Thermal and flammability studies of poly(vinyl alcohol) composites filled with sodium hydroxide

Abstract

Poly(vinyl alcohol) (PVA) is a polymer of great value due to its wide spread applications. The present article describes the effect of sodium hydroxide on the flammability, thermal degradation, and tensile strength properties of PVA. The PVA/sodium hydroxide composite films at different loading levels of sodium hydroxide, i.e., 0.5, 1, 2, 3, and 4.5 wt % were prepared by solution casting technique. Dynamic thermogravimetry was used to study the thermal degradation behavior of samples at four different linear heating rates, i.e., 2.5, 5, 10, and 20 °C min−1 under nitrogen atmosphere. The degradation activation energy values were calculated using reliable and preferred multiple‐heating rate methods. Limiting oxygen index (LOI) and UL 94 tests were carried out to check the flammability behavior of the samples. The presence of sodium hydroxide in PVA brought significant changes in the thermal and flammability performance. PVA/sodium hydroxide samples though showed lower initial decomposition temperature, but overall more thermal stability results as evidenced from the higher activation energy and char residue values. LOI and UL 94 tests indicate that sodium hydroxide greatly enhanced the flame retardancy of PVA/sodium hydroxide films. Based on the thermal and flammability level, the optimum concentration of sodium hydroxide is worked out. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Reduction of PVA Aerogel Flammability by Incorporation of an Alkaline Catalyst

“…With the increase in char yield from 7.9 to as much as 23.5% (at 0.5% NaOH), approximately logarithmic relations between NaOH concentration and char yield are observed, with the data point at 0.001 being the only outlier; by increasing the addition levels of the base, the maximum mass-decomposition rates (dW/dT) dropped, as expected from 2.71 to under 2.0. Previously reported work by Arora and coworkers [28], examining the effects of as much as 5 wt% NaOH to PVA films, proposes that dehydration of alcohol groups in PVA likely commence at decreased temperatures when the alkaline agent is added-this is consistent with our proposed alkaline catalysis in PVA aerogels. The previous workers observed an increase in limiting oxygen index (LOI) from 20.5 to 27.2 with the incorporation of 4.5% NaOH.…”

“…As can be seen in Table 2, the specific compressive moduli increased from 4.8 ± 1.6 to 16.3 ± 3.0 MPa cm 3 /g as the NaOH was increased from 0% to 9.1%. The increases in mechanical properties of the aerogels with increasing NaOH levels differs from the observed mechanical properties of PVA films, which incorporate that same additive [28]. Our previous work with PVA aerogels has shown that their mechanical properties are extremely sensitive to the skeletal density of aerogel "struts", which resemble the cellular walls in foams, as well as the morphology of the aerogels [3,5,[11][12][13].…”

“…The few known flame retardants that could potentially resolve the toxicity/mechanical Gels 2021, 7, 57 2 of 11 properties problems require high loadings, increasing final product densities and costs [22], limiting their commercial attractiveness [23,24]. The thermal degradation of PVA has been addressed by some authors, and to a limited extent the flammability of this polymer has also been explored [25][26][27][28]. These previous works have focused on dense films and molded PVA samples; one of those studies also showed that added NaOH could lower the flammability of the system, though no explanation for the effect was given [25].…”

Achieving Stable Molybdenum Oxide Cathodes for Aqueous Zinc‐Ion Batteries in Water‐in‐Salt Electrolyte

“…[ 12 ] These previous reports mainly focused on mitigating the dissolution and structural distortion of the cathode materials by sophisticated material composition tuning and/or incorporation of flammable PVA electrolyte additives. [ 13 ]…”

“…These previous reports mainly focused on mitigating the dissolution and structural distortion of the cathode materials by sophisticated material composition tuning and/or incorporation of flammable PVA electrolyte additives. [13] The 30 m ZnCl 2 WISE was first introduced in 2018, [14] enabling a dendrite-free Zn metal anode with a high Coulombic efficiency (CE) of 95.4%. The same group applied the ZnCl 2 WISE to a Ca 0.20 V 2 O 5 •0.80H 2 O cathode, [1a] and demonstrated increased operating potential and specific capacity compared to those obtained in the 1 m counterpart.…”