Fiber-Reinforced Polyurethane Foam Homogeneity
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Solution Overview
Problem
Current methods for producing low-density fiber-reinforced polyurethane and polyisocyanurate foams struggle with achieving homogeneous distribution of long continuous fibers, leading to nonhomogeneous structures and poor mechanical and thermal performance, while also incurring significant material losses during production.
Innovation Solution
A process involving the controlled impregnation of chemical components with specific dynamic viscosity and permeability characteristics, allowing for the gravitational flow over layers of long continuous fibers, ensuring impregnation times less than the cream time, and using a double belt laminator to constrain expansion and maintain homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high proportion of blowing agent is used to obtain low density foam, then the foam density decreases, but the blowing agent forms an emulsion that is difficult to stabilize and mix, resulting in nonhomogeneous fiber distribution
Solution Approach 1:
The patent applies preliminary action by pre-mixing the polyol and blowing agent to form a stable solution before adding the isocyanate. This preliminary mixing ensures the blowing agent is fully dissolved and stabilized in the polyol, preventing emulsion formation during the subsequent pouring stage and enabling homogeneous fiber distribution in the final foam product.
Solution Approach 2:
The patent uses the polyol as an intermediary medium to dissolve and stabilize the blowing agent before the foam expansion process. By having the blowing agent pre-dissolved in the polyol, the system avoids direct emulsion formation between blowing agent and isocyanate, allowing for controlled and homogeneous impregnation of fibers during the pouring stage.
2Quantity of substance
If the amount of nucleating gas is increased during polyol/isocyanate mixing, then the viscosity increases, but this makes it difficult to obtain good penetration of foam into fibers and homogeneous fiber distribution
Solution Approach 1:
The patent applies preliminary action by completing the dissolution of the blowing agent in the polyol before adding the isocyanate. This ensures that the nucleating gas is already integrated into the polyol matrix, allowing for controlled viscosity increase without forming difficult-to-mix emulsions, thereby maintaining good fiber impregnation quality.
3Strength
If fibers are incorporated to reinforce the foam, then the mechanical strength increases, but achieving homogeneous distribution of long continuous fibers in low density foam becomes very difficult
Solution Approach 1:
The patent applies preliminary action by preparing the polyol-blowing agent solution in advance, ensuring complete dissolution and stability before the pouring stage. This preliminary preparation allows the viscous mixture to properly impregnate long continuous fibers during pouring, achieving homogeneous distribution while maintaining the reinforcing effect of the fibers in the final low-density foam structure.
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
Results in a block of fiber-reinforced foam with excellent mechanical properties, uniform fiber distribution, and low thermal conductivity, minimizing material loss and maintaining thermal efficiency, suitable for cryogenic fluid storage applications.
Implementation Method 1
a stage of impregnation, by gravitational flow of the above-said mixture of chemical components, of a plurality of fiber reinforcements
Implementation Method 2
The formation of polyurethane-type foams is well known to a person skilled in the art. Its formation entails a multicomponent reaction between a polyol (compound carrying at least two hydroxyl groups), a polyisocyanate (compound carrying at least two isocyanate —NCO functional groups) and an expanding agent
Implementation Method 3
This condensation reaction is in particular catalyzed by compounds having basic and/or nucleophilic natures, such as tertiary amines or metal-carboxylate coordination complexes, such as tin or bismuth salts
Implementation Method 4
a stage of formation and of expansion of the fiber-reinforced polyurethane/polyisocyanurate foam
Implementation Method 5
a block of fiber-reinforced polyurethane/polyisocyanurate foam of a thermal insulation slab... composed of cells storing a gas, advantageously having low thermal conductivity
Data Source
AI summary
The present invention relates to a preparation of a block of fiber-reinforced polyurethane/polyisocyanurate foam in which the expansion of the foam is constrained by the walls of a double belt laminator forming a tunnel, the block of fiber-reinforced polyurethane/polyisocyanurate foam being composed of cells storing a gas, advantageously having low thermal conductivity, and exhibiting a density of less than 50 kg·m−3 with a content of fibers Cf representing at least 4% by weight of the block of fiber-reinforced foam, in which the impregnation time of the fibers ti is less than the cream time tc of the polyurethane/polyisocyanurate foam.