Qhov kev puas tsuaj ntawm PVC feem ntau yog tshwm sim los ntawm kev rhuav tshem cov chlorine atoms hauv lub molecule hauv qab cua sov thiab oxygen, ua rau muaj HCI. Yog li ntawd, PVC cov khoom siv cua sov feem ntau yog cov tshuaj uas tuaj yeem ua kom cov chlorine atoms hauv PVC molecules ruaj khov thiab tiv thaiv lossis lees txais kev tso tawm ntawm HCI. R. Gachter et al. faib cov teebmeem ntawm cov khoom siv cua sov ua kev tiv thaiv thiab kho. Tus thawj muaj cov haujlwm ntawm kev nqus HCI, hloov cov chlorine atoms tsis ruaj khov, tshem tawm cov chaw taws teeb, thiab tiv thaiv kev oxidation tsis siv neeg. Hom kho tom kawg lub hom phiaj yog ntxiv rau cov qauv polyene, cuam tshuam nrog cov khoom tsis muaj zog hauv PVC, thiab rhuav tshem cov carbocations. Tshwj xeeb, raws li hauv qab no:
(1) Nqus HC1 rho tawm ntawm PVC kom tiv thaiv nws tus kheej catalytic kev ua ub no. Cov khoom xws li cov ntsev txhuas, cov organic acid hlau xab npum, organotin compounds, epoxy compounds, amines, hlau alkoxides thiab phenols, thiab hlau thiols tuaj yeem cuam tshuam nrog HCI los tiv thaiv de HCI tshuaj tiv thaiv ntawm PVC.
Kuv (RCOO) 2+2HCI MeCl+2RCOOH
(2) Hloov lossis tshem tawm cov yam tsis ruaj khov xws li allyl chloride atoms lossis tertiary carbon chloride atoms hauv PVC molecules, thiab tshem tawm qhov pib ntawm HCI tshem tawm. Yog tias cov tin atoms ntawm cov organic tin stabilizers sib koom tes nrog cov chlorine atoms tsis ruaj khov ntawm PVC molecules, thiab cov sulfur atoms hauv organic tin sib koom tes nrog cov carbon atoms sib xws hauv PVC, cov sulfur atoms hauv lub cev sib koom tes hloov nrog cov chlorine atoms tsis ruaj khov. Thaum HC1 muaj, qhov sib koom tes sib cais, thiab pawg hydrophobic khi ruaj khov nrog cov carbon atoms hauv PVC molecules, yog li ntawd txwv tsis pub muaj kev cuam tshuam ntxiv ntawm HCI tshem tawm thiab tsim cov ntawv cog lus ob npaug. Ntawm cov xab npum hlau, xab npum zinc thiab xab npum lauj kaub muaj qhov hloov pauv sai tshaj plaws nrog cov chlorine atoms tsis ruaj khov, xab npum barium yog qhov qeeb tshaj plaws, xab npum calcium qeeb dua, thiab xab npum txhuas nyob hauv nruab nrab. Tib lub sijhawm, cov hlau chlorides tsim muaj ntau qib ntawm catalytic nyhuv rau kev tshem tawm ntawm HCI, thiab lawv lub zog yog raws li nram no:
ZnCl>CdCl>>BaCl, CaCh>R2SnCl2 (3) raug ntxiv rau cov ntawv cog lus ob npaug thiab cov ntawv cog lus sib txuas ob npaug kom tiv thaiv kev txhim kho ntawm cov qauv polyene thiab txo cov xim. Cov ntsev tsis muaj roj lossis cov khoom sib xyaw muaj cov ntawv cog lus ob npaug, uas dhau los ntawm kev sib xyaw diene nrog PVC molecules, yog li cuam tshuam lawv cov qauv covalent thiab tiv thaiv kev hloov xim. Tsis tas li ntawd, xab npum hlau yog nrog los ntawm kev hloov pauv ob npaug thaum hloov allyl chloride, ua rau puas tsuaj rau cov qauv polyene thiab yog li tiv thaiv kev hloov xim.
(4) Ntes cov free radicals kom tiv thaiv kev oxidation tsis siv neeg. Yog tias ntxiv cov phenolic heat stabilizers tuaj yeem thaiv kev tshem tawm ntawm HC1, nws yog vim tias cov hydrogen atom free radicals uas muab los ntawm phenols tuaj yeem ua ke nrog cov PVC macromolecular free radicals uas lwj, tsim cov khoom uas tsis tuaj yeem cuam tshuam nrog oxygen thiab muaj cov nyhuv thermal stabilization. Cov heat stabilizer no tuaj yeem muaj ib lossis ntau yam teebmeem.
Lub sijhawm tshaj tawm: Lub Peb Hlis-29-2024
