Dual-Cure Conformal Coating Composition for Shadow Cure and Thermal Shock
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Solution Overview
Problem
Conventional conformal coating compositions face issues with shadow cure due to high viscosity, leading to inadequate hardness and solvent resistance in shadow areas, and poor thermal shock resistance due to stress cracking, especially in high temperature environments.
Innovation Solution
A UV and moisture curable conformal coating composition comprising isocyanate functional acrylated polyurethane, acrylic monomer, photoinitiator, defoaming agent, dehydration agent, wetting agent, and coupling agent, with a rheology modifier, to ensure complete curing and improved thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-cure polyurethane resins are used to solve shadow cure, then moisture curing capability is improved, but viscosity increases
Solution Approach 1:
The patent changes the chemical composition parameters of the resin system by using isocyanate-terminated polyurethane oligomers with specific molecular weights and functionalities, combined with acrylic monomers and oligomers. This parameter optimization achieves low viscosity while maintaining dual-cure capability, resolving the contradiction between shadow cure effectiveness and viscosity.
Solution Approach 2:
The patent creates a composite resin system combining isocyanate-functional polyurethane components with acrylic components. This composite approach allows the formulation to achieve both low viscosity for good flow and adequate isocyanate content for effective moisture curing in shadow areas, resolving the technical contradiction.
2Stress or pressure
If reactive diluent is added to lower viscosity, then flowability is improved, but isocyanate group concentration decreases
Solution Approach 1:
Instead of using traditional reactive diluents that reduce isocyanate concentration, the patent changes the formulation approach by selecting isocyanate-terminated polyurethane oligomers with optimized molecular weights. This parameter change allows achieving low viscosity through molecular weight control rather than dilution, thereby maintaining adequate isocyanate group concentration for effective moisture curing.
3Ease of manufacture
If conventional conformal coating compositions are used, then ease of manufacture is maintained, but thermal shock resistance deteriorates due to stress cracking
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific acrylic monomers and oligomers with controlled functionality and molecular weight, combined with isocyanate-terminated polyurethane. This parameter optimization creates a formulation that is both easy to manufacture using conventional processes and provides superior thermal shock resistance by reducing stress cracking through improved flexibility and adhesion.
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 exhibits improved retention of properties during thermal ageing, reduced stress cracking, and enhanced thermal shock resistance, maintaining flexibility and electrical properties in extreme temperatures.
Implementation Method 1
UV curable conformal coating composition comprising isocyanate functional acrylated polyurethane, acrylic monomer, photoinitiator
Implementation Method 2
The atmospheric moisture reacts with free isocyanate groups in the dual cure resin forming an amine group(s). The amine groups react with other isocyanate groups to form a polyurea.
Implementation Method 3
The amine groups react with other isocyanate groups to form a polyurea
Implementation Method 4
coupling agent, wherein the coupling agent comprises an acrylate functional silane and/or methacrylate functional silane
Data Source
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AI summary
A UV and moisture curable conformal coating composition comprising: from 25 to 65 wt.% isocyanate functional acrylated polyurethane, from 30 to 65 wt.% acrylic monomer, from 3.5 to 5.5 wt.% photoinitiator, from 0.1 to 1 wt.% defoaming agent, from 0.5 to 1.5 wt.% dehydration agent, from 0.2 to 1.5 wt.% wetting agent, and from 0.5 to 2.5 wt.% coupling agent.