HFO Blowing Agent Polyurethane Foam Structural Support
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Solution Overview
Problem
There is a need for polyurethane foam compositions that utilize hydrofluoroolefin blowing agents to achieve high density structural foam layers with ASTM E84 Class A flame spread and smoke development characteristics, suitable for wall structures without the use of OSB or plywood, while minimizing material and labor costs.
Innovation Solution
The development of isocyanate-reactive compositions comprising an aromatic polyester polyol with a functionality greater than 2.5 and an OH number of at least 300 mg KOH/g, combined with a hydrofluoroolefin blowing agent in a specific weight ratio, to produce polyurethane foams with high density and Class A flame resistance at any foam thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If HFO blowing agent is used to reduce ozone depletion and global warming potential, then environmental performance is improved, but achieving high density and Class A flame resistance simultaneously becomes difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the polyol component by specifying aromatic polyester polyols with functionality greater than 2.5 and OH number of at least 300 mg KOH/g, and adjusts the HFO content to 1-6% by weight with specific water:HFO ratios of 4:1 to 8:1, thereby achieving both environmental performance and flame resistance
Solution Approach 2:
The patent creates a composite foam system combining aromatic polyester polyol, HFO blowing agent, and specific catalysts to produce a foam that simultaneously achieves low environmental impact and high flame resistance, where the composite composition synergistically provides both Class A flame spread characteristics and high density structural strength
2Ease of manufacture
If high density foam layer is used to provide structural support without OSB or plywood, then material and labor costs are reduced, but achieving high racking shear strength becomes more difficult
Solution Approach 1:
The patent optimizes the polyol functionality parameter (greater than 2.5) and OH number (at least 300 mg KOH/g) to achieve high crosslinking density in the foam structure, which provides both high density (at least 2.8 lb/ft³) and high racking shear strength simultaneously, eliminating the need for additional sheathing materials
3Strength
If aromatic polyester polyol with high functionality and OH number is used to achieve high density foam, then structural strength is improved, but flame spread and smoke development characteristics may worsen
Solution Approach 1:
The patent carefully balances the polyol parameters (functionality >2.5, OH number ≥300) with controlled HFO blowing agent content (1-6% by weight) and specific water:HFO ratios (4:1 to 8:1) to achieve the dual objective of high density structural strength and Class A flame spread characteristics with smoke developed index of 450 or less
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 solution enables the production of polyurethane foams with high racking shear strength and Class A flame spread and smoke development characteristics, providing structural support in wall structures without additional sheathing materials, while reducing material and labor costs.
Implementation Method 1
a foam layer received within at least a portion of one of the voids within the frame, wherein the foam layer adheres to at least a portion of the faced polyisocyanurate panel
Implementation Method 2
Spray polyurethane foams (SPFs) are often formed by combining a polyol component and a polyisocyanate in the presence of water and a physical blowing agent
Implementation Method 3
a foam layer received within at least a portion of one of the voids within the frame, wherein the foam layer adheres to at least a portion of the faced polyisocyanurate panel
Data Source
AI summary
Isocyanate-reactive compositions that include a hydrofluoroolefin blowing agent, polyurethane foam-forming compositions, as well as spray-applied polyurethane foams formed therefrom that can provide structural support to wall structures and can also exhibit ASTM E84-16 Class A flame spread and smoke development characteristics at a foam thickness of 4 inches.