Ma Radiation ndi Industrial Polymers Mitundu Yamachitidwe Okhudzidwa

Zochita zoyambitsidwa ndi ma radiation zitha kugawidwa m'magulu awiri: (1) crosslinking ndi scission ndi (2) kulumikiza ndi kuchiritsa.

Crosslinking ndi kupanga intermolecular chomangira unyolo polima.Digiri ya crosslinking imayenderana ndi mlingo wa radiation.Sichifuna unsaturated kapena magulu ena more reactive.Kupatulapo zina (monga ma polima okhala ndi aromatics), sizimasiyana kwambiri ndi kapangidwe ka mankhwala.Simasiyana kwambiri ndi kutentha.Ngakhale kuti njira yolumikizirana ndi ma radiation yakhala ikuphunziridwa kuyambira pomwe idapezeka koyamba, palibe mgwirizano wofala pachilengedwe chake.Njira ya crosslinking nthawi zambiri imasiyanasiyana ndi ma polima omwe akukhudzidwa.Makina ovomerezeka padziko lonse lapansi amaphatikiza kung'ambika kwa chomangira cha C-H pa unyolo umodzi wa polima kuti apange atomu ya haidrojeni, kutsatiridwa ndi kuchotsedwa kwa atomu yachiwiri ya haidrojeni ku unyolo woyandikana nawo kuti apange molekyulu ya haidrojeni.Ndiye awiri oyandikana ma polymeric radicals amaphatikizana kupanga crosslink.Chotsatira chonse cha crosslinking ndikuti kuchuluka kwa ma cell a polima kumawonjezeka pang'onopang'ono mlingo wa radiation, zomwe zimatsogolera ku unyolo wanthambi mpaka, potsirizira pake ma netiweki atatu amtundu wa polima amapangidwa pamene unyolo uliwonse wa polima ulumikizidwa. ku unyolo wina.

Mosiyana ndi izi, scission ndi njira yosiyana yolumikizirana momwe kupasuka kwa C-C bondsoccurs.Crosslinking imawonjezera kulemera kwa maselo pamene njira yotsirizayi imachepetsa.Ngati mphamvu ya radiation ndiyokwera kwambiri, kuthyoka kwa unyolo kumachitika kudzera pakuduka kwa chomangira cha C-C.Mu aeratedsolution medium, komabe, njira yamakina ya scission imapitilira mwanjira ina.Ma radicals aulere a Thepolymeric amapangidwa ndi zosungunulira zopanda zosungunulira, zomwe zimapangidwa kale ndi ma radiation.Kuphatikizika kwa oxygen ndi ma polymeric free radicals kumapanga mitundu ya peroxy, yomwe pakuwola imapanga mamolekyu ang'onoang'ono.Kuwonongeka kwa okosijeni kwa ma polima kumatengera kusungunuka kwadongosolo.Kwenikweni, kuwonongeka kwa polima kumapikisana ndi makutidwe ndi okosijeni wa zosungunulira.

Kumezanitsa ndi njira yomwe ma monomers amalowetsedwa motsatana ndi unyolo wa polima pomwe kutsimikizira ndiko kuphatikizika kofulumira kwa osakaniza a oligomer monomer kuti apange zokutira, zomwe zimalumikizidwa ndi mphamvu zakuthupi ku gawo lapansi.Mwachidule, njira zotere zimaphatikizapo machitidwe osiyanasiyana, gawo lapansi kukhala filimu, ulusi kapena ufa, wokhala ndi monomer ngati madzi opanda mpweya, nthunzi kapena njira.Pali ubale wapamtima pakati pa kumezanitsa ndi kuchiritsa ngakhale pali kusiyana kwina.Kwenikweni, palibe malire a nthawi ya ndondomeko ya kumezanitsa.Zitha kutenga mphindi, maola kapena masiku, pomwe kuchiritsa ndi njira yofulumira kwambiri yomwe imachitika pang'onopang'ono.Pakulumikiza, ma covalent C-C bond amapangidwa pomwe pakuchiritsa, kulumikizana nthawi zambiri kumaphatikizapo kufooka kwa der Waals kapena mphamvu zaku London.van der Waals bonding imagwira ntchito patali pomwe palibe kuphatikizika kapena kusinthanitsa ndipo nthawi zambiri imalumikizidwa ndi mphamvu zazing'ono.Komabe, covalentbonding, imagwira ntchito pamatali ang'onoang'ono a nyukiliya ndipo imalumikizidwa ndi kupindika kwa ma elekitironi, kusinthana, ndipo motero mphamvu zambiri.Chinthu chinanso chofunikira pakuchiritsa ndikuthekera kwakuti kulumikiza nthawi imodzi ndi kuchiritsa kumachitika kumapangitsa kuti zinthu zomwe zatsirizidwa ziziyenda bwino, makamaka pamamatira komanso kusinthasintha.

Kumezanitsa kumachitika m'njira zitatu zosiyana: (a) kuwunikira kusanachitike;(b) peroxidation ndi (c) njira yolumikizirana.Mu njira ya pre-irradiation, msana woyamba wa polima umawunikiridwa mu vacuum kapena pamaso pa mpweya wa inert kupanga ma free radicals.The walitsa polima gawo lapansi ndiye kuchitiridwa ndi monoma, amene mwina madzi kapena nthunzi kapena ngati njira mu zosungunulira abwino.Komabe, mu theperoxidation Ankalumikiza njira, thunthu polima ndi pansi mkulu-mphamvu cheza pamaso pa mpweya kapena mpweya.Zotsatira zake ndi kupangidwa kwa ma hydroperoxides kapena diperoxides kutengera mtundu wa msana wa polymeric ndi mikhalidwe yowunikira.Mankhwala a peroxy, omwe amakhala osasunthika, amathandizidwa ndi monomer pa kutentha kwakukulu, komwe peroxides amawola ma toradicals, omwe amayamba kulumikiza.Ubwino wa njirayi ndikuti ma peroxyproducts apakatikati amatha kusungidwa kwa nthawi yayitali asanayambe kulumikiza.Kumbali inayi, ndi njira yamutual irradiation ma polima ndi ma monomers amawunikiridwa nthawi imodzi kuti apange ma radicals aulere motero kuwonjezera kumachitika.Popeza ma monomers sawonetsedwa ndi ma radiation mu njira yowunikira isanachitike, mwayi wodziwikiratu wa njirayo ndikuti ilibe vuto la mapangidwe a homopolymer omwe amapezeka ndi njira imodzi.Komabe, kuipa kwa njira ya pre-irradiation ndi scission ya polima yoyambira chifukwa cha kuwongolera kwake, komwe kumabweretsa makamaka mapangidwe a block copolymers m'malo mwa graftcopolymers.