Reokinetičko izučavanje umrežavanja α,ω-dihidroksi oligo(alkilen maleata) triizocijanatima
| Autor: | Branko Dunjic, Maurice Sepulchre, Marie‐Odile Sepulchre, Nicolas Spassky, Slavko Vukasinovic, A Jasna Djonlagic |
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| Rok vydání: | 2003 |
| Předmět: |
02 engineering and technology
General Chemistry Dynamic mechanical analysis 010402 general chemistry 021001 nanoscience & nanotechnology rheokinetic analysis 01 natural sciences Chemical reaction Isocyanate 0104 chemical sciences Reaction rate Polyester lcsh:Chemistry chemistry.chemical_compound chemistry lcsh:QD1-999 polyurethane Autoacceleration Polymer chemistry 0210 nano-technology hydroxyl terminated polymaleates Prepolymer Polyurethane |
| Zdroj: | Journal of the Serbian Chemical Society Journal of the Serbian Chemical Society, Vol 68, Iss 3, Pp 147-162 (2003) |
| Popis: | The crosslinking reaction of three series of α,ω-dihydroxy oligo(alkylene maleate)s with a trifunctional isocyanate was followed by dynamic mechanical analysis and FTIR spectroscopy. The evaluation of rheological parameters such as storage G’ and loss modulus G", was recorded. A typical G’versus time curve has a characteristic "S" shape, indicating autoacceleration of the crosslinking reaction. The whole curing process starting from G’equal G", or the beginning of gelation is described by a second - order phenomenological rheokinetic equation which takes into account the autoacceleration effect, the latter being a consequence of the superposition of both the chemical reaction and phase segregation. It appears that the crosslinking reaction rate depends on the concentration of the functional groups, i.e., on the molecular weight of the polyester prepolymer and on the length of the aliphatic sequence in the repeating unit or the segmental mobility. The crosslinking rate decreases in the order: poly(octamethylene maleate) gt poly(hexamethylene maleate) gt poly(butylene maleate). Kinetika reakcije umrežavanja je izučavana pomoću dinamičke mehaničke analize i FTIR spektroskopije na tri serije α,ω-dihidroksi-oligo(alkilen-maleata) i trifunkcionalnog izocijanata. Reakcija umrežavanja polimera praćena je preko promene reoloških parametara kao što su modul sačuvane energije G’ i modul izgubljene energije G". Kriva zavisnosti G’ od vremena ima karakterističan "S" oblik, što ukazuje na samoubrzavanje pri reakciji umrežavanja. Ceo proces umrežavanja od početka želiranja, odnosno, od trenutka kada je G’ jednako G", je opisan fenomenološkom reokinetičkom jednačinom drugog reda koja uzima u obzir efekat samoubrzavanja, kao posledicu superpozicije hemijske reakcije i morfoloških promena. Pokazano je da brzina reakcije umrežavanja zavisi kako od koncentracije funkcionalnih grupa, tj. od molarne mase poliestarskog pretpolimera, tako i od dužine alifatične sekvence u osnovnom motivu ili segmentalne pokretljivosti. Brzina reakcije umrežavanja opada u nizu poli(oktametilen–maleat) gt poli(heksametilen–maleat) gt poli(butilen–maleat). |
| Databáze: | OpenAIRE |
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