Abin da ake kirapolyurethaneshine taƙaitaccen bayanin polyurethane, wanda aka samar ta hanyar amsawar polyisocyanates da polyols, kuma ya ƙunshi ƙungiyoyin amino ester da yawa masu maimaitawa (- NH-CO-O -) akan sarkar kwayoyin halitta. A cikin ainihin resin polyurethane da aka haɗa, ban da rukunin amino ester, akwai kuma ƙungiyoyi kamar urea da biuret. Polyols suna cikin ƙwayoyin sarka mai tsayi tare da ƙungiyoyin hydroxyl a ƙarshe, waɗanda ake kira "sassan sarka mai laushi", yayin da ake kiran polyisocyanates "sassan sarka mai tauri".
Daga cikin resin polyurethane da sassan sarka masu laushi da tauri ke samarwa, ƙaramin kaso ne kawai amino acid esters, don haka ba zai dace a kira su polyurethane ba. A fayyace ma'ana, polyurethane ƙari ne na isocyanate.
Nau'o'in isocyanates daban-daban suna amsawa da mahaɗan polyhydroxy don samar da nau'ikan polyurethane daban-daban, ta haka suna samun kayan polymer masu halaye daban-daban, kamar robobi, roba, shafi, zare, manne, da sauransu.
Robar polyurethane tana cikin wani nau'in roba na musamman, wanda ake yin ta hanyar yin amfani da polyether ko polyester tare da isocyanate. Akwai nau'ikan roba da yawa saboda nau'ikan kayan masarufi daban-daban, yanayin amsawa, da hanyoyin haɗin gwiwa. Daga mahangar tsarin sinadarai, akwai nau'ikan polyester da polyether, kuma daga mahangar hanyar sarrafawa, akwai nau'ikan guda uku: nau'in haɗawa, nau'in siminti, da nau'in thermoplastic.
Ana haɗa robar polyurethane mai roba gabaɗaya ta hanyar amfani da polyester mai layi ko polyether tare da diisocyanate don samar da prepolymer mai ƙarancin nauyin kwayoyin halitta, wanda daga nan ake fuskantar tasirin faɗaɗa sarka don samar da polymer mai nauyin kwayoyin halitta mai yawa. Sannan, ana ƙara sinadaran haɗin gwiwa masu dacewa kuma ana dumama su don warkar da su, suna zama roba mai lalacewa. Ana kiran wannan hanyar prepolymerization ko hanyar matakai biyu.
Haka kuma yana yiwuwa a yi amfani da hanyar mataki ɗaya - haɗa polyester mai layi ko polyether kai tsaye tare da diisocyanates, masu faɗaɗa sarka, da kuma abubuwan haɗin gwiwa don fara amsawa da samar da robar polyurethane.
Sashen A a cikin ƙwayoyin TPU yana sa sarƙoƙin macromolecular su zama masu sauƙin juyawa, yana ba da robar polyurethane mai kyau da sassauci, yana rage wurin laushi da wurin canzawa na biyu na polymer, kuma yana rage taurinsa da ƙarfin injiniya. Sashen B zai ɗaure juyawar sarƙoƙin macromolecular, yana sa wurin laushi da wurin sauyawa na biyu na polymer su ƙaru, wanda ke haifar da ƙaruwa a cikin tauri da ƙarfin injiniya, da raguwar sassauci. Ta hanyar daidaita rabon molar tsakanin A da B, ana iya samar da TPUs masu halaye daban-daban na injiniya. Tsarin haɗin giciye na TPU ba wai kawai ya kamata a yi la'akari da haɗin giciye na farko ba, har ma da haɗin giciye na biyu wanda aka samar ta hanyar haɗin hydrogen tsakanin ƙwayoyin. Babban haɗin giciye na polyurethane ya bambanta da tsarin vulcanization na robar hydroxyl. An shirya rukunin amino