then the adaptability is improved, but the foam rupture occurs during vacuum forming when forming temperature exceeds the melting point of polypropylene
Solution Approach 1:
The patent modifies the molecular parameters of the polypropylene resin by setting the weight average molecular weight to 200,000 or more and controlling the comonomer content (5-20 mass%). These parameter changes enhance the resin's thermal stability and elasticity, allowing the foam to maintain structural integrity during vacuum forming at high temperatures while enabling complex design patterns to be accurately transferred.
Solution Approach 2:
The patent applies different compositional characteristics to different aspects of the resin structure: the base polypropylene provides structural stability, while the controlled addition of comonomers (ethylene, propylene, or butylene) in specific ratios provides localized flexibility and formability. This local quality differentiation allows the foam to resist rupture while accommodating complex design requirements.
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 ensures that the foam maintains mechanical strength and flexibility, allowing for accurate pattern transfer and forming complex designs without rupture, even at elevated temperatures, thus improving the designability and formability of vehicle interior materials.
Implementation Method 1
a foam, more specifically a cross-linked polyolefin resin foam made by cross-linking a foamable composition and causing the composition to foam
Implementation Method 2
made by cross-linking and foaming a foamable composition
Data Source
AI summary
The present invention relates to a foam having a density of 0.036 g/cc or more and less than 0.133 g/cc, having an elongation (%) at break at 160°C of 150% or more as measured in accordance with JIS K6251, a value of 7 or more obtained by multiplying the elongation (%) at break by a 100% modulus (MPa) at 160°C as measured in accordance with JIS K6251, and a cross-linking degree of 30 to 50%.