Why isn't nylon as strong as kevlar? Why is Kevlar stronger than nylon? They both contain Hydrogen bonding and should have equal strength but this is not the case instead Kevlar is fire resistant. What makes it stronger. Greater hydrogen bonds?!
Kevlar is an A,B co-polymer where the monomers are terephthalic acid and 1,4-diaminobenzene. The amide linkage, together with the aromatic rings in the polymer, makes a very rigid polymeric structure that stacks the chains in an organized way, maximizing the effectiveness of hydrogen bonding between amide linkages, together with pi-stacking of the rings:

http://pubs.acs.org/cen/coverstory/8005/8005olympics.html

The chains form sheets that stack together along the axis of the fiber. In order for projectiles to break these fibers, these strong, inter-strand attractions must be overcome.

Standard Nylon is a similar polymer, where the aromatic moieties are replaced by aliphatic chains. These are much more flexible and give more degrees of freedom to the polymer chains. This results in a more random arrangement of chains that still hydrogen bond, but not in such an organized way, giving a weaker fiber.


https://www.researchgate.net/publication/305313239_Nylon_66_Nonwoven_Fabric_Separates_Oil_Contaminates_from_Oil-in-Water_Emulsions