Vehicle Polyurethane Foam Composition for Flame-Retardant Soundproofing
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Solution Overview
Problem
Existing flame-retardant soundproof materials for vehicles face challenges in balancing soundproofing and flame retardancy, as increasing the amount of expandable graphite to enhance flame retardancy leads to reduced deformation followability and shape retention, while using non-reactive phosphorus compounds can result in softness and poor designability.
Innovation Solution
A polyurethane foam is developed using a urethane resin composition with a specific mixture of 2,4′-diphenylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate, along with carbodiimide and uretonimine modified forms, and expandable graphite with an expansion starting temperature of 170° C. to 200° C., optimizing the content of these components to achieve both excellent flame retardancy and soundproofing properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of expandable graphite is increased to improve flame retardancy, then flame retardancy is improved, but the polyurethane foam becomes hard, lowering the deformation followability and soundproofing property
Solution Approach 1:
The patent applies parameter changes by carefully controlling the content of expandable graphite within a specific range (5-20 mass%) and adjusting the isocyanate index (1.05-1.30) to optimize the balance between flame retardancy and deformation followability. This quantitative parameter optimization resolves the contradiction by finding the optimal point where both requirements are satisfied.
Solution Approach 2:
The patent uses composite materials by combining expandable graphite with a specific polyol component (polyether polyol with specific molecular weight and hydroxyl value ranges) and isocyanate component (MDI with specific purity). This composite formulation achieves both flame retardancy and adequate deformation followability that cannot be achieved with single materials.
2Reliability
If a non-reactive phosphorus compound is used as a flame retardant, then the blending amount of expandable graphite can be reduced, but the polyurethane foam becomes too soft, lowering shape retention and designability
Solution Approach 1:
The patent extracts and eliminates the non-reactive phosphorus compound from the formulation, relying solely on expandable graphite as the flame retardant. This extraction approach avoids the softening effect caused by phosphorus compounds while maintaining flame retardancy through optimized expandable graphite content and distribution.
Solution Approach 2:
The patent changes the parameter of flame retardant type from non-reactive phosphorus compound to expandable graphite, and simultaneously optimizes the content parameters of expandable graphite (5-20 mass%) and isocyanate index (1.05-1.30) to achieve both flame retardancy and shape retention without the softening side effect.
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 polyurethane foam achieves V-0 level flame retardancy according to the UL94 standard in both normal conditions and after heat aging, maintaining soundproofing properties and moldability, allowing for applications requiring shape retention and designability.
Implementation Method 1
expandable graphite with an expansion starting temperature of 170° C. to 200° C.
Data Source
AI summary
A flame-retardant soundproof material for vehicles includes a polyurethane foam obtained by foam-molding a urethane resin composition. The urethane resin composition contains an isocyanate component (A), a polyol component (B), and an expandable graphite (C). The isocyanate component (A) includes a mixture of 2,4′-MDI and 4,4′-MDI, and one or more modified forms selected from carbodiimide modified forms and uretonimine modified forms of at least one of 2,4′-MDI and 4,4′-MDI. The content of the one or more modified forms in the urethane resin composition is 5.0 mass % to 8.8 mass %. The polyol component (B) includes a polyether polyol as a main constituent. The expandable graphite (C) has an expansion initiation temperature of 170° C. to 200° C., an expansion ratio of 10 or more at 250° C., and a content of 8 mass % to 20 mass % in the urethane resin composition.