Surface modification of montmorillonite - MMT nanofiller: How it affects both the rigid amorphous fraction (RAF) and the physical properties of polyamide 66

Abstract

Studying the impact of type (organo-modified montmorillonite - MMT) into polyamide 66 (PA66) on molecular motion of polymers within the space between polymer and nanoparticle is important to understand the improved properties of nanocomposites. The thermal, mechanical and electrical properties have been investigated using Dynamical Mechanical Thermal Analysis (DMTA), Differential Scanning Calorimetry (DSC), and Dielectric Relaxation Spectroscopy (DRS) techniques. DMTA technique is valuable and most sensitive thermal analysis methods to determine the glass transition temperature, T_g. DMTA in terms of loss modulus, G", storage modulus, G' and dissipation factor, tan δ were characterized for all samples, and show their unique dependence on temperature and MMT modified nanofiller types. The reinforcing effect of PA66 matrix by MMT loading justified by the increase in G' by 83% with C30B MMT nanofiller and lowering the T_g by 5.0 ^oC. The rigid amorphous fraction (RAF) of polyamide 66 based nanocomposites as a function of filler type was analyzed from heat capacity data obtained from StepScan ^TM differential scanning calorimetry (SSDSC). For polyamide 66 based nanocomposites, two different parts of RAF were detected; one is due to the interaction between inorganic nanofiller and polymer matrix and the other is due to the incorporation between crystallites and amorphous polymer. The fraction of immobilized interphase, RAF, caused by the filler increased especially in case of Cloisite30B nanocomposites and is about 32% of the polymer fraction. The disruption of crystallinity in the polymer is explained by the presence of RAF surrounding the nanofiller. Independent on the filler content crystallinity proceeds until growth is limited by mobility. However, the nonisothermal crystallization of PA66 in the nanocomposites is obstructed due to nanofiller. Using DRS technique, the electric and dielectric behavior of these tested samples was measured through the frequency range 0.03 Hz- 10⁷ Hz. The conduction mechanism inside all tested samples was confirmed to follow the correlated barrier hopping (CBH) mechanism.