Fast Curing Acrylic Structural Adhesive via Microcapsule Activation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional acrylic adhesives are limited by their slow curing speed and susceptibility to premature curing, making them unsuitable for high-speed industrial applications and difficult to use with robotic dispensing equipment due to residue issues.
Innovation Solution
A two-part structural adhesive system with aminoborane initiator and microcapsules containing interpolymer complexes of oppositely charged polymers and a hydrophobic carboxylic acid cure activator, where the microcapsules are dispersed in the adhesive suspension, allowing for controlled activation and rapid curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acrylic adhesives are used for fast curing, then curing speed is improved, but premature curing through heat activation occurs and shelf life is reduced
Solution Approach 1:
The adhesive system is divided into two separate components: Part A containing the aminoborane initiator and Part B containing the hydrophobic carboxylic acid cure activator encapsulated in microcapsules. This segmentation prevents premature curing by keeping the activator isolated until application, while enabling fast curing when the components are mixed. The microcapsule encapsulation specifically protects the carboxylic acid from premature reaction, extending shelf life.
Solution Approach 2:
The hydrophobic carboxylic acid encapsulated in microcapsules acts as an intermediary that controls the curing activation. The microcapsule wall serves as a barrier that prevents direct contact between the carboxylic acid and aminoborane initiator during storage, eliminating premature curing through heat activation while allowing controlled activation upon application.
2Reliability
If conventional acrylic adhesives are used for bonding, then bonding capability is achieved, but worklife is limited and equipment cleaning is required frequently
Solution Approach 1:
The two-part adhesive system is prepared in advance with all components separated and stable. Part A contains the aminoborane initiator and Part B contains the encapsulated hydrophobic carboxylic acid activator. This preliminary preparation allows the adhesive to be stored and handled indefinitely without premature curing, and can be mixed immediately before application to achieve fast curing and strong bonding, maximizing worklife and eliminating frequent equipment cleaning requirements.
3Strength
If two-part adhesives with peroxide initiation are used, then cross-linking is achieved, but curing is slow and prone to premature curing through heat activation
Solution Approach 1:
The patent changes the chemical parameters of the initiation system by replacing peroxide with an aminoborane-carboxylic acid system. This parameter change enables rapid curing through a different chemical mechanism that is not prone to heat activation during storage. The hydrophobic carboxylic acid encapsulated in microcapsules reacts with the aminoborane initiator to generate radicals that initiate fast polymerization, achieving both strong cross-linking and rapid curing without the drawbacks of peroxide systems.
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
Enables fast curing times of less than 1 second and eliminates the need for immediate equipment cleaning, as the adhesive remains inert until activated, optimizing handling and shelf life.
Implementation Method 1
The curing process is activated when the curing activator and the aminoborane initiator interact with each other. Direct contact can be achieved by high pressure, ultrasonic, or shock waves may cause the microcapsules to rupture, initiating rapid curing by radical polymerization.
Implementation Method 2
Direct contact can be achieved by high pressure, ultrasonic, or shock waves may cause the microcapsules to rupture, initiating rapid curing by radical polymerization.
Data Source
Figure 1
AI summary
An acrylic adhesive composition includes a first part including an aminoborane initiator and acrylate or/and methacrylate monomers, and a second part including inert microcapsules of a cure activator and acrylate monomers, wherein the microcapsules are breakable, such that when broken, the first part reacts with the second part and the acrylic adhesive begins to cure. A two-part structural adhesive includes a suspension component containing an aminoborane initiator, and microcapsules containing an encapsulated component, wherein the microcapsules are dispersed in the suspension component. A method of activating an aminoborane initiator suspension to form a structural adhesive includes adding microcapsules containing an encapsulated component, to the aminoborane initiator suspension at a predetermined ratio, and breaking the microcapsules to activate curing.