Ballistic nylon

Flak jackets were originally made out of ballistic nylon in World War II to protect airmen from shrapnel

Ballistic nylon is a thick, tough, nylon fabric with several uses. Ballistic nylon was developed by the DuPont corporation as a material for flak jackets for World War II airmen. It was called ballistic because, together with other components, it was intended to protect its wearers from flying debris and fragmentation from bullet and artillery-shell impacts.