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Ngaba izinto ze-polyurethane ziyamelana namaqondo obushushu aphezulu? Ngokubanzi, i-polyurethane ayimelani namaqondo obushushu aphezulu, nokuba inenkqubo ye-PPDI eqhelekileyo, umda wayo wobushushu ophezulu unokuba malunga ne-150° kuphela. Iintlobo ze-polyester eziqhelekileyo okanye ze-polyether zisenokungakwazi ukumelana namaqondo obushushu angaphezu kwe-120°. Nangona kunjalo, i-polyurethane yi-polymer e-polar kakhulu, kwaye xa ithelekiswa neeplastiki eziqhelekileyo, iyamelana ngakumbi nobushushu. Ke ngoko, ukuchaza uluhlu lobushushu lokumelana namaqondo obushushu aphezulu okanye ukwahlula ukusetyenziswa okuhlukeneyo kubaluleke kakhulu.
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Ngoko ke ukuzinza kobushushu bezinto ze-polyurethane kungaphuculwa njani? Impendulo esisiseko kukunyusa ubukhristale bezinto, njenge-isocyanate ye-PPDI eqhelekileyo ekhankanyiweyo ngaphambili. Kutheni ukwandisa ubukhristale be-polymer kuphucula uzinzo lwayo lobushushu? Impendulo yaziwa ngumntu wonke, oko kukuthi, ulwakhiwo lumisela iipropati. Namhlanje, singathanda ukuzama ukuchaza ukuba kutheni ukuphuculwa kokulungelelaniswa kwesakhiwo se-molecular kuzisa uphuculo kuzinzo lobushushu, ingcamango esisiseko ivela kwinkcazo okanye kwifomyula yamandla asimahla e-Gibbs, oko kukuthi △G=H-ST. Icala lasekhohlo le-G limele amandla asimahla, kwaye icala lasekunene le-equation H yi-enthalpy, i-S yi-entropy, kwaye u-T bubushushu.
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Amandla asimahla eGibbs yingcamango yamandla kwi-thermodynamics, kwaye ubukhulu bawo buhlala buyixabiso elihambelanayo, oko kukuthi umahluko phakathi kwamaxabiso okuqala nawokuphela, ngoko ke uphawu △ lusetyenziswa phambi kwalo, njengoko ixabiso elipheleleyo lingenakufumaneka okanye limelwe ngokuthe ngqo. Xa △G incipha, oko kukuthi xa i-negative, oko kuthetha ukuba impendulo yekhemikhali inokwenzeka ngokuzenzekelayo okanye ibe nefuthe kwimpendulo ethile elindelekileyo. Oku kungasetyenziselwa ukumisela ukuba impendulo ikhona okanye iyaguquka kwi-thermodynamics. Iqondo okanye izinga lokunciphisa linokuqondakala njenge-kinetics yempendulo ngokwayo. I-H ngokusisiseko yi-enthalpy, enokuqondakala phantse njengamandla angaphakathi emolekyuli. Inokuqikelelwa malunga nentsingiselo yomphezulu wabalinganiswa baseTshayina, njengoko umlilo ungenjalo.

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I-S imele i-entropy yenkqubo, eyaziwa ngokubanzi kwaye intsingiselo yayo icacile. Inxulumene okanye ichazwa ngokweqondo lobushushu u-T, kwaye intsingiselo yayo esisiseko liqondo lokuphazamiseka okanye inkululeko yenkqubo encinci encinci. Ngeli xesha, umhlobo omncinci oqaphelayo usenokuba uqaphele ukuba ubushushu u-T obunxulumene nokumelana nobushushu esixoxa ngabo namhlanje ekugqibeleni buvele. Makhe ndithethe kancinci malunga nengcamango ye-entropy. I-Entropy ingaqondwa ngobudenge njengento echasene ne-crystallinity. Okukhona ixabiso le-entropy liphezulu, kokukhona isakhiwo se-molecular siphazamiseka kwaye siphazamiseka. Okukhona ulungelelwano lwesakhiwo se-molecular luphezulu, kokukhona i-crystallinity ye-molecule ingcono. Ngoku, masinqumle isikwere esincinci kwi-roll yerabha ye-polyurethane kwaye sijonge isikwere esincinci njengenkqubo epheleleyo. Ubunzima bayo buzinzile, xa sicinga ukuba isikwere senziwe ngeemolekyuli ze-polyurethane ezili-100 (ngokwenene, zininzi i-N), njengoko ubunzima bayo kunye nomthamo zingatshintshi ngokusisiseko, singaqikelela i-△G njengexabiso elincinci kakhulu lamanani okanye elisondele kakhulu kwi-zero, ngoko ke ifomula yamandla asimahla eGibbs inokuguqulwa ibe yi-ST=H, apho u-T bubushushu, kwaye u-S yi-entropy. Oko kukuthi, ukumelana nobushushu kwesikwere esincinci se-polyurethane kuhambelana ne-enthalpy H kwaye kuhambelana ngokuphambeneyo ne-entropy S. Kakade ke, le yindlela eqikelelweyo, kwaye kungcono ukongeza i-△ phambi kwayo (efunyenwe ngokuthelekisa).
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Akunzima ukufumanisa ukuba ukuphuculwa kwekristalinity akunakunciphisa ixabiso le-entropy kuphela kodwa kukwanyusa ixabiso le-enthalpy, oko kukuthi, ukwandisa imolekyuli ngelixa kunciphisa i-denominator (T = H/S), nto leyo ecacileyo ekunyukeni kobushushu i-T, kwaye yenye yezona ndlela zisebenzayo neziqhelekileyo, nokuba i-T yiqondo lobushushu lotshintsho lweglasi okanye ubushushu bokunyibilika. Okufunekayo ukutshintshwa kukuba ulungelelwano kunye nekristalinity yesakhiwo semolekyuli ye-monomer kunye nolungelelwano olupheleleyo kunye nekristalinity ye-molecular solidification ephezulu emva kokuhlanganiswa ngokusisiseko zi-linear, ezinokulingana okanye ziqondwe ngendlela ethe ngqo. I-enthalpy H inegalelo kakhulu ngamandla angaphakathi emolekyuli, kwaye amandla angaphakathi emolekyuli sisiphumo sezakhiwo ezahlukeneyo zemolekyuli zamandla ahlukeneyo emolekyuli, kwaye amandla emolekyuli yi-chemical potential, isakhiwo semolekyuli siqhelekile kwaye sicwangcisiwe, oko kuthetha ukuba amandla emolekyuli aphezulu, kwaye kulula ukuvelisa i-crystallization phenomena, njengokuxinana kwamanzi abe ngumkhenkce. Ngaphandle koko, sicinge nje ngeemolekyuli ze-polyurethane ezili-100, amandla onxibelelwano phakathi kwezi molekyuli zili-100 aya kuchaphazela nokumelana nobushushu kwale roller incinci, njengeebhondi ze-hydrogen ezibonakalayo, nangona zingenamandla njengeebhondi zeekhemikhali, kodwa inani le-N likhulu, ukuziphatha okucacileyo kwebhondi ye-hydrogen yeemolekyuli kunokunciphisa inqanaba lokuphazamiseka okanye kuthintele uluhlu lokuhamba kwemolekyuli nganye ye-polyurethane, ngoko ke ibhondi ye-hydrogen iluncedo ekuphuculeni ukumelana nobushushu.