The influence of polyoxymethylene molar mass on the oxidative thermal degradation of its nanocomposites with hydroxyapatite

Abstract

In this paper, the influence of mass-average molar mass (M w ) of polyoxymethylene (POM) copolymer on the thermooxidative degradation behavior of its nanocomposites with hydroxyapatite (HAp) is reported. POM copolymers' thermal stability slightly decreases with a decrease in mass-average molar mass. Thermal stability of POM/HAp nanocomposites is lower in comparison with pure POM, and it gets lower with a decrease in massaverage molar mass of POM copolymer. For POM copolymer with the highest molar mass, thermal stability of POM/HAp nanocomposite was ca. 30°C lower than for pure POM. To get a more in-depth insight into the decomposition process, kinetic analysis of POM/HAp nanocomposite thermal degradation process was performed using Friedman, Ozawa-Flynn-Wall and multiple nonlinear regression methods. The best fit for pristine T2, T3 and T4 copolymers with different molar mass of 100768, 74727 and 68377 g mol -1 , respectively, was obtained for onestage degradation mechanism with autocatalysis, while for T2/10 % HAp and T3/10 % it was parallel reaction model with autocatalysis (Bna) and phase-boundary reaction models (R3). For T4/10 % HAp, the best approximation was found for R2-Bna-D3 reaction model. From hyphenated TG-MS and TG-FTIR thermoanalytical studies, it was found that the main degradation product for POM/HAp nanocomposites is formaldehyde and the amount of other degradation products is lower in comparison with nonmodified POM copolymers.

Thermal behaviour of low-rank Indian coal fines agglomerated with an organic binder

“…Approximately 10 mg of the sample was used for each experimental run for each of the samples. The role of mass transfer phenomena was also experimentally verified by comparing the TG/DTA plots for the same material, but at: (1) different particle sizes (0.075, 0.151, and 0.211 mm) (for internal diffusion) and (2) different flow rates (40,50, and 60 mL min -1 ) (for external diffusion).…”

“…The Netzsch Thermokinetics 3.1 (version 072010) was used for processing of the non-isothermal data [3,39,40]. The activation energies (E), which depend on the degree of conversion (a), were evaluated by this software package which allows the evaluation of the dependence of E on a by means of FR and FWO model-free methods.…”

Modeling of the Kinetics of Polyoxymethylene Decomposition under Oxidative and Non-Oxidative Conditions

“…The course of the curves shown in Figures 6-8 confirmed that the decomposition of homopolyacetals can be a single or multi-stage process depending on their origin and thermal history, which may result, among other factors, from only univariate or invariant apparent activation energy as the reaction progresses. Following the literature data, it would be expected that the activation energy for the homopolymer should be in the range of 40-160 kJ/mol [3,4]. In the case of the graph of changes in apparent activation energy as a function of the partial mass loss of the POM-P sample, a similar trend of changes in activation energy was observed in the range of 0.4-0.8 weight loss (regardless of the nature of the atmosphere in which TG measurements were carried out and the calculation model used).…”

“…Polyoxymethylene (polyacetal, polyformaldehyde, and POM), is a popular thermoplastic engineering polymer due to its good mechanical properties. It has a wide range of applications mainly in the mechanical industry [ 1 , 2 , 3 ]. However, POM is thermally unstable because its repeating oxymethylene chain units are usually terminated with hemi formal terminals [ 2 , 3 , 4 ].…”

Impact of adsorption of poly(aspartic acid) and its copolymers with polyethylene glycol on thermal characteristic of Cr2O3

“…The interactions between various polymers and the solid particles using the thermogravimetric methods are subject of numerous research [38][39][40][41][42][43][44][45][46][47][48][49][50]. Figures 7-10 present the TG, DTA and DTG curves for the chromium (III) oxide samples, both unmodified and modified with the adsorption layer formed by the analyzed homo-and copolymers.…”