Asbestos-Brucite-Polyphenylene Sulfide Composites. Part I: Chemical and Electrochemical Degradation in Hot Alkali

Abstract

Asbestos reinforced with 11-47% polyphenylene sulfide is 2.5-8 times more stable than plain asbestos or asbestos-brucite composites of equivalent composition when aged in boiling concentrated alkali. SEM and Ir spectroscopy show that asbestos hydrolysis is the main cause of material loss. Composites pressed between electrodes at 1 A/cm2 in 95 °C 50% KOH however undergo principal mechanical erosion and the minimum poly phenylene sulfide load to achieve satisfactory performance is ∼ 29%.

Organo-inorganic composite membranes: a mathematical modelling approach to the solid-liquid interaction properties of asbestos in its composites

“…The manufacture of the asbestos-PPS (ASB-PPS) composites from commercial crysotile asbestos (ASB) paper (0.55 mm thick) and polyphenylene sulphide, and of the asbestos-SPPS (ASB-SPPS) composites from ASB and polyphenylene sulphide sulphonic acid (SPPS) was accomplished as previously reported [2,6]. The polymer concentrations (% wt/wt) in the bulk (Xz) and in the surface (X2) phases of the membrane and the total polymer concentration (P) and brucite (B) concentration have been determined by infrared spectroscopy [2].…”

“…The polymer concentrations (% wt/wt) in the bulk (Xz) and in the surface (X2) phases of the membrane and the total polymer concentration (P) and brucite (B) concentration have been determined by infrared spectroscopy [2]. The acid equivalent concentration of the neat organic polymer (PAE = SO3H eq/g polymer) was obtained by titration with 0.1 y NaOH.…”

“…Also, because of the loss of silicon, the void volume of the initial material increases in the aged material and this also causes a change in the solid-liquid physical interaction. Degradation indeed involves a change in the initial microstructure, where asbestos is the mechanical support component [2], into one where the organic polymer seems to work as a binding agent [7] for the brucite particles formed. For the scope of this work, the fresh and aged materials have therefore been treated as separate sets.…”

“…At the same time, as the concentration ratio of the lipophilic organic polymer to the hydrophilic inorganic material increases, the chemical interaction between the solid phase and the external phase is subject to substantial changes. This manufacturing technique has also been found [2] to yield higher polymer concentration on the membrane surface faces than in the bulk of the solid phase. Therefore, both the physical structure and the chemical nature of the membrane change throughout the membrane phase.…”

“…Several multivariable mathematical models relating liquid sorption with the membrane polymer concentration and with the membrane acid equivalents, both in the bulk and surface phases, have been tested to fit the experimental data. The previous models [2] tested for asbestos coated with PPS did not account for the change in the polymer nature as given by the E W parameter.…”