Initially, the components of the WPC formulations were analyzed with two dynamic methods under oxygen or nitrogen atmosphere (Table 2). The thermal degradation behavior of PP copolymer is shown in Figs. 1 and 2.
In contrast to results under exposure of PP-copolymer to oxygen atmosphere, the main thermal degradation of PP-copolymer (99.3wt.%) under nitrogen atmosphere occurs in a narrow temperature region between 300 ◦ C and 500 ◦ C (Fig. 1; black curve). In addition, it can be seen in Fig. 1 that thermal degradation of PP-copolymer begins later under nitrogen atmosphere than under oxygen atmosphere. In Fig. 2, TGA-, DTG- and SDTA-curves of the PP-copolymer are shown. The first peak in the SDTA curve at 142 ◦ C represents the melting point of the PP-copolymer. The onset of the next peak in the SDTA curve is at approximately 310 ◦ C and represents the starting point of the thermal degradation of the polymer. At this temperature, however, no significant mass loss is visible yet in the TGA curve. The area under the second peak in the SDTA curve at 459 ◦ C represents the energy required for thermal degradation and evaporation of released gases. This second peak of the STDA curve almost coincides with the maximum mass loss rate which can be seen as the peak in the DTG curve at approximately 462 ◦ C.
For a good step separation and quantification of single components in WPC it is important that the degradation of wood flour occurs in a different temperature region than that of the polymer. The thermal degradation behavior of wood flour is shown in Fig. 3.