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