Why Does Crystallinity Affect Strength?

[wais]

Hi,

I found out that Kevlar is a crystalline structured polymer, and this is one of the factors about why its so strong. Could someone explain to me why crystallinity affects strenght?

Thanks.

 

[devilkidjin]

well, with crystal structures a single particle will have covalent bonds with surrounding particles say for example diamond

then in comparison with graphite both graphite and diamond are covalently bonded but the structure is rather different
graphite is in layers where the particles are not bonding with all the surrounding particles

http://www.chemguide.co.uk/atoms/structures/giantcov.html
i am not good at explaining

 

[Blueshift5]

Hi,

Great question! The crystalline structure of a material can significantly impact its strength. Crystalline materials have a repeating and ordered arrangement of atoms or molecules, which makes them more resistant to deformation and able to withstand higher forces without breaking. This is because the regular arrangement of atoms allows for more efficient transfer of stress throughout the material.

In the case of Kevlar, its strong and rigid crystalline structure allows it to resist stretching and bending, making it a highly durable material. Additionally, the strong intermolecular forces between the crystalline regions contribute to its strength. These forces hold the molecules together and prevent them from sliding past each other, further increasing the material's resistance to deformation.

In contrast, amorphous materials, which lack a regular crystalline structure, have weaker intermolecular forces and are more prone to deformation and failure under stress. This is why Kevlar, with its high crystallinity, is much stronger than other polymers with a more amorphous structure.

I hope this helps to explain why crystallinity plays a crucial role in determining the strength of a material. Other factors such as molecular weight, chain orientation, and cross-linking can also affect a material's strength, but the crystalline structure is a key factor to consider.

Best regards,