Tus hupolyurethaneyog cov ntawv luv ntawm polyurethane, uas yog tsim los ntawm cov tshuaj tiv thaiv ntawm polyisocyanates thiab polyols, thiab muaj ntau ntau cov amino ester pawg (- NH-CO-O -) ntawm cov saw molecular. Hauv qhov tseeb synthesized polyurethane resins, ntxiv rau cov amino ester pawg, kuj muaj cov pab pawg xws li urea thiab biuret. Polyols belongs rau cov saw ntev molecules nrog hydroxyl pawg thaum kawg, uas yog hu ua "mos saw segments", thaum polyisocyanates hu ua "cov saw nyuaj".
Ntawm cov polyurethane resins tsim los ntawm cov khoom muag muag thiab tawv tawv, tsuas yog ib feem me me yog cov amino acid esters, yog li nws yuav tsis tsim nyog hu lawv polyurethane. Hauv kev nkag siab dav, polyurethane yog ib qho ntxiv ntawm isocyanate.
Ntau hom isocyanates hnov mob nrog polyhydroxy compounds los tsim ntau yam qauv ntawm polyurethane, yog li tau txais cov ntaub ntawv polymer nrog cov khoom sib txawv, xws li yas, roj hmab, txheej, fibers, nplaum, thiab lwm yam. Polyurethane roj hmab
Polyurethane roj hmab belongs rau ib hom roj hmab tshwj xeeb, uas yog tsim los ntawm reacting polyether los yog polyester nrog isocyanate. Muaj ntau ntau yam vim muaj ntau hom khoom siv raw, cov txheej txheem tshuaj tiv thaiv, thiab txoj kev sib txuas. Los ntawm kev pom cov qauv tshuaj, muaj ntau hom polyester thiab polyether, thiab los ntawm txoj kev pom, muaj peb hom: sib xyaw hom, hom casting, thiab hom thermoplastic.
Synthetic polyurethane roj hmab feem ntau yog synthesized los ntawm reacting linear polyester los yog polyether nrog diisocyanate los ua ib tug uas tsis muaj molecular hnyav prepolymer, uas yog ces raug rau saw extension cov tshuaj tiv thaiv los tsim ib tug siab molecular hnyav polymer. Tom qab ntawd, cov neeg sawv cev sib txuas tsim nyog tau ntxiv thiab ua kom sov los kho nws, ua cov roj hmab vulcanized. Txoj kev no hu ua prepolymerization los yog ob-kauj ruam txoj kev.
Nws tseem tuaj yeem siv txoj hauv kev ib-kauj ruam - ncaj qha sib tov linear polyester los yog polyether nrog diisocyanates, saw extenders, thiab crosslinking agents los pib cov tshuaj tiv thaiv thiab tsim cov roj hmab polyurethane.
Lub A-segment nyob rau hauv TPU molecules ua rau cov macromolecular chains yooj yim tig, endowing polyurethane roj hmab nrog zoo elasticity, txo cov softening point thiab theem nrab hloov point ntawm lub polymer, thiab txo nws hardness thiab mechanical zog. B-segment yuav khi cov kev sib hloov ntawm macromolecular chains, ua rau lub softening point thiab lwm yam hloov pauv ntawm lub polymer kom nce, uas ua rau kom muaj zog hardness thiab mechanical zog, thiab txo elasticity. Los ntawm kev kho cov molar piv ntawm A thiab B, TPUs nrog cov khoom sib txawv tuaj yeem tsim tau. Cov qauv sib txuas ntawm TPU yuav tsum tsis yog tsuas yog xav txog kev sib txuas ntawm kev sib txuas, tab sis kuj tseem txuas ntxiv txuas ntxiv uas tsim los ntawm hydrogen bonds ntawm molecules. Thawj qhov sib txuas sib txuas ntawm polyurethane yog qhov sib txawv ntawm cov qauv vulcanization ntawm hydroxyl roj hmab. Nws cov amino ester pawg, pab pawg biuret, urea formate pawg thiab lwm pab pawg ua haujlwm tau teeb tsa hauv ntu ntu thiab ntu ntu ntu ntu, ua rau muaj cov qauv sib txuas ntawm cov roj hmab, uas muaj kev hnav zoo heev thiab lwm yam khoom zoo heev. Thib ob, vim muaj ntau pawg ua haujlwm sib