Fiber-Reinforced Polyurethane Foam Formulation for Overpacking Strength
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Solution Overview
Problem
Existing fiber-reinforced rigid polyurethane foams used in cryogenic applications suffer from significant loss of compressive strength when overpacked, necessitating costly trimming steps to achieve uniform dimensions, which also results in waste.
Innovation Solution
A polyol composition comprising specific ratios of non-amine-initiated polyether and polyester polyols, diols, and a surfactant, with minimal water and blowing catalyst, is used to create a foam precursor that maintains compressive strength even when overpacked, ensuring uniform foam distribution and reduced need for trimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the foam is overpacked to eliminate trimming, then manufacturing precision and productivity are improved, but compressive strength deteriorates
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyol formulation, specifically incorporating polyether polyols with hydroxyl numbers of 300-600 mg KOH/g and polyester polyols with hydroxyl numbers of 150-300 mg KOH/g in specific ratios. These parameter changes in the foam precursor composition enable the foam to maintain compressive strength even when overpacked, resolving the contradiction between manufacturing precision and strength.
2Ease of manufacture
If the foam precursor fluid viscosity is reduced to improve penetration through fiber mats, then ease of manufacture is improved, but foam structural integrity deteriorates
Solution Approach 1:
The patent optimizes the viscosity parameter of the foam precursor fluid by selecting polyols with specific hydroxyl numbers and functionalities. The polyether polyols (functionality 3-8, hydroxyl number 300-600) and polyester polyols (functionality 1.5-2.5, hydroxyl number 150-300) are chosen to achieve a balance: low enough viscosity for good penetration through fiber mats, yet high enough to maintain structural integrity and cell structure during expansion and curing.
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 formulation allows for the production of fiber-reinforced polyurethane foam with maintained compressive strength and uniform dimensions, reducing waste and costs associated with trimming.
Implementation Method 1
a foam precursor fluid is applied onto the fiber mats. The foam precursor fluid must penetrate through the fiber mats as it expands and cures to form the foam
Implementation Method 2
the foam precursor fluid does not penetrate adequately through the fibers if it is too viscous
Implementation Method 3
0.1 to 2.5 weight percent of a surfactant, based on the weight of the polyol composition
Implementation Method 4
in the presence of a physical blowing agent
Data Source
AI summary
A polyol composition suitable for making rigid polyurethane foam includes a combination of five polyols, a surfactant and a polyurethane gelling catalyst. The polyol composition contains at most a very small quantity of a blowing catalyst. The polyol composition surprisingly produces, upon reaction with a polyisocyanate in the presence of a physical blowing agent, a polyurethane foam that exhibits little or no loss of compressive strength when overpacked. The polyol composition is especially useful for making fiber-reinforced rigid foams useful in cryogenic applications.