On the viscoelastic properties of poly(vinyl alcohol) and chemically crosslinked poly(vinyl alcohol)

Abstract

Poly(vinyl alcohol)(PVA) films chemically crosslinked with glutaraldehyde(GA) in the presence of HCl were prepared by casting from aqueous solutions. The PVA and PVA gels were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA); their swelling characteristics and tensile strength were also determined. The DSC results for the gels displayed depressions of the melting and crystallization temperatures, as well as a decrease of the heat of fusion, when compared to those of PVA free of crosslinker. The DMA analysis revealed that: (1) The glass transition temperature of the wet PVA was lower than that of the dry one, indicating that the water had a plasticizing effect.(2) The gels had a lower glass transition temperature than PVA. (3) The glass transition temperature of the wet gels increased with increasing crosslink density. Possible explanations are provided for these observations. Whereas the thermogravimetric curves of PVA exhibited a single degradation peak, two degradation peaks were detected for the crosslinked PVA. The wet PVA and PVA gels displayed lower tensile strengths and higher elongations than the dried ones.

Investigation on the thermal properties of new thermo-reversible networks based on poly(vinyl furfural) and multifunctional maleimide compounds

“…The first one is attributed to the local relaxation of the crystalline phase, while the second one is caused by the melting of the crystalline domains [39][40][41]. In our case the first peak of PVA is shifted to higher temperatures (147.6°C), while the melting of the crystalline domains could not be observed.…”

“…The drop of E! and two peaks of E% and tan & centred at 42.4 and 54.4°C, respectively can be attributed to the glass transition of the amorphous phase [39][40][41]. Moreover, the small decrease of E!…”

Influence of Glyoxal in the Physical Characterization of PVA Nanofibers

“…Table 2 illustrates that when glyoxal is introduced in PVA solution T m is more or less the same for every sample and we can´t suggest there is a variation as very little changes can be observed. Previous studies have reported that, crystallinity is reduced as glyoxal content increases [14,29], and they concluded that the crosslinking reaction reduced PVA crystallinity due to change of crystalline morphology induced by the crosslinker. Thus fits with our analysis for glyoxal samples when concentration is higher than 0.4 g/L.…”

Electrospun protective self‐healing coatings for light alloys: A better understanding of the intrinsic potential of the technology

“…Thermally treated PVA mats at 120°C and 150°C containing either organic or inorganic cerium showed significant decrease in the melting temperature and crystallinity degree compared to as‐spun (without treatment) mats (i.e., 220°C and 43% for S0–1 and 212°C and 46% for S0–2, respectively). Previous studies have reported that the activation of the cross‐linking reaction resulted in lower crystallinity degree accompanied by decreased melting temperatures. The X c values of the electrospun mats containing organic cerium were about 27% and 38% for S1 and S2 samples, respectively.…”