Halogen-Free Flame Retardant TPU Composition for Cable Sheathing
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Solution Overview
Problem
Conventional halogen-free flame retardants for thermoplastic polyurethane (TPU) compositions struggle to achieve both good mechanical properties and effective flame retardancy, particularly in suppressing smoke and passing stringent tests like the VW-1 test, especially when used in cable jacketing applications.
Innovation Solution
A halogen-free flame retardant TPU composition comprising 10 wt% to 90 wt% TPU resin, 5 wt% to 90 wt% metal hydrate, 2 wt% to 50 wt% nitrogen-based phosphorus flame retardant, and 2 wt% to 20 wt% liquid phosphate modifier, with optional additives like antioxidants and UV-stabilizers, forming a cable outer sheath that contacts a thermoplastic inner sheath, providing a thickness of 0.1mm to 0.8mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional halogen-free flame retardants (e.g., organic phosphates like RDP and BPADP) are used in TPU compositions, then the composition is free from halogenated substances, but the flame retardancy and smoke suppression performance are insufficient
Solution Approach 1:
The patent uses a composite flame retardant system combining metal hydrate (ATH or MDH) with nitrogen-based phosphorus flame retardant (melamine polyphosphate or melamine cyanurate) in specific ratios. This composite approach creates synergistic effects that achieve superior flame retardancy and smoke suppression compared to single additives, while maintaining halogen-free status. The metal hydrate provides char formation and heat absorption, while the nitrogen-phosphorus compounds contribute to flame inhibition and smoke reduction
Solution Approach 2:
The patent optimizes the ratios of different flame retardant components (metal hydrate at 5-90 wt%, nitrogen-based phosphorus flame retardant at 2-50 wt%) to achieve the desired balance between flame retardancy, smoke suppression, and mechanical properties. By adjusting these parameters within specific ranges, the composition passes the VW-1 test while maintaining acceptable tensile strength and elongation
2Object-affected harmful factors
If halogen-free flame retardants are used to ensure environmental safety, then health and environmental concerns are addressed, but the composition fails to pass stringent flame retardancy tests like VW-1
Solution Approach 1:
The patent employs a multi-component flame retardant system where metal hydrate (5-90 wt%) works synergistically with nitrogen-based phosphorus flame retardant (2-50 wt%). This composite approach achieves the required flame retardancy to pass VW-1 test while maintaining halogen-free status for environmental safety. The liquid phosphate modifier (2-20 wt%) further enhances the flame retardant performance and compatibility
Solution Approach 2:
The patent applies different flame retardant mechanisms at different stages of combustion: metal hydrate decomposes at lower temperatures to absorb heat and release water vapor, while nitrogen-based phosphorus compounds activate at higher temperatures to form protective char layers and release flame-inhibiting gases. This localized action at different temperature zones ensures comprehensive flame retardancy
3Reliability
If flame retardant additives are incorporated into TPU composition to achieve flame resistance, then flame retardancy is improved, but mechanical properties such as tensile strength and elongation deteriorate
Solution Approach 1:
The patent optimizes the total flame retardant loading and the ratio between metal hydrate and nitrogen-based phosphorus flame retardant to achieve the minimum effective concentration for flame resistance while minimizing impact on mechanical properties. The liquid phosphate modifier enhances compatibility and dispersion, reducing aggregation that would otherwise act as stress concentration points
Solution Approach 2:
The synergistic combination of flame retardants creates a more efficient system where lower total concentrations are needed to achieve the same flame retardancy level, thereby preserving mechanical properties. The metal hydrate and nitrogen-phosphorus compounds work together to provide flame protection with reduced overall additive loading
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 composition achieves satisfactory flame resistance without halogenated flame retardants, passing the VW-1 test and non-migration tests, while maintaining acceptable tensile strength, elongation, and heat deformation properties, thus addressing environmental and health concerns associated with halogen-based flame retardants.
Implementation Method 1
metal hydrate
Implementation Method 2
nitrogen-based phosphorus flame retardant
Data Source
Figure 1
AI summary
The present disclosure provides a wire or cable comprising a flame retardant-free thermoplastic inner sheath and an outer sheath composition comprising, based on the weight of the composition, (a) 10 wt% to 90 wt% of a TPU based resin, (b) 5 wt% to 90 wt% of a metal hydrate, (c) 2 wt% to 50 wt% of a nitrogen-based phosphorus flame retardant, and (d) 2 wt% to 50 wt% liquid phosphate modifier, wherein the outer sheath is in contact with the insulation covering, and wherein the outer sheath has a thickness from greater than zero to 0.8mm.