Silicone Rubber Adhesion Mediator for Polyolefins
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Solution Overview
Problem
The challenge lies in achieving strong adhesion between silicone elastomers and chemically inert thermoplastic substrates like polyolefins, which are difficult due to their low surface energy and lack of polar functional groups, leading to limited composite formation with existing adhesives, especially in regulated applications such as skin contact and food contact.
Innovation Solution
An adhesion mediator composition comprising trialkoxysilane, platinum group metal-based hydrosilylation reaction catalyst, alkoxy titanium compound, and polyorganosiloxane is used, which reacts with the hydrosilylation curable silicone rubber composition to form a strong bond without the need for volatile organic solvents or primers, allowing immediate overmolding and reducing processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional primer-based methods are used to improve adhesion between silicone elastomers and thermoplastics, then adhesion strength is improved, but volatile organic compounds are released causing environmental and regulatory issues
Solution Approach 1:
The invention changes the chemical composition parameters of the adhesion mediator by formulating it as a solvent-free composition containing specific components (trialkoxysilane, alkoxy titanium compound, polyorganosiloxane) in controlled ratios. This parameter change eliminates VOC emission while maintaining adhesion promotion functionality through the reactive chemical components that form bonds with both the thermoplastic substrate and silicone elastomer.
Solution Approach 2:
The adhesion mediator composition acts as an intermediary substance between the thermoplastic substrate and the silicone elastomer. It contains reactive components that chemically interact with both materials, forming a bridging layer that promotes strong adhesion without requiring volatile organic solvents. The mediator enables bond formation through its functional groups while remaining environmentally benign.
2Reliability
If primers with volatile organic solvents are used to achieve reliable adhesion, then adhesion reliability is improved, but processing time increases due to drying/curing requirements
Solution Approach 1:
The invention enables continuous processing by eliminating the drying/curing wait time associated with traditional primers. The solvent-free adhesion mediator composition can be applied and immediately followed by silicone elastomer application, as the reactive components remain active and ready to bond without requiring solvent evaporation or extended curing. This creates a continuous manufacturing process.
Solution Approach 2:
The invention extracts and removes the volatile organic solvent component from the primer formulation, retaining only the essential adhesion-promoting functional ingredients. This extraction eliminates the drying step entirely while preserving the adhesion reliability function, as the reactive components (trialkoxysilane, titanium compound, polyorganosiloxane) directly enable bond formation without needing a solvent carrier.
3Adaptability or versatility
If thermoplastic substrates are pre-activated to increase chemical reactivity, then adhesion capability is improved, but manufacturing complexity increases
Solution Approach 1:
The adhesion mediator composition is formulated in advance with pre-selected reactive components (trialkoxysilane, alkoxy titanium compound, polyorganosiloxane) that are designed to interact with thermoplastic substrates. This preliminary formulation of the mediator with appropriate chemical functionality eliminates the need for complex substrate pre-activation steps, as the mediator itself provides the necessary chemical reactivity when applied to the substrate surface.
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
This solution provides a reliable and environmentally friendly method for creating composite parts with improved adhesion and productivity, avoiding the issues of volatile organic compounds and regulatory concerns associated with traditional primer-based methods.
Implementation Method 1
Hydrosilylation curable silicone rubber compositions cure to provide silicone elastomeric materials via a hydrosilylation (addition) cure process
Implementation Method 2
A trialkoxysilane, of the formula Si(OR)3R1 wherein R is independently selected from C1-C6 alkyl and R1 is independently selected from C6-C12 aryl
Implementation Method 3
A trialkoxysilane, of the formula Si(OR)3R1 wherein R is independently selected from C1-C6 alkyl and R1 is independently selected from C6-C12 aryl
Data Source
AI summary
There is provided an adhesion mediator composition for use in the adhesion of silicone elastomers made from hydrosilylation curable silicone rubber compositions to thermoplastic substrates, especially polyolefin substrates and a process for adhering said silicone elastomers to said thermoplastic substrates using the aforementioned adhesion mediator composition.