Polyurethane Adhesive for Wind Rotor Blades
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Solution Overview
Problem
Two-component polyurethane adhesives used for structural applications, such as rotor blade construction in wind power plants, face challenges with short open time and deteriorated mechanical properties due to humidity, leading to reduced adhesion and strength.
Innovation Solution
A two-component polyurethane composition comprising castor oil, alkoxylated aromatic diol, and polyols with 5-8 hydroxyl groups, which maintains high mechanical strength and balance between tensile strength and strain even after exposure to high humidity, allowing for extended open time and effective curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high cross-linking density is used to achieve high strengths, then adhesive strength is improved, but open time is shortened due to rapid curing
Solution Approach 1:
The patent changes the chemical parameters of the polyol component by specifying molecular weight ranges (1,000-10,000 g/mol) and hydroxyl number ranges (20-100 mg KOH/g), which control the curing rate and open time while maintaining adhesive strength. This allows optimization of both contradictory properties through precise parameter control.
Solution Approach 2:
The patent uses a composite polyol system combining multiple polyols with different molecular weights and hydroxyl numbers, creating a balanced formulation that provides both adequate open time and final adhesive strength. The composite approach allows synergistic effects between different polyol components.
2Reliability
If elevated humidity is present, then side reactions consume isocyanate groups, but this shortens open time and deteriorates mechanical properties
Solution Approach 1:
The patent converts the harmful effect of humidity into a beneficial one by formulating the adhesive to tolerate moisture exposure during application. The specific polyol composition and stoichiometric balance allow the adhesive to maintain adequate open time even in humid conditions, turning a previously detrimental environmental factor into an acceptable processing condition.
Solution Approach 2:
The patent adjusts the stoichiometric ratio of NCO to OH groups and controls the polyol molecular weight and hydroxyl number to compensate for moisture-induced side reactions. This parameter optimization ensures sufficient isocyanate groups remain available for cross-linking even when some are consumed by water, maintaining both open time and final properties.
3Duration of action of moving object
If high molecular weight polyols are used, then viscosity is reduced and open time is extended, but cross-linking density may be insufficient for structural strength
Solution Approach 1:
The patent employs a composite polyol system with multiple components of different molecular weights (1,000-10,000 g/mol range) and hydroxyl numbers (20-100 mg KOH/g range). This composite approach allows the formulation to benefit from the low viscosity and long open time of higher molecular weight polyols while the combined hydroxyl functionality ensures adequate cross-linking density for structural strength.
Solution Approach 2:
The patent optimizes the hydroxyl number parameter (20-100 mg KOH/g) as a key control variable that balances viscosity and cross-linking potential. By controlling this parameter within the specified range, the adhesive achieves both adequate open time and sufficient cross-linking density for structural applications.
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 tensile strength, E-modulus, and elongation at break, ensuring reliable adhesion and structural integrity under humid conditions, particularly suitable for large-area applications like rotor blade assembly.
Implementation Method 1
Two-component polyurethane adhesives based on polyols and polyisocyanates have already been used for a long time
Implementation Method 2
The presence of elevated humidity leads to an increased side reaction of the isocyanate groups in the isocyanate component with water. The additional isocyanate groups are consumed that are no longer available for the construction of a cross-linked polyurethane. Furthermore, a foaming of the adhesive due to the development of carbon dioxide can occur
Data Source
AI summary
The invention relates to two-component polyurethane compositions which have a long open time and, even alter extended exposure to a high-moisture climate (for example 70% relative humidity), even after 40 minutes, and in particular even after 60 minutes, can still be glued and cured to form polymers having high mechanical strength, whereby a structural adhesive bond is created. The composition comprises castor oil, at least one alkoxylated aromatic diol, at least one polyol having 5 to 8 hydroxyl groups, and at least one polyisocyanate. The two-component polyurethane compositions are suitable in particular for use as structural adhesives, in particular for the adhesive bonding of wing half-shells of rotor blades for wind power plants.