2.1.2. Substrate Materials

Poly(lactic acid) films (2002D, NatureWorks LLC, Minnetonka, MN, USA) with a thickness of 25 μm were provided by Fraunhofer IVV (Freising, Germany). Material properties of 2002D were determined by other groups: Murphy et al. [37] report a melting temperature *T*m of 154 ◦C and a glass transition temperature *T*<sup>g</sup> of 55 ◦C as well as a D-lactide content of 4% and a molecular weight *M*<sup>W</sup> of 194,000 g mol−1. Ge et al. [38] report values of *T*<sup>m</sup> of 168.2 ◦C, *T*<sup>g</sup> of 58.6 ◦C, a D-lactide content of 4%, a L-lactide content of 96% and a *M*<sup>W</sup> of 121,400 g mol<sup>−</sup>1. Mihai et al. [39] report semi-crystallinity of 2002D.

Paper sheets (Metalkote Evolution, Ahlstrom-Munksjö Group, Stockholm, Sweden) with a grammage of 65 g m−<sup>2</sup> were also provided by Fraunhofer IVV (Freising, Germany). Untreated (bare) substrates were tested as reference materials.
