Ukusabela okuqalwe ngemisebe kungahlukaniswa ngokwezigaba njengezinhlobo ezimbili: (1) ukuphambana kanye ne-scission kanye (2) nokuxhunyelelwa kanye nokwelapha.
I-Crosslinking wukwakheka kwebhondi ye-intermolecular yamaketanga e-polymer.I-degree of crosslinking ilingana nomthamo wemisebe.Ayidingi amaqoqo angagcwele noma amanye asebenzayo.Okunye okuhlukile (njengakuma-polymers aqukethe ama-aromatics), ayihlukani kakhulu nesakhiwo samakhemikhali.Ayihlukani kakhulu nezinga lokushisa.Nakuba indlela yokuxhumanisa ngemisebe iye yacutshungulwa kusukela ekutholweni kwayo kokuqala, akukabikho isivumelwano esisabalele mayelana nemvelo yayo.Indlela ye-crosslinking ngokuvamile iyahluka ngama-polymers athintekayo.Indlela eyamukelwa emhlabeni wonke ihlanganisa ukuqhekeka kwebhondi ye-C–H kuchungechunge lwe-polymer eyodwa ukuze kwakhe i-athomu ye-athomu, okulandelwa ukukhishwa kwe-athomu yesibili ye-hydrogen ochungechungeni elingumakhelwane ukuze kukhiqizwe i-hydrogen yamangqamuzana.Khona-ke ama-radicals e-polymeric amabili aseduze ayahlangana enze i-crosslink.Umphumela ophelele wokuphambana ukuthi inqwaba yamangqamuzana e-polymer ikhula kancane kancane umthamo wokukhipha imisebe, okuholela emaketangeni anegatsha kuze kube, ekugcineni kwakheka inethiwekhi ye-polymer enezinhlangothi ezintathu lapho iketango le-polymer lixhunywa. kwelinye iketango.
Ngokuphambene, i-scission inqubo ephambene yokuxhumanisa lapho ukugqashuka kwe-C–C bondsoccurs.I-Crosslinking inyusa isilinganiso sesisindo samangqamuzana kanti inqubo yakamuva iyasinciphisa.Uma amandla emisebe ephezulu, ukugqashuka kweketango kwenzeka ngokuqhekeka kwebhondi ye-C-C.Ku-aeratedsolution medium, nokho, indlela ye-mechanistic yesikesi iqhubeka ngendlela engaqondile.Ama-radicals amahhala e-Thepolymeric akhiqizwa ama-radicals angenayo i-solvent, asevele enziwe ngemisebe.Ukwengezwa kwe-oksijini nama-polymeric free radicals kwakha izinhlobo ze-peroxy, okuthi lapho ku-decom-position yakhe ama-molecule amancane.Ukuwohloka kwe-oxidative kwama-polymers kuncike ekuxazululeni kwesistimu.Eqinisweni, ukuwohloka kwe-polymer kuncintisana ne-oxidation ye-solvent.
Ukuxhunyelelwa kuyindlela lapho ama-monomers ethulwa eceleni kweketango le-polymer lapho i-ascuring iyi-polymerisation esheshayo yengxube ye-oligomer monomer ukuze kwakhe ukunamathela, okuyi-essen-tially eboshwe ngamandla angokwenyama ku-substrate.Ngendlela elula kakhulu, lezo zindlela zibandakanya amasistimu ahlukene, i-substrate eyifilimu, i-fibre noma impushana, ene-monomer njengoketshezi olungahlanzekile, umhwamuko noma isixazululo.Kunobudlelwane obuseduze phakathi kokuxhunyelelwa kanye nokwelapha nakuba kunomehluko othize.Eqinisweni, asikho isikhathi esinqunyiwe senqubo yokuxhunyelelwa.Kungathatha imizuzu, amahora noma izinsuku, kanti ukwelapha kuyinqubo evamise ukushesha okwenzeka engxenyeni yesibili.Ekuxhunyelelweni, amabhondi e-C-C aqinile ayakhiwa kanti ekwelapheni, ukubopha kuvame ukubandakanya i- weakervan der Waals noma amabutho e-London dispersion.I-van der Waals bonding isebenza ezindaweni ezikude lapho kunokugqagqana khona okuncane noma kungashintshisani futhi ngokuvamile kuhlotshaniswa namandla amancane.Nokho, i-covalentbonding, iyasebenza emabangeni amancane e-internuclear futhi ihlotshaniswa nokugqagqana kwama-electron, ukushintshana, futhi ngenxa yalokho namandla aphezulu.Esinye isici esibalulekile sokusabela kokwelapha ukuthi kungenzeka ukuthi ukuxhunyelelwa kanyekanye nokwelapha kwenzeke okuholela ekuthuthukisweni kwezakhiwo zomkhiqizo oqediwe, ikakhulukazi ekunamatheleni nasekuguquguqukeni.
Ukuxhunyelelwa kuqhubeka ngezindlela ezintathu ezihlukene: (a) ngaphambi kokukhipha imisebe;(b) i-peroxidation kanye (c) ne-mutual irradia-tion technique.Enqubweni ye-pre-irradiation, umgogodla wokuqala we-polymer ufakwa ku-vacuum noma phambi kwegesi engasebenzi ukuze kwakhe ama-radicals mahhala.I-polymer substrate ene-radiated polymer bese iphathwa nge-monomer, okungaba uketshezi noma umhwamuko noma njengesixazululo ku-solvent efanele.Kodwa-ke, endleleni yokuxhunyelelwa kwe-theperoxidation, i-polymer ye-trunk ibhekana nemisebe enamandla amakhulu lapho kukhona umoya noma umoya-mpilo.Umphumela uba ukwakheka kwe-hydroperoxides noma i-diperoxides kuye ngohlobo lomgogodla we-polymeric kanye nezimo zokushiswa kwe-irradiation.Imikhiqizo ye-peroxy, ezinzile, bese iphathwa nge-monomer emazingeni okushisa aphezulu, lapho ama-peroxides ethola ama-radicals okubola, abese eqala ukuxhunyelelwa.Inzuzo yale nqubo ukuthi ama-peroxyproducts aphakathi angagcinwa isikhathi eside ngaphambi kokwenza isinyathelo sokuxhunyelelwa.Ngakolunye uhlangothi, nge-themutual irradiation technique i-polymer kanye nama-monomers afakwa imisebe kanye kanye ukuze akhe ama-radicals amahhala futhi ngaleyo ndlela ukungezwa kwenzeka.Njengoba ama-monomers engabonakali emisebeni yenqubo yokukhipha imisebe yangaphambi kokukhanya, inzuzo esobala yaleyo ndlela ukuthi ikhululekile enkingeni yokwakheka kwe-homopolymer okwenzeka ngendlela efanayo.Kodwa-ke, ukungalungi okunqunyiwe kwesu langaphambi kwe-irradiation ukusika kwe-polymer eyisisekelo ngenxa yokukhanya kwayo, okuletha ikakhulukazi ukwakheka kwama-block copolymers kune-graftcopolymers.
Isikhathi sokuthumela: May-03-2017