Polyurethane Adhesive for Wind Turbine Rotor Blade Joints
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Solution Overview
Problem
Two-component polyurethane adhesives used in wind power rotor blades face challenges with short open time and mechanical property deterioration due to high humidity, leading to issues with joint and gap filling and structural integrity.
Innovation Solution
A two-component polyurethane composition comprising a polyol component with castor oil, high-functional polyols, and specific polyether/polyester polyols, combined with a polyisocyanate component, which provides a balance of elongation at break and tensile strength, maintaining mechanical properties even under high humidity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high crosslinking density is achieved by increasing functional group concentration and using higher-functional polyols or polyamines and higher-functional polyisocyanates, then tensile strength is improved, but open time is reduced and mechanical properties deteriorate under high humidity
Solution Approach 1:
The patent changes the chemical composition parameters of the polyol component by incorporating castor oil (providing hydroxyl groups) combined with specific polyether and polyester polyols having controlled OH numbers (150-200 and 210-300 mg KOH/g). This parameter modification allows achieving adequate crosslinking density while maintaining slower reaction kinetics that extend open time under high humidity conditions.
Solution Approach 2:
The invention uses a composite polyol system combining castor oil with polyether and polyester polyols in specific proportions. This composite approach creates a balanced chemical system that provides both the necessary reactivity for structural strength and the controlled reaction rate needed for extended open time, resolving the contradiction between strength and working time.
2Strength
If high crosslinking density is achieved by increasing functional group concentration, then tensile strength is improved, but elasticity is reduced
Solution Approach 1:
The patent modifies the polyol composition parameters by selecting polyols with specific OH numbers (150-200 and 210-300 mg KOH/g) and combining castor oil with polyether and polyester polyols in controlled proportions (10-30 wt% castor oil, 5-20 wt% polyether, 5-20 wt% polyester). This parameter optimization achieves adequate crosslinking for strength while maintaining polymer chain flexibility that provides 5-15% elongation at break.
3Duration of action of moving object
If the adhesive is exposed to high humidity conditions, then the reaction with humidity shortens open time and deteriorates mechanical properties, but the adhesive needs to maintain long open time and high mechanical strength
Solution Approach 1:
The patent converts the harmful effect of humidity into a beneficial feature by using a polyol composition that reacts controllably with moisture. The castor oil-polyether-polyester system is designed to undergo gradual reaction with atmospheric humidity, extending the open time rather than shortening it, while still achieving adequate crosslinking for structural strength.
Solution Approach 2:
The invention changes the chemical parameters of the polyol component to be less sensitive to humidity-induced premature curing. By using castor oil combined with polyether and polyester polyols having specific OH numbers and proportions, the system achieves a balanced reaction rate that maintains long open time (at least 60 minutes) even at 70% relative humidity, while preserving mechanical 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 composition achieves a long open time and maintains high mechanical strength and elasticity, suitable for structural gluing and filling joints and gaps in rotor blades, with tensile strength over 15 MPa and elongation at break between 5-15%, even after extended exposure to high humidity.
Implementation Method 1
Two-component polyurethane adhesives on the basis of polyols and polyisocyanates have long been used
Implementation Method 2
The presence of high humidity leads to increased side reaction of the isocyanate groups in the isocyanate component with water. In this case, additional isocyanate groups are consumed, which are no longer available to set up a crosslinked polyurethane. Furthermore, it may lead to foaming of the adhesive by carbon dioxide evolution.
Data Source
AI summary
The present invention relates to two-component polyurethane compositions which on the one hand have a long open time and, even after extended exposure to a climate with high atmospheric humidity (e.g., 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. The composition comprises castor oil, at least one polyol having 5-8 hydroxyl groups, a mixture of two different polyether alcohols and/or polyester polyols on the basis of castor oil or soybean oil and at least one polyisocyanate. The two-component polyurethane compositions are suitable in particular for non-positive filling joints or gaps that are joined by large-surface area structural gluing, in particular of vane half shells of rotor blades for wind power plants.