Addition-Curable Silicone Rubber Self-Bonding to Thermoplastics
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Solution Overview
Problem
Existing addition-curable silicone rubber compositions face challenges in achieving robust bonding to thermoplastics without primers, leading to issues like mold fouling, delamination at high temperatures, and turbidity in cured articles, while also requiring multiple processing steps and additives that can embrittle the silicone rubber.
Innovation Solution
An addition-curable silicone rubber composition comprising polyorganosiloxanes, polyorganohydrogensiloxanes, a hydrosilylation catalyst, an organosilicon compound with a polyvalent aromatic group, and an aromatic compound with unsaturated hydrocarbyl residues, which enables self-bonding to thermoplastics without primers, reducing mold fouling, and maintaining ductility at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If organosilicon compounds containing phenylene groups and hydrosilyl groups are added to achieve self-bonding capability, then bonding strength to thermoplastics is improved, but mold fouling increases and material buildup occurs on molds
Solution Approach 1:
The patent introduces a silane-modified polyethylene glycol as an intermediary substance that mediates between the organosilicon bonding agents and the mold surface. This intermediary layer prevents direct deposition of bonding materials on the mold while maintaining effective bonding to thermoplastics, thereby reducing mold fouling and buildup issues
Solution Approach 2:
The patent modifies the chemical parameters of the organosilicon compounds by introducing specific silane modifications and controlling the ratios of phenylene groups to hydrosilyl groups. These parameter changes optimize the bonding mechanism to reduce unwanted side reactions that cause mold fouling, while maintaining strong adhesion to thermoplastic substrates
2Strength
If high levels of organosilicon compounds and ester compounds are used to improve bonding performance, then adhesion to thermoplastics is enhanced, but the silicone rubber becomes brittle and loses ductility
Solution Approach 1:
The patent precisely controls the concentration parameters of organosilicon compounds and ester compounds within optimal ranges, and introduces silane-modified polyethylene glycol as a plasticizing agent. This parameter optimization ensures sufficient adhesion strength while preventing excessive crosslinking that would cause brittleness, thereby maintaining the ductility of the cured silicone rubber
Solution Approach 2:
The patent creates a composite bonding system combining organosilicon compounds, ester compounds, and silane-modified polyethylene glycol in specific proportions. This composite approach balances the rigid bonding function of organosilicon compounds with the flexible plasticizing effect of the polyethylene glycol, achieving both strong adhesion and maintained ductility
3Temperature
If aromatic compounds are incorporated to enhance bonding at high temperatures, then thermal stability is improved, but color formation and yellowing occur upon oxidation and UV exposure
Solution Approach 1:
The patent carefully selects and controls the type and amount of aromatic compounds used, opting for specific structures that provide thermal stability with lower susceptibility to oxidation-induced yellowing. By optimizing the concentration and molecular structure parameters, the patent achieves high-temperature bonding performance while minimizing color formation and yellowing during service
Solution Approach 2:
The patent employs antioxidant additives that act as sacrificial protective agents, consuming oxidation damage before it affects the aromatic compounds. These short-living antioxidants protect the aromatic bonding agents from oxidative yellowing, maintaining aesthetic appearance while preserving thermal stability
4Strength
If multiple additives are used to achieve robust bonding without primers, then bonding performance is improved, but the number of processing steps and device complexity increases
Solution Approach 1:
The patent combines multiple bonding-functional additives (organosilicon compounds, ester compounds, silane-modified polyethylene glycol) into a single integrated LSR composition formulation. This merging eliminates the need for separate primer application steps and multiple processing operations, achieving robust bonding through a simplified one-step injection molding process
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 strong, primer-less bonding to various substrates at high temperatures, reduces mold fouling, and maintains the ductility of silicone rubber, enabling efficient two-shot or multiple-shot molding processes while preventing delamination and turbidity in optically clear articles.
Implementation Method 1
an addition-curable silicone rubber composition comprising polyorganosiloxanes, polyorganohydrogensiloxanes, a hydrosilylation catalyst
Implementation Method 2
an organosilicon compound with a polyvalent aromatic group, and an aromatic compound with unsaturated hydrocarbyl residues, which enables self-bonding to thermoplastics without primers
Data Source
AI summary
The present invention relates to an addition-curable silicone rubber composition having self-bonding capability. The addition-curable silicone rubber composition exhibits self-bonding capability in particular to substrates that contain residual hydroxyl groups or other residual hydrosilyl-reacting groups on their surface, including polycarbonate, polyester, polyamide, polysulfone, polyurethane, phenolic resin, epoxy resin, cellulose, glass and the mixture thereof.