ester ɗinsa, rukunin biuret, rukunin urea formate da sauran ƙungiyoyin aiki a cikin sashin sarƙoƙi na yau da kullun da sarari, wanda ke haifar da tsarin hanyar sadarwa na yau da kullun na roba, wanda ke da kyakkyawan juriya ga lalacewa da sauran kyawawan halaye. Abu na biyu, saboda kasancewar ƙungiyoyi masu aiki da yawa kamar urea ko carbamate a cikin robar polyurethane, haɗin hydrogen da aka samar tsakanin sarƙoƙin kwayoyin halitta yana da ƙarfi mai yawa, kuma haɗin haɗin gwiwa na biyu da aka samar ta hanyar haɗin hydrogen suma suna da tasiri mai mahimmanci akan halayen robar polyurethane. Haɗin haɗin gwiwa na biyu yana ba da damar robar polyurethane ta mallaki halayen elastomers masu saita thermosetting a gefe ɗaya, kuma a gefe guda, wannan haɗin haɗin gwiwa ba shi da alaƙa da gaske, wanda hakan ya sa ya zama haɗin gwiwa na kama-da-wane. Yanayin haɗin gwiwa ya dogara da zafin jiki. Yayin da zafin jiki ke ƙaruwa, wannan haɗin gwiwa yana raguwa a hankali kuma yana ɓacewa. Polymer yana da wani ruwa kuma ana iya yin aikin thermoplastic. Lokacin da zafin jiki ya ragu, wannan haɗin gwiwa a hankali yana murmurewa kuma yana sake samuwa. Ƙara ƙaramin adadin cikawa yana ƙara tazara tsakanin ƙwayoyin halitta, yana raunana ikon samar da haɗin hydrogen tsakanin ƙwayoyin halitta, kuma yana haifar da raguwar ƙarfi mai ƙarfi. Bincike ya nuna cewa tsarin kwanciyar hankali na ƙungiyoyi daban-daban masu aiki a cikin robar polyurethane daga sama zuwa ƙasa shine: ester, ether, urea, carbamate, da biuret. A lokacin tsufan robar polyurethane, mataki na farko shine karya haɗin da ke tsakanin biuret da urea, sannan kuma karya haɗin carbamate da urea, wato, babban sarkar da ke karyewa.
01 Rage Tausasawa
Elastomers na polyurethane, kamar sauran kayan polymer, suna laushi a yanayin zafi mai yawa kuma suna canzawa daga yanayin roba zuwa yanayin kwarara mai ƙauri, wanda ke haifar da raguwar ƙarfin injina cikin sauri. Daga mahangar sinadarai, zafin laushi na sassauci ya dogara ne akan abubuwa kamar abubuwan da ke cikin sinadarai, nauyin kwayoyin halitta, da yawan haɗin gwiwa.
Gabaɗaya dai, ƙara nauyin kwayoyin halitta, ƙara taurin ɓangaren tauri (kamar shigar da zoben benzene cikin ƙwayar) da kuma abun da ke cikin ɓangaren tauri, da kuma ƙara yawan haɗin gwiwa duk suna da amfani wajen ƙara zafin laushi. Ga elastomers na thermoplastic, tsarin ƙwayoyin halitta galibi layi ne, kuma zafin laushi na elastomer shima yana ƙaruwa lokacin da aka ƙara nauyin kwayoyin halitta.
Ga polyurethane elastomers masu haɗin giciye, yawan haɗin giciye yana da tasiri mafi girma fiye da nauyin kwayoyin halitta. Saboda haka, lokacin ƙera elastomers, ƙara aikin isocyanates ko polyols na iya samar da tsarin haɗin giciye mai ƙarfi na hanyar sadarwa a cikin wasu ƙwayoyin elastic, ko amfani da rabon isocyanate mai yawa don samar da tsarin haɗin giciye mai ƙarfi na isocyanate a cikin jikin roba hanya ce mai ƙarfi don inganta juriyar zafi, juriyar narkewa, da ƙarfin injina na elastomer.
