Radiation-Curable Adhesive Composition for Dissimilar Substrate Bonding
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Solution Overview
Problem
Existing curable adhesive compositions struggle to maintain high adhesive strength and flexibility over a broad temperature range, especially when bonding dissimilar substrates with varying coefficients of thermal expansion, due to the limitations of plasticizers and monomers in controlling properties like modulus and Tg.
Innovation Solution
A curable adhesive composition comprising radiation-curable oligomers or prepolymers with carbon-carbon double bonds, diluent monomers, adhesion-promoting additives, and optional rheological modifiers, plasticizers, and additives, which provides flexibility and high adhesive strength across a broad temperature range without extensive use of plasticizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If plasticizers are used to increase flexibility, then flexibility is improved, but adhesive strength decreases
Solution Approach 1:
The patent changes the chemical composition parameters by using specific monomers (acrylic acid, carboxylic acid containing monomers) and controlling their concentration ratios to achieve both flexibility and adhesive strength without relying on traditional plasticizers that cause strength loss
Solution Approach 2:
The patent creates a composite adhesive system combining multiple monomers (acrylic prepolymers, carboxylic acid containing monomers, and other functional monomers) that work synergistically to provide both flexibility and high adhesive strength, replacing the single-function plasticizer approach
2Shape
If monomers are used to control flexibility, then flexibility is improved, but high temperature toughness decreases
Solution Approach 1:
The patent carefully controls the concentration parameters of flexibilizing monomers within specific ranges (e.g., 1-50 wt% acrylic acid, 1-20 wt% carboxylic acid containing monomer) to achieve flexibility while preserving high-temperature toughness through the synergistic effect of multiple monomer components
Solution Approach 2:
The patent develops a composite monomer system where carboxylic acid containing monomers work together with acrylic prepolymers and other functional monomers to provide both low-temperature flexibility and high-temperature structural integrity, overcoming the limitations of single-monomer approaches
3Strength
If adhesive strength is increased, then bonding capability is improved, but flexibility decreases
Solution Approach 1:
The patent adjusts the molecular weight and composition parameters of the acrylic prepolymers and monomer ratios to achieve optimal balance between adhesive strength and flexibility, using the specific chemical interactions between carboxylic acid containing monomers and the polymer matrix to maintain both properties
4Reliability
If the adhesive is made flexible to withstand thermal stress, then thermal cycling resistance is improved, but bond strength decreases
Solution Approach 1:
The patent modifies the glass transition temperature and molecular architecture parameters through selective monomer choice and concentration control to enable the adhesive to flex with thermal expansion differences while maintaining sufficient bond strength through the crosslinked network structure formed by the multifunctional monomer system
Solution Approach 2:
The patent creates a composite adhesive system where the synergistic interaction between carboxylic acid containing monomers, acrylic prepolymers, and other functional monomers produces a material that simultaneously achieves thermal cycling resistance and high bond strength through enhanced molecular-level adhesion and flexibility
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 exhibits greater than 50% cohesive failure and retains adhesive strength from -20 to 120°C, demonstrating extreme flexibility with a tensile modulus of less than 100 and elongation at break of greater than 200%, effectively bonding dissimilar substrates like metal to plastic.
Implementation Method 1
Curable adhesive compositions are finding a wide range of applications in bonding... these compositions cure when exposed to actinic radiation such as ultraviolet (UV) radiation
Data Source
AI summary
A composition that cures when exposed to actinic radiation. In some embodiments the curable adhesive composition comprises: a) one or more radiation curable oligomers or prepolymers terminally having at least one carbon-carbon double bond-containing group; b) one or more diluent monomer components containing at least one polymerizable group; c) optionally one or more adhesion promoting additives of an organic or inorganic acid acrylic monomer; and optionally one or more rheological modifiers; one or more plasticizers and; one or more additives. The curable composition can be used in an adhesive that structurally bonds many substrates including dissimilar substrates. In some embodiments cured reaction products of the composition have a broad service temperature range from −20 to 120° C. Cured reaction products of this embodiment will exhibit greater than 50% cohesive failure in this temperature range. The cured composition will retain adhesive strength at temperatures above its Tg.