koom ua ke xws li urea lossis carbamate pawg hauv polyurethane roj hmab, hydrogen bonds tsim ntawm molecular chains muaj zog, thiab cov kev sib txuas sib txuas sib txuas ua ke tsim los ntawm hydrogen bonds kuj muaj qhov cuam tshuam loj rau cov khoom ntawm polyurethane roj hmab. Secondary cross-linking enables polyurethane roj hmab kom muaj cov yam ntxwv ntawm thermosetting elastomers ntawm ib sab tes, thiab ntawm qhov tod tes, qhov kev sib txuas ntawm no tsis yog kev sib txuas tiag tiag, ua rau nws muaj kev sib txuas sib txuas. Txoj kev sib txuas sib txuas yog nyob ntawm qhov kub thiab txias. Raws li qhov kub thiab txias, qhov kev sib txuas sib txuas no maj mam tsis muaj zog thiab ploj mus. Cov polymer muaj qee yam fluidity thiab tuaj yeem raug rau kev ua cov thermoplastic. Thaum qhov kub thiab txias txo, qhov kev sib txuas ntawm qhov sib txuas no maj mam rov qab thiab rov ua dua. Qhov sib ntxiv ntawm ib qho me me ntawm cov muab tub lim nce qhov kev ncua deb ntawm cov molecules, tsis muaj peev xwm tsim cov hydrogen bonds ntawm cov molecules, thiab ua rau lub zog qis dua. Kev tshawb fawb tau pom tias qhov kev txiav txim ntawm kev ruaj ntseg ntawm ntau pawg ua haujlwm hauv polyurethane roj hmab los ntawm siab mus rau qis yog: ester, ether, urea, carbamate, thiab biuret. Thaum lub sij hawm kev laus ntawm cov roj hmab polyurethane, thawj kauj ruam yog kev rhuav tshem ntawm kev sib txuas ntawm kev sib txuas ntawm biuret thiab urea, ua raws li kev tawg ntawm carbamate thiab urea bonds, uas yog, cov saw tseem ceeb tawg.
01 Mos
Polyurethane elastomers, zoo li ntau cov ntaub ntawv polymer, soften ntawm qhov kub thiab txias thiab hloov los ntawm lub xeev elastic mus rau lub viscous flow xeev, uas ua rau ib tug ceev ceev ntawm mechanical zog. Los ntawm kev xav tshuaj, qhov muag kub ntawm elasticity feem ntau yog nyob ntawm cov khoom xws li nws cov tshuaj muaj pes tsawg leeg, qhov hnyav molecular, thiab crosslinking ntom.
Feem ntau hais lus, nce qhov hnyav ntawm cov txheeb ze molecular, ua kom cov rigidity ntawm cov ntu nyuaj (xws li qhia lub nplhaib benzene rau hauv cov molecule) thiab cov ntsiab lus ntawm cov ntu nyuaj, thiab ua kom cov crosslinking ntom ntom yog txhua yam muaj txiaj ntsig rau kev ua kom qhov muag kub. Rau cov thermoplastic elastomers, cov qauv molecular feem ntau yog linear, thiab softening kub ntawm elastomer kuj nce thaum cov txheeb ze molecular hnyav nce.
Rau crosslinked polyurethane elastomers, crosslinking ntom muaj qhov cuam tshuam ntau dua li qhov hnyav ntawm cov txheeb ze molecular. Yog li ntawd, thaum tsim elastomers, ua kom lub functionality ntawm isocyanates los yog polyols yuav tsim ib tug thermally ruaj khov network tshuaj cross-linking qauv nyob rau hauv ib co ntawm cov elastic molecules, los yog siv ntau tshaj isocyanate ratios los tsim ib tug ruaj khov isocyanate cross-linking qauv nyob rau hauv lub elastic lub cev yog. ib tug haib txhais tau tias los txhim kho lub tshav kub tsis kam, hnyav kuj, thiab mechanical zog ntawm lub elastomer.
Thaum PPDI (p-phenyldiisocyanate) yog siv los ua cov khoom siv raw, vim yog kev sib txuas ncaj qha ntawm ob pawg isocyanate rau lub nplhaib benzene, cov ntu nyuaj tsim muaj ntau dua benzene nplhaib cov ntsiab lus, uas txhim kho cov rigidity ntawm cov ntu nyuaj thiab yog li txhim kho. qhov kub tsis kam ntawm elastomer.