Lokacin da ake amfani da PPDI (p-phenyldiisocyanate) a matsayin kayan da aka samar, saboda haɗin kai tsaye na ƙungiyoyin isocyanate guda biyu zuwa zoben benzene, ɓangaren da aka samar mai tauri yana da mafi girman abun ciki na zoben benzene, wanda ke inganta tauri na ɓangaren tauri kuma don haka yana ƙara juriyar zafi na elastomer.
Daga hangen nesa na zahiri, zafin laushi na elastomers ya dogara ne da matakin rabuwar microphase. A cewar rahotanni, zafin laushi na elastomers waɗanda ba sa rabuwa da microphase yana da ƙasa sosai, tare da zafin sarrafawa na kimanin 70 ℃ kawai, yayin da elastomers waɗanda ke rabuwa da microphase na iya kaiwa 130-150 ℃. Saboda haka, ƙara matakin rabuwar microphase a cikin elastomers yana ɗaya daga cikin hanyoyin inganta juriyar zafi.
Za a iya inganta matakin rabuwar microphase na elastomers ta hanyar canza rarraba nauyin kwayoyin halitta na sassan sarka da kuma abubuwan da sassan sarka masu tauri ke ciki, ta haka ne za a ƙara juriyarsu ga zafi. Yawancin masu bincike sun yi imanin cewa dalilin rabuwar microphase a cikin polyurethane shine rashin daidaiton thermodynamic tsakanin sassan laushi da tauri. Nau'in mai faɗaɗa sarka, ɓangaren tauri da abun da ke ciki, nau'in ɓangaren tauri, da haɗin hydrogen duk suna da tasiri mai mahimmanci a kansa.
Idan aka kwatanta da masu faɗaɗa sarkar diol, masu faɗaɗa sarkar diamine kamar MOCA (3,3-dichloro-4,4-diaminodiphenylmethane) da DCB (3,3-dichloro-biphenylenediamine) suna samar da ƙarin ƙungiyoyin amino ester na polar a cikin elastomers, kuma ana iya ƙirƙirar ƙarin haɗin hydrogen tsakanin sassa masu tauri, wanda ke ƙara hulɗa tsakanin sassa masu tauri da inganta matakin rabuwar microphase a cikin elastomers; Masu faɗaɗa sarkar aromatic masu simitric kamar p, p-dihydroquinone, da hydroquinone suna da amfani don daidaitawa da matse sassan masu tauri, don haka inganta rabuwar microphase na samfura.
Sassan amino ester da isocyanates na aliphatic suka samar suna da kyakkyawan jituwa da sassan laushi, wanda ke haifar da ƙarin sassa masu tauri suna narkewa a cikin sassan laushi, wanda ke rage matakin rabuwar microphase. Sassan amino ester da isocyanates na aromatic suka samar ba su da daidaito mai kyau da sassan taushi, yayin da matakin rabuwar microphase ya fi girma. Polyolefin polyurethane yana da kusan cikakken tsarin rabuwar microphase saboda gaskiyar cewa sashin taushi baya samar da haɗin hydrogen kuma haɗin hydrogen na iya faruwa ne kawai a cikin sashin mai tauri.
Tasirin haɗin hydrogen akan wurin laushi na elastomers shima yana da mahimmanci. Duk da cewa polyethers da carbonyls a cikin sashin laushi na iya samar da adadi mai yawa na haɗin hydrogen tare da NH a cikin sashin mai tauri, yana kuma ƙara zafin laushi na elastomers. An tabbatar da cewa haɗin hydrogen har yanzu yana riƙe da kashi 40% a zafin ℃ 200.
02 Rushewar zafi
Ƙungiyoyin amino ester suna fuskantar irin wannan rugujewa a yanayin zafi mai yawa:
- RNHCOOR – RNC0 HO-R
- RNHCOOR – RNH2 CO2
- RNHCOOR – RNHR CO2
Akwai manyan nau'ikan rugujewar zafi guda uku na kayan polyurethane:
① Samar da isocyanates da polyols na asali;
② α— Haɗin iskar oxygen da ke kan tushen CH2 ya karye kuma ya haɗu da haɗin hydrogen guda ɗaya akan CH2 na biyu don samar da amino acid da alkenes. Amino acid yana rikidewa ya zama babban amine da carbon dioxide:
③ Amine na biyu na Form 1 da carbon dioxide.
