Silicone Composition with Dual Polymers for Tear Resistance
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Solution Overview
Problem
Silicone compositions used as adhesives and sealants have low tear propagation resistance and are challenging to produce with common, inexpensive fillers while maintaining low viscosity for easy pumpability.
Innovation Solution
A silicone composition comprising at least two reactive polydiorganosiloxane polymers with differing reactivities and molecular weights, combined with a filler such as precipitated or fumed silica and chalk, to enhance tear resistance without increasing viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If specific fillers (surface-modified precipitated silica and coated precipitated calcium carbonate) are used to improve tear resistance, then tear propagation resistance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces expensive, specially modified fillers with common, inexpensive fillers (precipitated silica and/or precipitated calcium carbonate) that do not require complex surface modifications. This achieves tear resistance improvement through polymer composition rather than expensive filler treatments, directly addressing the contradiction between strength improvement and manufacturing ease.
Solution Approach 2:
The patent changes the parameters of the polyorganosiloxane polymers (molecular weight, reactivity, end-group functionality) rather than changing filler properties. By adjusting polymer parameters (using at least two polymers with different molecular weights and reactivities), the patent achieves tear resistance without requiring complex filler modifications, resolving the contradiction between strength and ease of manufacture.
2Strength
If tear resistance is improved through conventional methods, then tear propagation resistance is improved, but viscosity increases making the composition difficult to pump
Solution Approach 1:
The patent uses parameter changes in the polymer composition (combining polymers with different molecular weights and reactivities) to achieve tear resistance without the viscosity increase that typically accompanies filler addition. The specific parameter range (molecular weights, reactivity ratios) allows independent optimization of tear resistance and viscosity.
Solution Approach 2:
The patent creates a composite polymer system combining at least two polyorganosiloxane polymers with different properties (molecular weight, reactivity). This composite approach allows the benefits of both polymers (tear resistance from one, low viscosity from the other) to work together, resolving the contradiction between strength and ease of operation.
3Ease of manufacture
If common fillers are used to reduce cost, then manufacturing cost decreases, but tear propagation resistance remains low
Solution Approach 1:
The patent changes the parameters of the polyorganosiloxane polymers (using at least two polymers with different molecular weights, reactivities, and end-group functionalities) to compensate for the use of common, unmodified fillers. This allows tear resistance to be improved through polymer chemistry rather than expensive filler modifications, resolving the contradiction between cost and strength.
Solution Approach 2:
The patent effectively copies the tear resistance function from expensive surface-modified fillers through a different mechanism - using reactive polymer end-groups that interact with common fillers. This achieves the same functional outcome (tear resistance) through a cheaper pathway, resolving the contradiction between manufacturing cost and strength.
4Strength
If polymer reactivity is increased to improve crosslinking and tear resistance, then tear propagation resistance is improved, but viscosity increases reducing pumpability
Solution Approach 1:
The patent segments the polymer system into at least two distinct polyorganosiloxane polymers with different reactivities and molecular weights. One polymer provides reactivity for tear resistance, while the other maintains low viscosity for pumpability. This segmentation resolves the contradiction by distributing different functions across separate polymer components.
Solution Approach 2:
The patent uses specific parameter ranges for the two polymers (molecular weights, reactivity levels, end-group types) to achieve the desired balance. By carefully controlling these parameters, the patent ensures that high reactivity (for tear resistance) and low viscosity (for pumpability) are both achieved through optimized polymer selection rather than compromise.
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 improved tear resistance and low viscosity, making it easier to pump and use in various applications, such as construction and sealing, while being cost-effective with common fillers.
Implementation Method 1
the reactive polyorganosiloxane polymer P1 a higher reactivity in condensation crosslinking with crosslinker v than the reactive polyorganosiloxane polymer P2
Data Source
AI summary
The invention relates to a silicon composition comprising the following:- at least two reactive polydiorganosiloxane polymers P1 and P2 which together make up 20 to 60 wt.%, based on the total silicon composition, - at least one cross-linking agent for polydiorganosiloxanes with a content of 0.5 to 5 wt.%, based on the total silicon composition, - at least one catalyst with a content of 0.001 to 0.1 wt.%, based on the total silicon composition, and - at least one optionally hydrophobic filler selected from the group comprising precipitated or fumed silicic acid and ground or precipitated chalk, with a content of 10 to 70 wt.%, based on the total silicon composition. The invention is characterized in that the reactive polyorganosiloxane polymer P1 has a higher reactivity in the condensation cross-linking process using the cross-linking agent than the reactive polyorganosiloxane polymer P2, and the molar ratio of P1 : P2 in the composition lies between 0.1 and 15. Such compositions are suitable in particular as adhesives, sealants, coatings, or molding compositions and are characterized by a high tear propagation resistance with a simultaneously low viscosity and improved pumpability.