Mframa a ano yɛ den a ɛma obi ho yɛ hyew a ɛma obi ho kyere no .
Owia no mframa a ano yɛ den no a wɔde di dwuma no betumi asɛe plastic bere a bere kɔ so no. Polymer photodegradation ba bere a ultraviolet radiation a aniwa nhu a ɛyɛ asorɔkye ntiantiaa no bubu polymer nkɔnsɔnkɔnsɔn wɔ plastic mu. Wɔfrɛ eyi sɛ photodegradation nhyehyɛe. Ɛfiri mframa a ano yɛ den a ɛwɔ nipadua no mu no mu na ɛma honam fam ahoɔden so tew. Eyinom bi ne ahoɔden a ɛyera, kɔla a ɛsakra, mpaapaemu, elongation a ɛyera ne ahoɔden a ɛtwetwe, ne chalking a ɛwɔ soro. Sɛ nhwɛso no, photodegradation a UV radiation de ba no betumi ama turo mu nkongua ayɛ fĩ na ayɛ mmerɛw. Nea ɛka ho no, agumadibea nkongua no kɔla bɛda adi sɛ ɛyɛ chalky, na plastic bi mpo bɛyɛ kɔkɔɔ na apaapae.
Su horow bi a ɛwɔ ultraviolet mframa mu .
Ultraviolet mframa no yɛ owia no mu ɔha biara mu nkyem 4.6 pɛ. Wɔsusu no wɔ nanometer (NM) mu na ɛfiri 290 kɔsi 400. Nanso, UVB kwan no fã a ɛyɛ basabasa paa ne asorɔkye tenten tiawa paa a ɛwɔ 280 ne 315 nanometer ntam. Enti, UV radiation energy a wɔde hyɛ mu (irradiation) dodow no gyina baabi a wowɔ wɔ wiase no so.
Dɛn ne irradiation .
Irradiance yɛ ultraviolet radiant ahoɔden a ɛba wɔ beae pɔtee bi wɔ bere bi mu. 1LY= 1 cal/cm 2=4.184 e 4 joule/m 2 (LY=Langley) enti, afe biako a wɔde di dwuma wɔ abɔnten a ɛkɔ so wɔ Sudan mu wɔ Sudan, ahoɔden a wɔde kɔ plastic no mu no, wɔde kɔ 20kcal/year is imyere im ing im im, im im, im im, im im, im im, im im, im im, im, im im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im, im im.
Plastik biara yɛ nea ɛyɛ mmerɛw wɔ asorɔkye tenten bi ho wɔ 290-400 nm UV mantam no mu. Enti, polypropylene wɔ maxima abiɛsa wɔ 290-300, 330 ne 370 nm. Nylon fi 290-315, bere a PVC homopolymer yɛ 320.
Polymers a ɛresɛe denam UV radiation so .
Polymer photodegradation ba bere a ultraviolet mframa a efi owia mu no nam nnuru akuw a ɛwɔ polymer nhyehyɛe a wɔfrɛ no chromophores no mu no twetwe. Chromophore yɛ "atɔm anaa atɔm kuw a ne ba a ɛwɔ hɔ no na ɛkyerɛ kɔla a ɛwɔ aduru bi mu". Polymer formulations betumi ayɛ nneɛma afoforo a wɔde ka ho te sɛ halogenated flame retardants, fillers ne pigments. Enti, wɔyɛɛ UV stabilizers na wɔde kaa polymers ho de siw photoitiation nhyehyɛe no ano. Nneɛma abiɛsa a edi kan no yɛ UV absorbers, quenchers, ne esiw amine light stabilizers (HALs) kwan.
1) UV a ɛtwetwe nsu no .
Absorbers yɛ photostabilizers a ɛyɛ adwuma denam chromophores a wɔde si akan de twetwe UV mframa no so. Enti, absorber no dannan UV mframa a epira no ma ɛyɛ infrared radiation anaa ɔhyew a asiane biara nni ho a ɛnam polymer matrix no so sɛe no. UV absorbers wɔ mfasoɔ a ɛne sɛ ɛho ka sua, nanso ɛbɛtumi ayɛ nea ɛfata ma ɛyɛ tiawa-bere a ɛda adi no nko ara. UV absorbers no bi ne:
Absorber .