Los ntawm kev pom lub cev, qhov muag kub ntawm elastomers nyob ntawm seb qhov kev sib cais ntawm microphase. Raws li cov lus ceeb toom, qhov softening kub ntawm elastomers uas tsis dhau microphase sib cais yog tsawg heev, nrog ib tug ua kub ntawm tsuas yog hais txog 70 ℃, thaum elastomers uas undergo microphase sib cais yuav ncav cuag 130-150 ℃. Yog li ntawd, nce qib ntawm microphase sib cais hauv elastomers yog ib txoj hauv kev zoo los txhim kho lawv cov cua sov.
Lub degree ntawm microphase kev sib cais ntawm elastomers tuaj yeem txhim kho los ntawm kev hloov cov txheeb ze molecular hnyav faib ntawm cov saw ntu thiab cov ntsiab lus ntawm cov saw hlau nruj, yog li txhim kho lawv cov cua sov. Cov kws tshawb fawb feem ntau ntseeg tias yog vim li cas rau kev sib cais microphase hauv polyurethane yog qhov thermodynamic incompatibility ntawm cov mos thiab tawv ntu. Hom saw txuas ntxiv, ntu nyuaj thiab nws cov ntsiab lus, hom mos ntu, thiab hydrogen bonding tag nrho muaj qhov cuam tshuam loj rau nws.
Piv nrog diol saw extenders, diamine chain extenders xws li MOCA (3,3-dichloro-4,4-diaminodiphenylmethane) thiab DCB (3,3-dichloro-biphenylenediamine) tsim ntau polar amino ester pawg hauv elastomers, thiab ntau dua hydrogen bonds tau. tsim los ntawm cov ntu nyuaj, ua kom muaj kev sib cuam tshuam ntawm cov ntu nyuaj thiab txhim kho qib ntawm microphase sib cais hauv elastomers; Symmetric aromatic chain extenders xws li p, p-dihydroquinone, thiab hydroquinone yog qhov zoo rau qhov normalization thiab nruj ntim ntawm cov ntu nyuaj, yog li txhim kho microphase sib cais ntawm cov khoom.
Cov amino ester ntu tsim los ntawm aliphatic isocyanates muaj kev sib raug zoo nrog cov ntu mos, ua rau cov ntu nyuaj ntau dua hauv cov ntu mos, txo cov qib ntawm microphase sib cais. Cov amino ester ntu tsim los ntawm cov tshuaj tsw qab isocyanates muaj qhov tsis zoo sib xws nrog cov ntu mos, thaum lub sijhawm sib cais ntawm microphase ntau dua. Polyolefin polyurethane muaj ib qho yuav luag tiav microphase sib cais qauv vim qhov tseeb tias cov ntu mos tsis tsim hydrogen bonds thiab hydrogen bonds tsuas yog tshwm sim hauv ntu nyuaj.
Cov nyhuv ntawm hydrogen bonding ntawm lub softening point ntawm elastomers kuj tseem ceeb. Txawm hais tias polyethers thiab carbonyls nyob rau hauv cov mos mos tuaj yeem tsim muaj ntau ntawm hydrogen bonds nrog NH nyob rau hauv ib qho nyuaj, nws kuj ua rau cov softening kub ntawm elastomers. Nws tau raug lees paub tias hydrogen bonds tseem khaws 40% ntawm 200 ℃.
02 Thermal decomposition
Amino ester pawg tau txais cov hauv qab no decomposition ntawm qhov kub thiab txias:
- RNHCOOR - RNC0 HO-R
- RNHCOOR - RNH2 CO2 ene
- RNHCOOR - RNHR CO2 ene
Muaj peb yam tseem ceeb ntawm thermal decomposition ntawm polyurethane raws li cov ntaub ntawv:
① Tsim thawj isocyanates thiab polyols;
② α— Cov pa hluav taws xob ntawm CH2 lub hauv paus tawg thiab ua ke nrog ib daim ntawv cog lus hydrogen ntawm CH2 thib ob los tsim cov amino acids thiab alkenes. Amino acids decompose rau hauv ib qho tseem ceeb amine thiab carbon dioxide:
③ Daim ntawv 1 theem nrab amine thiab carbon dioxide.
