Understanding thermal decomposition kinetics of flame-retardant thermoset polylactic acid

Abstract

The Flynn-Wall-Ozawa method was applied to study the local activation energy of flame retardant thermoset PLA, and the results showed that with an increase of conversion of thermal degradation, the local activation energy was increased slowly. When the conversion of thermal degradation was under 15%, the activation energy of flame retardant thermoset PLA was lower than that of thermoset PLA, attributed to the low bond energy of P-C bond. When the conversion of thermal degradation exceeded 15%, the dehydration charcoal effect of phosphorous compound slowed down the process of thermal degradation, and the activation energy of flame retardant thermoset PLA was higher than that of thermoset PLA, indicating that the addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) enhances the thermal stability of thermoset PLA. The Coats-Redfern method and invariant kinetic parameters method were used to understand kinetics details about this process including the activation energy and apparent pre-exponential factor, and estimated contribution ratios for the 18 kinetic functions. The results showed that the addition of DOPO didn't impact the most important mechanism of thermal degradation but changed the contribution ratios of the 18 kinetic functions.According to the functional relationship between decomposition rate with temperature and quality conversion rate, three-dimension surface plots were made to understand the change regulation of decomposition rate. We found that the addition of DOPO reduced the decomposition rate of thermoset PLA, attributing to the dehydration charcoal effect of phosphorous compound which restrained the interesterification of PLA, and thus enhancing the thermal stability of thermoset PLA.

Nacre-Mimetic Green Flame Retardant: Ultra-High Nanofiller Content, Thin Nanocomposite as an Effective Flame Retardant

“…This is an isoconversional method which is independent of the conversion function. From this method, it is possible to quantify the activation energy (E a ) that can be obtained from the slope of the straight line by plotting log 10 β as a function of 1000/ T d as long as a single degradation mechanism is observed [ 62 ]. The Flynn-Wall-Ozawa method can be expressed by the Equation (1): where β is the constant heating rate, and T is the degradation temperature value at a given conversion α. E a is the activation energy for thermal degradation, R is the gas constant, and A is the frequency factor.…”

“…This is an isoconversional method which is independent of the conversion function. From this method, it is possible to quantify the activation energy (E a ) that can be obtained from the slope of the straight line by plotting log 10 β as a function of 1000/T d as long as a single degradation mechanism is observed [62]. The Flynn-Wall-Ozawa method can be expressed by the Equation (1):…”

Synthesis and Application Studies of DOPO-Based Organophosphorous Derivatives to Modify the Thermal Behavior of Polybenzoxazine

“…To obtain E a , TGA experiments were performed with different heating regimes under nitrogen atmosphere, and the Flynn–Wall–Ozawa (FWO) method [ 47 ] was used for the calculations for pBF-a and reactive mixtures with 3 mol% of DOPO-AP, DOPO-Van and DOPO-HQ. The FWO method is an isoconversional method that does not depend on the conversion function [ 48 ]. As long as the degradation mechanism stays the same for the investigated area, the method does not change with different heating rates for different conversions.…”

Recent Progress in Enhancing Poly(Lactic Acid) Stereocomplex Formation for Material Property Improvement

“…In order to address this grand challenge, tremendous efforts have been focused on the development of sustainable polymers toward an environmentally friendly future (Schneiderman and Hillmyer, 2017 ). Among various materials that have been proposed as promising candidates, polylactic acid (PLA) currently holds the leading position with the largest industrial production scale and explosive market growth (Murariu and Dubois, 2016 ), which has received significant attention for various applications such as biodegradable thermosets (Li et al, 2019 ), drug delivery (Casalini et al, 2019 ), shape memory materials (Cai et al, 2019 ), and food packaging (Bai et al, 2014 ; Tawakkal et al, 2014 ). However, key bottlenecks still remain for fully utilizing its potential for implementation into wide practical applications, which are associated with their inherently unsatisfactory material performances including low heating distortion temperature, brittleness, and poor thermal and hydrolytic stability (Rasal et al, 2010 ; Ren, 2010 ).…”