Thermal characterisation of photo‐oxidized HDPE/Mater‐Bi and LDPE/Mater‐Bi blends buried in soil

Abstract

Blends of high and low density polyethylene with a commercial biodegradable material (Mater-Bi) were subjected to an accelerated soil burial test. A set of samples was previously photo-oxidized to evaluate the effects of UV-irradiation on the degradation in soil process of these blends. Thermogravimetric as well as calorimetric analysis were performed to study the biodegradation, photo-degradation and their synergetic effects. Differential scanning calorimetry was carried out to analyze the morphological changes as a consequence of the photo-oxidation process. UV-irradiation slightly modifies the crystalline content of HDPE/Mater-Bi blends, increasing the heterogeneity of this blend. Criado master curves were plotted to analyses the degradation kinetic model. Broido and Coats-Redfern methods have been used for calculating the Ea of the thermal decomposition mechanisms. Thermogravimetric results reveal that noncomplexed starch is more affected by biodegradation than the polyethylene matrix and the starch/ EVOH complexes chains from Mater-Bi. However, the effects of both photo-oxidation and biodegradation processes on the thermal decomposition of Mater-Bi is influenced by the polymeric matrix used. Previous photo-oxidation finds to slow down the degradative effects caused by the soil burial test on the HDPE/Mater-Bi blends.

Effect of a natural polyphenolic extract on the properties of a biodegradable starch-based polymer

“…4a) were more thermally stable than the untreated ones in the first weight-loss stage. The increased stability can be due to starch crosslinking, as already reported for Mater-Bi-based systems [39]. In the DTG curves, starch degradation showed a complex peak with a shoulder between 280 and 340 C. This pattern was also observed by other authors [42], and may be due to the different degradation rate of amylose and amylopectin.…”

“…At higher temperatures (>350 C), the thermal decomposition of the polyester portion could be observed [5,39]. In this range of weight loss, MB and MB4 displayed a similar behavior and the influence of the additive on the thermal stability was negligible.…”

“…That is, during aging, owing to the high temperature it is likely that the hydroxyl groups of pyranose rings in the starch fraction undergo condensation, resulting in water removal, and consequent ether linkage formation [38,39]:…”

Protection of high‐density polyethylene–silicon composites from ultraviolet–visible photodegradation

“…The mechanism of thermooxidative decomposition has been well reported and starts with the formation of radicals groups, which act as precursors of a complex process that dramatically reduces the molar mass of the original sample . As expected, the thermal decomposition of the commercial HDPE with oxygen showed a pattern that was more complex than that under an inert atmosphere, where just a peak at 485 °C at 10 °C/min is usually found . Complex decomposition steps were also discussed by Camacho et al .…”

Assessing the influence of cotton fibers on the degradation in soil of a thermoplastic starch‐based biopolymer

“…Scott et al [5] suggested that traditional techniques, as the measurement of weight loss changes for studying polymer biodegradation, have some limitations because of the adhesion of soil and fungi to the polymer, which can mask real results and thus induce misleading information. In contrast to this weight loss conventional technique, earlier studies have shown that thermal analysis can be an alternative to assess the degradation in soil studies, providing useful information about the irreversible macroscopic effects on the polymers caused by the degradation process [6–9]. Composites prepared from a thermoplastic starch‐based matrix (Mater‐Bi KE03B1®) reinforced with cotton fibers were characterized in the present work to study the influence of natural fibers on its degradation process in soil.…”