▁Items ▁made ▁from ▁poly car bon ate ▁can ▁contain ▁the ▁prec ursor ▁mon omer ▁bis phen ol ▁A ▁( B PA ). ▁ ▁Poly ether ▁sul f one ▁Poly ether ▁sul f one ▁( P ES ) ▁or ▁pol ys ulf one ▁is ▁a ▁class ▁of ▁spe cially ▁engine ered ▁therm op last ics ▁with ▁high ▁thermal , ▁ox id ative , ▁and ▁hydro ly t ic ▁stability , ▁and ▁good ▁resistance ▁to ▁a que ous ▁min eral ▁ac ids , ▁alk alis , ▁salt ▁solutions , ▁o ils ▁and ▁gre ases . ▁ ▁Poly ox ym eth yl ene ▁Poly ox ym eth yl ene ▁( P OM ), ▁also ▁known ▁as ▁ac etal ,[ 2 ] ▁poly ac etal ▁and ▁poly form al de hy de , ▁is ▁an ▁engineering ▁therm op last ic ▁used ▁in ▁precision ▁parts ▁requiring ▁high ▁st iff ness , ▁low ▁fr iction , ▁and ▁excellent ▁dimensional ▁stability . ▁As ▁with ▁many ▁other ▁synth etic ▁polym ers , ▁it ▁is ▁produced ▁by ▁different ▁chemical ▁fir ms ▁with ▁slightly ▁different ▁formulas ▁and ▁sold ▁various ly ▁by ▁such ▁names ▁as ▁Del rin , ▁Cel con , ▁R amt al , ▁D ura con , ▁K ep ital ▁and ▁H osta form . ▁ ▁Poly ether ether ▁k et one ▁Poly ether ▁ ether ▁k et one ( PE E K ) ▁is ▁a ▁colour less ▁organ ic ▁therm op last ic ▁polym er ▁in ▁the ▁poly ary le ther ket one ▁( PA E K ) ▁family , ▁used