Fumed Silanized Silica Dispersion in Silicone Rubber
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Solution Overview
Problem
Fumed silica agglomerates in liquid systems are difficult to disperse effectively with low energy input, leading to inadequate viscosities and thixotropy, and existing methods often result in reagglomeration during storage, especially when using hydrophobic silica additives.
Innovation Solution
The process involves silanizing fumed silica with dimethyldichlorosilane to create a hydrophobic surface, which is then ground using mills like pinned-disc or air-jet mills, resulting in a silica with a grindometer value below 20 μm and tamped density of 25 to 85 g/l, preventing reagglomeration and enhancing dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fumed silica is dispersed in liquid systems using simple agitator mechanisms, then energy input and processing time are reduced, but dispersion quality and homogeneity are insufficient
Solution Approach 1:
The silica is pre-treated with a coupling agent (silane) before incorporation into the liquid system. This preliminary chemical modification reduces surface energy and improves wettability, allowing simple agitators to achieve effective dispersion without requiring high energy input or complex mixing devices
Solution Approach 2:
The surface properties of the silica are chemically modified by introducing organic groups through silane coupling. This changes the surface energy, hydrophobicity, and interparticle interaction parameters, enabling dispersion in low-viscosity systems with simple mixing equipment
2Reliability
If hydrophobic silica is used as an additive, then dispersion stability is improved, but reagglomeration occurs during storage
Solution Approach 1:
The silica surface is modified with silane coupling agents that introduce organic groups, changing the surface energy and hydrophobicity parameters. This chemical modification creates a steric barrier that prevents reagglomeration during storage while maintaining dispersion stability
Solution Approach 2:
The invention creates a composite structure where inorganic silica particles are coated with organic silane layers. This composite approach combines the stability benefits of hydrophobic surfaces with the dispersibility advantages of modified surface properties, preventing reagglomeration
3Ease of manufacture
If coarse silica agglomerates are used, then material handling and storage are simplified, but viscosity enhancement and thixotropy are insufficient
Solution Approach 1:
The silica is pre-modified with coupling agents before incorporation, ensuring that even coarse agglomerates disperse effectively upon addition. This preliminary treatment maintains handling simplicity while ensuring adequate viscosity enhancement through proper distribution of primary particles
Solution Approach 2:
Surface energy and wettability parameters are modified through chemical treatment, enabling coarse agglomerates to break down and disperse effectively in the liquid matrix, providing sufficient viscosity contribution without requiring fine initial particle size
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 treated silica achieves improved dispersion and stability, maintaining low grindometer values even after compaction, and is used as a filler in silicone rubber compounds to produce vulcanizates with high-grade surfaces and optimal thickening properties.
Implementation Method 1
The process involves silanizing fumed silica with dimethyldichlorosilane to create a hydrophobic surface
Implementation Method 2
ground using mills like pinned-disc or air-jet mills, resulting in a silica with a grindometer value below 20 μm
Data Source
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AI summary
Fumed silanized silica with the following physico-chemical data: Grindometer value less than 20 μm Tamped density 25 to 85 g/1 is prepared by grinding fumed silica which has been silanized. It can be used in silicone rubber.