Acrylic Adhesive Composition for High-Temperature Shear Resistance
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Solution Overview
Problem
Acrylic pressure-sensitive adhesives (PSAs) exhibit poor high-temperature performance and limited resistance to deformation, necessitating an improvement in shear adhesion failure temperature (SAFT) and viscoelastic properties to maintain bonding efficacy at elevated temperatures.
Innovation Solution
An adhesive composition comprising a crosslinkable acrylic copolymer, a multi-functionalized crosslinkable oligomer, and a photoinitiator, undergoing two sequential curing stages to achieve enhanced stiffness and temperature resistance, with a tan delta value greater than 0.8 and a storage modulus of at least 300,000 Pa at 20 °C, and a shear adhesion failure temperature of at least 425 °F (218.3 °C).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acrylic pressure-sensitive adhesive is used to ensure ease of application and low cost, then the adhesive can be easily applied and conforms well to substrates, but the shear adhesion failure temperature is low and high temperature performance is poor
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the acrylic PSA through copolymerization with specific comonomers (carboxylic acid, hydroxyl, or amino functional groups) and adjusting the molecular weight distribution. This allows the adhesive to achieve both ease of application and improved high-temperature resistance by changing the chemical structure parameters rather than fundamentally altering the adhesive type
Solution Approach 2:
The patent creates a composite adhesive system by combining acrylic PSA with specific functional comonomers and additives that provide both the ease of application characteristic of acrylics and the high-temperature resistance needed. The composite nature of the adhesive formulation allows simultaneous achievement of contradictory properties
2Temperature
If the adhesive is formulated to have high stiffness and temperature resistance, then the shear adhesion failure temperature improves, but the ease of application decreases due to reduced flow ability
Solution Approach 1:
The patent applies dynamics by creating an adhesive system that exhibits different mechanical properties at different temperatures and times. The adhesive flows easily at application temperature (room temperature) but develops high stiffness and temperature resistance after curing. This dynamic property change resolves the contradiction between ease of application and high-temperature performance
Solution Approach 2:
The patent uses preliminary action through a two-stage curing process where the adhesive is first applied in a flowable state to ensure good substrate conformability, then cured to develop the required stiffness and temperature resistance. The preliminary application phase ensures ease of use before the adhesive sets into its final high-performance state
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 demonstrates improved wet-out characteristics, stiffness, and temperature resistance, ensuring effective bonding and durability at elevated temperatures, with a room temperature shear adhesion value of at least 500 hours and visible light transmission between 80 to 100%.
Implementation Method 1
a photoinitiator which initiates polymerization of the oligomer
Data Source
AI summary
The present invention is directed to an adhesive composition comprising a crosslinkable acrylic copolymer, a multi-functionalized crosslinkable oligomer and a photoinitiator wherein the composition exhibits excellent wet out characteristics as reflected in a tan delta value of at least 0.5, preferably greater than 0.5, more preferable greater than 0.8 as measured at 20 °C resulting from a first curing stage, and improved stiffness and temperature resistance as reflected in a storage elastic modulus of at least 300,000 Pa at 20 °C and a shear adhesion failure temperature of at least 425 °F (218.3 °C) at 1 Kg/in2 (0.155 Kg/cm2), respectively, which result from a second sequential curing stage.