Crystallization behavior of nanocomposites based on poly(L-lactide) and layered double hydroxides -- Unbiased determination of the rigid amorphous phases due to the crystals and the nanofiller.

Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAF$_{\mathrm{crystal}})$ and the filler (RAF$_{\mathrm{filler}})$. In most cases a separation of both contributions is not possible without further assumptions. Here polymer nanocomposite based on poly(L-lactide) and layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA its crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAF$_{\mathrm{crystal}}$, and RAF$_{\mathrm{filler}}$ could be estimated without any assumption. Two different systems with a different degree of exfoliation were prepared and discussed in detail.