Strategies to improve the mechanical properties of high-density polylactic acid foams

Abstract

In this study, different strategies to improve the mechanical properties of physically foamed high-density polylactic acid sheets were examined to produce polylactic acid foam sheets with tailor-made mechanical properties. The first part was the determination of the effect of different blowing agents (CO 2 and N 2 ) on the foam morphology. The second part of the study was the modification of the formulation. For this purpose, both a linear and a branching chain extender and a thermoplastic elastomer were used to improve the elongational properties (tensile modulus and strain at break) of the polylactic acid foam sheets. Additionally, the effect of the addition of cellulose fibers on the foam morphology and the mechanical properties was investigated. All experiments were carried out on a laboratory flat-film line. This extrusion line consists of a 30-mm single-screw extruder attached with a 250-mm flat sheet die. The results show a strong influence of the material formulation on the mechanical properties of the high-density foam sheets. Both the mechanical properties and foam morphology could be improved by the right material formulation. The addition of the thermoplastic elastomer leads to a better foam morphology and also to a reduced brittleness of the foam sheets. Furthermore, it could be demonstrated that cellulose fiber can be used as a nucleating agent for polylactic acid but causes a further decrease in the strain at break.

Foamability and viscosity behavior of extrusion foamed PLA–pulp fiber biocomposites

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Extrusion foaming of thermoplastic cellulose acetate sheets with HFO‐1234ze and co‐blowing agents

“…Extrusion foaming of thermoplastics with physical blowing agents (BAs) is a key‐enabling technology that can help to save primary resources such as crude oil by reducing the product's density. In order to control the foam properties, many studies on foam extrusion have focused on the optimization of process parameters such as foaming temperature, pressure gradient and die geometry or the modification of the molecular properties of the plastics . Another possibility to control the foaming process is the use of different BAs or BA mixtures that are commonly applied in foam board extrusion .…”

Effect of processing conditions on crystallization behavior and mechanical properties of poly(lactic acid) staple fibers

“…PLA can be processed by conventional processing techniques such as injection molding, film extrusion, or melting spinning. Typical applications are packaging elements, medical devices, films, agricultural products, and foams . Especially for the textile industry, the production of PLA staple fibers via melt spinning is of great technological interest.…”