Effect of interfacial interaction on free volumes in phenol-formaldehyde resin–carbon nanotube composites: positron annihilation lifetime and age momentum correlation studies

Abstract

The phenol-formaldehyde-carbon nanotube composites were characterized for their free volume properties and interfacial interactions between nanotubes and the polymer matrix. The base polymeric material was a novolac type phenol-formaldehyde (PF) condensation resin cross-linked with para-toluene sulfonic acid. Multi-wall carbon nanotubes (MWCNTs) were synthesized using a catalytical chemical vapor deposition method and characterized using high-resolution transmission electron microscopy. The PF resin-carbon nanotubes composites having 2, 5, 10 and 20% (w/w%) MWCNTs were prepared. The crystallinity and morphology of the samples were characterized using X-ray diffraction and scanning electron microscopy. The free volume size in the polymer nanocomposites was observed to increase with the increase in nanotube content. Positron age momentum correlation (AMOC) studies revealed the electronic environment around different positron annihilation sites. The studies showed that ortho-positronium principally annihilates from interfacial regions of polymer and nanotubes in the nanocomposite. The positron lifetime studies together with AMOC measurements indicate an increase in the free volumes at the interface of polymer and MWCNTs in the composite. The free positron intensities showed that the polymer and nanotubes are weakly interacting in this system.

Graphene networks and their influence on free-volume properties of graphene–epoxidized natural rubber composites with a segregated structure: rheological and positron annihilation studies

“…[75][76][77] The free-volume hole probability density function V f (pdf) is shown in Fig. 44,75 As shown in Fig. The appearance of lower size freevolume holes can be attributed to the formation of GE networks which provide a high density interfacial region that is missing in the neat ENR.…”

“…The o-Ps annihilation lifetime distributions obtained from CONTIN analysis can be transformed into free-volume hole distributions according to eqn (4) and (5) [74][75][76] …”

“…[75][76][77] The free-volume hole probability density function V f (pdf) is shown in Fig. [75][76][77] The free-volume hole probability density function V f (pdf) is shown in Fig.…”

Free volume and lamellar structure of poly vinyl alcohol-nanosized BaTiO3 composite: Positron annihilation and small angle X-ray scattering study

“…PALS has been shown to be an efficient technique for the investigation of the changes in free volume structure of polymer matrix through annihilation parameters of o-Ps probe [14,15,[19][20][21]26,27]. In order to elucidate the changes in the free volume structure of PVA matrix, the PALS spectra were analysed using a computer program PALSFIT [28].…”

“…In last few years, we have used positron annihilation lifetime spectroscopy (PALS) for the characterization of molecular packing (free volume structure) of polymer nanocomposites [14,15,[19][20][21]. It has been shown through these studies that like pure polymers, the molecular packing of amorphous phase of a semicrystalline polymer in its nanocomposites can be efficiently characterized through the ortho-positronium probe.…”