Lub polymerization cov tshuaj tiv thaiv

Polymers - tebchaw uas muaj lub siab molecular yuag xeeb ob peb txhiab tus units. Lub polymerization cov tshuaj tiv thaiv yog lub hauv paus ntawm niaj hnub ntaub ntawv tau txais ntau muaj nuj nqi thiab zog. Lawv yog cov nyob rau ib tug tsawg ceev no mas check, tau muag thaum rhuab thiab yooj yim succumb mus rau molding, uas tso cai rau kom tau cov khoom ntawm ntau yam designs thiab ntau thiab tsawg. Lub polymers yog inert rau corrosive npuas, muaj hluav taws xob insulating zog thiab tsis corrode. Vim nws cov cim zog, uas yuav muab tau yooj yim tom nyob rau theem ntawm cov synthesis, kev siv uas niaj hnub polymeric ntaub ntawv yog lossi expanding.

Thaum cua sov thiab cua txias ntawm cov khoom ntawm tshuaj ntau lawm coj nyob rau hauv ob txoj kev.

Ib txhia muag thaum rhuab thiab thiaj thaum txias dua. Tej ntaub ntawv muaj xws li khoom raws li kev npaj uas dag, piv txwv li, lub polymerization cov tshuaj tiv thaiv ntawm alkenes, i.e., polyethylene thiab polypropylene. Lawv hu ua thermoplastic cov ntaub ntawv. Nws muaj ntsis zoo zog raws li polyvinyl tshuaj dawb thiab polystyrene.

Polymers ntawm lwm yam tej zaum yuav tau rhuab ib zaug xwb, txij li thaum lawv tawv tom qab txias thiab ntau tsis muag nyob rau hauv cov cua kub. Cov ntaub ntawv no yog hu ua thermosetting, lawv muaj xws li phenol-formaldehyde los yog urea-formaldehyde resins. Thermoplastics thiab thermosets muaj lawv zoo. Thawj ua nyob rau hauv granular daim ntawv. Ntawm lawv, tom qab cua sov thiab softening npaj tej yam uas ua yam zoo, tab sis lawv muaj peev xwm tsis tau rhuab thaum lub sij hawm lub lag luam. Cov yav tas yog ua raws li ib tug gummy loj.

ethylene polymerization cov tshuaj tiv thaiv yuav muab sau raws li nram no: CH2 = CH2 → (-CH2-CH2-) n. Nyob rau hauv tej yam tej yam kev mob, nyob rau hauv lub xub ntiag ntawm ib initiator (lawv nyiam cov pa roj los yog ib tug tov ntawm cov organic peroxide nyob rau hauv cov roj) yuav siv sij hawm qhov chaw ntawm carbon atoms π-khi kis (txwv tsis pub ib tug muab ob npaug rau daim ntawv cog lus) thiab ib tug compound ntawm n-Nogo tooj ntawm tsim dawb radicals. Lub polymerization cov tshuaj tiv thaiv hais los ntawm ib tug radical saw mechanism. Lub molecular ceeb thawj los ntawm lub polymer khoom yog ncaj qha nyob rau hauv lub xov tooj n, nrog nws ua nws hlob. By kho cov tej yam kev mob ntawm lub polymerization cov tshuaj tiv thaiv, tus synthesis of polyethylene neeg teb xov tooj achieves tau ib cov ntaub ntawv uas nrog yam zog: fluidity (los yog yaj index), lub zog, ceev, dielectric tsis tangent, dielectric tsis tu ncua, thiab lwm tus neeg.

Synthesis of high-siab polyethylene los yog lub polymerization cov tshuaj tiv thaiv yog nqa tawm nyob rau hauv autoclave los yog tubular reactors ntawm kub txog li 300 ° C thiab ib tug siab ntawm 1000 mus 3000 atm. Qhov no tso ib tug zoo kawg li tus nqi ntawm tshav kub. Nws yog muab tshem tawm nrog dej kub uas yog txhab khoom mus rau reactor tsho. Lub degree ntawm kev coj dawb huv txhab khoom mus rau thaum tshav kub kub cov dej tshem tawm nyob lom zem ntau rau qhov zoo ntawm cov polymeric cov ntaub ntawv thiab cov txheej txheem kev nyab xeeb. Yog hais tias cov dej yog tsis zoo ntxuav thiab muaj ntau impurities (e.g., hardness ntsev li calcium thiab magnesium cations, anions silicic acid, tshuaj, thiab lwm yam), cov reactor tsho tsim deposits los yog hlau pib corrode. Vim cov kev hloov nyob rau hauv reactor phab ntsa thickness ntawm tshav kub dissipation thoob plaws nws saum npoo yuav sis tsis ncaj, thiab qhov kub thiab txias ntawm polymerization tej yam kev mob tej zaum yuav ua unmanageable. Nrog tus ua txoj kev nce ntawm cov oxidation kub ntawm lub polymer zaum yuav tshwm sim los yog decomposition nrog kev puas tsuaj ntawm cov reactor.

Lub polymerization cov tshuaj tiv thaiv, raws li ib tug tshwm sim ntawm uas tus tsim polyethylene, yuav coj qhov chaw nyob rau sab kub thiab siab. Tab sis qhov no yuav tsum tau ib lub hauv paus. Uas muaj unreacted ethylene, uas yog ces sib cais thiab lub polymer twb pelletized, lub polyethylene ua nyob rau hauv tsis tshua muaj siab, nyob rau hauv lub reactor raws li ib tug hmoov, los yog ib tug es ncua kev kawm ntawv nyob rau hauv ib tug hydrocarbon kuab yog ib tug kub siab polyethylene los ntawm cov reactor raws li ib tug yaj nyob. Lub hmoov twb sib cais los ntawm lub kuab thiab cov impurities ntxuav los ntawm lub catalyst, thiab ces granulated thiab tshwj xeeb cov khoom hu ua extruder.

Yog li, lub polymerization cov tshuaj tiv thaiv ntawm ethylene nyob rau hauv lub lag luam yog siv rau cov synthesis ntawm polyethylene. GOST 16338-85 tsim tsawg-siab polyethylene slurry thiab roj theem qhab nia, raws li GOST 16337-77 tawm raws li ib tug high-siab polyethylene autoclave los yog tubular nyiaj muas.