Tsawg-Density polyethylene (LDPE) tsis yog tsuas yog siv dav dav- lub hom phiaj yas hauv kev lag luam, tab sis kuj tseem muaj qhov tseem ceeb ntawm kev tshawb fawb hauv polymer science thiab cov ntaub ntawv engineering.Raws li thawj cov khoom siv polyolefin kom ua tiav kev lag luam- nplai ntau lawm los ntawm siab -siab dawb radical polymerization, nws qhov kev tshawb pom 5} ntau lawm, ntau lawm, ib qho tseem ceeb paradigm rau kev tshawb fawb tom ntej ntawm polymerization mechanisms, kev tshawb fawb ntawm cov qauv molecular- kev sib raug zoo ntawm vaj tse, thiab tsim cov khoom siv.
Los ntawm keeb kwm kev xav, cov synthesis ntawm LDPE tsoo cov kev txwv ntawm cov polymers thaum ntxov, uas tsuas yog npaj tau nyob rau hauv cov mob me me los ntawm ionic lossis kev sib koom ua ke catalysis. Nyob rau xyoo 1930, Imperial Chemical Industries (ICI) hauv tebchaws Askiv tau npaj txhij tau txais polyethylene nrog cov qauv zoo heev los ntawm kev siv cov dawb radical- pib ethylene polymerization nyob rau hauv siab siab (1000-3000 atm) thiab kub (kwv yees li 150-300 degree). Qhov tshwm sim no qhia tau hais tias cov kev tawm tsam dawb radical tuaj yeem ua rau cov saw hlau hloov mus thiab cov ceg ntoo thaum lub sij hawm cov saw hlau loj hlob, ua rau cov xeev thiab cov khoom sib txawv ntawm cov qauv linear. Qhov no tau tsav kev tsim cov dawb radical polymerization kinetics thiab statistical theories ntawm branching. Tom qab ntawd, raws li cov yam ntxwv ntawm LDPE, cov kws tshawb fawb tau tshawb fawb txog kev sib raug zoo ntawm cov qib kev sib tw, crystallinity, thiab macroscopic mechanical zog, nteg lub hauv paus rau kev nkag siab txog cov teebmeem ntawm cov cheeb tsam amorphous thiab kev ua siab ntev ntawm qhov tsis xws luag hauv cheeb tsam crystalline hauv polymer physics.
Ntawm qib molecular science, kev sib koom ua ke ntawm random ntev thiab luv ceg hauv LDPE ua rau nws yog ib qho qauv zoo tagnrho rau kev kawm saw entanglement, yaj rheological cwj pwm, thiab crystallization kinetics. Nws tsis tshua muaj crystallinity thiab saj zawg zog qaum cia cov tswv yim xws li X-ray diffraction, sib txawv scanning calorimetry, thiab dynamic thermomechanical tsom xam ncaj qha mus ntes cov lus teb cov yam ntxwv ntawm amorphous cheeb tsam, yog li ntawd tob tob rau kev nkag siab ntawm synergistic los ntawm multiphase lug nyob rau hauv semi-crystalline polymers. Tsis tas li ntawd, qhov tseem ceeb shear-thinning tus cwj pwm tshwm sim los ntawm LDPE nyob rau hauv lub xeev molten muab kev sim ua pov thawj los tsim cov kev sib npaug sib npaug thiab cov lej simulation txoj kev rau polymer melts, txhawb kev txhim kho cov ntaub ntawv suav nrog kev tshawb fawb thiab kev ua rheology.
Lub synthesis ntawm LDPE kuj tau tshwm sim los ntawm kev tsim cov polyolefins functionalized. Los ntawm kev tswj cov polymerization siab, qhov kub thiab txias, thiab cov txheej txheem pib, cov ceg ntom ntom thiab kev faib tawm tuaj yeem hloov pauv lub hom phiaj, yog li cuam tshuam rau cov khoom siv pob tshab, permeability, thiab tiv thaiv ib puag ncig kev ntxhov siab tawg. Txoj kev tshawb no ntawm kev sib txuas ntawm kev sib txuas ntawm cov qauv thiab cov khoom nteg lub hauv paus theoretical rau kev txhim kho ntawm cov tshiab polyolefin elastomers, cov yeeb yaj kiab uas muaj pob tshab, thiab cov ntaub ntawv thaiv.
Hauv kev tshawb fawb txog kev txhim kho kom ruaj khov, kev rov ua dua tshiab thiab kev ua kom tsis zoo ntawm LDPE yog qhov muaj txiaj ntsig sib npaug. Nws cov thermoplastic reversible crystallization thiab melting yam ntxwv pab txhawb lub cev rov ua dua txheej txheem; Thaum tshawb nrhiav cov duab-oxidation, thermal oxidation, thiab biodegradation mechanisms txhawb kev tsim kho ntawm biodegradable polyolefin composite systems.
Hauv cov ntsiab lus, tsawg-polyethylene ntom ntom tau ua rau muaj txiaj ntsig zoo rau kev txhim kho cov txheej txheem polymerization, kev tshuaj xyuas cov qauv- kev sib raug zoo ntawm vaj tse, kev kho kom zoo ntawm rheological txoj kev xav, thiab tsim cov khoom siv ruaj khov. Nws qhov tseem ceeb ntawm kev tshawb fawb tau dhau los ntawm thaj chaw ntawm cov khoom siv hauv kev lag luam, dhau los ua ib qho kev tshawb fawb tseem ceeb thiab qhov chaw ntawm kev paub hauv kev tshawb fawb ntawm polymer thiab engineering.