Thermal decomposition ntawm carbamate qauv:
Aryl NHCO Aryl, ~ 120 ℃;
N-alkyl-NHCO-aryl, ~ 180 ℃;
Aryl NHCO n-alkyl, ~ 200 ℃;
N-alkyl-NHCO-n-alkyl, ~ 250 ℃.
Lub thermal stability ntawm amino acid esters muaj feem xyuam rau cov hom pib cov ntaub ntawv xws li isocyanates thiab polyols. Aliphatic isocyanates siab dua cov tshuaj tsw qab isocyanates, thaum cov cawv muaj roj ntau dua li cov cawv muaj ntxhiab. Txawm li cas los xij, cov ntaub ntawv qhia tias cov thermal decomposition kub ntawm aliphatic amino acid esters yog nyob nruab nrab ntawm 160-180 ℃, thiab cov aromatic amino acid esters yog nyob nruab nrab ntawm 180-200 ℃, uas yog inconsistent nrog cov ntaub ntawv saum toj no. Yog vim li cas tej zaum yuav muaj feem xyuam rau txoj kev xeem.
Qhov tseeb, aliphatic CHDI (1,4-cyclohexane diisocyanate) thiab HDI (hexamethylene diisocyanate) muaj cov cua sov zoo dua li siv cov tshuaj tsw qab MDI thiab TDI. Tshwj xeeb tshaj yog cov trans CHDI nrog symmetrical qauv tau raug lees paub tias yog cov feem ntau kub-resistant isocyanate. Polyurethane elastomers npaj los ntawm nws muaj kev ua tau zoo, zoo heev hydrolysis tsis kam, siab softening kub, tsis tshua muaj iav hloov kub, tsis tshua muaj thermal hysteresis, thiab siab UV tsis kam.
Ntxiv rau cov amino ester pawg, polyurethane elastomers kuj muaj lwm pab pawg ua haujlwm xws li urea formate, biuret, urea, thiab lwm yam. Cov pab pawg no tuaj yeem raug thermal decomposition ntawm qhov kub thiab txias:
NHCONCOO - (aliphatic urea formate), 85-105 ℃;
- NHCONCOO - (aromatic urea formate), ntawm qhov kub ntawm 1-120 ℃;
- NHCONCONH - (aliphatic biuret), ntawm qhov kub ntawm 10 ° C txog 110 ° C;
NHCONCONH - (aromatic biuret), 115-125 ℃;
NHCONH - (aliphatic urea), 140-180 ℃;
- NHCONH - (aromatic urea), 160-200 ℃;
Isocyanurate nplhaib> 270 ℃.
Lub thermal decomposition kub ntawm biuret thiab urea raws li formate yog qis dua li ntawm aminoformate thiab urea, thaum isocyanurate muaj qhov zoo tshaj plaws thermal stability. Hauv kev tsim cov elastomers, ntau cov isocyanates tuaj yeem cuam tshuam ntxiv nrog cov tsim aminoformate thiab urea los ua urea raws li formate thiab biuret cross-linked lug. Txawm hais tias lawv tuaj yeem txhim kho cov khoom siv ntawm elastomers, lawv tsis ruaj tsis khov rau cov cua sov.
Txhawm rau txo cov thermal tsis ruaj khov xws li biuret thiab urea formate hauv elastomers, nws yog ib qho tsim nyog yuav tsum xav txog lawv cov khoom siv raw thiab cov txheej txheem ntau lawm. Kev siv ntau dhau ntawm isocyanate yuav tsum tau siv, thiab lwm txoj hauv kev yuav tsum tau siv ntau npaum li qhov ua tau ua ntej ua ib feem ntawm isocyanate rings hauv cov ntaub ntawv raw (feem ntau yog isocyanates, polyols, thiab chain extenders), thiab tom qab ntawd qhia lawv mus rau hauv elastomer raws li cov txheej txheem ib txwm muaj. Qhov no tau dhau los ua txoj kev siv ntau tshaj plaws los ua cov khoom siv hluav taws xob thiab hluav taws xob tiv thaiv polyurethane elastomers.
