Radiation-initiated cov tshuaj tiv thaiv tuaj yeem raug faib ua ob hom: (1) crosslinking thiab scissionand (2) grafting thiab curing.
Crosslinking yog qhov sib xyaw ua ke ntawm cov khoom sib txuas ntawm cov saw hlau polymer.Thedegree ntawm crosslinking yog proportional rau lub radiation koob.Nws tsis tas yuav unsaturated los yog lwm cov pab pawg neeg ntau dua.Nrog qee qhov kev zam (xws li hauv cov polymers uas muaj aromatics), nws tsis txawv heev nrog cov qauv tshuaj.Nws tsis txawv heev nrog kub.Txawm hais tias cov txheej txheem ntawm kev sib txuas los ntawm hluav taws xob tau kawm txij li thaum nws qhov kev tshawb pom thawj zaug, tseem tsis tau muaj kev pom zoo dav dav ntawm nws qhov tseeb.Cov txheej txheem ntawm crosslinking feem ntau txawv nrog cov polymers txhawj xeeb.Kev lees paub thoob ntiaj teb suav nrog kev sib cais ntawm C-H daim ntawv cog lus ntawm ib lub xov tooj polymer los tsim cov atom ahydrogen, tom qab ntawd los ntawm abstraction ntawm lub thib ob hydrogen atom los ntawm ib tug nyob sib ze chain toproduce molecular hydrogen.Tom qab ntawd ob lub polymeric radicals uas nyob ib sab ua ke los ua ib qho crosslinking.Qhov tag nrho cov txiaj ntsig ntawm crosslinking yog tias cov molecular loj ntawm cov polymer tsis tu ncua nce nrog cov tshuaj tiv thaiv kab mob, ua rau cov saw hlau txuas mus txog, thaum kawg ntawm peb-dimensional polymer network isformed thaum txhua cov saw hlau txuas. mus rau lwm txoj saw.
Nyob rau hauv sib piv, scission yog tus txheej txheem rov qab ntawm crosslinking nyob rau hauv uas lub rupturing ntawm C-C bondsoccurs.Crosslinking nce qhov nruab nrab qhov hnyav molecular whereas cov txheej txheem tom kawg txo nws.Yog hais tias lub zog ntawm cov hluav taws xob muaj siab, cov saw tawg tshwm sim los ntawm kev sib cais ntawm C-C daim ntawv cog lus.Hauv aeratedsolution nruab nrab, txawm li cas los xij, txoj kev siv tshuab ntawm kev sib tsoo pib los ntawm kev tsis ncaj ncees.Thepolymeric dawb radicals yog tsim los ntawm hnyav-dawb radicals, uas twb tsim los ntawm hluav taws xob.Qhov sib ntxiv ntawm oxygen nrog cov polymeric dawb radicals tsim cov peroxy hom, uas nyob rau hauv decom-txoj hauj lwm cov ntaub ntawv me me molecules.Lub oxidative degradation ntawm cov polymers yog nyob ntawm cov kuab tshuaj nyob rau hauv lub system.Qhov tseeb, cov polymer degradation sib tw nrog oxidation ntawm cov kuab tshuaj.
Grafting yog ib txoj hauv kev uas cov monomers tau qhia tom qab rau ntawm cov saw hlau polymer qhov twg ascuring yog lub polymerization sai ntawm oligomer monomer sib tov los tsim ib txheej, uas yog essen-tially bonded los ntawm lub cev rog rau lub substrate.Hauv daim ntawv yooj yim tshaj plaws, cov txheej txheem no suav nrog cov txheej txheem thev naus laus zis, lub substrate ua ib zaj duab xis, fiber lossis txawm tias hmoov, nrog cov monomer li aneat kua, vapor lossis tov.Muaj kev sib raug zoo ntawm grafting thiab kho txawm tias muaj qee qhov sib txawv.Qhov tseeb, tsis muaj sijhawm txwv rau cov txheej txheem ntawm grafting.Nws tuaj yeem siv sijhawm li feeb, teev lossis ib hnub, qhov kev kho yog qhov txheej txheem nrawm heev tshwm sim hauv ib feem ntawm thib ob.Nyob rau hauv grafting, covalent C-C daim ntawv cog lus yog tsim thaum nyob rau hauv kev kho, kev sib raug zoo feem ntau yog weakervan der Waals los yog London dispersion rog.van der Waals kev sib txuas ua haujlwm ntawm qhov deb uas muaj me me lossis tsis sib tshooj lossis sib pauv thiab nws feem ntau cuam tshuam nrog lub zog me.Txawm li cas los xij, covalentbonding, muaj txiaj ntsig zoo ntawm qhov kev ncua deb me me thiab cuam tshuam nrog electron sib tshooj, sib pauv, thiab ua rau muaj zog dua.Lwm qhov tseem ceeb ntawm kev kho cov tshuaj tiv thaiv yog qhov muaj peev xwm ua tau zoo sib xws nrog kev kho mob tshwm sim ua rau txhim kho cov khoom ntawm cov khoom tiav, feem ntau hauv adhesion thiab elasticity.
Grafting pib ua peb txoj kev sib txawv: (a) pre-irradiation;(b) peroxidation thiab (c) kev sib nrig sib irradia-tion txheej txheem.Nyob rau hauv cov txheej txheem ua ntej irradiation, thawj cov pob txha polymer yog irradiated nyob rau hauv lub tshuab nqus tsev los yog nyob rau hauv lub xub ntiag ntawm ib tug inert roj los tsim dawb radicals.Tom qab ntawd cov irradiated polymer substrate yog kho nrog cov monomer, uas yog kua los yog vapor los yog raws li ib tug tov nyob rau hauv ib tug haum hnyav.Txawm li cas los xij, nyob rau hauv txoj kev peroxidation grafting, lub cev polymer yog raug rau lub zog hluav taws xob ntau nyob rau hauv lub xub ntiag ntawm huab cua los yog oxygen.Qhov tshwm sim yog tsim ntawm hydroperoxides los yog diperoxides nyob ntawm seb qhov xwm ntawm cov pob txha polymeric thiab irradiation tej yam kev mob.Cov khoom lag luam peroxy, uas ruaj khov, tom qab ntawd kho nrog cov monomer ntawm qhov kub siab dua, thaum twg cov peroxides tau decomposition toradicals, uas tom qab ntawd pib grafting.Qhov zoo ntawm cov txheej txheem no yog qhov nruab nrab peroxyproducts tuaj yeem khaws cia rau lub sijhawm ntev ua ntej ua cov kauj ruam grafting.Ntawm qhov tod tes, nrog lawv cov txheej txheem irradiation cov txheej txheem polymer thiab cov monomers yog irradiated ib txhij los tsim cov dawb radicals thiab yog li ntxiv qhov chaw.Txij li thaum cov monomers tsis raug hluav taws xob nyob rau hauv cov txheej txheem ua ntej irradiation, qhov pom tseeb qhov zoo ntawm txoj kev yog tias nws tsis muaj teeb meem ntawm homopolymer tsim uas tshwm sim nrog cov txheej txheem ib txhij.Txawm li cas los xij, qhov kev txiav txim siab tsis zoo ntawm cov txheej txheem ua ntej irradiation yog qhov sib tsoo ntawm lub hauv paus polymer vim nws cov directirradiation, uas ua rau feem ntau tsim cov block copolymers es tsis yog graftcopolymers.
Post lub sij hawm: May-03-2017