Ukuwohloka kwe-PVC kubangelwa kakhulu kukubola kweeathom ze-chlorine ezisebenzayo kwimolekyuli eshushu neoksijini, nto leyo ebangela ukuveliswa kwe-HCI. Ke ngoko, iziqinisi zobushushu ze-PVC ikakhulu ziikhompawundi ezinokuzinzisa iiathom ze-chlorine kwiimolekyuli ze-PVC kwaye zithintele okanye zamkele ukukhululwa kwe-HCI. U-R. Gachter et al. bachaze iziphumo zeziqinisi zobushushu njengezokuthintela kunye nezokulungisa. Eyokuqala inemisebenzi yokufunxa i-HCI, ithathe indawo yeeathom ze-chlorine ezingazinzanga, isuse imithombo yokutsha, kwaye ithintele i-oxidation ezenzekelayo. Uhlobo lokugqibela lokulungisa lujolise ekongezeni kwisakhiwo se-polyene, luphendule kwiindawo ezingagcwaliyo kwi-PVC, kwaye lutshabalalise ii-carbocations. Ngokukodwa, ngolu hlobo lulandelayo:
(1) Funxa i-HC1 ekhutshwe kwi-PVC ukuze ithintele umsebenzi wayo wokuzivuselela. Iimveliso ezifana neetyuwa ze-lead, isepha zesinyithi ze-organic acid, iikhompawundi ze-organotin, iikhompawundi ze-epoxy, ii-amines, ii-alkoxides zesinyithi kunye nee-phenols, kunye nee-metal thiols zonke zinokusabela kwi-HCI ukuze zithintele ukusabela kwe-de HCI ye-PVC.
Mna (RCOO) 2+2HCI MeCl+2RCOOH
(2) Buyisela okanye ususe izinto ezingazinzanga ezifana neeathom ze-allyl chloride okanye iiathom ze-tertiary carbon chloride kwiimolekyuli ze-PVC, kwaye ususe indawo yokuqala yokususwa kwe-HCI. Ukuba iiathom ze-tin ze-organic tin stabilizers zihambelana neeathom ze-chlorine ezingazinzanga zeemolekyuli ze-PVC, kwaye iiathom ze-sulfur kwi-organic tin zihambelana neeathom ze-carbon ezihambelanayo kwi-PVC, iiathom ze-sulfur emzimbeni wokudibanisa zithatha indawo yeeathom ze-chlorine ezingazinzanga. Xa i-HC1 ikhona, i-coordination bond iyahlukana, kwaye iqela le-hydrophobic libopha ngokuqinileyo neeathom ze-carbon kwiimolekyuli ze-PVC, ngaloo ndlela lithintela ezinye iimpendulo zokususwa kwe-HCI kunye nokwenziwa kweebhondi ezimbini. Phakathi kweesepha zesinyithi, isepha ye-zinc kunye nesepha yembiza zinempendulo ekhawulezayo yokutshintshwa kweeathom ze-chlorine ezingazinzanga, isepha ye-barium yeyona icothayo, isepha ye-calcium icothayo, kwaye isepha ye-lead iphakathi. Kwangaxeshanye, ii-chloride zesinyithi ezivelisiweyo zinefuthe elahlukileyo lokususa i-HCI, kwaye amandla azo ngala alandelayo:
I-ZnCl>CdCl>>I-BaCl, i-CaCh>I-R2SnCl2 (3) yongezwa kwiibhondi eziphindwe kabini kwaye idityaniswe neebhondi eziphindwe kabini ukuthintela uphuhliso lwezakhiwo ze-polyene kunye nokunciphisa umbala. Iityuwa ze-asidi ezingagcwaliyo okanye ii-complexes zinebhondi eziphindwe kabini, ezidlula kwi-diene addition reaction kunye nee-molecule ze-PVC, ngaloo ndlela ziphazamisa isakhiwo sazo se-covalent kwaye zithintele utshintsho lombala. Ukongeza, isepha yesinyithi ihamba nokudluliselwa kweebhondi eziphindwe kabini ngelixa ithatha indawo ye-allyl chloride, ibangela umonakalo kwisakhiwo se-polyene kwaye ngaloo ndlela ithintela utshintsho lombala.
(4) Bamba ii-free radicals ukuthintela i-oxidation ezenzekelayo. Ukuba ukongeza iziqinisi zobushushu ze-phenolic kunokuthintela ukususwa kwe-HC1, kungenxa yokuba ii-hydrogen atom free radicals ezibonelelwa zii-phenols zinokudibana nee-PVC macromolecular free radicals eziwohlokileyo, zenze into engenakukwazi ukusabela kwi-oxygen kwaye inefuthe lokuzinzisa ubushushu. Esi siqinisi sobushushu sinokuba nefuthe elinye okanye amaninzi.
Ixesha leposi: Matshi-29-2024
