Compatibilization of Poly(Lactic Acid) (PLA)/Plasticized Cellulose Acetate Extruded Blends through the Addition of Reactively Extruded Comb Copolymers

Alkali, thermal, or thermo-alkali pre-treatment to improve the anaerobic digestion of poly(lactic acid)?

Replacing petroleum-based plastics with biodegradable polymers is a major challenge for modern society especially for food packaging applications. To date, poly(lactic acid) represents 25 % of the total biodegradable plastics and it is estimated that, in the future, it could become the main contributor to the biodegradable plastics industry. Anaerobic digestion is an interesting way for the poly(lactic acid) end of life, even if its biodegradability is limited in mesophilic conditions. The aims of this study were to identify the best pre-treatment for maximizing the methane yield, minimizing the anaerobic digestion duration and limiting residual plastic fragments in the digestate. A systematic comparison was carried out between thermal, chemical, and thermo-chemical pre-treatment. Pre-treatment with 4 M KOH for 48 h at 35°C was effective in improving the mesophilic anaerobic digestion of the poly(lactic acid). Such pre-treatment allows obtaining 90 % of the theoretical methane potential, in 24 - 30 days. Importantly, such pre-treatment completely solubilized the poly(lactic acid), leaving no solid residues in the digestate. In addition, using KOH permits to avoid the sodication of the soil due to the digestate application as fertilizer.

Evaluation of Thermal Decomposition Kinetics of Poly (Lactic Acid)/Ethylene Elastomer (EE) Blends

The influences of ethylene-based elastomer (EE) and the compatibilizer agent ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) on the thermal degradation of PLA/EE blends were evaluated by the thermal degradation kinetics and thermodynamic parameters using thermogravimetry. The presence of EE and EBAGMA synergistically improved the PLA thermal stability. The temperature of 10% of mass loss (T10%) of PLA was around 365 °C, while in the compatibilized PLA/EE blend, this property increased to 370 °C. The PLA average activation energy (Ea¯) reduced in the PLA/EE blend (from 96 kJ/mol to 78 kJ/mol), while the presence of EBAGMA in the PLA/EE blend increased the Ea¯ due to a better blend compatibilization. The solid-state thermal degradation of the PLA and PLA/EE blends was classified as a D-type degradation mechanism. In general, the addition of EE increased the thermodynamic parameters when compared to PLA and the compatibilized blend due to the increase in the collision rate between the components over the thermal decomposition.

Tailoring the Barrier Properties of PLA: A State-of-the-Art Review for Food Packaging Applications

It is now well recognized that the production of petroleum-based packaging materials has created serious ecological problems for the environment due to their resistance to biodegradation. In this context, substantial research efforts have been made to promote the use of biodegradable films as sustainable alternatives to conventionally used packaging materials. Among several biopolymers, poly(lactide) (PLA) has found early application in the food industry thanks to its promising properties and is currently one of the most industrially produced bioplastics. However, more efforts are needed to enhance its performance and expand its applicability in this field, as packaging materials need to meet precise functional requirements such as suitable thermal, mechanical, and gas barrier properties. In particular, improving the mass transfer properties of materials to water vapor, oxygen, and/or carbon dioxide plays a very important role in maintaining food quality and safety, as the rate of typical food degradation reactions (i.e., oxidation, microbial development, and physical reactions) can be greatly reduced. Since most reviews dealing with the properties of PLA have mainly focused on strategies to improve its thermal and mechanical properties, this work aims to review relevant strategies to tailor the barrier properties of PLA-based materials, with the ultimate goal of providing a general guide for the design of PLA-based packaging materials with the desired mass transfer properties.

Chain Extension of Poly(Lactic Acid) (PLA)-Based Blends and Composites Containing Bran with Biobased Compounds for Controlling Their Processability and Recyclability

The present work focused on the research, design, and study of innovative chain extender systems of renewable origin for PLA-based biocomposites, reinforced with wheat bran as filler. The majority of employed chain extender compounds belongs to fossil world, affecting the biodegradability property which characterizes biopolymers. The aim of this work was thus to find promising biobased and sustainable alternatives to provide the same enhancements. According to this objective, epoxidized soybean oil (ESO) was chosen as principal component of the chain extender systems, together with a dicarboxylic acid, malic acid (MA), or succinic acid (SA). The reactivity of the modifier systems was previously studied through thermogravimetric analysis (TGA) and IR spectroscopy, to hypothesize the reaction mechanism in bran-filled blends. Hence, small-scale extrusion was carried out to investigate the effects of ESO/MA and ESO/SA on formulations of different composition (both pure PLA blends and composites). The variation of melt fluidity parameters was analyzed to define the optimized concentration of modifier systems. A comparison between the effects on blends of designed biobased systems and the action of fossil-based Joncryl was performed, to understand if the developed green solutions could represent competitive and efficient substitutes. The modified composites were characterized in terms of mechanical tests, degradation and thermal studies (TGA and DSC), and morphological analysis (SEM), to figure out their main features and to understand their potential in possible industrial applications.