Tsarin aikin daidaita PVC

Lalacewar PVC galibi yana faruwa ne sakamakon rugujewar ƙwayoyin chlorine masu aiki a cikin ƙwayoyin halitta a ƙarƙashin dumama da iskar oxygen, wanda ke haifar da samar da HCI. Saboda haka, masu daidaita zafin PVC galibi mahadi ne waɗanda zasu iya daidaita ƙwayoyin chlorine a cikin ƙwayoyin PVC kuma su hana ko karɓar sakin HCI. R. Gachter et al. sun rarraba tasirin masu daidaita zafi a matsayin rigakafi da magani. Na farko yana da ayyukan shaye HCI, maye gurbin ƙwayoyin chlorine marasa ƙarfi, kawar da tushen ƙonewa, da hana iskar shaka ta atomatik. Nau'in gyara na ƙarshe yana nufin ƙarawa ga tsarin polyene, amsawa da sassan da ba su cika ba a cikin PVC, da kuma lalata carbocations. Musamman, kamar haka:

(1) Shanye HC1 da aka cire daga PVC don hana tasirinsa na kansa. Kayayyaki kamar gishirin gubar, sabulun ƙarfe na acid na halitta, mahaɗan organotin, mahaɗan epoxy, amines, ƙarfe alkoxides da phenols, da ƙarfe thiols duk suna iya amsawa tare da HCI don hana amsawar de HCI na PVC.

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

(2) Maye gurbin ko kawar da abubuwan da ba su da tabbas kamar atoms na allyl chloride ko atoms na carbon chloride na uku a cikin ƙwayoyin PVC, sannan a kawar da wurin fara cire HCI. Idan atoms na tin na masu daidaita tin na halitta suka haɗu da atoms na chlorine marasa tabbas na ƙwayoyin PVC, kuma atoms na sulfur a cikin tin na halitta suka haɗu da atoms na carbon masu dacewa a cikin PVC, atoms na sulfur a cikin jikin haɗin gwiwa sun maye gurbinsu da atoms na chlorine marasa tabbas. Lokacin da HC1 ya kasance, haɗin haɗin gwiwa zai rabu, kuma ƙungiyar hydrophobic ta haɗu sosai da atoms na carbon a cikin ƙwayoyin PVC, ta haka ne ke hana ƙarin martanin cire HCI da ƙirƙirar haɗin gwiwa biyu. Daga cikin sabulun ƙarfe, sabulun zinc da sabulun tukunya suna da saurin maye gurbin amsawa tare da atoms na chlorine marasa tabbas, sabulun barium shine mafi jinkiri, sabulun calcium yana da jinkiri, sabulun gubar kuma yana tsakiya. A lokaci guda, chlorides na ƙarfe da aka samar suna da matakai daban-daban na tasirin catalytic akan cire HCI, kuma ƙarfinsu kamar haka:

Ana ƙara ZnCl>CdCl>>BaCl, CaCh>R2SnCl2 (3) a cikin haɗin gwiwa biyu da haɗin gwiwa biyu don hana ci gaban tsarin polyene da rage launi. Gishirin acid mara cikawa ko hadaddun suna da haɗin gwiwa biyu, waɗanda ke fuskantar amsawar ƙarin diene tare da ƙwayoyin PVC, ta haka suna wargaza tsarin covalent ɗinsu kuma suna hana canjin launi. Bugu da ƙari, sabulun ƙarfe yana tare da canja wurin haɗin gwiwa biyu yayin maye gurbin allyl chloride, yana haifar da lalacewa ga tsarin polyene kuma don haka yana hana canjin launi.

(4) Kama free radicals don hana oxidation ta atomatik. Idan ƙara phenolic zafi mai daidaita zafi zai iya toshe cire HC1, saboda hydrogen atom free radicals da phenols ke bayarwa na iya haɗuwa da lalatattun PVC macromolecular free radicals, suna samar da wani abu wanda ba zai iya amsawa da oxygen ba kuma yana da tasirin daidaita zafi. Wannan mai daidaita zafi na iya samun tasiri ɗaya ko da yawa.