2024 Tus sau: Elizabeth Oswald | [email protected]. Kawg hloov kho: 2024-01-13 00:07
In 1919, Hans John (1891–1942) ntawm Prague, Czechoslovakia, tau txais thawj patent rau UF resin. Urea-formaldehyde yog qhov teeb meem ntawm kev txiav txim los ntawm European Tsev Hais Plaub Kev Ncaj Ncees (tam sim no CJEU) ntawm 5 Lub Ob Hlis 1963, Case 26–62 Van Gend & Loos v Netherlands Inland Revenue Administration.
Urea formaldehyde tuaj qhov twg?
Urea-formaldehyde resin, ib chav kawm ntawm cov khoom siv hluavtaws tau los ntawm cov tshuaj sib xyaw ua ke ntawm urea (cov khoom siv lead ua tau los ntawm ammonia)thiab formaldehyde (cov roj muaj zog heev tau txais los ntawm methane).
Dab tsi yog qee qhov kev siv tseem ceeb ntawm urea formaldehyde resin?
Urea-formaldehyde (UF) resin, yog ib qho tseem ceeb tshaj plaws formaldehyde resin adhesives, yog cov khoom siv polymeric condensation ntawm formaldehyde nrog urea, thiab tau siv dav rau tsim cov ntoo ua vaj huam sib luag, xws li plywood, particleboard, thiab fiberboard.
Urea resin yog dab tsi?
Lub workhorse ntawm amino resin thev naus laus zis, urea resins yog siv feem ntau hauv kev lag luam khoom ntoo thiab muaj ntau yam, siv tau zoo, ua pov thawj. Cov txheej txheem thermosetting polymers no feem ntau yog ua los ntawm urea thiab formaldehyde, nrog formaldehyde ua tus ntoo khaub lig-linker.
Dab tsi yog qhov phom sij ntawm urea formaldehyde resin?
Formaldehyde yog muaj tshuaj lom rau tib neeg, tsis hais txog kev noj haus. Txawm luv-Lub sij hawm raug formaldehyde irritates lub qhov muag, ua rau mob, liab, tsis pom kev thiab dej loj heev. Nws tuaj yeem ua rau lub qhov ntswg thiab caj pas, ua rau txham, mob, hnoos, ua tsis taus pa, mob taub hau, thiab xeev siab.
Pom zoo:
Leej twg nrhiav tau induced haum txoj kev xav?
Tus qauv tsim kom haum yog thawj zaug los ntawm Koshland hauv xyoo 1958 los piav qhia txog kev hloov pauv ntawm cov protein hauv cov txheej txheem khi. Cov qauv no qhia tau hais tias ib qho enzyme, thaum khi nrog nws cov substrate, optimizes lub interface los ntawm lub cev kev sib cuam tshuam los tsim ib tug complex qauv.
Leej twg nrhiav tau sulfuric acid?
Qhov kev tshawb pom ntawm sulfuric acid tau lees paub rau 8th caug xyoo alchemist Jabir ibn Hayyan. Sulfuric acid ua ntej li cas? Nyob rau xyoo pua 17th, German-Dutch chemist Johann Glauber tau npaj sulfuric acid los ntawm kev hlawv sulfur ua ke nrog ntsev (potassium nitrate, KNO 3 ), nyob rau hauv lub xub ntiag ntawm chav.
Leej twg nrhiav tau chorten kora?
Chorten Kora loj, tab sis tsis ze li qhov loj npaum li lub stupa ntawm Bodhnath hauv Nepal, tom qab ntawd nws tau ua qauv. Nws tau tsim nyob rau xyoo 1740 los ntawm Lama Ngawang Loday nco txog nws tus txiv ntxawm, Jungshu Phesan, thiab kom tshem tawm cov dab hauv zos.
Leej twg tau spayed thiab leej twg tau txais neutered?
Kev npam tus dev hais txog kev tshem tus poj niam dev lub cev xeeb tub, hos neutering yog hais txog cov txheej txheem uas ua rau txiv neej. Thaum tus poj niam tus dev tau spayed, tus kws kho tsiaj tshem nws zes qe menyuam thiab feem ntau nws lub tsev menyuam thiab.
Puas nrhiav tau lossis nrhiav tau?
Yog li, koj yuav tsum tau siv "could find". Lub modal verb, tau yog twb nyob rau hauv nws paste-form: ua. Yog li koj tsis tas yuav hloov pauv los nrhiav. Yuav nrhiav tau lossis nrhiav tau? "Ntaus" yog sib npaug. "
