Halogen-Free Flame Retardant TPU Composition
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Solution Overview
Problem
Halogen-free, flame retardant thermoplastic polyurethane (TPU) compositions with ethylene vinyl acetate (EVA) copolymer struggle to meet heat deformation specifications at 150°C, exhibiting higher material density and poor insulation resistance compared to halogen-containing compositions, while also being more costly.
Innovation Solution
A halogen-free, flame retardant composition comprising a thermoplastic polyurethane (TPU) and a silane-grafted, crosslinked ethylene vinyl acetate (Si-g-EVA) copolymer, combined with organic phosphate ester, metal hydrate, and char forming agents, such as epoxidized novolac resin, to enhance mechanical properties and flame retardancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If halogen-free TPU compositions are used to replace halogen-containing compositions, then flame retardant performance and mechanical properties are improved, but material density increases and insulation resistance deteriorates
Solution Approach 1:
The patent creates a composite material system by blending TPU with crosslinked EVA copolymer. This composite approach allows the formulation to achieve flame retardancy through the crosslinked network structure while managing density and electrical properties through component selection and ratio optimization.
Solution Approach 2:
The patent modifies the chemical structure and physical properties of EVA by introducing silane grafting and crosslinking. This parameter change transforms EVA from a simple additive into an active component that contributes to flame retardancy through crosslinked structure formation, while controlling the impact on density and insulation properties.
2Weight of stationary object
If EVA copolymer is blended with TPU to improve insulation resistance and reduce density, then these properties are improved, but heat deformation performance deteriorates
Solution Approach 1:
The patent fundamentally changes the thermal properties of EVA by inducing crosslinking through silane grafting. This parameter change elevates the heat deformation temperature of the EVA component, allowing it to maintain structural integrity at higher temperatures while still providing the desired density reduction and insulation properties.
Solution Approach 2:
The patent creates a composite system where crosslinked EVA forms a thermally stable network within the TPU matrix. This composite structure combines the low density and good insulation properties of EVA with the thermal stability provided by the crosslinked network, resolving the heat deformation issue.
3Temperature
If silane-grafted crosslinked EVA is used to improve heat deformation performance, then temperature resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs silane grafting and crosslinking of EVA before blending with TPU. This preliminary action prepares the EVA with the desired crosslinked structure and thermal properties in advance, simplifying the final compounding process and allowing for better process control.
Solution Approach 2:
The silane-grafted EVA acts as an intermediary component that bridges the gap between simple EVA and fully crosslinked systems. The gradual introduction of crosslinking through silane grafting provides a controlled transition that balances manufacturing ease with improved thermal performance.
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 TPU/Si-g-EVA composition achieves satisfactory flame resistance and heat deformation performance at 150°C, reducing material density and improving insulation resistance, while avoiding the use of halogenated flame retardants, thus addressing cost and performance limitations.
Implementation Method 1
a silane-grafted, crosslinked ethylene vinyl acetate (Si-g-EVA) copolymer
Implementation Method 2
at least one organic phosphate ester and/or at least one metal hydrate and a char forming agent
Implementation Method 3
at least one organic phosphate ester and/or at least one metal hydrate and a char forming agent, e.g., an epoxidized novolac resin
Data Source
AI summary
Halogen-free, flame retardant compositions comprising in weight percent based on the weight of the composition: A. 20 to 60% TPU/Si-g-EVA polymer blend in which the Si-g-EVA is crosslinked, B. 1 to 25% organic phosphate ester, C. 30 to 60% metal hydrate, and D. 0.1 to 10% epoxidized novolac. Optionally, the compositions further comprise in weight percent based on the weight of the composition, one or more of: E. 0.01 to 0.5% anti-dripping agent, F. 0.1 to 2% additive; and G. 0.1 to 5% filler.