Two-Part Silicone Rubber Composition for High Elongation
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Solution Overview
Problem
Current silicone elastomers face challenges in achieving high elongation-at-break values while maintaining durability and tensile strength, particularly when incorporating crosslinkers, which often result in brittleness and reduced flexibility.
Innovation Solution
A two-part curable liquid silicone rubber composition is developed, comprising specific components such as alkenyl group-containing organopolysiloxane, diorganohydrogensiloxy-terminated polydiorganosiloxane, and organosilicon crosslinker, with precise ratios of hydrogen atoms to alkenyl groups and crosslinker content, to achieve high elongation-at-break values without compromising durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If crosslinkers are incorporated into silicone elastomer composition to improve tensile strength and durability, then the elastomer becomes more brittle and less flexible, reducing elongation-at-break
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of hydrogen atoms to alkenyl groups (RHalk) within a specific range of 1.00 to 1.35, and adjusting the crosslinker content to optimize the balance between tensile strength and flexibility. This quantitative parameter control allows the elastomer to achieve high elongation-at-break (≥800%) while maintaining durability through controlled crosslinking.
2Reliability
If crosslinker content is increased to improve durability and tensile strength, then elongation-at-break value decreases due to brittleness
Solution Approach 1:
The patent resolves this contradiction by establishing an optimal parameter range for the hydrogen-to-alkenyl ratio (RHalk: 1.00-1.35) and controlling crosslinker content within specific limits. This parameter optimization enables the elastomer to simultaneously achieve high durability through adequate crosslinking and high elongation-at-break (≥800%) by preventing excessive crosslinking that would cause brittleness.
Solution Approach 2:
The patent employs a composite composition strategy by combining multiple components including alkenyl group-containing organopolysiloxane, diorganohydrogensiloxy-terminated polydiorganosiloxane, organosilicon crosslinker, and fillers in specific proportions. This composite approach allows the system to achieve both durability and high elongation-at-break by distributing the functional requirements across different material components rather than relying on a single component.
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 yields silicone elastomers with elongation-at-break values of at least 800%, demonstrating high stretchability and durability, capable of withstanding elongation without breaking and maintaining shape, while also offering suitable hardness for various applications.
Implementation Method 1
A typical two-component system based on an 'addition' or hydrosilylation cure consists of a first part, which contains a vinyl-functional base polymer, a catalyst and optionally a reinforcing agent, and a second part, which typically contains the same vinyl-functional base polymer and a hydride-functional crosslinking polymer. When the two parts are mixed together, the crosslinking reaction commences and an elastomer forms.
Data Source
AI summary
A two-part curable liquid silicone rubber composition is provided in which the first liquid composition and the second liquid composition yield, upon mixing, a curable liquid silicone rubber composition which, when cured, yields a silicone elastomer having an elongation-at-break value of at least 800%. The silicone elastomers of the invention comprise at least one alkenyl group-containing organopolysiloxane having two silicon-bonded alkenyl groups per molecule, at least one diorganohydrogensiloxy-terminated polydiorganosiloxane, at least one organosilicon crosslinker containing at least 3 silicon-bonded hydrogen atoms per molecule, at least one addition reaction catalyst, and at least one filler. Also provided are silicone elastomers having an elongation-at-break value of at least 800% and withstand elongation without breaking. An article for a medical device comprising a cured product of the two-part curable liquid silicone rubber compositions or the silicone elastomers of the invention are also provided.