Heat Curable Elastomer with Modified Silica Filler
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Solution Overview
Problem
Elastomeric compositions used for sealing applications face challenges with high compression set, low tensile strength, low modulus, low elongation, high viscosity, and high moisture and gas permeability, which affect their sealing performance and mechanical properties.
Innovation Solution
A heat curable elastomer composition is developed, incorporating a modified silica filler treated with alkyl and alkenyl silanes, combined with a polyolefin backbone elastomeric hydrocarbon polymer and a silicon-hydride crosslinker, along with a hydrosilylation catalyst, to enhance mechanical properties and reduce permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silica filler material is added to improve mechanical properties, then tensile strength and modulus increase, but viscosity increases to unusable levels
Solution Approach 1:
The patent applies parameter changes by modifying the surface chemistry of silica filler through treatment with specific silane compounds (hexamethyldisilazane and other hydrophobic silicon compounds). This chemical modification changes the interaction between filler particles and polymer matrix, allowing higher filler loading (improving tensile strength and modulus) without causing excessive viscosity increase that would prevent processing.
2Strength
If more filler is added to improve mechanical properties, then elongation and tensile strength improve, but compression set increases above 20%
Solution Approach 1:
The patent changes the chemical parameters of the filler surface by treating silica with hydrophobic silicon compounds, which modifies how filler particles interact with the polymer matrix during curing. This results in better distribution and bonding, achieving high tensile strength and elongation while maintaining compression set below 20%, thus resolving the contradiction between strength improvement and compression set control.
3Reliability
If silicone based rubber is used to achieve good elastomeric properties, then compression set and mechanical properties improve, but moisture and gas permeability becomes very high
Solution Approach 1:
The patent creates a composite material system combining polyisobutylene polymer matrix with hydrophobically modified silica filler. This composite approach leverages the low permeability of polyisobutylene while incorporating modified silica to achieve good compression set and mechanical properties, thus obtaining a material that simultaneously achieves low compression set and low moisture/gas permeability.
Solution Approach 2:
The patent applies parameter changes by selecting and modifying filler materials to work synergistically with polyisobutylene polymer. The hydrophobic modification of silica filler parameters enables the composition to achieve both good compression set (through proper filler-polymer interaction) and low moisture/gas permeability (through the inherent properties of polyisobutylene enhanced by hydrophobic filler surface).
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 composition achieves low compression set, high tensile strength, high modulus, high elongation, low viscosity, and low moisture and gas permeability, making it suitable for applications like fuel cell sealing without increasing viscosity to unusable levels.
Implementation Method 1
a modified silica filler comprising silica that has been modified by treatment with at least one alkyl silane having a C 1 to C 30 alkyl group and at least one alkenyl silane having a C 2 to C 30 alkenyl group
Implementation Method 2
a silicon-hydride crosslinker having at least two SiH functional groups; c) a hydrosilylation catalyst
Data Source
AI summary
Disclosed is modified silica filler material wherein the silica filler material has been surface treated with both an alkyl silane and an alkenyl silane. The modified silica filler material, when included in an elastomeric composition, results in lower compression set and improved mechanical properties including viscosity, tensile strength, modulus and elongation. The filler material can be used at high levels in elastomeric compositions and does not raise the viscosity to unusable levels. The elastomeric composition including the modified filler material finds special use in the formation of gaskets for fuel cells.