03 Hydrolysis thiab thermal oxidation
Polyurethane elastomers feem ntau ua rau thermal decomposition hauv lawv cov ntu nyuaj thiab hloov tshuaj lom neeg hauv lawv cov ntu muag ntawm qhov kub thiab txias. Polyester elastomers muaj dej tsis zoo thiab muaj kev xav hnyav dua rau hydrolyze ntawm qhov kub thiab txias. Lub neej kev pab cuam ntawm polyester / TDI / diamine tuaj yeem ncav cuag 4-5 lub hlis ntawm 50 ℃, tsuas yog ob lub lis piam ntawm 70 ℃, thiab tsuas yog ob peb hnub saum 100 ℃. Ester bonds tuaj yeem decompose rau hauv cov kua qaub thiab cawv thaum raug dej kub thiab chav dej, thiab urea thiab amino ester pawg hauv elastomers tuaj yeem ua rau cov tshuaj tiv thaiv hydrolysis:
RCOOR H20- → RCOOR HOR
Ester cawv
Ib RNHCONHR ib H20- → RXHCOOH H2NR -
Ureamide
Ib RNHCOOR-H20- → RNCOOH HOR -
Amino formate ester Amino formate cawv
Polyether raws li elastomers muaj cov thermal oxidation tsis zoo, thiab ether raws li elastomers α- Cov hydrogen ntawm cov pa roj carbon atom yooj yim oxidized, tsim hydrogen peroxide. Tom qab ntxiv decomposition thiab cleavage, nws generates oxide radicals thiab hydroxyl radicals, uas nws thiaj li decompose rau hauv formates los yog aldehydes.
Cov polyesters sib txawv muaj qhov cuam tshuam me ntsis ntawm cov cua sov ntawm elastomers, thaum cov polyethers sib txawv muaj qee yam cuam tshuam. Piv nrog rau TDI-MOCA-PTMEG, TDI-MOCA-PTMEG muaj lub zog tensile tuav tus nqi ntawm 44% thiab 60% raws li thaum muaj hnub nyoog ntawm 121 ℃ rau 7 hnub, nrog rau tom kawg yog ho zoo dua qub. Yog vim li cas tej zaum yuav yog tias PPG molecules muaj ceg saws, uas tsis tsim nyog rau cov txheej txheem tsis tu ncua ntawm elastic molecules thiab txo cov cua sov ntawm lub cev elastic. Lub thermal stability ntawm polyethers yog: PTMEG>PEG>PPG.
Lwm pab pawg ua haujlwm hauv polyurethane elastomers, xws li urea thiab carbamate, kuj raug oxidation thiab hydrolysis cov tshuaj tiv thaiv. Txawm li cas los xij, pawg ether yog qhov yooj yim tshaj plaws oxidized, thaum pawg ester yog qhov yooj yim tshaj plaws hydrolyzed. Qhov kev txiav txim ntawm lawv cov antioxidant thiab hydrolysis kuj yog:
Antioxidant kev ua haujlwm: esters> urea> carbamate> ether;
Hydrolysis tsis kam: ester
Txhawm rau txhim kho oxidation tsis kam ntawm polyether polyurethane thiab hydrolysis tsis kam ntawm polyester polyurethane, additives kuj ntxiv, xws li ntxiv 1% phenolic antioxidant Irganox1010 rau PTMEG polyether elastomer. Lub zog tensile ntawm no elastomer tuaj yeem nce ntxiv los ntawm 3-5 zaug piv rau yam tsis muaj cov tshuaj tua kab mob antioxidant (kuaj cov txiaj ntsig tom qab kev laus ntawm 1500C rau 168 teev). Tab sis tsis yog txhua tus antioxidant muaj kev cuam tshuam rau polyurethane elastomers, tsuas yog phenolic 1rganox 1010 thiab TopanOl051 (phenolic antioxidant, hindered amine light stabilizer, benzotriazole complex) muaj cov teebmeem tseem ceeb, thiab cov qub yog qhov zoo tshaj plaws, tej zaum vim phenolic antioxidants muaj kev sib raug zoo nrog elastomers. Txawm li cas los xij, vim yog lub luag haujlwm tseem ceeb ntawm phenolic hydroxyl pawg hauv kev ua kom ruaj khov ntawm phenolic antioxidants, kom tsis txhob muaj cov tshuaj tiv thaiv thiab "tsis ua haujlwm" ntawm pawg phenolic hydroxyl no nrog cov pab pawg isocyanate hauv lub cev, qhov piv ntawm isocyanates rau polyols yuav tsum tsis txhob ua. loj heev, thiab antioxidants yuav tsum tau ntxiv rau prepolymers thiab chain extenders. Yog hais tias ntxiv thaum lub sij hawm zus tau tej cov prepolymers, nws yuav zoo heev cuam tshuam cov nyhuv stabilization.
