Open spaces and molecular motions of acrylic epoxy-based network polymers probed by positron annihilation

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

“…It is worth to note that the value of v h increases as hardener chemical structure grows in complexity (see Table 1) and that such a complexity could hinder good packaging of the molecular structures. These results are in good agreement with other literature reports [5,6,[25][26][27][28],…”

“…The mean size of the holes forming the free volume can be roughly estimated by means of a simple quantum mechanical model [24][25][26]. o-Ps in a hole is approximated to a particle in a spherical potential well with radius R 0 .…”

Network Formation and Physical Properties of Epoxy Resins for Future Practical Applications

“…159 The effect of change in the architecture of the epoxy−amine network on the free volume content has been studied using positron annihilation lifetime spectroscopy (PALS). 160,161 PALS is an analytical technique that can quantify nanoholes on the order of 0.2−2.0 nm in diameter, which are consistent with the interchain dimensions of most polymers. 160 Pujari et al reported that the free volume fraction increased with increasing cross-linking density although the size decreased.…”

“…160,161 PALS is an analytical technique that can quantify nanoholes on the order of 0.2−2.0 nm in diameter, which are consistent with the interchain dimensions of most polymers. 160 Pujari et al reported that the free volume fraction increased with increasing cross-linking density although the size decreased. 162 This is in good accordance with the result shown in Figure 15.…”

“…For example, as the cross-linking density increases, the T g also increases. , This is generally explained in terms of the dense glassy state, in which network chains tightly pack together, leading to a reduction in the free volume. , If dangling chains exist in the network, the T g tends to decrease because chains can be actively moved within a certain part of the free space . The effect of change in the architecture of the epoxy–amine network on the free volume content has been studied using positron annihilation lifetime spectroscopy (PALS). , PALS is an analytical technique that can quantify nanoholes on the order of 0.2–2.0 nm in diameter, which are consistent with the interchain dimensions of most polymers . Pujari et al reported that the free volume fraction increased with increasing cross-linking density although the size decreased .…”