Kinetics of the Thermal Degradation of Poly(lactic acid) and Polyamide Bioblends

Abstract

Poly(lactic acid) (PLA) and biosourced polyamide (PA) bioblends, with a variable PA weight content of 10–50%, were prepared by melt blending in order to overcome the high brittleness of PLA. During processing, the properties of the melt were stabilized and enhanced by the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE). The general analytical equation (GAE) was used to evaluate the kinetic parameters of the thermal degradation of PLA within bioblends. Various empirical and theoretical solid-state mechanisms were tested to find the best kinetic model. In order to study the effect of PA on the PLA matrix, only the first stage of the thermal degradation was taken into consideration in the kinetic analysis (α < 0.4). On the other hand, standardized conversion functions were evaluated. Given that it is not easy to visualize the best accordance between experimental and theoretical values of standardized conversion functions, an index, based on the integral mean error, was evaluated to quantitatively support our findings relative to the best reaction mechanism. It was demonstrated that the most probable mechanism for the thermal degradation of PLA is the random scission of macromolecular chains. Moreover, y(α) master plots, which are independent of activation energy values, were used to confirm that the selected reaction mechanism was the most adequate. Activation energy values were calculated as a function of PA content. Moreover, the onset thermal stability of PLA was also determined.

Improvement of the Thermal Stability of Polymer Bioblends by Means of Reactive Extrusion

“…For both types of bioblends (with and without reactive), the mechanism leading to lower IME values (4.6–7.2%) was that of random scission of macromolecular chains. This mechanism for neat PLA, PLA-containing blends and PLA-containing nanocomposites was already elucidated in previous works [ 6 , 34 , 35 , 36 ]. It must be noted that diffusion mechanisms are the least suitable given that they presented IME values of 42.0–67.3%.…”

Multiple Reprocessing of Conductive PLA 3D-Printing Filament: Rheology, Morphology, Thermal and Electrochemical Properties Assessment

“…For all materials, there are two thermal degradation steps. The first one with maximal degradation temperature T max1 ~ 365 °C is related to the decomposition of PLA [ 36 ], while the second one T max2 ~ 460 °C is probably from a polymeric additive used by the producer of the conductive PLA 3D filament. According to the technical specifications, the basic composition of the filament employed is the following: poly(lactic acid) >65%, carbon black <21.4%, and polymer (unknown composition—used probably as a plasticizer or an adhesive agent) <12.7%, which is in agreement with our results and the recently published papers [ 37 , 38 ].…”

Medical-Grade Poly(Lactic Acid)/Hydroxyapatite Composite Films: Thermal and In Vitro Degradation Properties

“…In addition to total weight loss, the thermogravimetric analysis has indicated changes in the thermal stability of prepared samples. Depending on the degree of crystallinity, molecular weight, the PLA enantiomer ratio and polymer purity, the degradation temperature of PLA polymer usually varies between 290–380 °C [ 21 , 22 ]. Each of the mentioned PLA properties can significantly influence thermal and degradation properties and cannot be considered in an isolated way.…”