Premium
Composition‐dependent properties of segmented polyurethanes
Author(s) -
Privalko Valery P.,
Shapoval Raissa L.,
Usenko Andrey A.,
Oranskaya Elena I.
Publication year - 1997
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11743
Subject(s) - materials science , volume fraction , dispersity , glass transition , polymer chemistry , adipate , molar mass , mole fraction , thermodynamics , polymer , composite material , chemistry , physics
We studied segmented polyurethanes (SPU) from poly(diethylene glycol adipate) with molar masses M SFT = 780, 1365, 1780 and 3200 g/mol (soft fragments, SFT), 2,4‐toluene diisocyanate and 2,4‐toluene diamine (stiff fragments, STF) with essentially monodisperse molar mass distribution of STF. They were characterized by WAXS, SAXS, heat capacity measurements, mainly from 150–450 K, and enthalpies of solution in dimethyl formamide at room temperature, ΔH sol . The experimental results may be summarized as follows.The glass transition temperatures of SFT decrease with an increase of M SFT , but remain essentially composition‐invariant at fixed M SFT , whatever the STF volume fraction φ. The surface‐to‐volume ratio of STF domains exhibits sudden, jump‐like transitions at volume fractions φ* = 0.23 and φ** = 0.40, respectively. Exothermic (i.e., negative) values of Δ H SOl exhibit a jump‐like decrease at φ* = 0.23.It has been shown that the main cause of the latter effect is the transition of SFT from a somewhat extended to an essentially unperturbed conformation.