Rushewar yanayin zafi na tsarin carbamete:
Aryl NHCO Aryl,~120 ℃;
N-alkyl-NHCO-aryl,~180 ℃;
Aryl NHCO n-alkyl,~200 ℃;
N-alkyl-NHCO-n-alkyl, ~250 ℃.
Daidaiton zafin amino acid esters yana da alaƙa da nau'ikan kayan farawa kamar isocyanates da polyols. Aliphatic isocyanates sun fi aromatic isocyanates girma, yayin da fatty alcohols sun fi aromatic alcohols girma. Duk da haka, wallafe-wallafen sun ba da rahoton cewa zafin rugujewar zafi na aliphatic amino acid esters yana tsakanin 160-180 ℃, kuma na aromatic amino acid esters yana tsakanin 180-200 ℃, wanda bai yi daidai da bayanan da ke sama ba. Dalilin na iya danganta da hanyar gwaji.
A zahiri, aliphatic CHDI (1,4-cyclohexane diisocyanate) da HDI (hexamethylene diisocyanate) suna da juriyar zafi mafi kyau fiye da MDI da TDI da ake amfani da su akai-akai. Musamman trans CHDI mai tsarin daidaitawa an gane shi a matsayin isocyanate mafi jure zafi. Polyurethane elastomers da aka shirya daga gare shi suna da kyakkyawan ikon sarrafawa, kyakkyawan juriyar hydrolysis, zafin jiki mai laushi, ƙarancin zafin canzawar gilashi, ƙarancin hysteresis na zafi, da kuma juriyar UV mai yawa.
Baya ga rukunin amino ester, polyurethane elastomers suna da wasu ƙungiyoyi masu aiki kamar urea formate, biuret, urea, da sauransu. Waɗannan ƙungiyoyin na iya fuskantar rugujewar zafi a yanayin zafi mai yawa:
NHCONCOO – (aliphatic urea format), 85-105 ℃;
- NHCONCOO – (ƙamshi urea), a zafin jiki na 1-120 ℃;
- NHCONCONH – (aliphatic biuret), a zafin jiki daga 10 ° C zuwa 110 ° C;
NHCONCONH – (ƙanshi mai ƙanshi), 115-125 ℃;
NHCONH – (aliphatic urea), 140-180 ℃;
- NHCONH – (urea mai ƙamshi), 160-200 ℃;
Zoben Isocyanurate> 270 ℃.
Zafin rugujewar zafi na tsarin biuret da urea ya yi ƙasa da na aminoformate da urea, yayin da isocyanurate ke da mafi kyawun kwanciyar hankali na zafi. A cikin samar da elastomers, isocyanates masu yawa za su iya ƙara amsawa tare da aminoformate da urea da aka samar don samar da tsarin formate da biuret masu alaƙa da juna. Duk da cewa suna iya inganta halayen injiniya na elastomers, ba su da ƙarfi sosai don zafi.
Domin rage ƙungiyoyin da ba su da ƙarfi kamar biuret da urea formate a cikin elastomers, ya zama dole a yi la'akari da rabon kayansu da tsarin samarwa. Ya kamata a yi amfani da rabon isocyanate da ya wuce kima, kuma a yi amfani da wasu hanyoyi gwargwadon iko don fara samar da zoben isocyanate na ɓangare a cikin kayan (galibi isocyanates, polyols, da masu faɗaɗa sarka), sannan a shigar da su cikin elastomer bisa ga tsari na yau da kullun. Wannan ya zama hanyar da aka fi amfani da ita don samar da elastomers masu jure zafi da kuma masu jure wuta.
