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Ngaba izinto ze-polyurethane ziyamelana nobushushu obuphezulu? Ngokuqhelekileyo, i-polyurethane ayimelani nokushisa okuphezulu, nangona inkqubo ye-PPDI eqhelekileyo, umda wayo ophezulu weqondo lokushisa unokuba malunga ne-150 ° kuphela. Iintlobo zepolyester eziqhelekileyo okanye i-polyether ayinakukwazi ukumelana namaqondo okushisa angaphezu kwe-120 °. Nangona kunjalo, i-polyurethane yipolymer ephezulu kakhulu, kwaye xa ithelekiswa neeplastiki eziqhelekileyo, iyakwazi ukumelana nobushushu. Ke ngoko, ukucacisa ubungakanani bobushushu bokumelana nobushushu obuphezulu okanye ukwahlula ukusetyenziswa kwezinto ezahlukeneyo kubaluleke kakhulu.
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Ngoko ke ungaphuculwa njani ukuzinza kwe-thermal ye-polyurethane? Impendulo esisiseko kukunyusa i-crystallinity yezinto eziphathekayo, njenge-isocyanate ye-PPDI eqhelekileyo ekhankanywe ngaphambili. Kutheni ukwandisa icrystallinity yepolymer kuphucula ukuzinza kwayo kwe-thermal? Impendulo iyaziwa kuwo wonke umntu, oko kukuthi, isakhiwo simisela iipropati. Namhlanje, singathanda ukuzama ukucacisa ukuba kutheni ukuphuculwa kwe-molecular structure rhoqo kuzisa ukuphuculwa kozinzo lwe-thermal, ingcamango esisiseko ivela kwinkcazo okanye ifomula ye-Gibbs yamandla asimahla, okt △G=H-ST. Icala lasekhohlo le-G limele amandla amahhala, kwaye icala lasekunene le-equation H liyi-enthalpy, i-S yi-entropy, kunye ne-T yiqondo lokushisa.
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I-Gibbs amandla asimahla yingcamango yamandla kwi-thermodynamics, kwaye ubungakanani bayo buhlala buba nexabiso elihambelanayo, oko kukuthi umahluko phakathi kwamaxabiso okuqala kunye nokuphela, ngoko uphawu △ lusetyenziswe phambi kwayo, njengoko ixabiso elipheleleyo alinakufunyanwa ngokuthe ngqo okanye limelwe. Xa u-△G esihla, okt xa i-negative, ithetha ukuba ukusabela kweekhemikhali kunokuthi kwenzeke ngokuzenzekelayo okanye kukulungele ukusabela okuthile okulindelweyo. Oku kusenokusetyenziswa ukufumanisa ukuba ingaba i-reaction ikhona okanye iyabuyiselwa umva kwi-thermodynamics. Iqondo okanye izinga lokunciphisa linokuqondwa njenge-kinetics ye-reaction ngokwayo. I-H yi-enthalpy, enokuthi iqondwe njengamandla angaphakathi e-molecule. Inokuqikelelwa ngokuqikelelwa kwintsingiselo engaphezulu yeempawu zesiTshayina, njengoko umlilo ungenjalo

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I-S imele i-entropy yenkqubo, eyaziwa ngokubanzi kunye nentsingiselo yentsingiselo ecacileyo. Inxulumene okanye ibonakaliswe ngokwemiqathango yeqondo lobushushu T, kwaye intsingiselo yayo esisiseko liqondo lokuphazamiseka okanye inkululeko yenkqubo encinci ye-microscopic. Ngeli xesha, umhlobo omncinci oqapheleyo usenokuba uye waqaphela ukuba ubushushu be-T bunxulumene nokumelana nobushushu esixoxa ngalo namhlanje ekugqibeleni kwavela. Makhe ndiqhube kancinci malunga nombono we-entropy. I-Entropy inokuqondwa ngobudenge njengento echasene nekristallinity. Ukuphakama kwexabiso le-entropy, kokukhona i-disordered kunye ne-chaotic isakhiwo se-molecular. Ukuphakama kwesakhiwo semolekyuli, kokukhona i-crystallinity yemolekyuli ingcono. Ngoku, masisike isikwere esincinci kumqulu werabha wepolyurethane kwaye sithathe isikwere esincinci njengenkqubo epheleleyo. Ubunzima bayo bulungisiwe, kucingwa ukuba isikwere senziwe ngama-athomu angama-100 e-polyurethane (enyanisweni, kukho i-N ezininzi), njengoko ubunzima bayo kunye nomthamo bungatshintshi, sinokuqikelela △G njengexabiso elincinci kakhulu lenani okanye ngokungenasiphelo kwi-zero, emva koko i-Gibbs ifomula yamandla yamahhala inokuguqulwa ibe yi-ST = H, kunye ne-T yi-enro yeqondo lokushisa. Okokuthi, ukuchasana kwe-thermal yesikwere esincinci se-polyurethane silingana ne-enthalpy H kunye ne-inversely proportional kwi-entropy S. Ngokuqinisekileyo, le yindlela eqikelelweyo, kwaye kungcono ukongeza △ phambi kwayo (efunyenwe ngokuthelekisa).
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Akunzima ukufumanisa ukuba ukuphuculwa kwe-crystallinity akunakunciphisa kuphela ixabiso le-entropy kodwa nokunyusa ixabiso le-enthalpy, oko kukuthi, ukwandisa i-molecule ngelixa unciphisa i-denominator (T = H / S), ecacileyo ngokunyuka kweqondo lokushisa T, kwaye yenye yezona ndlela zisebenzayo kwaye ziqhelekileyo, kungakhathaliseki ukuba i-T yiqondo lokushisa lokutshintsha kweglasi okanye ukushisa okunyibilikayo. Yintoni ekufuneka iguqulwe kukuba isiqhelo kunye nekristali ye-monomer yesakhiwo semolekyuli kunye nesiqhelo esipheleleyo kunye nekristali yokuqina okuphezulu kweemolekyuli emva kokudityaniswa ngokusisiseko kunomgca, onokuthi ulingane okanye uqondwe ngendlela ehambelanayo. I-enthalpy H ubukhulu becala igalelo lamandla angaphakathi kwimolekyuli, kwaye amandla angaphakathi emolekyuli sisiphumo seendlela ezahlukeneyo zemolekyuli zamandla anokubakho emolekyuli, kwaye amandla anokubakho kwimolekyuli anokubakho kwimichiza, ulwakhiwo lwemolekyuli luqhelekile kwaye luyalelwa, oku kuthetha ukuba amandla anokubakho emolekyuli angaphezulu, kwaye kulula ukuvelisa izinto zecrystallization, njengamanzi ajiya abe ngumkhenkce. Ngaphandle koko, sicingela iimolekyuli ze-polyurethane ezili-100, amandla okunxibelelana phakathi kwezi molekyuli ze-100 ziya kuchaphazela ukuxhathisa kwe-thermal yale roller encinci, njengamabhondi e-hydrogen ngokomzimba, nangona aqinile njengamabhondi ekhemikhali, kodwa inani le-N likhulu, ukuziphatha okucacileyo kwe-molecular more molecular hydrogen bond kunokunciphisa izinga lokuphazamiseka okanye ukunqanda i-polythane ye-polythane intshukumo nganye. ukumelana nobushushu.