Cov additives siv los tiv thaiv hydrolysis ntawm polyester polyurethane elastomers yog tsuas yog carbodiimide tebchaw, uas react nrog carboxylic acids generated los ntawm ester hydrolysis nyob rau hauv polyurethane elastomer molecules los tsim acyl urea derivatives, tiv thaiv ntxiv hydrolysis. Qhov sib ntxiv ntawm carbodiimide ntawm ib feem ntawm 2% mus rau 5% tuaj yeem ua kom cov dej ruaj khov ntawm polyurethane los ntawm 2-4 zaug. Tsis tas li ntawd, tert butyl catechol, hexamethylenetetramine, azodicarbonamide, thiab lwm yam kuj muaj qee yam los tiv thaiv hydrolysis.
04 Cov yam ntxwv tseem ceeb ntawm kev ua haujlwm
Polyurethane elastomers yog cov txheej txheem ntau qhov thaiv copolymer, nrog cov saw hlau molecular tsim los ntawm cov ntu hloov tau yooj yim nrog cov iav hloov pauv kub qis dua chav sov thiab ntu ntu nrog iav hloov kub siab dua chav sov. Ntawm lawv, oligomeric polyols tsim cov ntu hloov tau yooj yim, thaum diisocyanates thiab cov saw hlau me me txuas ntxiv ua ntu ntu. Lub embedded qauv ntawm saj zawg zog thiab nruj ntu ntu txiav txim siab lawv cov kev ua tau zoo:
(1) Lub hardness ntau yam ntawm cov roj hmab zoo tib yam yog feem ntau ntawm Shaoer A20-A90, thaum hardness ntau yam ntawm yas yog txog Shaoer A95 Shaoer D100. Polyurethane elastomers tuaj yeem ncav cuag qis li Shaoer A10 thiab siab li Shaoer D85, tsis tas yuav muaj kev pabcuam muab tub lim;
(2) Lub zog siab thiab elasticity tseem tuaj yeem khaws cia nyob rau hauv ntau yam hardness;
(3) Kev hnav zoo heev, 2-10 npaug ntawm cov roj hmab ntuj;
(4) Kev tiv thaiv zoo rau dej, roj, thiab tshuaj lom neeg;
(5) Kev tiv thaiv siab, qaug zog, thiab kev co tsis kam, haum rau kev siv ntau zaus bending;
(6) Ua haujlwm kub tsis zoo, nrog qis-kub brittleness hauv qab -30 ℃ lossis -70 ℃;
(7) Nws muaj kev ua haujlwm zoo rwb thaiv tsev, thiab vim nws cov thermal conductivity tsawg, nws muaj cov rwb thaiv tsev zoo dua piv rau roj hmab thiab yas;
(8) Zoo biocompatibility thiab anticoagulant zog;
(9) Cov rwb thaiv tsev zoo heev, pwm tsis kam, thiab UV stability.
Polyurethane elastomers tuaj yeem tsim siv cov txheej txheem tib yam li cov roj hmab zoo tib yam, xws li plasticization, sib tov, thiab vulcanization. Lawv tuaj yeem raug molded nyob rau hauv daim ntawv ntawm cov kua roj hmab los ntawm pouring, centrifugal molding, los yog txau. Lawv kuj tuaj yeem ua rau hauv cov ntaub ntawv granular thiab tsim los ntawm kev txhaj tshuaj, extrusion, dov, tshuab molding, thiab lwm yam txheej txheem. Nyob rau hauv txoj kev no, nws tsis tsuas yog txhim kho kev ua haujlwm ntawm kev ua haujlwm, tab sis kuj tseem txhim kho qhov raug thiab qhov zoo ntawm cov khoom.
Post lub sij hawm: Dec-05-2023