Polyurethane Composites Vacuum Infusion Process
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Solution Overview
Problem
The production of large composite articles, such as wind turbine blades, is limited by the need for a polyurethane-forming system with a low viscosity to effectively infuse into reinforcing materials without premature setting, which has not been successfully achieved in vacuum infusion processes.
Innovation Solution
A polyurethane-forming system with a viscosity of less than 600 mPas at 25°C for at least 30 minutes and a gel time of greater than 60 minutes, comprising an isocyanate component and an isocyanate-reactive component, including specific polyols and flow additives, to allow for efficient infusion and curing of large composite articles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a polyurethane-forming system with low viscosity is used to enable thorough penetration of reinforcing material, then the system can be successfully infused into large composite articles, but the reactivity may be too slow making production economically impractical
Solution Approach 1:
The patent applies parameter changes by carefully controlling the viscosity of the polyurethane-forming system to remain below 600 mPas for at least 30 minutes at 25°C, and setting the gel time to greater than 60 minutes. These parameter optimizations enable the system to maintain low viscosity long enough for complete infusion of large composite articles while still achieving practical production speeds, resolving the contradiction between infusion capability and production efficiency
2Manufacturing precision
If the polyurethane-forming reaction is made slower to allow complete infusion, then the system can penetrate reinforcing material thoroughly, but the production time becomes excessively long
Solution Approach 1:
The patent optimizes the reaction parameters by specifying a gel time of greater than 60 minutes, which provides sufficient time for complete infusion and thorough penetration of the polyurethane-forming system into the reinforcing material. This parameter setting ensures manufacturing precision while keeping production time economically acceptable
3Manufacturing precision
If a longer gel time is used to allow complete infusion, then the system can fill the mold completely, but the production cycle becomes uneconomical
Solution Approach 1:
The patent establishes an optimal gel time parameter of greater than 60 minutes that balances mold filling completeness with production efficiency. This parameter ensures the polyurethane-forming system remains fluid long enough to completely fill large molds while preventing the production cycle from becoming excessively long and uneconomical
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 system enables the production of composite articles with enhanced green strength, allowing for demolding in 6 hours or less and exhibiting superior tensile fatigue and inter-laminar fracture toughness, making them suitable for large-scale applications like wind turbine blades.
Implementation Method 1
The pressure within this vacuum chamber is then drawn down. The pressure differential, between the bag in which the pressure has been reduced and the atmospheric pressure on the reactive mixture to be fed into the bag pushes the reactive mixture into the bag and into the reinforcing material.
Data Source
AI summary
A polyurethane-forming system having a viscosity at 25° C. of less than 600 mPas for at least 30 minutes, a gel time at ambient temperature of greater than 60 minutes and a water content of less than 0.06% by weight, based on total system weight, is used to produce composites by a vacuum infusion process. This system makes it possible to produce large composites such as wind turbine blades having excellent physical properties.