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Ingabe izinto ze-polyurethane ziyamelana namazinga okushisa aphezulu? Ngokuvamile, i-polyurethane ayimelani nokushisa okuphezulu, ngisho nesistimu ye-PPDI evamile, umkhawulo wayo ophezulu wokushisa ungaba ngu-150 ° kuphela. I-polyester evamile noma izinhlobo ze-polyether zingase zingakwazi ukumelana namazinga okushisa angaphezu kuka-120 °. Kodwa-ke, i-polyurethane iyi-polar esezingeni eliphakeme kakhulu, futhi uma iqhathaniswa nepulasitiki evamile, imelana kakhulu nokushisa. Ngakho-ke, ukuchaza ibanga lokushisa lokumelana nezinga lokushisa eliphezulu noma ukuhlukanisa ukusetshenziswa okuhlukile kubaluleke kakhulu.
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Ngakho-ke kungathuthukiswa kanjani ukuzinza okushisayo kwe-polyurethane? Impendulo eyisisekelo ukukhulisa ubucwebe bezinto ezibonakalayo, njenge-PPDI isocyanate evamile okukhulunywe ngayo ngaphambili. Kungani ukwandisa ubucwebe be-polymer kuthuthukisa ukuzinza kwayo okushisayo? Impendulo iyaziwa yiwo wonke umuntu, okungukuthi, isakhiwo sinquma izakhiwo. Namuhla, singathanda ukuzama ukuchaza ukuthi kungani ukuthuthukiswa kokujwayelekile kwesakhiwo samangqamuzana kuletha intuthuko ekuzinzeni kokushisa, umbono oyisisekelo usuka encazelweni noma kwifomula yamandla amahhala e-Gibbs, okungukuthi △G=H-ST. Uhlangothi lwesobunxele luka-G lumelela amandla amahhala, futhi uhlangothi lwesokudla lwe-equation H luyi-enthalpy, S yi-entropy, kanti u-T yizinga lokushisa.
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I-Gibbs yamandla amahhala ingumqondo wamandla ku-thermodynamics, futhi ubukhulu bayo buvame ukuba yinani elihlobene, okungukuthi umehluko phakathi kwamanani okuqala nawokugcina, ngakho uphawu △ lusetshenziswa phambi kwayo, njengoba inani eliphelele alikwazi ukutholwa ngokuqondile noma ukumelwa. Uma △G yehla, okungukuthi uma inegethivu, kusho ukuthi ukusabela kwamakhemikhali kungenzeka ngokuzenzakalelayo noma kube kuhle ekuphenduleni okuthile okulindelekile. Lokhu kungasetshenziswa futhi ukunquma ukuthi ukusabela kukhona noma kuyabuyiseleka emuva ku-thermodynamics. Izinga noma izinga lokunciphisa lingaqondwa njenge-kinetics yokusabela ngokwayo. H ngokuyisisekelo i-enthalpy, engaqondwa cishe njengamandla angaphakathi e-molecule. Kungaqagelwa cishe ngencazelo engaphezulu yezinhlamvu zesiShayina, njengoba umlilo ungenjalo

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U-S umele i-entropy yesistimu, eyaziwa ngokuvamile futhi incazelo engokoqobo icacile. Ihlobene noma ivezwa ngokwezinga lokushisa elingu-T, futhi incazelo yalo eyisisekelo izinga lokuphazamiseka noma inkululeko yohlelo oluncane oluncane olubonwa ngamehlo abomvu. Kuleli qophelo, umngane omncane oqaphelayo kungenzeka ukuthi uqaphele ukuthi izinga lokushisa T elihlobene nokumelana nokushisa esixoxa ngalo namuhla ekugcineni livele. Ake ngiqhubeke kancane mayelana nomqondo we-entropy. I-Entropy ingaqondwa ngobuwula njengokuphambene nekristallinity. Lapho inani le-entropy liphakeme, kulapho ukwakheka kwamangqamuzana kuphazamiseke kakhulu futhi kuphazamisekile. Lapho ukwakheka kwamangqamuzana kuphakeme njalo, kuba ngcono ukucwebezela kwe-molecule. Manje, ake sisike isikwele esincane kumqulu wenjoloba we-polyurethane futhi sibheke isikwele esincane njengohlelo oluphelele. Ubukhulu bawo bunqunyiwe, kucatshangwa ukuthi isikwele sakhiwe ama-molecule e-polyurethane angu-100 (empeleni, kukhona ama-N amaningi), njengoba ubukhulu bawo kanye nevolumu ngokuyisisekelo kungaguquki, singalinganisa u-△G njengenani lenombolo elincane kakhulu noma elisondele kakhulu ku-zero, khona-ke ifomula yamahhala ye-Gibbs ingaguqulwa ibe yi-ST=H, i-tro kanye ne-T iyizinga lokushisa. Okungukuthi, ukumelana nokushisa kwesikwele esincane se-polyurethane kuhambisana ne-enthalpy H futhi ngokuphambene ngokulingana ne-entropy S. Yiqiniso, lena indlela elinganiselwe, futhi kungcono ukwengeza △ ngaphambi kwayo (etholakala ngokuqhathanisa).
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Akunzima ukuthola ukuthi ukuthuthukiswa kwe-crystallinity akukwazi nje ukunciphisa inani le-entropy kodwa futhi kwandise inani le-enthalpy, okungukuthi, ukwandisa i-molecule ngenkathi kunciphisa i-denominator (T = H / S), okusobala ngokunyuka kwezinga lokushisa T, futhi ingenye yezindlela eziphumelela kakhulu nezivamile, kungakhathaliseki ukuthi i-T iyisigungu sokushintsha ingilazi noma izinga lokushisa elincibilikayo. Okudinga ukushintshwa ukuthi ukujwayela nokucwebezela kwesakhiwo semolekyuli ye-monomer kanye nokujwayela okuphelele nokucwebezela kokuqiniswa kwamangqamuzana aphezulu ngemva kokuhlanganisa kuqondile ngokuyisisekelo, okungacishe kulingane noma kuqondwe ngendlela yomugqa. I-enthalpy H inikezwa ngokuyinhloko amandla angaphakathi e-molecule, futhi amandla angaphakathi e-molecule angumphumela wezinhlaka ezahlukene zamangqamuzana anamandla ahlukene e-molecule, futhi amandla anamandla e-molecular amandla amakhemikhali, isakhiwo samangqamuzana sivamile futhi siyayalwa, okusho ukuthi amandla angaba namandla aphezulu, futhi kulula ukukhiqiza izenzakalo ze-crystallization, njengamanzi ahlangana abe yiqhwa. Ngaphandle kwalokho, sisanda kucabangela ama-molecule angu-100 e-polyurethane, amandla okusebenzelana phakathi kwalawa ma-molecule ayi-100 azophinde athinte ukumelana nokushisa kwalesi roller esincane, njengezibopho ze-hydrogen ngokomzimba, nakuba azinamandla njengezibopho zamakhemikhali, kodwa inombolo engu-N inkulu, ukuziphatha okusobala kwesibopho se-molecule ye-hydrogen kunganciphisa izinga lokuphazamiseka noma ukuvinjelwa kwe-polythane ngayinye ezuzisa ukunyakaza. ukumelana nokushisa.