Kev sib piv ntawm LLDPE thiab LDPE.

Linear low density polyethylene, structurally txawv los ntawm cov tsis tshua muaj ntom polyethylene, vim tias tsis muaj cov saw ntev ntev. Lub linearity ntawm LLDPE nyob ntawm qhov sib txawv ntau lawm thiab ua cov txheej txheem ntawm LLDPE thiab LDPE. LLDPE feem ntau yog tsim los ntawm copolymerization ntawm ethylene thiab siab dua alpha olefins xws li butene, hexene los yog octene ntawm qhov kub thiab txias. Lub LLDPE polymer tsim los ntawm cov txheej txheem copolymerization muaj qhov nqaim molecular hnyav dua li LDPE dav dav, thiab tib lub sijhawm muaj cov qauv kab uas ua rau nws muaj cov khoom sib txawv.

melt flow properties

Cov yam ntxwv yaj ntawm LLDPE tau yoog raws li cov kev xav tau ntawm cov txheej txheem tshiab, tshwj xeeb tshaj yog cov txheej txheem extrusion zaj duab xis, uas tuaj yeem tsim cov khoom zoo LLDPE. LLDPE yog siv nyob rau hauv tag nrho cov tsoos lag luam rau polyethylene. Txhim khu kev ncab, nkag mus, cuam tshuam thiab tsim kua muag ua rau LLDPE haum rau cov yeeb yaj kiab. Nws zoo heev tiv thaiv rau ib puag ncig kev ntxhov siab tawg, tsis tshua muaj kev kub ntxhov thiab kev ua tsov rog ua rau LLDPE txaus nyiam rau cov yeeb nkab, ntawv extrusion thiab txhua daim ntawv thov molding. Daim ntawv thov tshiab kawg ntawm LLDPE yog ua cov mulch rau landfills thiab hauv ob sab phlu rau cov pas dej khib nyiab.

Kev tsim khoom thiab cov yam ntxwv

Kev tsim cov LLDPE pib nrog kev hloov pauv hlau catalysts, tshwj xeeb tshaj yog ntawm Ziegler lossis Phillips hom. Cov txheej txheem tshiab raws li cycloolefin hlau derivative catalysts yog lwm qhov kev xaiv rau LLDPE ntau lawm. Qhov tseeb polymerization cov tshuaj tiv thaiv tuaj yeem nqa tawm hauv kev daws teeb meem thiab roj theem reactors. Feem ntau, octene yog copolymerized nrog ethylene thiab butene hauv cov tshuaj theem reactor. Hexene thiab ethylene yog polymerized nyob rau hauv ib tug roj theem reactor. LLDPE resin ua nyob rau hauv cov roj theem reactor yog nyob rau hauv cov ntaub ntawv feem ntau thiab yuav raug muag raws li ib tug hmoov los yog ntxiv ua rau pellets. Ib tiam tshiab ntawm super LLDPE raws li hexene thiab octene tau tsim los ntawm Txawb, Union Carbide. Cov tuam txhab xws li Novacor thiab Dow Plastics launched. Cov ntaub ntawv no muaj qhov txwv loj thiab muaj peev xwm tshiab rau kev siv lub hnab tshem tawm tsis siv neeg. Tsawg ntom ntom PE resin (qhov ceev qis dua 0.910g / cc.) kuj tau tshwm sim nyob rau xyoo tas los no. VLDPES muaj qhov yooj thiab softness uas LLDPE tsis tuaj yeem ua tiav. Cov yam ntxwv ntawm cov resins feem ntau yog tshwm sim nyob rau hauv melt index thiab ntom. Lub melt index qhia qhov nruab nrab molecular hnyav ntawm cov resin thiab feem ntau tswj los ntawm cov tshuaj tiv thaiv kub. Qhov nruab nrab molecular hnyav yog ywj siab ntawm molecular hnyav faib (MWD). Kev xaiv Catalyst cuam tshuam rau MWD. Qhov ceev yog txiav txim los ntawm qhov concentration ntawm comonomer hauv cov saw hlau polyethylene. Lub comonomer concentration tswj tus naj npawb ntawm cov ceg luv luv (qhov ntev ntawm qhov nyob ntawm hom comonomer) thiab yog li tswj cov resin ntom. Qhov siab dua qhov comonomer concentration, qhov qis dua resin ceev. Raws li txoj cai, LLDPE txawv ntawm LDPE nyob rau hauv tus naj npawb thiab hom ceg, siab-siab LDPE muaj ceg ntev, thaum linear LDPE tsuas muaj luv ceg.

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Ob leeg LDPE thiab LLDPE muaj rheology zoo heev los yog yaj ntws. LLDPE muaj tsawg shear rhiab heev vim nws nqaim molecular hnyav tis thiab luv saw ceg. Thaum lub sij hawm shearing (xws li extrusion), LLDPE khaws cov viscosity ntau dua thiab yog li ntawd nyuaj rau txheej txheem ntau dua li LDPE nrog tib lub yaj qhov ntsuas. Nyob rau hauv extrusion, qhov qis shear rhiab heev ntawm LLDPE tso cai rau kom ceev kev ntxhov siab so ntawm cov polymer molecular chains, thiab yog li txo rhiab heev ntawm lub cev zog rau cov kev hloov nyob rau hauv tshuab-up ratio. Nyob rau hauv yaj txuas ntxiv, LLDPE txawv nyob rau hauv ntau hom Feem ntau muaj qis viscosity ntawm ceev. Ntawd yog, nws yuav tsis tawv tawv thaum ncab zoo li LDPE. Nce nrog deformation tus nqi ntawm polyethylene. LDPE qhia tau hais tias muaj kev nce ntxiv hauv cov viscosity, uas yog tshwm sim los ntawm kev cuam tshuam ntawm cov saw hlau molecular. Qhov tshwm sim no tsis tau pom hauv LLDPE vim tias tsis muaj cov saw ntev ntev hauv LLDPE ua rau cov polymer tsis muaj kev cuam tshuam. Cov cuab yeej no tseem ceeb heev rau daim ntawv thov nyias nyias. Vim tias LLDPE cov yeeb yaj kiab tuaj yeem yooj yim ua cov yeeb yaj kiab thinner thaum tuav lub zog thiab tawv. Cov khoom rheological ntawm LLDPE tuaj yeem muab sau ua "nruj hauv shear" thiab "soft in extension".