Low-Viscosity RTV Silicone Elastomer for High PCM Loading
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Solution Overview
Problem
Existing crosslinked rubber compositions based on RTV silicone elastomers with phase-change materials (PCMs) have limited PCM content, resulting in reduced thermal energy storage and release capabilities, which are insufficient for demanding applications.
Innovation Solution
A crosslinked rubber composition using an RTV silicone elastomer with low dynamic viscosity, allowing for higher PCM content (up to 300 phr) and incorporation of thermally conductive fillers, enabling increased thermal energy storage and release, with a mass enthalpy of change of state greater than 70 J/g and thermal conductivity greater than 0.2 W.m-1K-1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional RTV silicone elastomer with high dynamic viscosity (e.g., 15,000 mPa.s) is used to disperse PCM, then the elastomer provides sufficient structural stability, but the maximum PCM content is limited to about 43 phr (30% mass fraction), resulting in low mass enthalpy of change of state (50-70 J/g)
Solution Approach 1:
The patent changes the viscosity parameter of the RTV silicone elastomer from conventional high values (15,000 mPa.s) to very low values (≤5000 mPa.s, preferably ≤1000 mPa.s). This parameter change enables much higher PCM content (100-300 phr) to be dispersed while maintaining composition homogeneity and flexibility, thereby achieving mass enthalpy of change of state greater than 70 J/g (advantageously 80-200 J/g).
Solution Approach 2:
The patent creates a composite material system consisting of low-viscosity RTV silicone elastomer, non-encapsulated PCM (powder or liquid state), and optionally thermally conductive fillers. This composite structure allows for optimized thermal energy storage capabilities while maintaining mechanical flexibility and processability.
2Quantity of substance
If high PCM content (greater than 50 phr, especially 100-300 phr) is incorporated into the elastomer, then the mass enthalpy of change of state increases to greater than 70 J/g, but the composition may lose flexibility and become too rigid for practical applications
Solution Approach 1:
The patent uses very low viscosity RTV silicone elastomer (≤5000 mPa.s, preferably ≤1000 mPa.s) as the binding matrix. This low viscosity parameter enables the elastomer to effectively bind high amounts of PCM (100-300 phr) while maintaining composition homogeneity and flexibility, overcoming the rigidity issue that would normally occur with high PCM loading.
3Stability of the object's composition
If the elastomer viscosity is reduced to enable high PCM content, then dispersibility and homogeneity improve, but the elastomer may lose structural stability and strength
Solution Approach 1:
The patent carefully selects and controls the viscosity parameter of the RTV silicone elastomer, reducing it to very low values (≤5000 mPa.s, preferably ≤1000 mPa.s) but not eliminating it completely. This optimized viscosity level provides the right balance: low enough to ensure excellent dispersibility and homogeneity of high PCM content, yet sufficient to maintain structural stability and mechanical strength of the final composition.
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 enhanced thermal energy absorption and release capabilities, suitable for demanding applications such as passive air conditioning and heating systems, with improved flexibility and temperature resistance.
Implementation Method 1
crosslinked rubber composition based on at least one 'RTV' silicone elastomer vulcanized at room temperature
Implementation Method 2
crosslinked by polyaddition or polycondensation
Implementation Method 3
crosslinked by polyaddition or polycondensation
Implementation Method 4
PCM materials such as fatty acids, salts or paraffins, in particular, to release or absorb heat by change of state thanks to the latent heat of fusion which characterizes these PCMs
Implementation Method 5
release or absorb heat by change of state thanks to the latent heat of fusion which characterizes these PCMs
Implementation Method 6
pass from the liquid state to the solid state by releasing heat during their crystallization
Implementation Method 7
the composition then possibly having a thermal conductivity greater than 0.2 W.m-1K-1 and advantageously greater than 1 W.m-1K-1
Data Source
AI summary
The present invention relates to a crosslinked rubber composition based on at least one room-temperature vulcanized "RTV" silicone elastomer and comprising at least one phase-change material (PCM), its preparation process, a flexible element comprising at least one elastomer layer capable of storing and releasing thermal energy, which is made of this composition, and a thermal control or regulation system incorporating at least one such flexible element. A composition according to the invention is such that said at least one silicone elastomer has a viscosity measured at 23°C according to ISO 3219 that is less than or equal to 5000 mPa·s. Advantageously, this silicone elastomer is of the two-component type A and B and is crosslinked by polyaddition or polycondensation, and the composition comprises the unencapsulated, micronized PCM in an amount greater than 50 parts per hundred (ppm).