Acrylic Adhesive Blend for High-Temperature Shear Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing adhesive compositions face challenges in achieving a balance between high molecular weight and low molecular weight acrylic copolymers to optimize stress relaxation and shear strength, particularly at elevated temperatures, due to limitations in hydrogen bonding and crosslinking.
Innovation Solution
A blend of high molecular weight and low molecular weight acrylic copolymers is used, where the low molecular weight copolymer contains greater than 10 parts by weight of a monomer with reactive hydrogen bonding groups, combined with controlled crosslinking through electron beam irradiation to achieve a stress relaxation ratio of less than 0.30 at 70°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight acrylic copolymer is used to improve shear strength, then shear strength is improved, but stress relaxation ability deteriorates
Solution Approach 1:
The adhesive composition is segmented into two distinct copolymer components with different molecular weights (high Mn ≥150,000 and low Mn <70,000). Each segment performs a specific function: the high molecular weight copolymer provides shear strength while the low molecular weight copolymer provides stress relaxation ability. This segmentation allows both contradictory requirements to be satisfied simultaneously by assigning different functions to different molecular weight segments.
Solution Approach 2:
The invention creates a composite adhesive system by blending two acrylic copolymers with different molecular weights and complementary monomer compositions. The high molecular weight copolymer (with less than 10 pbw of monomer B) and low molecular weight copolymer (with greater than 10 pbw of monomer D) work together synergistically, where each component contributes its unique properties to the overall adhesive performance, resolving the contradiction between shear strength and stress relaxation.
2Stability of the object's composition
If low molecular weight copolymer with high reactive group content is used to improve stress relaxation, then stress relaxation is improved, but shear strength deteriorates
Solution Approach 1:
The adhesive system segments the stress relaxation function into the low molecular weight copolymer component, which contains greater than 10 parts by weight of monomer D with reactive hydrogen bonding groups. This segmentation allows the low molecular weight component to specialize in stress relaxation through enhanced hydrogen bonding, while the high molecular weight component specializes in providing shear strength, thus resolving the contradiction.
Solution Approach 2:
The invention changes the molecular weight parameter (Mn <70,000 for low molecular weight copolymer) and monomer composition parameter (greater than 10 pbw of monomer D) of one component to optimize stress relaxation, while simultaneously maintaining a different molecular weight parameter (Mn ≥150,000) in the other component to maintain shear strength. This parameter differentiation resolves the contradiction by allowing each component to be optimized for its specific function.
3Reliability
If hydrogen bonding is increased to improve adhesion, then adhesion is improved, but thermal stability deteriorates
Solution Approach 1:
The invention segments the adhesive functions by assigning hydrogen bonding primarily to the low molecular weight copolymer component (with greater than 10 pbw of monomer D), while the high molecular weight copolymer component (with less than 10 pbw of monomer B) provides thermal stability. This segmentation allows hydrogen bonding to be concentrated in the component where it provides maximum adhesion benefit without compromising overall thermal stability.
Solution Approach 2:
The adhesive composition creates a composite system where two copolymers with different monomer compositions work synergistically. The low molecular weight copolymer with higher reactive group content enhances adhesion through hydrogen bonding, while the high molecular weight copolymer with lower reactive group content maintains thermal stability, resolving the contradiction between adhesion and thermal stability.
4Strength
If crosslinking is increased to improve shear strength, then shear strength is improved, but stress relaxation deteriorates
Solution Approach 1:
The invention segments the molecular weight distribution into high and low molecular weight components, where the low molecular weight copolymer (Mn <70,000) with greater than 10 pbw of monomer D provides stress relaxation ability that counteracts the stress relaxation deterioration caused by crosslinking. This segmentation allows crosslinking to proceed for shear strength enhancement while the low molecular weight component maintains stress relaxation.
Solution Approach 2:
The invention changes the molecular weight parameter of one component to Mn <70,000 and increases the reactive group content (greater than 10 pbw of monomer D) to enhance stress relaxation. This parameter change in the low molecular weight component compensates for the stress relaxation deterioration that would otherwise result from crosslinking, allowing both improved shear strength and maintained stress relaxation.
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 solution enhances the adhesive's ability to deform under continuous load and resist deformation, maintaining performance at high temperatures with improved shear strength and stability.
Implementation Method 1
monomer B has at least one reactive group that is capable of hydrogen bonding
Implementation Method 2
controlled crosslinking through electron beam irradiation
Data Source
AI summary
Adhesive compositions comprising a high molecular weight acrylic copolymer and a low molecular weight copolymer are disclosed. Adhesive articles and methods of making adhesive compositions and articles are also described.