What Makes Kevlar Highly Heat Resistant?

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    Heat Resistivity
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Discussion Overview

The discussion focuses on the properties of Kevlar, particularly its heat resistance and flammability. Participants explore the molecular structure of Kevlar and its implications for stability and burning, as well as inquiries about specific properties like self-extinguishing capabilities and calculations related to heat application.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant suggests that Kevlar's low flammability is due to its high carbon:hydrogen ratio, questioning whether carbon's non-flammability contributes to this property.
  • Another participant explains that the stability of Kevlar's molecular structure, particularly the presence of hydrogen-hydrogen bonds, contributes to its high tensile strength and melting point, which is noted to be around 500 degrees Celsius.
  • A participant inquires about the mechanism behind Kevlar's self-extinguishing property, seeking clarification on how this works.
  • Another participant asks for guidance on calculating the heat required to induce a reaction in Kevlar, indicating an interest in including this calculation in their presentation.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the properties of Kevlar, with no consensus reached on the specifics of its self-extinguishing property or the calculations related to heat application.

Contextual Notes

Some assumptions about molecular stability and the relationship between structure and flammability are not fully explored, and the discussion includes unresolved questions about the mechanisms involved in Kevlar's properties.

Who May Find This Useful

Individuals interested in materials science, polymer chemistry, or those preparing presentations on Kevlar and its properties may find this discussion relevant.

wais
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Hey,

I'm doing a presentation on Kevlar, and was asked to state its properties and why it has those. I came across the fact that kevlar has a low flamability due to the high carbon:hydrogen ratio, I'm assuming that carbon doesn't burn whereas hydrogen does. Am i correct? Sorry it may be a bit of a silly question but I just wanted to confirm it.

Thanks.
 
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The flammability or burning has to do with stability of the molecule - e.g. the forces that hold the bonds together. In this case there are a lot of hydrogen-hydrogen bonds, which make the Kevlar and other amide polymers have a high tensile strength as well as their melting point (MP of Kevlar is 500 deg C). There are other factors that affect flammability but basically because carbon is unsaturated in Kevlar it is more stable, and therefore harder to "oxygenate" (burn), or react chemically so it broke apart the bonds and released heat in exothermic reaction.


From wikipedia I pulled up the following table of approximate intermolecular forces and their strenght comparisons:

Ionic bonds
1000
Hydrogen bonds
100
Dipole-dipole
10
London Forces
1
 
Ah great thanks. I also saw that kevlar has a "self extinguishing" property, could you tell me how this would work?
 
How could I calculate the amount of heat needed to apply to make kevlar react? I know its 500c but I just want to add into my presentation the calculation used.

Thanks.
 

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