Non-Aromatic Urea Accelerators for Epoxy Resin Toughness
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Solution Overview
Problem
Heat-curing epoxy resin compositions face challenges with brittleness leading to cracks and destruction under stress, and aromatic accelerants used to achieve rapid curing at low temperatures compromise storage stability.
Innovation Solution
A heat-curing epoxy resin composition incorporating an accelerant of specific formula (Ia) or (Ib), which includes aliphatic or cycloaliphatic radicals, enhancing impact toughness and storage stability while allowing rapid curing at 170° C to 160° C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aromatic ureas are used as accelerants to achieve rapid curing at low temperatures (150-170°C), then curing speed is improved, but storage stability deteriorates
Solution Approach 1:
The patent changes the chemical structure parameter of the urea accelerant from aromatic to non-aromatic (aliphatic or cycloaliphatic). This structural parameter change reduces reactivity at storage temperature while maintaining adequate curing speed at application temperature (160-170°C), thereby resolving the contradiction between storage stability and curing speed.
2Strength
If epoxy resin compositions are used to achieve strong bonding, then strength is improved, but brittleness increases leading to cracks under stress
Solution Approach 1:
The patent creates a composite epoxy resin system by combining epoxy resin with non-aromatic urea accelerants and optional impact modifiers. This composite formulation maintains the high bonding strength of epoxy while reducing brittleness through the specific chemical interactions and physical properties of the non-aromatic urea components, enabling the material to withstand impact stresses without cracking.
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 achieves high impact toughness and storage stability, enabling effective use as a one-component adhesive and structural foam for vehicle construction, with improved mechanical properties and rapid curing at low temperatures.
Implementation Method 1
at least one accelerant C of the formula (Ia) or (Ib)... which is activated by elevated temperature and is an amine, amide, carboxylic anhydride or polyphenol
Implementation Method 2
Heat-curing epoxy resin compositions... after the epoxy resin composition has been applied, the body is heated in a cathodic dipcoating oven, in an operation which also cures... the heat-curing epoxy resin composition
Data Source
AI summary
Heat-curing epoxy resin compositions are characterized by high impact strength, good storage stability, and a low curing temperature. The epoxy resin compositions are suitable for use as a construction shell adhesive and for producing structural foams. They can already be cured in so-called bottom-baking conditions. Furthermore, it has been found that the use of an accelerator of the formula (Ia) or (Ib) results in an increase of the impact strength of heat-curing epoxy resin compositions.