Direct relationships between volume variations at macro and nanoscale in epoxy systems. PALS/PVT measurements

GOYANES, SILVIA; SALGUEIRO WALTER,; SOMOZA ALBERTO,; JOSE ANGEL, RAMOS; MONDRAGON IÑAKI,

POLYMER

Elsevier

Lugar: Amsterdam; Año: 2004 vol. 45 p. 6691 - 6697

0032-3861

 Abstract  The free volume in epoxy systems fully cured with aminic hardeners having different chemical structures was studied by means of positron  annihilation lifetimes spectroscopy. The results are compared with those obtained from the analysis of the macroscopic specific volume  changes by using pressure?volume?temperature experimental technique. An excellent correlation between the volumes measured at macro  and nanoscales was found. From this fact, it can be asserted that the variation of the specific volume is mainly controlled by the variation in  the average size of sub-nanometer size local free volumes, which are fixed by the chemical structure of hardener in fully crosslinked epoxy  networks. These results give the first evidence of the direct relation existing between macro and nanoscales in thermosetting networks. Keywords: Epoxy; Hardener; Chemical structure Epoxy; Hardener; Chemical structure Epoxy; Hardener; Chemical structure