A Kinetic Analysis of the Thermal Degradation Behaviours of Some Bio-Based Substrates.

Ananya Thomas,Khalid Moinuddin,Paul Joseph,Svetlana Tretsiakova-Mcnally

doi:10.3390/polym12081830

Ananya Thomas, Khalid Moinuddin + Show 2 more

Open Access

https://doi.org/10.3390/polym12081830

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Journal: Polymers	Publication Date: Aug 15, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Victoria University, University of Ulster

Abstract

In the present paper, we report on a detailed study regarding the thermal degradation behaviours of some bio-sourced substrates. These were previously identified as the base materials in the formulations for fireproofing wood plaques through our investigations. The substrates included: β-cyclodextrin, dextran, potato starch, agar-agar, tamarind kernel powder and chitosan. For deducing the Arrhenius parameters from thermograms obtained through routine thermogravimetric analyses (TGA), we used the standard Flynn–Wall–Ozawa (FWO) method and employed an in-house developed proprietary software. In the former case, five different heating rates were used, whereas in the latter case, the data from one dynamic heating regime were utilized. Given that the FWO method is essentially based on a model-free approach that also makes use of multiple heating rates, it can be considered in the present context as superior to the one that is dependent on a single heating rate. It is also relevant to note here that the values of energy of activation (Ea) obtained in each case should only be considered as apparent values at best. Furthermore, some useful, but limited, correlations were identified between the Ea values and the relevant parameters obtained earlier by us from pyrolysis combustion flow calorimetry (PCFC).

Highlights

The worldwide interest in bio-based and degradable polymeric substrates has significantly accelerated in recent years [1,2,3,4]
For the calculations involving the Flynn–Wall–Ozawa (FWO) method [16,17,21], initially, the data points obtained from the thermogravimetric analyses (TGA) runs at various heating rates were transferred into an Excel file, and subsequently, the degrees of conversion were calculated using the following formula: α =/(mi − mf )
Given that the FWO method is essentially based on a model-free approach that makes use of multiple heating rates, it can be considered, in the present context, as superior to the in-house method, where the input data are essentially gathered from a thermogram obtained at a heating rate of 10 ◦ C·min−1

Summary

Introduction

The worldwide interest in bio-based and degradable polymeric substrates has significantly accelerated in recent years [1,2,3,4]. Most of these materials are thermally unstable compared to their synthetic counterparts, and are relatively flammable These effects often exacerbate the limitations in their wider applicability [8,9]. In order to address such issues, it is imperative to study the thermal degradation profiles of biomaterials with a view to deciphering the physio–chemical processes underpinning their degradation behaviours and combustion attributes. Once this goal is achieved, it is prudent to seek ways of improving the thermal stability and means of mitigating the overall fire hazards of such materials. These attempts would definitely lead to the utilization of better performing systems as environmentally benign fireproof coatings for wood materials [9]

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