Liquid Silicone Composition for High Hardness Without Post-Cure
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Solution Overview
Problem
Existing liquid silicone rubber compositions face limitations in achieving high hardness (≥ 75 Shore A) without post-cure, often resulting in high viscosities and prolonged cure times, which hinder productivity and mechanical strength.
Innovation Solution
A liquid curable silicone elastomer composition comprising specific organopolysiloxanes with varying alkenyl and silicon-bonded hydrogen content, combined with a platinum-based catalyst and silica filler, allowing for a multimodal network structure that achieves hardness ≥ 75 Shore A without post-cure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liquid silicone rubber compositions are formulated to achieve high hardness (≥ 75 Shore A), then hardness is improved, but viscosity increases and cure time is prolonged
Solution Approach 1:
The patent segments the organopolysiloxane components into distinct functional types: vinyl-containing organopolysiloxane (A), silicon-bonded hydrogen-containing organopolysiloxane (B), and optionally additional vinyl-containing organopolysiloxane (C). This segmentation allows each component to contribute specifically to the crosslinking network, achieving high hardness through controlled composition rather than increasing overall viscosity or extending cure time.
2Strength
If liquid silicone rubber compositions are formulated to achieve high hardness (≥ 75 Shore A), then hardness is improved, but viscosity increases
Solution Approach 1:
The patent changes the chemical parameters of the composition by specifying precise compositional ratios: vinyl content of 0.01-5.0 mmol/g, silicon-bonded hydrogen content of 0.01-5.0 mmol/g, and specific weight ratios of components (A):(B) from 95:5 to 5:95. These parameter changes enable high hardness to be achieved through molecular structure and crosslinking density rather than increasing filler content or viscosity.
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 high hardness and rapid curing (Tc10 < 100 seconds, Tc90 < 150 seconds) with viscosity < 1000 Pa.s, enhancing processing conditions and mechanical properties without the need for post-curing.
Implementation Method 1
platinum cured silicone elastomers (addition reaction, otherwise known as hydrosilylation)
Implementation Method 2
a platinum based catalyst (C)
Data Source
AI summary
The present invention relates to a liquid curable silicone elastomer composition comprising an organopolysiloxane (A) comprising an organopolysiloxane (A1) containing at least 2 alkenyl groups bonded to silicon atom per molecule and having a total alkenyl content of from 0.01 to 1.5 mmol/g, and an organopolysiloxane (A2) containing at least 2 alkenyl groups bonded to silicon atom per molecule and having a total alkenyl content of from 5.0 to 15.0 mmol/g; an organopolysiloxane (B) comprising an organopolysiloxane (B1) containing at least 2 silicon-bonded hydrogen atoms per molecule, wherein said silicon-bonded hydrogen atoms are provided in the form of siloxy units of the type (R2HSiO1/2) x where R is independently selected from hydrogen, aliphatic hydrocarbyl, aromatic hydrocarbyl, or organyl group and x ≥ 2; and an optional organopolysiloxane (B2) containing at least 2 silicon-bonded hydrogen atoms per molecule, wherein said silicon-bonded hydrogen atoms are provided in the form of siloxy units of the type (RHSiO2/2) z where R is independently selected from hydrogen, aliphatic hydrocarbyl, aromatic hydrocarbyl, or organyl group and z ≥ 2, wherein the molar amount of silicon-bonded hydrogen in the form of siloxy units of the type (R2HSiO1/2) x is >40mol% of the total silicon-bonded hydrogen atoms content of organopolysiloxane (B); a platinum based catalyst (C); an inhibitor (D) selected from the group consisting of acetylenic alcohols and their derivative; a silica filler (E).