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Polylactide (PLA) is one of the most important bioplastics on the market with a permanent growth in production capacity. Due to its good mechanical properties, it is comparable to polystyrene. But in terms of foaming the melt strength and extensibility of commercial polylactide are rather low. Therefore such commercial grades often need to be chemically modified to induce crosslinking, chain extension or grafting by means of reactive extrusion on a twin-screw extruder. In this work different polylactide grades were used, to better understand the influence of the molecular characteristics, such as molecular weight, acid value and D-content, not only on the modification mechanism, but also on the foam properties. [ABSTRACT FROM AUTHOR]

The major drawbacks of Poly(lactic acid) (PLA) bioplastic are its cost and brittleness. This study aims to reduce the cost by foaming PLA reinforced with wood flour. A series of PLA/ natural fiber (WF) composite was prepared by using WF of selected conifers up to 5 wt%; each composite formulation was then foamed using 2 wt% of Azodicarbonamide (ADC) as chemical foaming agent. ADC effectively reduced the density of PLA and the PLA/WF composite foam by about 45% to 0.64 g/cm³ from 1.24 g/cm³ of neat PLA and 1.26 g/cm3 of PLA/WF composites when 2 wt% ADC was applied. Mechanical behaviors in terms of compressive and impact properties were investigated. With the presence of WF, the compressive stress increased with the WF content due to the good interfacial adhesion between the PLA matrix and the WF. This was verified by microscopic observation, leading to efficient stress transfer at the interface between PLA matrix and the WF. The presence of WF raised the specific compressive modulus and strength of PLA/WF composites to around 0.94 GPa·cm3/g and 2.65 MPa·cm3/g but foaming the PLA or the PLA/WF composites led to a dramatic reduction of the compressive modulus to 0.2-0.4 GPa·cm3/g, implying that the PLA and the PLA/WF foams had become softened. This was evidently observed in the significant reduction of hardness coupled with the vast drop of stress required to compressively deform the foams. [ABSTRACT FROM AUTHOR]

Blends of Poly-L-Lactic Acid (PLLA) with two Poly-Lactic Acid (PLA) in different proportions (90/10 and 70/30) were utilized in order to produce biodegradable and biocompatible scaffolds for soft tissue engineering applications. The scaffolds were produced via thermally induced phase separation (TIPS) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection). Moreover a DSC analysis was carried out on the as-obtained scaffold in order to obtain information about theirs thermal properties (enthalpy of melt and crystallization). The results showed that is possible to prepare scaffolds of PLLA/PLA via TIPS. Moreover, the PLA seems to influences the TIPS process in terms of demixing temperatures. The data confirm that the morphology and the mechanical properties of the scaffold can be tuned, starting from PLLA blends and using PLA with different molecular weights. [ABSTRACT FROM AUTHOR]