Liquid Silicone Rubber Composition Thermal Conductivity
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Solution Overview
Problem
The challenge is to develop a liquid silicone rubber composition for thermal fixing devices in electrophotographic image forming apparatuses that balances high thermal conductivity, low thermal capacity, and excellent surface smoothness, as existing compositions with higher metallic silicon particles compromise surface smoothness due to increased viscosity and sagging issues.
Innovation Solution
A liquid silicone rubber composition with 35-45% volume of metallic silicon particles, a specific particle diameter range, and a viscosity ratio of 2.0 or less at different shear rates, combined with a mixing process involving organopolysiloxane and metallic silicon powder, allowing the mixture to stand for extended periods to form bound rubber, which reduces shear rate dependence and enhances smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a larger amount of metallic silicon particles is added to increase thermal conductivity, then thermal conductivity is improved, but viscosity increases and surface smoothness deteriorates
Solution Approach 1:
The patent optimizes the content of metallic silicon particles within a specific range (35-45 vol%) and controls the viscosity ratio A/B to be 2.0 or less. By adjusting these parameters, the composition achieves high thermal conductivity while preventing excessive viscosity increase and maintaining surface smoothness during molding.
Solution Approach 2:
The patent creates a composite liquid silicone rubber composition by combining metallic silicon particles with silicone rubber in a specific ratio. This composite structure enables the material to simultaneously achieve high thermal conductivity from the metallic particles and adequate processability from the silicone rubber matrix.
2Temperature
If a larger amount of metallic silicon particles is added to obtain higher thermal conductivity, then thermal conductivity is improved, but the viscosity of the composition increases
Solution Approach 1:
The patent specifies that the viscosity ratio A/B (where A is viscosity at 0.02/sec shear rate and B is viscosity at 1/sec shear rate) should be 2.0 or less. This parameter control ensures the composition has appropriate flow characteristics for molding while containing high levels of metallic silicon particles for thermal conductivity.
3Temperature
If the viscosity of the composition increases due to higher metallic silicon content, then thermal conductivity is improved, but the smoothness of the molded product surface decreases
Solution Approach 1:
The patent establishes a specific viscosity ratio A/B ≤ 2.0 as a key parameter to control surface smoothness. This ratio ensures that even with high metallic silicon content (35-45 vol%), the composition maintains proper leveling behavior during the molding process, preventing surface defects and achieving smooth finished surfaces.
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 thermal conductivity, low thermal capacity, and excellent surface smoothness by controlling viscosity and forming bound rubber, preventing sagging and ensuring smooth film formation.
Implementation Method 1
the elastic layer is required to have high thermal conductivity
Implementation Method 2
allowing the obtained mixture to stand for 30 days or more
Data Source
AI summary
A liquid silicone rubber composition contains metallic silicon particles. The content of the metallic silicon particles is 35% by volume or more and 45% by volume or less. The volume average particle diameter of the metallic silicon particles is 1 μm or more and 20 μm or less. The ratio A/B of viscosity A at a shear rate of 0.02/sec to viscosity B at a shear rate of 1/sec of the composition is 2.0 or less.