Low-Friction Silicone Elastomers via High-Viscosity Crosslinking
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Solution Overview
Problem
Existing addition-crosslinkable silicone compositions with low-viscosity silicone oils result in a delayed formation of a lubricating film, leading to a time- and temperature-dependent coefficient of friction, and subsequent contamination issues, as the oil exudes and forms an oily film on the surface, which is not immediately effective and is difficult to maintain.
Innovation Solution
Incorporating high-viscosity polydiorganosiloxanes with alkenyl groups and SiH-functional crosslinking agents, along with a non-functionalized polydiorganosiloxane and reinforcing fillers, to create silicone elastomers that reduce friction immediately after crosslinking without forming a greasy oil film, ensuring consistent and long-lasting low friction coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low-viscosity silicone oils are added to reduce friction, then the coefficient of friction is reduced, but the oily film forms only after storage and causes contamination
Solution Approach 1:
The patent changes the viscosity parameter of the silicone oil from low (5-1000 mPas) to high (5000-50,000,000 mPas), which fundamentally alters the oil's behavior. The high viscosity prevents exudation and film formation on the surface, while still providing friction reduction through the crosslinked network structure
Solution Approach 2:
The patent creates a composite system by crosslinking the high-viscosity silicone oil with silane crosslinking agents, forming a crosslinked silicone rubber network. This composite structure traps the oil molecules within the network, preventing their migration to the surface while maintaining the lubricating effect through the crosslinked architecture
2Ease of operation
If low-viscosity silicone oils are used, then friction is reduced over time, but the effect is delayed and depends on storage conditions
Solution Approach 1:
The patent performs preliminary action by incorporating the high-viscosity silicone oil into the crosslinked network structure before the elastomer is put into service. The crosslinking process pre-positions the oil molecules within the network, ensuring immediate friction reduction upon crosslinking rather than requiring subsequent storage time for oil migration
3Ease of operation
If silicone oil migrates to the surface, then friction is reduced, but the oil film is unbound and easily removed
Solution Approach 1:
The patent creates a crosslinked composite structure where the silicone oil is chemically bound within the crosslinked network. The silane crosslinking agents form covalent bonds that trap the oil molecules, creating a durable, bound lubricating system that cannot be easily removed by wiping or mechanical contact
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 solution achieves immediate reduction in coefficient of friction post-crosslinking, prevents oil film formation on the silicone surface, and maintains low friction without exudation, reducing contamination risks and ensuring consistent mechanical properties.
Implementation Method 1
addition-crosslinkable organopolysiloxane compositions containing a high viscosity polydiorganosiloxane free of alkenyl groups
Data Source
AI summary
Addition-crosslinkable silicone compositions contain(A) 100 parts by weight of polydiorganosiloxane(s) which has alkenyl groups and whose viscosity is from 5000 to 50,000,000 mPas at 25° C., having at least 2 alkenyl groups per molecule, and at least 0.15 mol % of alkenylsiloxane units, based on all siloxane units,(B) from 1 to 50 parts by weight of polydiorganosiloxane(s) whose viscosity is at least 5,000,000 mPas at 25° C., and having no alkenyl groups,(C) SiH-functional crosslinking agent(s),(D) hydrosilylation catalyst(s), and(E) from 3 to 90 parts by weight of filler(s) whose BET specific surface area is at least 50 m2/g. Vulcanizates of the addition-crosslinkable silicone compositions have low coefficients of friction.