03 Hydrolysis da thermal oxidation
Elastomers na Polyurethane suna da saurin rugujewar zafi a cikin sassansu masu tauri da canje-canjen sinadarai masu dacewa a cikin sassansu masu laushi a yanayin zafi mai yawa. Elastomers na Polyester ba su da juriya ga ruwa kuma suna da mummunan yanayin hydrolyze a yanayin zafi mai yawa. Rayuwar sabis na polyester/TDI/diamine na iya kaiwa watanni 4-5 a zafin 50 ℃, makonni biyu kawai a zafin 70 ℃, kuma kwanaki kaɗan sama da 100 ℃. Haɗin Ester na iya rugujewa zuwa acid da barasa masu dacewa lokacin da aka fallasa su ga ruwan zafi da tururi, kuma ƙungiyoyin urea da amino ester a cikin elastomers suma suna iya fuskantar halayen hydrolysis:
RCOOR H20- → RCOOH HOR
Barasa na Ester
RNHCONHR ɗaya H20- → RXHCOOH H2NR -
Ureamide
Ɗaya daga cikin RNHCOOR-H20- → RNCOOH HOR -
Amino formate ester Amino formate alcohol
Elastomers da ke tushen Polyether ba su da isasshen kwanciyar hankali na iskar shaka ta thermal, da kuma elastomers da ke tushen ether α- Hydrogen da ke kan atom ɗin carbon yana da sauƙin oxidize, yana samar da hydrogen peroxide. Bayan ƙarin rugujewa da raba shi, yana samar da oxide radicals da hydroxyl radicals, waɗanda daga ƙarshe suka rikide suka zama siffofi ko aldehydes.
Polyester daban-daban ba su da wani tasiri sosai kan juriyar zafi na elastomers, yayin da polyether daban-daban ke da wani tasiri. Idan aka kwatanta da TDI-MOCA-PTMEG, TDI-MOCA-PTMEG yana da ƙimar riƙe ƙarfin tensile na 44% da 60% bi da bi lokacin da ya tsufa a 121 ℃ na tsawon kwanaki 7, yayin da na biyun ya fi na farko kyau. Dalilin na iya zama cewa ƙwayoyin PPG suna da sarƙoƙi masu reshe, waɗanda ba su dace da tsarin yau da kullun na ƙwayoyin roba ba kuma suna rage juriyar zafi na jikin roba. Tsarin kwanciyar hankali na zafi na polyethers shine: PTMEG>PEG>PPG.
Sauran ƙungiyoyin aiki a cikin polyurethane elastomers, kamar urea da carbamate, suma suna fuskantar oxidation da hydrolysis reactions. Duk da haka, ƙungiyar ether ita ce mafi sauƙin oxidation, yayin da ƙungiyar ester ita ce mafi sauƙin hydrolyzed. Tsarin juriyarsu ga antioxidant da hydrolysis shine:
Aikin hana tsufa: esters> urea> carbamate> ether;
Juriyar Hydrolysis: ester
Domin inganta juriyar iskar shaka ta polyether polyurethane da juriyar hydrolysis na polyester polyurethane, ana kuma ƙara ƙarin abubuwa, kamar ƙara 1% na phenolic antioxidant Irganox1010 zuwa PTMEG polyether elastomer. Ƙarfin wannan elastomer zai iya ƙaruwa da sau 3-5 idan aka kwatanta da ba tare da antioxidants ba (sakamakon gwaji bayan tsufa a 1500C na tsawon awanni 168). Amma ba kowane antioxidant ke da tasiri ga polyurethane elastomers ba, phenolic 1rganox 1010 da TopanOl051 (phenolic antioxidant, hana amine light stabilizer, benzotriazole complex) ne kawai ke da tasiri mai mahimmanci, kuma na farko shine mafi kyau, wataƙila saboda phenolic antioxidants suna da kyakkyawan jituwa da elastomers. Duk da haka, saboda muhimmiyar rawar da ƙungiyoyin phenolic hydroxyl ke takawa a cikin tsarin daidaita antioxidants na phenolic, domin guje wa amsawa da "gazawa" na wannan rukunin phenolic hydroxyl tare da ƙungiyoyin isocyanate a cikin tsarin, rabon isocyanates zuwa polyols bai kamata ya yi yawa ba, kuma dole ne a ƙara antioxidants zuwa prepolymers da masu faɗaɗa sarka. Idan aka ƙara shi yayin samar da prepolymers, zai yi tasiri sosai ga tasirin daidaitawa.
