Flexible Polyurethane Gel Coats for Epoxy Resins
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Solution Overview
Problem
Existing polyurethane gel coats for composite materials face issues such as short lamination times, poor adhesion to epoxy and vinyl ester resins, surface defects like sink marks, and limited weathering resistance, which restrict their use in high-temperature curing processes and applications requiring long-term stability.
Innovation Solution
A two-component composition comprising a polyol component with low and higher molecular weight polyols and light-resistant aromatic amines, combined with a polyisocyanate component, to produce flexible polyurethane gel coats that offer extended lamination times, improved adhesion, and enhanced weathering resistance, while maintaining mechanical stability and preventing surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional polyurethane gel coats are used, then the gel coat provides a surface coating for composite materials, but the lamination time is too short to ensure adequate adhesion between synthetic resin and gel coat
Solution Approach 1:
The patent changes the chemical parameters of the polyol component by selecting specific molecular weights (160-600 g/mol) and hydroxyl group concentrations (5 to less than 20 mol/kg), which optimizes the reaction kinetics to extend lamination time while maintaining adhesion reliability
Solution Approach 2:
The patent creates a composite gel coat system combining polyol component (A) with specific polyisocyanate component (B), where the synergistic interaction between components extends the working time while preserving bonding capability through controlled crosslinking density
2Ease of manufacture
If polyurethane gel coats are used for composite materials, then the gel coat can be applied as a surface coating, but adhesion to epoxy and vinyl ester resins is poor
Solution Approach 1:
The patent optimizes the hydroxyl group concentration parameter (5 to less than 20 mol/kg) and molecular weight parameters of the polyol to achieve balanced reactivity that ensures both ease of application and strong adhesion to epoxy and vinyl ester resins
Solution Approach 2:
The patent creates different local properties within the gel coat system: the polyol component provides adhesion to the composite material substrate, while the polyisocyanate component provides crosslinking for surface durability, with each component optimized for its specific function
3Shape
If gel coats are applied to composite material surfaces, then the surface appearance is improved, but surface defects like sink marks occur during high-temperature curing
Solution Approach 1:
The patent selects polyols with specific molecular weights (160-600 g/mol) and hydroxyl concentrations that provide optimal viscosity and reactivity balance, preventing sink marks during high-temperature curing while maintaining smooth surface appearance
Solution Approach 2:
The patent formulates the gel coat with extended lamination time that allows the gel coat to fully adhere to the composite material before curing begins, cushioning against the development of surface defects like sink marks during subsequent high-temperature processing
4Ease of manufacture
If conventional gel coats are used, then the gel coat provides surface coating functionality, but weathering resistance and long-term stability are limited
Solution Approach 1:
The patent creates a composite polyurethane system combining specific polyol and polyisocyanate components that work synergistically to provide both ease of application and superior weathering resistance through enhanced crosslinking density and chemical stability
Solution Approach 2:
The patent optimizes the molecular weight and hydroxyl group concentration parameters to achieve a crosslinking density that provides long-term weathering stability and chemical resistance while maintaining the desired surface coating properties
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 provides gel coats with Shore D hardness greater than 65, elongation at break greater than 3%, and excellent adhesion to epoxy and vinyl ester resins, ensuring cohesive fracture within the synthetic resin laminate, and exhibits superior weathering and chemical resistance without reactive diluents or plasticizers, allowing for smooth surfaces and extended use temperatures.
Implementation Method 1
a two-component composition, which comprises a polyol component and a polyisocyanate component, for the production of flexible polyurethane gel coats
Implementation Method 2
The layer obtained after gelling is sufficiently mechanically stable not to be damaged during the application of the synthetic resin
Implementation Method 3
A3) one or more light-resistant aromatic amines
Implementation Method 4
excellent adhesion to epoxy and vinyl ester resins, ensuring cohesive fracture within the synthetic resin laminate
Data Source
AI summary
The invention relates to the use of a two-component composition comprising a polyol component and a polyisocyanate component, for producing flexible polyurethane gel coats for epoxy-resin and vinyl-ester resin composite materials.