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Polymer foams offer high sustainable performance in terms of their lightweight potential, insulation and high specific mechanical properties. The foaming of polymers depends on the properties of gas-laden solids or liquids. For foaming in the solid state, the foaming temperature must be higher than the glass transition temperature of the saturated polymer system. Moreover, the knowledge of sorption conditions and thermal properties is crucial for foam formation. In this study, the correlation between the glass transition temperature and the sorption conditions was investigated. This comparison was made by determining the sorption behavior for different pressure levels and the corresponding glass transition temperature using a high-pressure differential scanning calorimetry. The time, pressure and CO2 content were varied. For the first time, the Chow model could be verified for PLA with a coordination number of 3. [ABSTRACT FROM AUTHOR]

Polylactide has emerged as one of the most promising biopolymers due to its good mechanical properties, as reflected by the continual increase in its production volume per year. However, one of the main drawbacks of polylactide is its low melt strength, which is disadvantageous in terms of foaming. To overcome this issue, in this study, several chemical modifiers that induce crosslinking, chain extension or grafting were incorporated by reactive extrusion, which greatly affected the foaming process by increasing the molecular weight and thereby the melt properties of polylactide. By means of gel permeation chromatography, an increase in the molecular weight was observed in the modified polylactides. Elongational viscosity measurements indicate a dramatic viscosity increase for polylactide modified with a multifunctional epoxide and an organic peroxide. With pressure-induced batch foaming, almost all modifications, with the exception of styrene maleic anhydride, led to a decrease in foam density compared to the neat polylactide. [ABSTRACT FROM AUTHOR]