Polyethylene terephthalate (PET) yog ib qho semi crystalline polymer muaj cov tshuaj tiv thaiv zoo heev, yaj txav mus los thiab spinnability. Lub polymer yog tsim los ntawm kev rov ua dua units raws li qhia hauv daim duab 1. Txhua chav tsev muaj lub cev ntev li ntawm 1.09 nm thiab qhov hnyav molecular ntawm ~ 200. Thaum nws yog tsim los ntawm cov tshuaj tiv thaiv ntawm terephthalic acid thiab ethylene glycol, nws yog capped ntawm sab laug los ntawm H- thiab sab xis los ntawm -OH. Polymerization yog li ntawd nrog cov khoom siv dej uas tau muab tshem tawm hauv qhov kub thiab txias. Raws li qhov muaj dej hauv lub xeev molten yuav sai sai depolymerize cov qauv kom huv si qhuav ntawm cov polymer ua ntej yuav tsum tau yaj spinning fibers.

Lub nplhaib aromatic txuas nrog luv luv aliphatic saw ua rau cov polymer ib lub zog molecule piv rau lwm cov aliphatic polymers xws li polyolefin los yog polyamide. Qhov tsis muaj segmental txav mus los hauv cov saw hlau polymer ua rau muaj qhov thermal stability. Cov ntaub ntawv qib polymer yuav muaj qhov nruab nrab ntawm 100 rov ua dua chav nyob rau ib lub molecule kom qhov ntev ntawm cov khoom siv polymer yog li 100nm nrog qhov hnyav molecular txog 20,000. Cov qib siab ntawm polymerization ua rau muaj zog fiber ntau dua, tab sis cov yaj viscosity thiab ruaj khov ntawm cov yaj mus rau qhov me me ntawm cov dej noo ua rau hydrolytic degradation. Kev ntsuas qhov nruab nrab ntawm cov txheej txheem polymerization yog ua los ntawm molten viscosity (los ntawm kev ntsuas lub siab poob los ntawm calibrated orifice) los yog viscosity ntawm diluted polymer nyob rau hauv ib qho hnyav hnyav. Qhov tom kawg yog kev ntsuas ntawm cov saw hlau ntev lub npe hu ua Intrinsic viscosity lossis IV thiab tus nqi rau cov qib fiber ntau polymer yog 0.6 dl / g hauv 60/40 w / w sib tov ntawm phenol thiab tetrachloroethane hnyav. Qhov IV hauv cov kuab tshuaj tom kawg yog cuam tshuam nrog Mv (Viscosity nruab nrab molecular hnyav) ntawm cov polymer los ntawm Mark Howink equation (Equation 1).