Njira yogwirira ntchito yokhazikika ya PVC

Kuwonongeka kwa PVC kumachitika makamaka chifukwa cha kuwonongeka kwa maatomu a chlorine omwe amagwira ntchito mu molekyulu yomwe imatenthedwa ndi mpweya, zomwe zimapangitsa kuti HCI ipangidwe. Chifukwa chake, zolimbitsa kutentha za PVC makamaka ndi mankhwala omwe amatha kukhazikika maatomu a chlorine mu mamolekyu a PVC ndikuletsa kapena kuvomereza kutulutsidwa kwa HCI. R. Gachter et al. adagawa zotsatira za zolimbitsa kutentha ngati zopewera komanso zochizira. Choyamba chili ndi ntchito zoyamwa HCI, kusintha maatomu a chlorine osakhazikika, kuchotsa magwero oyatsira moto, ndikuletsa kusungunuka kwamadzimadzi. Mtundu womaliza wa chokonzanso cholinga chake ndi kuwonjezera kapangidwe ka polyene, kuchitapo kanthu ndi zigawo zosakhuta mu PVC, ndikuwononga ma carbocations. Makamaka, motere:

(1) Yamwani HC1 yotengedwa mu PVC kuti ilepheretse ntchito yake yodzipangira yokha. Zinthu monga mchere wa lead, sopo wachitsulo wa organic acid, mankhwala a organotin, mankhwala a epoxy, amines, metal alkoxides ndi phenols, ndi zitsulo zonse zimatha kuchita ndi HCI kuti ziletse kuchita kwa de HCI kwa PVC.

Ine (RCOO) 2+2HCI MeCl+2RCOOH

(2) Sinthani kapena chotsani zinthu zosakhazikika monga maatomu a allyl chloride kapena maatomu atatu a carbon chloride m'mamolekyu a PVC, ndikuchotsa malo oyambira kuchotsa HCI. Ngati maatomu a tin a organic tin stabilizers agwirizana ndi maatomu osakhazikika a chlorine a mamolekyu a PVC, ndipo maatomu a sulfure mu organic tin amagwirizana ndi maatomu ofanana a carbon mu PVC, maatomu a sulfure m'thupi logwirizana amalowa m'malo ndi maatomu osakhazikika a chlorine. HC1 ikakhalapo, mgwirizano wolumikizana umagawanika, ndipo gulu la hydrophobic limalumikizana mwamphamvu ndi maatomu a carbon m'mamolekyu a PVC, motero kuletsa zochita zina za kuchotsa HCI ndikupanga ma bond awiri. Pakati pa sopo zachitsulo, sopo wa zinc ndi sopo wa mphika zimakhala ndi njira yosinthira mwachangu kwambiri ndi maatomu osakhazikika a chlorine, sopo wa barium ndiye wochedwa kwambiri, sopo wa calcium ndi wochedwa, ndipo sopo wa lead uli pakati. Nthawi yomweyo, ma chloride achitsulo opangidwa amakhala ndi mphamvu zosiyanasiyana pakuchotsa HCI, ndipo mphamvu zawo ndi izi:

ZnCl>CdCl>>BaCl, CaCh>R2SnCl2 (3) imawonjezeredwa ku ma bond awiri ndipo imagwirizanitsidwa ndi ma bond awiri kuti ipewe kukula kwa mapangidwe a polyene ndikuchepetsa utoto. Mchere wa asidi wosaturated kapena ma complexes ali ndi ma bond awiri, omwe amakumana ndi diene addition reaction ndi mamolekyu a PVC, motero amasokoneza kapangidwe kawo ka covalent ndikuletsa kusintha kwa mtundu. Kuphatikiza apo, sopo wachitsulo umaphatikizidwa ndi double bond transfer pamene ikusintha allyl chloride, zomwe zimapangitsa kuwonongeka kwa kapangidwe ka polyene motero kuletsa kusintha kwa mtundu.

(4) Kugwira ma free radicals kuti mupewe kusungunuka kwa okosijeni. Ngati kuwonjezera ma phenolic heat stabilizers kungalepheretse kuchotsa HC1, ndichifukwa chakuti ma hydrogen atomu free radicals omwe amaperekedwa ndi ma phenols amatha kugwirizanitsa ndi ma PVC macromolecular free radicals omwe awonongeka, ndikupanga chinthu chomwe sichingagwirizane ndi mpweya ndipo chimakhala ndi mphamvu yokhazikika ya kutentha. Chokhazikika ichi cha kutentha chingakhale ndi zotsatirapo chimodzi kapena zingapo.