Polymerization of epoxy resins studied by positron annihilation

Citation
T. Suzuki et al., Polymerization of epoxy resins studied by positron annihilation, MAT RES INN, 4(5-6), 2001, pp. 273-277
Citations number
14
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
MATERIALS RESEARCH INNOVATIONS
ISSN journal
1432-8917 → ACNP
Volume
4
Issue
5-6
Year of publication
2001
Pages
273 - 277
Database
ISI
SICI code
1432-8917(200104)4:5-6<273:POERSB>2.0.ZU;2-N
Abstract
Positron annihilation lifetime spectroscopy (PALS) has been applied to stud y polymerization of epoxy resins of cresole novolac with a hardener of phen ol novolac. PALS uses positrons to probe the microstructure of a nanometer (nm) size. Using PALS polymerization can be followed through three states: powder (monomer), liquid and solid. PALS is a unique method for the detecti on of intermolecular spaces, hence polymerization was followed from the poi nt of view of free spaces (inter-molecular spaces) between polymer networks . The glass transition temperature (T-g) was determined from the temperatur e dependence of the positronium (Ps) lifetime. Although Tg determined by PA LS is usually lower than that determined by a mechanical analysis (TMA), it was observed that T-g approached the value determined by TMA after long cu ring. Ps can form bubbles in a liquid, and the surface tension of a mixture of the resin and the hardener was calculated from a simple empirical formu la using the Ps lifetime; the resulting value is similar to that of the bis phenol-A epoxy resin. Gelation was observed as an increase in the intensity of Ps and a sharp decrease in the lifetime.