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Ingabe izinto ze-polyurethane ziyamelana namazinga okushisa aphezulu? Ngokuvamile, i-polyurethane ayimelani namazinga okushisa aphezulu, ngisho noma inesistimu ye-PPDI evamile, umkhawulo wayo wokushisa ophezulu ungaba cishe ku-150° kuphela. Izinhlobo ze-polyester ezijwayelekile noma ze-polyether zingase zingakwazi ukumelana namazinga okushisa angaphezu kuka-120°. Kodwa-ke, i-polyurethane iyi-polymer e-polar kakhulu, futhi uma iqhathaniswa nepulasitiki ejwayelekile, imelana kakhulu nokushisa. Ngakho-ke, ukuchaza ububanzi bokushisa bokumelana namazinga okushisa aphezulu noma ukuhlukanisa ukusetshenziswa okuhlukile kubaluleke kakhulu.
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Ngakho-ke ukuzinza kokushisa kwezinto ze-polyurethane kungathuthukiswa kanjani? Impendulo eyisisekelo iwukukhulisa ubukristalu bezinto ezibonakalayo, njenge-isocyanate ye-PPDI ejwayelekile kakhulu okukhulunywe ngayo ngaphambili. Kungani ukwandisa ubukristalu be-polymer kuthuthukisa ukuzinza kwayo kokushisa? Impendulo yaziwa yiwo wonke umuntu, okungukuthi, isakhiwo sinquma izakhiwo. Namuhla, singathanda ukuzama ukuchaza ukuthi kungani ukuthuthukiswa kokujwayelekile kwesakhiwo sama-molecule kuletha ukuthuthuka ekuzinzeni kokushisa, umqondo oyisisekelo uvela encazelweni noma efomini yamandla amahhala e-Gibbs, okungukuthi △G=H-ST. Uhlangothi lwesobunxele lwe-G lumelela amandla amahhala, kanti uhlangothi lwesokudla lwesibalo u-H yi-enthalpy, u-S yi-entropy, kanti u-T uyizinga lokushisa.
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Amandla amahhala e-Gibbs angumqondo wamandla ku-thermodynamics, futhi ubukhulu bawo buvame ukuba yinani elihlobene, okungukuthi umehluko phakathi kwamanani okuqala nawokuphela, ngakho-ke uphawu △ lusetshenziswa phambi kwalo, njengoba inani eliphelele lingenakutholakala noma limelelwe ngqo. Uma △G yehla, okungukuthi uma i-negative, kusho ukuthi ukusabela kwamakhemikhali kungavela ngokuzenzakalelayo noma kube kuhle kumpendulo ethile elindelekile. Lokhu kungasetshenziswa futhi ukunquma ukuthi ukusabela kukhona noma kuyaguqulwa ku-thermodynamics. Izinga noma izinga lokunciphisa lingaqondwa njenge-kinetics yokusabela uqobo. I-H ngokuyisisekelo i-enthalpy, engaqondwa cishe njengamandla angaphakathi e-molecule. Kungaqagelwa cishe kusukela encazelweni ebusweni bezinhlamvu zesiShayina, njengoba umlilo ungekho

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I-S imele i-entropy yesistimu, eyaziwa kabanzi futhi incazelo engokoqobo icacile impela. Ihlobene noma ivezwa ngokwezinga lokushisa i-T, futhi incazelo yayo eyisisekelo izinga lokuphazamiseka noma inkululeko yesistimu encane encane. Kuleli qophelo, umngane omncane oqaphelayo kungenzeka ukuthi waphawula ukuthi izinga lokushisa i-T elihlobene nokumelana nokushisa esixoxa ngakho namuhla ekugcineni lavela. Ake ngikhulume kancane ngomqondo we-entropy. I-entropy ingaqondwa ngobuwula njengokuphambene ne-crystallinity. Lapho inani le-entropy liphakeme, kulapho isakhiwo sama-molecule siphazamiseka futhi siphazamiseka khona. Lapho ukuqina kwesakhiwo sama-molecule kuphakeme, kulapho i-crystallinity ye-molecule iba ngcono. Manje, ake sinqume isikwele esincane ku-roll yerabha ye-polyurethane bese sibheka isikwele esincane njengohlelo oluphelele. Ubunzima bayo buqinile, uma sicabanga ukuthi isikwele sakhiwe ngama-molecule e-polyurethane ayi-100 (empeleni, kune-N eningi), njengoba ubunzima bayo kanye nomthamo kungashintshile ngokuyisisekelo, singalinganisa u-△G njengenani elincane kakhulu lezinombolo noma eduze kakhulu no-zero, khona-ke ifomula yamandla amahhala e-Gibbs ingaguqulwa ibe yi-ST=H, lapho u-T kuyizinga lokushisa, kanti u-S uyi-entropy. Okusho ukuthi, ukumelana nokushisa kwesikwele esincane se-polyurethane kuhambelana ne-enthalpy H futhi kuhambelana ngokuphambene ne-entropy S. Yiqiniso, lena yindlela elinganiselwe, futhi kungcono ukwengeza u-△ ngaphambi kwayo (okutholakala ngokuqhathanisa).
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Akunzima ukuthola ukuthi ukuthuthukiswa kwe-crystallinity akugcini nje ngokunciphisa inani le-entropy kodwa futhi kwandisa inani le-enthalpy, okungukuthi, ukwandisa i-molecule ngenkathi kunciphisa i-denominator (T = H/S), okusobala ngokwanda kwezinga lokushisa i-T, futhi kungenye yezindlela eziphumelela kakhulu nezivamile, kungakhathaliseki ukuthi i-T iyizinga lokushisa lokushintsha kwengilazi noma izinga lokushisa lokuncibilika. Okudingeka kuguqulwe ukuthi ukulingana kanye ne-crystallinity yesakhiwo sama-molecule se-monomer kanye nokujwayelekile kanye ne-crystallinity iyonke yokuqina kwama-molecule aphezulu ngemva kokuhlanganiswa ngokuyisisekelo kuqondile, okungaba cishe okulingana noma okuqondwe ngendlela eqondile. I-enthalpy H inikezwa kakhulu ngamandla angaphakathi e-molecule, futhi amandla angaphakathi e-molecule angumphumela wezakhiwo ezahlukene zama-molecule zamandla ahlukene e-molecule potential, futhi amandla e-molecule potential yi-chemical potential, isakhiwo sama-molecule sijwayelekile futhi sihlelekile, okusho ukuthi amandla e-molecule potential aphezulu, futhi kulula ukukhiqiza izimo ze-crystallization, njengokujiya kwamanzi abe yiqhwa. Ngaphandle kwalokho, sisanda kucabangela ama-molecule e-polyurethane ayi-100, amandla okusebenzisana phakathi kwala ma-molecule ayi-100 azophinde athinte ukumelana nokushisa kwale roller encane, njengezibopho ze-hydrogen ezibonakalayo, yize zingenamandla njengezibopho zamakhemikhali, kodwa inombolo u-N inkulu, ukuziphatha okusobala kwesibopho se-hydrogen sama-molecule amaningi kunganciphisa izinga lokuphazamiseka noma kuvimbele uhla lokuhamba kwe-molecule ngayinye ye-polyurethane, ngakho-ke isibopho se-hydrogen siwusizo ekuthuthukiseni ukumelana nokushisa.