Two-Part Hybrid Adhesive for Low Surface Energy Plastics
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Solution Overview
Problem
Existing two-part adhesive systems face challenges with poor shelf stability and excessively fast reactions when bonding plastics, often requiring high amine levels and exotic stabilizers, which can lead to premature polymerization and inadequate bonding time, and the use of high heat capacity fillers can cause separation and dispensing issues.
Innovation Solution
A two-part hybrid adhesive system where one part contains an organoborane-amine complex and the other part contains a polyisocyanate, allowing simultaneous step-growth formation of polyurea/urethane and addition polymerization of acrylic monomers/oligomers, with a nitrogen to boron ratio less than 4 and no polyol, enabling controlled reaction and strong bonding without high heat or separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high levels of amine are used to complex organoborane, then shelf stability is improved, but the reaction becomes excessively fast and generates excessive heat
Solution Approach 1:
The adhesive system is divided into two separate parts: Part A contains the organoborane-amine complex with controlled N/B ratio, while Part B contains the polyisocyanate and acrylic components. This segmentation allows the complex to remain stable during storage, and only upon mixing do the components react to liberate borane and initiate polymerization at a controlled rate.
Solution Approach 2:
The invention changes the nitrogen to boron ratio parameter from the conventional high ratios (above 4, up to 34) to a controlled ratio of less than 4. This parameter change maintains sufficient complex stability for shelf life while preventing excessively fast reaction rates and excessive heat generation when the decomplexing agent is added.
2Stability of the object's composition
If high levels of amine are used to complex organoborane, then shelf stability is improved, but adhesion to plastics deteriorates due to premature polymerization
Solution Approach 1:
The organoborane is pre-complexed with amine in controlled ratios to create a stable precursor that prevents premature polymerization during storage. This preliminary complexation action protects the system from degradation while maintaining the ability to initiate polymerization on-demand when mixed with the polyisocyanate component.
Solution Approach 2:
The amine acts as an intermediary substance that temporarily binds the organoborane in a stable complex during storage. Upon mixing with polyisocyanate, the amine is consumed in the decomplexing reaction, releasing the borane to initiate polymerization only at the appropriate time for bonding.
3Temperature
If high heat capacity fillers are used to control reaction heat, then temperature control is improved, but separation and dispensing difficulties occur
Solution Approach 1:
The invention extracts the high heat capacity filler from the system by replacing it with a two-part formulation approach. The reaction heat is managed through the controlled decomplexing mechanism and the inherent heat capacity of the adhesive components themselves, eliminating the need for filler additives that would compromise dispensing properties.
Solution Approach 2:
The invention changes the approach to heat management from adding high heat capacity fillers (which affect dispensing) to controlling the reaction rate through the organoborane-amine complex stoichiometry. By adjusting the N/B ratio and using controlled decomplexing, the reaction proceeds at a manageable rate without requiring filler additives.
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 system achieves good stability, high adhesion to untreated plastics, and suitable processing characteristics, ensuring a strong bond is formed without premature polymerization or separation, while maintaining ease of use in conventional equipment.
Implementation Method 1
the polyisocyanate reacts with the amine to liberate the borane
Implementation Method 2
which subsequently initiates free radical polymerization of the acrylic monomers/oligomers
Implementation Method 3
step-growth formation of a polyurea/urethane occurs simultaneously with addition polymerization of acrylic monomers/oligomers
Data Source
AI summary
Provided are two part hybrid adhesives that comprise an organoborane amine complex, a polyamine, a component polymerizable by free radical polymerization, and a polyisocyanate component. An isocyanate terminated prepolymer can advantageously be used in the practice of the invention. The adhesive is particularly well suited for low surface energy plastic bonding.