The curing process of layered silicate/epoxy nanocomposites

Abstract

The industrial methods of processing polymeric thermoset matrix nanocomposites require a good knowledge of the matrix curing process. The dispersion of nanoparticles in the matrix effects the curing process due to the interaction between nanoparticles and the matrix at the atomic level, especially when the nanoparticles have been treated with a surfactant agent ( alquilammonium) that is in competition with the reactive groups of the hardener.

This thesis investigates the curing process of a nanocomposite consisting of a trifunctional epoxy resin, montmorillonite (MMT) nanoparticles treated with octadecyl ammonium and a curing agent containing reactive primary amine groups. The curing reaction was followed using near-infrared spectroscopy (FT-NIR) concentrating on the decrease of primary amine and epoxy functional group bands.

The curing process was carried out using five weight percentages of MMT: 2, 5, 8, 10 and 12 wt%. The amount of MMT affected the mixing time of the mixture MMT/epoxy. After 5 minutes of manual mixing, an ultrasonic bath was used to obtain a good homogenous dispersion. The mixture times used were in the bath were, 1+1 hour for the 2wt%, 1 hours for the 5 and 8 wt% and 3 hours for the 10 and 12 wt%. For the curing process, the selected cycle was as follows: 4h at 100ºC, 2h at 150 ºC and 4h at 200 ºC.

The study revealed that the MMT nanoparticles accelerate the curing process, in particular in the first steps of the curing process, pointed out by the disappearing of the primary amine and epoxy group bands in the curing process. This was followed on the near-infrared region (NIR), by selecting the appropriate bands of the NIR spectra.