Positron annihilation and electrical studies on the influence of loading magnesia nanoribbons on PVA-PVP blend. (September 2020)

• Record Type: Journal Article
• Authors: El-Gamal, S.; Elsayed, M.
• Is Part Of: Polymer testing. Volume 89(2020)
• Publication Date: 2020-09
• Subjects: Positron annihilation lifetime -- Free volume -- Nanocomposites -- PVA-PVP -- Magnesia -- J-E characteristics; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2020.106681
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: This work aims to study the effect of loading magnesia (0.5–2.0 wt% ) on the positron annihilation parameters and electrical properties of the PVA-PVP blend. The films were synthesized by solution casting and checked by different techniques. XRD and HR-TEM of sol-gel prepared magnesia revealed that the average crystallite size was 14.29 nm with ribbon-like morphology with varying widths and lengths up to a few micrometers. SEM showed that the blend surface appeared smooth and homogenous and this confirmed the compatibility between PVA and PVP. However, loading magnesia increased surface roughness. TGA confirmed the thermal stability enhancement of blend film with magnesia incorporation. Ortho–positronium lifetime τ3 and the free volume V f decrease with loading magnesia while the intensity I3 is nearly constant. These features were interpreted in view of the hole-filling mechanism, the interaction between magnesia & blend and magnesia morphology. The equilibrium swelling ratio ESR was found for the studied films and a positive correlation between ESR and V f was reported. The current density-electric field, J-E, characteristics were of non-ohmic type. J increased with increasing magnesia levels and heating. The Richardson-Schottky effect was the dominant dc conduction mechanism at low temperature and low magnesia loading levels while it changed to Poole–Frenkel emission at higher values. Finally, a correlation between Log J and the intensity I 2 was reported. Highlights: PVA-PVP was loaded by magnesia nanoribbons of different ratios which greatly affects the properties of the blend. Loading MgO increases the thermal stability of PVA-PVP. So, the films have the potential to be used as flame-retardants. The ortho-Ps lifetime and free volume decreases after loading and were discussed in view of the hole-filling mechanism. The Richardson-Schottky effect is the mechanism at low T & low levels MgO and changed to Poole–Frenkel at higher values.