Effect of curing agent polarity on water absorption and free volume in epoxy resin studied by PALS

Low-temperature positron annihilation study of B+-ion implanted PMMA

“…In the present work temperature dependent PALS measurements in the range of 50-300 K have been carried out to study positronium formation in the 40 keV B:PMMA with two ion doses of 3.13·10 15 …”

“…One of the methods widely used to study structureproperties relationships in polymeric materials is positron annihilation lifetime spectroscopy (PALS) (see, for instance [11][12][13][14][15][16][17] and references therein). The various important information on the positronium (Ps) formation (the electronpositron bound state) [18,19] in polymers can be extracted from PALS analysis.…”

Water transport in an epoxy–phenolic coating

“…Despite some apparently contradictory results, a picture has emerged where resins containing a greater proportion of free volume absorb more water when polarity is controlled [29][30][31][32][33]. However, equilibrium water uptake is primarily determined by the hydrogen bonding capability of the network (polarity) [34][35][36][37][38]. Meanwhile, water in epoxy resins has long been established by FTIR techniques to exist in both a free form (not interacting with the resin), and also in a bound state, hydrogen bonded to polymeric sites [39][40][41][42][43].…”

Mapping water uptake in an epoxy-phenolic coating

“…[36][37] [38][39] [40] Equilibrium water uptake is, however, primarily determined by the hydrogen bonding capability of the network (polarity). [41][42] [43] [44] In such studies, the polarity and/or free volume of resins is commonly controlled using the cross-linker to epoxy ratio [33] [45] or else the chemical structure of the cross-linker. [36][46] [47] When considering localised water uptake however, a major source of heterogeneity lies in the distribution of cross-linking density, which is typically large for epoxy resins (characterised by high molecular weight distributions prior to gelation, yielding broad Tg transitions by DSC analysis [48][49]).…”