Partially Blocked Polyurethane Toughener for Stable Epoxy Toughening
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyurethane tougheners for epoxy compositions suffer from residual blocking agents acting as chain stoppers, negatively affecting thermal and mechanical properties and storage stability, and there is a need for improved phase separation and toughening performance across a wide range of curing temperatures.
Innovation Solution
A polyurethane toughener is produced through a reaction of a polymeric polyol with a partially blocked polyisocyanate, formed by reacting a polyisocyanate with a blocking agent, to create a partially blocked polyisocyanate, which is then reacted with the polymeric polyol to form a polyurethane toughener suitable for epoxy compositions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blocking agents are used in excess to fully block NCO-groups in polyurethane prepolymers, then complete blocking is achieved, but residual blocking agent acts as chain stopper negatively affecting thermal and mechanical properties and storage stability
Solution Approach 1:
The patent applies partial blocking of NCO-groups instead of complete blocking. The polyisocyanate component contains 0.1-5.0 wt% unblocked NCO-groups, which is intentionally left unreacted to avoid the harmful effects of excess blocking agents while still achieving sufficient blocking to prevent premature reaction. This partial action resolves the contradiction by eliminating residual blocking agents that act as chain stoppers while maintaining the stability benefits of blocking.
Solution Approach 2:
The patent changes the parameter of blocking degree from complete (100%) to partial (90-99.9% blocked with 0.1-5.0 wt% unblocked). This parameter change optimizes the balance between stability (achieved through blocking) and mechanical properties (maintained by avoiding excess blocking agents). The controlled parameter of unblocked NCO-groups (0.1-5.0 wt%) directly addresses the contradiction by preventing chain stopping while maintaining reliability.
2Strength
If conventional polyurethane tougheners are used to improve impact resistance, then toughness is enhanced, but thermal and mechanical properties deteriorate due to residual blocking agents
Solution Approach 1:
The patent uses partial blocking with controlled unblocked NCO-groups (0.1-5.0 wt%) to achieve optimal performance. This partial action allows the polyisocyanate component to provide sufficient blocking for stability while avoiding the accumulation of residual blocking agents that would otherwise deteriorate thermal and mechanical properties. The result is improved impact resistance without the harmful side effects.
Solution Approach 2:
The patent optimizes the blocking degree parameter to 90-99.9% with 0.1-5.0 wt% unblocked NCO-groups. This parameter optimization resolves the contradiction by finding the sweet spot where impact resistance is enhanced through phase separation while thermal and mechanical properties are preserved by minimizing residual blocking agents.
3Stability of the object's composition
If blocking agents are used to stabilize polyisocyanate prepolymers, then storage stability is improved, but phase separation and toughening performance are compromised
Solution Approach 1:
The patent applies partial blocking rather than complete blocking, leaving 0.1-5.0 wt% unblocked NCO-groups. This partial action provides sufficient blocking for storage stability while maintaining enough reactive NCO-groups to enable proper phase separation during curing. The result is improved storage stability without compromising the phase separation mechanism essential for toughening performance.
Solution Approach 2:
The patent changes the blocking degree parameter from complete to partial (90-99.9% blocked), with controlled unblocked content (0.1-5.0 wt%). This parameter change resolves the contradiction by optimizing the balance between storage stability (achieved through blocking) and phase separation quality (maintained by preserving some unblocked NCO-groups for reaction-induced phase separation).
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 resulting polyurethane toughener enhances impact resistance and mechanical strength of epoxy compositions while maintaining low viscosity, improving thermal and mechanical properties and storage stability.
Implementation Method 1
a partially blocked polyisocyanate being a reaction product of a reactant mixture B comprising: a polyisocyanate, and a blocking agent
Implementation Method 2
a polyurethane toughener being a reaction product of a reactant mixture A comprising: a polymeric polyol, and the partially blocked polyisocyanate
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a polyurethane toughener suitable for epoxy composition, in particular a polyurethane toughener providing for epoxy composition with excellent mechanical strength as well as corrosion resistance while possessing low viscosity, to the method of producing the polyurethane toughener, to a curable epoxy composition comprising the polyurethane toughener, and a method of bonding substrates by using the curable epoxy composition.