Ƙarin da ake amfani da su don hana hydrolysis na polyester polyurethane elastomers galibi mahaɗan carbodiimide ne, waɗanda ke amsawa da carboxylic acid da ester hydrolysis ke samarwa a cikin ƙwayoyin polyurethane elastomer don samar da abubuwan da suka samo asali daga acyl urea, wanda ke hana ƙarin hydrolysis. Ƙara carbodiimide a cikin ƙaramin rabo na 2% zuwa 5% na iya ƙara daidaiton ruwa na polyurethane sau 2-4. Bugu da ƙari, tert butyl catechol, hexamethylenetetramine, azodicarbonamide, da sauransu suma suna da wasu tasirin hana hydrolysis.
04 Babban halayen aiki
Elastomers na polyurethane sune nau'ikan copolymers na toshe-bulo iri-iri, tare da sarƙoƙin kwayoyin halitta waɗanda suka ƙunshi sassa masu sassauƙa tare da zafin canjin gilashi ƙasa da zafin ɗaki da kuma sassa masu tauri tare da zafin canjin gilashi sama da zafin ɗaki. Daga cikinsu, polyols na oligomeric suna samar da sassa masu sassauƙa, yayin da diisocyanates da ƙananan masu faɗaɗa sarƙoƙin ƙwayoyin halitta suna samar da sassa masu tauri. Tsarin da aka haɗa na sassan sarƙoƙi masu sassauƙa da tauri yana ƙayyade aikinsu na musamman:
(1) Taurin roba na yau da kullun gabaɗaya yana tsakanin Shaoer A20-A90, yayin da taurin filastik yake kusan Shaoer A95 Shaoer D100. Elastomers na Polyurethane na iya kaiwa ƙasa da Shaoer A10 da kuma sama da Shaoer D85, ba tare da buƙatar taimakon cikawa ba;
(2) Har yanzu ana iya kiyaye ƙarfi da sassauci mai yawa a cikin nau'ikan tauri iri-iri;
(3) Kyakkyawan juriya ga lalacewa, sau 2-10 fiye da robar halitta;
(4) Kyakkyawan juriya ga ruwa, mai, da sinadarai;
(5) Juriyar tasiri mai yawa, juriya ga gajiya, da juriya ga girgiza, wanda ya dace da aikace-aikacen lanƙwasa mai yawa;
(6) Kyakkyawan juriya ga ƙarancin zafin jiki, tare da raunin ƙarancin zafin jiki ƙasa da -30 ℃ ko -70 ℃;
(7) Yana da kyakkyawan aikin rufi, kuma saboda ƙarancin ƙarfin zafi, yana da ingantaccen tasirin rufi idan aka kwatanta da roba da filastik;
(8) Kyakkyawan daidaiton halittu da kaddarorin hana zubar jini;
(9) Kyakkyawan rufin lantarki, juriya ga mold, da kuma kwanciyar hankali na UV.
Ana iya ƙirƙirar elastomers na polyurethane ta amfani da hanyoyi iri ɗaya kamar robar yau da kullun, kamar plasticization, gaurayawa, da vulcanization. Haka kuma ana iya ƙera su ta hanyar robar ruwa ta hanyar zubawa, centrifugal molding, ko feshi. Haka kuma ana iya yin su da kayan granular kuma ana samar da su ta amfani da allura, extrusion, birgima, busa ƙaho, da sauran hanyoyin. Ta wannan hanyar, ba wai kawai yana inganta ingancin aiki ba, har ma yana inganta daidaiton girma da bayyanar samfurin.
Lokacin Saƙo: Disamba-05-2023