The compression moduli E L and the densities * of the extruded and foamed materials without the chain extender are given in Figure 8 for the different processing conditions. The influence of molar mass degradation on the foam properties is clear from comparison of the data points for GPLA and EP0 with similar foam densities (cf. the black arrow in Figure 8 for Tsat¼155C and dp/dt¼4 bar/s). It follows that the influence of MFC on the compression modulus could only be assessed directly from comparison of EP0, EP1 and EP5, i.e. for the same processing history. For these materials, the compression modulus of the foams increased from around 20MPa to 50MPa as the MFC content was increased from 0 to 5wt%, regardless of Tsat and dp/dt. However, the foam densities also increased from around 0.15 to 0.35g/cm3 in the presence of the MFC, as indicated by the grey arrow in Figure 8 for Tsat¼155C and dp/dt¼4bar/s. It should be emphasized that this density increase could not be explained directly by the presence of the MFC, because the density of cellulose is only slightly higher than that of the PLA matrix (1.5g/cm3 for the cellulose fibrils as opposed to 1.25g/cm3 for the PLA).41 It was rather a consequence of factors referred to previously, such as