Browsing by Author "Dreier, Julia"

Now showing 1 - 3 of 3

Open Access
Biobased immiscible polylactic acid (PLA) : poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blends : impact of rheological and non-isothermal crystallization on the bead foaming behavior
(2024) Brütting, Christian; Dreier, Julia; Bonten, Christian; Ruckdäschel, Holger
Nowadays, bead foams are of great interest due to their high lightweight potential. The processing of such foams strongly depends on the crystallization and rheological behavior of the polymers used. By blending polymers, these properties can be tailored to obtain beaded foams with low density, small cell size and high cell density. As a bio-based polymer, PLA is of great interest due to its renewable carbon source. PLA suffers from its low thermal and rheological properties, which can be compensated by using blends. The correlation between the PLA/PHBV ratio and the rheological as well as the crystallization behavior was investigated. The use of PHBV as a minor phase significantly changes the rheological properties and increases the crystallization behavior of PLA. These findings were applied to the foam extrusion process to obtain low density bead foams. Bead foams with densities below 100 kg/m 3 , mean cell sizes below 50 µm and cell densities of 1 × 10 7 cells/cm 3 were obtained.
Open Access
Investigation of the thermal and hydrolytic degradation of polylactide during autoclave foaming
(2021) Dreier, Julia; Brütting, Christian; Ruckdäschel, Holger; Altstädt, Volker; Bonten, Christian
Polylactide (PLA) is one of the most important bioplastics worldwide and thus represents a good potential substitute for bead foams made of the fossil-based Polystyrene (PS). However, foaming of PLA comes with a few challenges. One disadvantage of commercially available PLA is its low melt strength and elongation properties, which play an important role in foaming. As a polyester, PLA is also very sensitive to thermal and hydrolytic degradation. Possibilities to overcome these disadvantages can be found in literature, but improving the properties for foaming of PLA as well as the degradation behavior during foaming have not been investigated yet. In this study, reactive extrusion on a twin-screw extruder is used to modify PLA in order to increase the melt strength and to protect it against thermal degradation and hydrolysis. PLA foams are produced in an already known process from the literature and the influence of the modifiers on the properties is estimated. The results show that it is possible to enhance the foaming properties of PLA and to protect it against hydrolysis at the same time.
Open Access
Miscibility and phase separation in PMMA/SAN blends investigated by nanoscale AFM-IR
(2021) Resch, Julia; Dreier, Julia; Bonten, Christian; Kreutzbruck, Marc