Effect of epoxide equivalent on microstructure of epoxy/rectorite nanocomposite studied by positrons

Free-volume properties of epoxy composites and its relation to macrostructure properties

“…The shortest and intermediate lifetime components, ( 1 and I 1 ) and ( 2 and I 2 ) were assigned to p-Ps and free positron annihilation, respectively. The longest component ( 3 and I 3 ) is attributed to the o-Ps pick-off annihilation in the free-volume holes of polymer [18]. The o-Ps lifetime ( 3 ) directly correlates with the size (V h ) of freevolume hole whereas its intensity (I 3 ) contains information about the fraction (F) of the free-volume holes [25].…”

“…Accordingly, a strong interaction is created between the filler and the molecules of epoxy matrix. This interaction can enhance the interfacial adhesion and leads to interfacial layer formation [18] as well as a creation of free-volume holes with large sizes and low fractions. On the other hand, SiC, TiO 2 and Al 2 O 3 as fillers have the same influence on free-volume properties of cured epoxy.…”

“…Positronium (Ps) has two spin states called ortho-positronium (o-Ps) and para-positronium (p-Ps), which have lifetimes of 0.125 and 140 ns in vacuum, respectively. Several investigations used PALS to determine the mean size of the free-volume holes and its fraction in polymers as a function of filler contents [18][19][20].…”

Non‐destructive fatigue damage detection of carbon fiber‐reinforced thermoplastics using positron annihilation method

“…The authors applied two positron annihilation methods for the detection of fatigue damage in Type 316 stainless steel, in which the positron annihilation parameters increased with increasing fatigue loading cycles, and those parameters were related to the small fatigue crack growth behavior 14 . For polymer materials, Liu et al estimated free volume radius in epoxy/rectorite nanocomposite using positron annihilation lifetime spectroscopy and found the dependence of free volume radius on epoxy equivalent values 16 . There have been a few attempts to evaluate free volume properties using positron annihilation methods 17,18 .…”

The use of positron annihilation to study polyacrylamide and polymethylmethacrylate—Alcohols and diols mixture

“…It was also noticed that the DB spectroscopy was very sensitive to the microstructural change in HDPE (CB)/EPDM composites. In addition, the microstructure of epoxy/ rectorite nanocomposites with different epoxide equivalent ranging from 188 to 1110 is investigated by Liu et al [5] using PAL and DBAR techniques. They found that the fractional free volume dramatically decreases with increasing epoxide equivalent and free-volume hole size is slightly affected by epoxide equivalent.…”