Mechanism o ka PVC stabilizer hana

ʻO ka hoʻohaʻahaʻa o PVC ka mea nui ma muli o ka decomposition o nā chlorine ikaika i loko o ka mole ma lalo o ka hoʻomehana a me ka oxygen, ka hopena i ka hana ʻana o HCI. No laila, ʻo ka PVC heat stabilizers ka mea nui i hiki ke hoʻopaʻa i ka chlorine atoms i nā molekala PVC a pale a ʻae paha i ka hoʻokuʻu ʻana o HCI. R. Gachter et al. hoʻokaʻawale i nā hopena o nā mea hoʻopaʻa wela ma ke ʻano he pale a hoʻoponopono. Loaʻa i ka mea mua nā hana o ka lawe ʻana i ka HCI, ka hoʻololi ʻana i nā ʻātoma chlorine paʻa ʻole, ka hoʻopau ʻana i nā kumu ignition, a me ka pale ʻana i ka oxidation aunoa. ʻO ke ʻano hoʻoponopono hope e manaʻo e hoʻohui i ka hale polyene, e hana me nā ʻāpana unsaturated i loko o PVC, a luku i nā carbocation. ʻOiaʻiʻo, penei:

(1) Hoʻopau i ka HC1 i unuhi ʻia mai PVC e kāohi i kāna hana catalytic ponoʻī. ʻO nā huahana e like me nā paʻakai alakaʻi, nā kopa metala waikawa organik, nā pūhui organotin, nā pūhui epoxy, nā amine, nā alkoxide metala a me nā phenols, a me nā thiols metala hiki ke hana like me ka HCI e kāohi i ka hopena de HCI o PVC.

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

(2) Hoʻololi a hoʻopau paha i nā mea paʻa ʻole e like me allyl chloride atoms a i ʻole tertiary carbon chloride atoms i loko o nā molekala PVC, a hoʻopau i ka wahi hoʻomaka o ka wehe ʻana o HCI. Inā hui pū nā ʻātoma tin o nā mea hoʻopaʻa kino kino me nā ʻātoma chlorine paʻa ʻole o nā molekala PVC, a ʻo nā ʻātoma sulfur i loko o nā kinikini kūlohelohe e hui pū me nā ʻātoma kalapona e pili ana i PVC, ua hoʻololi nā ʻātoma sulfur i loko o ke kino hui me nā ʻātoma chlorine paʻa ʻole. Ke hiki mai ka HC1, hoʻokaʻawale ka paʻa hoʻohui, a hoʻopaʻa paʻa ka hui hydrophobic me nā ʻātoma kalapona i loko o nā molekala PVC, no laila ke kāohi nei i nā hopena hou aʻe o ka wehe ʻana o HCI a me ka hoʻokumu ʻana i nā paʻa pālua. Ma waena o nā kopa metala, ʻo ke kopa zinc a me ka kopa ipu ka wikiwiki loa o ka hoʻololi ʻana me nā ʻātoma chlorine paʻa ʻole, ʻo ke kopa barium ka lohi, ʻoi aku ka lohi o ke kopa calcium, a ʻo ke kopa kepau ka waena. I ka manawa like, he ʻokoʻa nā degere o ka hopena catalytic i ka wehe ʻana o HCI, a penei ko lākou ikaika:

Hoʻohui ʻia ʻo ZnCl>CdCl>>BaCl, CaCh>R2SnCl2 (3) i nā mea paʻa pālua a me nā mea paʻa paʻa i hoʻohui ʻia e pale i ka ulu ʻana o nā hale polyene a hoʻemi i ke kala. Loaʻa i nā paʻakai ʻakika unsaturated a paʻakikī paha nā paʻa paʻa, e loaʻa ana i ka hopena hoʻohui diene me nā molekala PVC, a laila e hoʻopau i ko lākou ʻano covalent a pale i ka loli kala. Eia kekahi, hui pū ʻia ke kopa metala me ka hoʻoili paʻa pālua i ka wā e pani ana i ka allyl chloride, e hōʻino ai i ka hale polyene a no laila ke keʻakeʻa nei i ka loli kala.

(4) Hoʻopaʻa i nā radical manuahi e pale i ka oxidation aunoa. Inā hiki i ka hoʻohui ʻana i nā mea hoʻopaʻa wela phenolic hiki ke pale i ka wehe ʻana o HC1, no ka mea hiki i ka hydrogen atom free radical i hāʻawi ʻia e nā phenols hiki ke hui pū me nā radical free macromolecular PVC degraded, e hana ana i kahi mea hiki ʻole ke hoʻopili me ka oxygen a loaʻa ka hopena thermal stabilization. Hiki i kēia mea hoʻopaʻa wela ke loaʻa i hoʻokahi a i ʻole kekahi mau hopena.