▁called ▁poly am ides . ▁It ▁has ▁served ▁as ▁a ▁substitute ▁mainly ▁for ▁h emp , ▁cot ton ▁and ▁sil k , ▁in ▁products ▁such ▁as ▁par ach utes , ▁c ords , ▁s ails , ▁fla k ▁v ests ▁and ▁cl othing . ▁N yl on ▁fib ers ▁are ▁useful ▁in ▁making ▁fab rics , ▁ro pe , ▁car p ets ▁and ▁musical ▁strings , ▁whereas ▁in ▁bulk ▁form , ▁n yl on ▁is ▁used ▁for ▁mechanical ▁parts ▁including ▁machine ▁sc rew s , ▁g ears ▁and ▁power ▁tool ▁cas ings . ▁In ▁addition , ▁it ▁is ▁used ▁in ▁the ▁manufact ure ▁of ▁heat - res istant ▁composite ▁materials . ▁ ▁P LA ▁Poly la ctic ▁acid ▁( poly la ct ide ) ▁is ▁a ▁comp ost able ▁therm op last ic ▁ali ph atic ▁poly ester ▁derived ▁from ▁renew able ▁resources , ▁such ▁as ▁corn ▁st arch ▁( in ▁the ▁United ▁States ), ▁t api oca ▁roots , ▁ch ips ▁or ▁st arch ▁( most ly ▁in ▁Asia ), ▁or ▁sugar c ane . ▁It ▁is ▁one ▁of ▁the ▁materials ▁used ▁for ▁ 3 D ▁printing ▁with ▁f used ▁de position ▁model ing ▁( F DM ) ▁techniques . ▁ ▁Poly ben z im id az ole ▁Poly ben z im id az ole ▁( P BI , ▁short ▁for ▁Poly - [ 2 , 2 ’ -( m - phen y len )- 5 , 5 ’ - bis ben z im id az ole ]) ▁fi ber ▁is ▁a