UV absorbers wɔ mfasoɔ a ɛne sɛ ɛho ka sua, nanso ɛbɛtumi ayɛ nea ɛfata ma ɛyɛ tiawa-bere a ɛda adi no nko ara. UV absorbers no bi ne:
Carbon black yɛ UV mframa a ɛtwetwe nneɛma a etu mpɔn sen biara na wɔtaa de di dwuma no mu biako.
UV absorber foforo ne rutile titanium oxide, a ɛyɛ adwuma yiye wɔ 300-400 nm mu. Nanso, ɛho nni mfaso kɛse wɔ asorɔkye tenten a ɛyɛ tiaa koraa UVB a ɛwɔ ase 315 no mu.
Hydroxybenzophenone .
Hydroxyphenyl benzotriazole nso yɛ UV stabilizer a wonim no yiye a mfaso wɔ so sɛ ɛfata sɛ wɔde di dwuma wɔ afã biara anaasɛ ɛda adi pefee. Hydroxyphenylbenzotriazoles ho nni mfaso kɛse wɔ mmeae a ɛyɛ tratraa a ɛwɔ microns 100 ase.
Benzophenone a wɔde yɛ PVC .
Anzotriazoles ne hydroxyphenyltriazines a wɔde yɛ polycarbonates.
Oxalanilide a wɔde yɛ polyamides .
2) Ɔdum a ɛma obi yɛ adwuma .
quenchers san de chromophore no tebea a ɛyɛ anigye no kɔ fam tebea no mu denam ahoɔden a wɔde kɔ baabi foforo so. Nneɛma a ɛma ahoɔden kɔ baabi foforo no yɛ adwuma denam carbonyl akuw a ɛyɛ anigye a ɛba bere a wɔreyɛ plastic no mu nneɛma a wɔde yɛ mfonini no mu a ɛyɛ anigye a wodum ne hydroperoxides a ɛporɔw so. Eyi mma nhama no bubu na awiei koraa no ɛyɛ free radicals a ɛba no.
Nickel a wɔde dum nipadua no yɛ adwuma .
Nickel quencher yɛ nea wɔtaa de di dwuma wɔ kuayɛ sini mu. Wɔmfa eyinom nni dwuma kɛse efisɛ dade a emu yɛ duru wɔ mu na ɛma nea etwa to no kɔla yɛ tan anaasɛ ɛyɛ ahabammono. Nanso, te sɛ amine hann a ɛma ɛyɛ den a wɔasiw ano a wɔaka ho asɛm wɔ ase hɔ no, nikel a wɔde dum no ntumi nyɛ adwuma yiye wɔ UV mframa a ɛma ɛyɛ den no mu.
3) Esiw Amine a ɛma hann no tumi gyina (HALS) kwan .
HALS yɛ tenten-a ɛyɛ ɔhyew stabilizers a ɛtra hɔ daa a ɛyɛ adwuma denam free radicals a ɛba bere a wɔreyɛ photooxidation wɔ plastic nneɛma mu a ɛkyere so. Enti HAL ahorow no to photodegradation nhyehyɛe no ano hye. Yebetumi akyerɛkyerɛ tumi a HALS tumi de di dwuma wɔ radicals free radicals a efi UV mframa a ɛtwetwe mu ba no mu denam nitroxyl akuw a wɔhyehyɛ wɔ adeyɛ bi a wɔfrɛ no denisov kyinhyia mu no so.
Ɛwom sɛ HALS nneɛma a wɔtɔn no gu ahorow no gu ahorow kɛse wɔ ne nhyehyɛe mu de, nanso ne nyinaa wɔ 2,2,6,6-tetramethylpiperidine ring nhyehyɛe. HaLs yɛ UV radiation stabilizers a ɛyɛ adwuma yiye sen biara no bi.
UV stabilizers a wɔde yɛ plastic ahorow .
Sɛ nhwɛso no, HALS aboa ma polypropylene anya nkɔso wɔ kar adwumayɛ mu. Bere a HALS nso yɛ adwuma yiye wɔ polyolefins, polyethylene ne polyurethane mu no, wontumi mfa nyɛ stabilizers mma UV radiation wɔ PVC mu.
UV stabilizers a wɔaka abom .
Esiane sɛ dwumadi abiɛsa no nyinaa nam akwan horow so yɛ adwuma nti, wɔtaa ka bom yɛ UV mframa a ɛtwetwe nneɛma a ɛka bom yɛ adwuma. Sɛ nhwɛso no, wɔtaa de benzotriazoles di dwuma de ka HAL ahorow ho de siw ayera ne nsakrae a ɛba wɔ kɔla nhyehyɛe mu no ano.
