EVA-Polyamide Blend for Heat Aging Resistance
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Solution Overview
Problem
Ethylene vinyl acetate (EVA) copolymers used in automotive applications face challenges with heat resistance, as they degrade under high temperatures, leading to reduced extensibility and increased hardness, and existing methods to enhance heat aging resistance are insufficient.
Innovation Solution
Incorporating small amounts of polyamide (up to 10 wt%) into EVA copolymers with a melting peak temperature of 100° C or less, along with a peroxide curative, to create a curable EVA-polyamide blend that exhibits enhanced resistance to physical property loss during hot air aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the vinyl acetate content is reduced to increase melting peak temperature above 100°C, then the EVA copolymer becomes difficult to mix with peroxide without causing scorch or premature curing, but the high crystallinity results in a stiff and inelastic cured article
Solution Approach 1:
The invention changes the key parameter of melting peak temperature to remain at or below 100°C by maintaining sufficient vinyl acetate content (20-40 wt%), thereby avoiding scorch during peroxide mixing while still achieving the desired crosslinked elastomeric properties through controlled curing
2Temperature
If the vinyl acetate content is reduced to increase melting peak temperature above 100°C, then the EVA copolymer becomes difficult to mix with peroxide without causing scorch or premature curing, but the high crystallinity results in a stiff and inelastic cured article
Solution Approach 1:
The invention maintains melting peak temperature at or below 100°C through appropriate vinyl acetate content (20-40 wt%), which preserves the elasticity and flexibility of the cured elastomeric article while enabling successful peroxide crosslinking without scorch
Solution Approach 2:
The invention creates a composite system by crosslinking the EVA copolymer with peroxide to form a vulcanized elastomeric network, combining the flexibility of low melting point EVA with the structural integrity provided by crosslinking, achieving both ease of processing and desirable elastic properties
3Reliability
If conventional antioxidant systems are used to enhance heat aging resistance, then some improvement is achieved, but the heat or hot air aging resistance of EVA copolymers remains insufficient for high temperature automotive applications
Solution Approach 1:
The invention changes the chemical composition parameter by incorporating polyamide (5-50 wt%) into the EVA copolymer matrix, creating a composite material that provides superior heat aging resistance compared to conventional antioxidant systems, while maintaining processability and elastomeric properties
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 EVA-polyamide blend composition maintains similar Shore A hardness, tensile strength, and tensile elongation to break while significantly improving heat aging resistance, with a reduction in tensile elongation loss and Shore A hardness increase, even after prolonged exposure to high temperatures.
Implementation Method 1
EVA copolymers may be crosslinked by free radial generators such as peroxides, azides, or high energy radiation to form elastomeric or flexible articles
Implementation Method 2
The EVA copolymer-polyamide blend composition is crosslinked with a peroxide curative to form a thermoset elastomeric composition
Implementation Method 3
degradation of physical properties through oxidative embrittlement can occur... it is possible to produce cured EVA articles that exhibit excellent heat aging resistance by dispersing small amounts of polyamide (up to 10 wt %) in the EVA copolymer
Data Source
AI summary
Disclosed herein are curable heat resistant ethylene vinyl acetate copolymer-polyamide blend compositions, wherein the ethylene vinyl acetate copolymer has a melting peak temperature of 100° C. or less. The blend compositions comprise 0.1 to 10 weight percent dispersed polyamide, and may be cured to form articles having improved heat resistance while maintaining the desirable physical properties of unmodified, cured ethylene vinyl acetate articles.