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Shin kayan polyurethane suna jure yanayin zafi? Gabaɗaya, polyurethane baya jure yanayin zafi, koda tare da tsarin PPDI na yau da kullun, iyakar zafinsa na iya zama kusan 150 ° kawai. Nau'in polyester ko polyether na yau da kullun bazai iya jure yanayin zafi sama da 120° ba. Duk da haka, polyurethane shine polymer polar sosai, kuma idan aka kwatanta da robobi na gaba ɗaya, ya fi tsayayya da zafi. Don haka, ayyana kewayon zafin jiki don juriya mai zafi ko bambance amfani daban-daban yana da matukar mahimmanci.
2
Don haka ta yaya za a inganta kwanciyar hankali na thermal na kayan polyurethane? Amsar asali ita ce ƙara kristal ɗin kayan, kamar PPDI isocyanate na yau da kullun da aka ambata a baya. Me yasa karuwar crystallinity na polymer ke inganta kwanciyar hankali ta thermal? Amsar ita ce ainihin sananne ga kowa, wato, tsari yana ƙayyade kaddarorin. A yau, muna so mu yi ƙoƙari mu bayyana dalilin da ya sa inganta tsarin kwayoyin halitta na yau da kullum yana kawo ci gaba a cikin kwanciyar hankali na thermal, ainihin ra'ayin shine daga ma'anar ko tsarin Gibbs makamashi kyauta, watau △G=H-ST. Gefen hagu na G yana wakiltar makamashi kyauta, kuma gefen dama na lissafin H yana da kuzari, S shine entropy, kuma T shine zafin jiki.
3
Gibbs kyauta makamashi ra'ayi ne na makamashi a cikin thermodynamics, kuma girmansa sau da yawa yana da darajar dangi, watau bambanci tsakanin ƙimar farawa da ƙarewa, don haka alamar △ ana amfani da ita a gabansa, saboda ba za a iya samun cikakkiyar darajar kai tsaye ko wakilci ba. Lokacin da △G ya ragu, watau lokacin da ba shi da kyau, yana nufin cewa halayen sinadarai na iya faruwa ba da dadewa ba ko kuma ya dace da wani abin da ake tsammani. Hakanan za'a iya amfani da wannan don sanin ko akwai abin da ya faru ko kuma yana iya jujjuyawa a cikin thermodynamics. Za'a iya fahimtar digiri ko ƙimar raguwa azaman motsin motsin kansa. H yana da ban sha'awa, wanda za'a iya fahimta kusan a matsayin makamashin ciki na kwayar halitta. Ana iya yin kisa sosai daga saman ma'anar haruffan Sinanci, kamar yadda ba wuta ba

4
S yana wakiltar entropy na tsarin, wanda aka sani gabaɗaya kuma ma'anar zahiri ta fito fili. Yana da alaƙa da ko bayyana cikin sharuddan zafin jiki T, kuma ainihin ma'anarsa shine matakin rashin ƙarfi ko 'yanci na ƙananan ƙananan ƙwayoyin cuta. A wannan lokaci, ɗan ƙaramin aboki mai lura zai iya lura cewa zafin jiki T da ke da alaƙa da juriya na thermal da muke magana a yau ya bayyana a ƙarshe. Bari in dan yi tsokaci a kan ra'ayin entropy. Entropy za a iya fahimta da wauta a matsayin kishiyar crystallinity. Mafi girman darajar entropy, mafi rikicewa da rikicewar tsarin kwayoyin halitta. Mafi girman tsarin tsarin kwayoyin halitta, mafi kyawun crystallinity na kwayoyin halitta. Yanzu, bari mu yanke karamin murabba'i daga rubutun roba na polyurethane kuma muyi la'akari da ƙananan filin a matsayin cikakken tsarin. Its taro an gyarawa, zaton cewa square ne ya ƙunshi 100 polyurethane kwayoyin (a gaskiya, akwai N yawa), kamar yadda ta taro da girma ne m canza ba, za mu iya kusantar △G a matsayin wani sosai kananan lamba darajar ko mara iyaka kusa da sifili, sa'an nan Gibbs free makamashi dabara za a iya canza zuwa ST = H, da zazzabi. Wato, juriya na thermal na ƙananan murabba'i na polyurethane yana daidai da enthalpy H kuma ya bambanta da entropy S. Tabbas, wannan hanya ce ta kimanin, kuma yana da kyau a ƙara △ a gabansa (samu ta hanyar kwatanta).
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Ba shi da wuya a gano cewa haɓakar crystallinity ba zai iya rage darajar entropy kawai ba amma har ma yana ƙara darajar enthalpy, wato, ƙara yawan kwayoyin halitta yayin da yake rage ma'auni (T = H / S), wanda yake a fili don karuwar yawan zafin jiki T, kuma yana daya daga cikin mafi inganci da hanyoyin da aka saba, ko da kuwa T shine gilashin canji zafin jiki ko zafin jiki na narkewa. Abin da ake buƙatar canzawa shi ne cewa daidaito da kristal na tsarin kwayoyin halitta na monomer da kuma gaba ɗaya na yau da kullum da crystallinity na babban ƙarfin kwayoyin halitta bayan tarawa su ne ainihin layi, wanda zai iya zama kusan daidai ko fahimta ta hanya madaidaiciya. The enthalpy H aka yafi bayar da gudunmawar da ciki makamashi na kwayoyin, da kuma ciki makamashin kwayoyin ne sakamakon daban-daban kwayoyin tsarin na daban-daban kwayoyin m makamashi, da kuma kwayoyin m makamashi ne da sinadaran m, da kwayoyin tsarin ne na yau da kullum da kuma oda, wanda ke nufin cewa kwayoyin m makamashi ne mafi girma, kuma yana da sauki don samar da crystallization, kamar ruwa condenaden. Bayan haka, mun zaci kwayoyin polyurethane guda 100 kawai, sojojin hulɗar tsakanin waɗannan ƙwayoyin 100 kuma za su shafi juriya na thermal na wannan ƙaramin abin nadi, kamar haɗin gwiwar hydrogen na zahiri, kodayake ba su da ƙarfi kamar haɗin sinadarai, amma adadin N yana da girma, halayen bayyane na in mun gwada da ƙarin ƙwayoyin ƙwayoyin cuta na iya rage ƙimar haɓakar haɓakar haɓakar hydrogenane don haka tasirin hydrogenane zai iya rage ƙimar haɓakar haɓakar haɓakar kowane nau'in hydrogen. thermal juriya.