During isothermal crystallization of numerous polymers the base-line heat capacity decreases below the expected value when a two phase model is applied, where only rigid crystalline and mobile amorphous regions are assumed. It can be shown that the formation of a rigid amorphous fraction, which can be quantified by the heat capacity step at glass transition satisfies the obtained value. In some polymers, the rigid amorphous fraction is developed simultaneously with the crystal formation and not upon further cooling [1]. On the other hand, it was found that polymer composites based on inorganic nano-sized fillers distributed in an amorphous polymer matrix show a rigid amorphous fraction, too [2]. In this contribution we will discuss rigid amorphous fractions in crystallizable polymer nanocomposites. The rigid amorphous material in this class of polymers originates simultaneously from two different interaction mechanisms: (i) rigid amorphous due to interaction of the polymer with the crystals and (ii) rigid amorphous due to interaction of the polymer with the nanofillers. We present heat capacity data which allow determining fractions of different mobility for different filler contents (see fig. 1).

Fig. 1: Rigid amorphous fraction (RAF), crystalline fraction (CF), and mobile amorphous fraction (MAF) in semicrystalline Polyamide-6.6, filled with organophilically modified layered silicate Nanofil919 as a function of filler concentration. MAF was determined from heat capacity step at TG, CF from the melting enthalpy, and RAF as the remaining.

The remaining mobile amorphous fraction in polyamide-6.6/Nanofil 919 nanocomposites seems to be independent on the filler content as well as on the total rigid fraction (RF = CF + RAF). Only the distribution of crystalline and rigid amorphous fraction changes as a function of filler content.

1. Schick C, Wurm A, Mohammed A. Therm. Acta 2003:396(1-2):119

2. Sargsyan A, Tonoyan A, Davtyan S, Schick C. Europ. Polym. Jour. 2007:43:3113

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