1
Ibikoresho bya polyurethane birwanya ubushyuhe bwinshi? Muri rusange, polyurethane ntishobora kwihanganira ubushyuhe bwinshi, kabone niyo yaba isanzwe ya PPDI, ubushyuhe bwayo ntarengwa bushobora kuba hafi 150 °. Ubwoko busanzwe bwa polyester cyangwa polyether ntibishobora kwihanganira ubushyuhe buri hejuru ya 120 °. Nyamara, polyurethane ni polymer cyane, kandi ugereranije na plastiki rusange, irwanya ubushyuhe. Kubwibyo, gusobanura ubushyuhe bwubushyuhe bwo guhangana nubushyuhe bwo hejuru cyangwa gutandukanya imikoreshereze itandukanye ni ngombwa cyane.
2
Nigute dushobora gutezimbere ubushyuhe bwibikoresho bya polyurethane? Igisubizo cyibanze nukwongera kristu yibikoresho, nkibisanzwe PPDI isocyanate yavuzwe haruguru. Kuki kongera kristu ya polymer itezimbere ubushyuhe bwayo? Igisubizo kizwi nabantu bose, ni ukuvuga imiterere igena imiterere. Uyu munsi, turashaka kugerageza gusobanura impamvu kunoza imiterere ya molekuline isanzwe izana iterambere ryumuriro, igitekerezo cyibanze kiva mubisobanuro cyangwa formulaire ya Gibbs ingufu zubusa, ni ukuvuga △ G = H-ST. Uruhande rw'ibumoso rwa G rugaragaza ingufu z'ubuntu, naho uruhande rw'iburyo rwo kugereranya H ni ishyaka, S ni entropiya, na T ni ubushyuhe.
3
Ingufu za Gibbs nubusa ni igitekerezo cyingufu muri thermodynamic, kandi ubunini bwacyo akenshi ni agaciro kagereranijwe, ni ukuvuga itandukaniro riri hagati yo gutangira no kurangiza, bityo ikimenyetso △ gikoreshwa imbere yacyo, kuko agaciro katagereranywa ntigashobora kuboneka cyangwa guhagararirwa. Iyo △ G igabanutse, ni ukuvuga iyo ari bibi, bivuze ko imiti yimiti ishobora guhita ibaho cyangwa ikaba nziza kubitekerezo byateganijwe. Ibi birashobora kandi gukoreshwa kugirango umenye niba reaction ibaho cyangwa ihinduka muri thermodynamic. Urwego cyangwa igipimo cyo kugabanuka birashobora kumvikana nkibikorwa bya reaction ubwayo. H mubyukuri irashimishije, irashobora kumvikana nkimbaraga zimbere ya molekile. Irashobora gukekwa hafi yubusobanuro bwibisobanuro byabashinwa, nkumuriro ntabwo

4
S yerekana entropiya ya sisitemu, isanzwe izwi kandi ibisobanuro nyabyo birasobanutse neza. Bifitanye isano cyangwa bigaragazwa ukurikije ubushyuhe T, kandi igisobanuro cyacyo cyibanze ni urwego rwimivurungano cyangwa umudendezo wa sisitemu nto ya microscopique. Aha, inshuti nto yitegereza ishobora kuba yarabonye ko ubushyuhe T bujyanye nubushyuhe bwumuriro tuganira uyu munsi amaherezo bwagaragaye. Reka mvuge gato kubijyanye na entropiya. Entropy irashobora kumvikana mubucucu nkibinyuranye na kristu. Iyo hejuru ya entropiya agaciro, niko imiterere idahwitse kandi irimo akajagari imiterere ya molekile ni. Iyo urwego rwa molekile ruri hejuru, niko kristu ya molekile iba nziza. Noneho, reka dukate kare kare kuri polyurethane reberi hanyuma turebe kare kare nka sisitemu yuzuye. Ubwinshi bwayo burakosowe, ukeka ko kare igizwe na molekile 100 ya polyurethane (mubyukuri, hariho N benshi), kubera ko ubwinshi bwayo nubunini bwayo bidahindutse cyane, dushobora kugereranya △ G nkigiciro gito cyane cyumubare cyangwa hafi ya zeru, noneho formulaire yingufu za Gibbs irashobora guhinduka muri ST = H, aho T nubushyuhe, na S ni entropy. Nukuvuga ko, ubushyuhe bwumuriro wa polyurethane ntoya iringaniye na enthalpy H kandi igereranya na entropiya S. Birumvikana ko ubu ari uburyo bugereranijwe, kandi nibyiza kongeramo △ mbere yacyo (byabonetse kubigereranya).
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Ntabwo bigoye kubona ko iterambere rya kristaliste ridashobora kugabanya agaciro ka entropiya gusa ahubwo rishobora no kongera agaciro keza, ni ukuvuga kongera molekile mugihe ugabanya icyerekezo (T = H / S), ibyo bikaba bigaragara ko izamuka ryubushyuhe T, kandi ni bumwe muburyo bukomeye kandi busanzwe, tutitaye ko T ari ubushyuhe bwikirahure cyangwa ubushyuhe bwo gushonga. Igikenewe guhinduka ni uko ubudahwema hamwe na kristu ya monomer ya molekulire ya monomer hamwe nubusanzwe muri rusange hamwe na kristu yo gukomera kwa molekile ndende nyuma yo guteranya ni umurongo, ushobora kuba uhwanye cyangwa wunvikana muburyo bumwe. Ishyaka H ritangwa cyane cyane nimbaraga zimbere za molekile, kandi ingufu zimbere za molekile nigisubizo cyimiterere ya molekile itandukanye yingufu za molekile zitandukanye, kandi ingufu za molekile zishobora kuba imiti, imiterere ya molekile isanzwe kandi ikanategekwa, bivuze ko ingufu za molekile zishobora kuba nyinshi, kandi byoroshye kubyara ibintu bya kristu, nkamazi yegeranya mu rubura. Uretse ibyo, twatekereje gusa kuri molekile 100 ya polyurethane, imbaraga zikorana hagati yizi molekile 100 nazo zizagira ingaruka ku kurwanya ubushyuhe bw’uruziga ruto, nk’imigozi ya hydrogène physique, nubwo idakomeye nk’imigozi y’imiti, ariko umubare N ni munini, imyitwarire igaragara y’imisemburo ya hydrogène isa naho ishobora kugabanya urugero rw’imivurungano cyangwa kugabanya umuvuduko w’imikorere ya buri molekile ya polyurethane, bityo hydrogène ikagira akamaro mu kuzamura ubushyuhe bw’umuriro.