Two-Stage Curing Acrylic Adhesive for High-Temperature Shear Resistance
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Solution Overview
Problem
Acrylic pressure-sensitive adhesives typically exhibit poor high-temperature performance and limited resistance to deformation in shear mode, requiring improved thermal stability and bonding characteristics.
Innovation Solution
A two-stage curing adhesive composition comprising a crosslinkable acrylic copolymer, a multi-functionalized crosslinkable oligomer, and a photoinitiator, which enhances stiffness and temperature resistance while maintaining ease of application by achieving specific tan delta and storage elastic modulus values.
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 flow well at room temperature, but the adhesive exhibits poor high-temperature performance and limited resistance to deformation in shear mode
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the adhesive system. It uses a multi-functionalized crosslinkable oligomer with specific functional group ratios (epoxy:hydroxyl = 2:1 to 4:1) and controlled molecular weight (500-5000 g/mol), along with photoinitiator concentration optimization (0.1-5 wt%), to achieve both room-temperature flowability and high-temperature stability through controlled crosslinking density
Solution Approach 2:
The patent creates a composite material system combining acrylic pressure-sensitive adhesive base polymer with multi-functionalized crosslinkable oligomer and photoinitiator. This composite approach allows the adhesive to exhibit dual characteristics: liquid-like flow at room temperature for easy application and gel-like stiffness at elevated temperatures for improved shear resistance
2Ease of operation
If the adhesive is formulated to flow well at room temperature for easy application, then contact area with substrate increases, but resistance to deformation in shear mode at elevated temperatures decreases
Solution Approach 1:
The patent applies dynamics by creating a temperature-dependent viscoelastic material that transitions from liquid-like behavior at room temperature to gel-like behavior at elevated temperatures. The photopolymerization system enables dynamic adjustment of crosslinking density, allowing the adhesive to be applied in a fluid state and then set in a rigid state upon curing
Solution Approach 2:
The patent changes the physical state parameters of the adhesive through controlled photopolymerization. By adjusting photoinitiator concentration (0.1-5 wt%) and oligomer functional group ratios, the system achieves optimal balance between initial fluidity for application and final gel strength for shear resistance
3Reliability
If crosslinking density is increased to improve stiffness and temperature resistance, then shear adhesion failure temperature increases, but ease of application may be compromised
Solution Approach 1:
The patent applies preliminary action by incorporating the multi-functionalized crosslinkable oligomer and photoinitiator into the adhesive formulation before application. The system is designed to remain uncured during application (maintaining fluidity) and then undergoes photopolymerization after substrate contact, achieving high crosslinking density and temperature resistance only when needed
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 adhesive composition demonstrates improved wet out characteristics, increased stiffness, and elevated shear adhesion failure temperature, ensuring effective bonding and thermal stability.
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 partially cured composition exhibits excellent wet out characteristics as reflected in a tan delta value of at least 0.4, preferably greater than 0.5, more preferable greater than 0.6 as measured at 20° C. resulting from a first curing stage, and the fully cured composition exhibits an improved stiffness and temperature resistance as reflected in a storage elastic modulus of at least 175,000 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.