Abstract

AbstractIt is well known that polylactide (PLA) is difficult to foam due to its low melt strength. Thus, many ways were described in the literature to enhance the foamability. However, the melt strength was actually determined only in a limited number of publications. In this study, the addition of chemical modifiers was used to change the rheological behavior of PLA and thereby improve its foamability in foam extrusion process. For the first time the use of dicumyl peroxide modified PLA in foam extrusion is described. Both modifications lead to a distinct increase in melt strength. Here, the highest increase was shown for the PLA modified with dicumyl peroxide. Furthermore, strain hardening was observed for PLA modified with the peroxide. Low density foams were achieved for neat and modified PLA in foam extrusion. Neat PLA showed a density of 45 kg/m3, while the peroxide modified PLA showed the highest expansion with a density reduction down to 32 kg/m3. Both modifications result in a more uniform cell structure and an improved compression strength. Here, the foamed, peroxide modified PLA showed outstanding performance compared to neat PLA foam with twice the compression strength (151 Pa) even at a 30% lower density.

Highlights

  • The melt strength of PLA was increased by a multifunctional epoxide and dicumyl peroxide, respectively

  • Low density foams were achieved by foam extrusion

  • The cost of the peroxide is approximately just a fifth compared to the commercial chain extender; even at a significantly lower concentration of 0.2 wt%, dicumyl peroxide was found to be more efficient than the commercial chain extender Joncryl at 1 wt% to increase the melt strength

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Summary

Introduction

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