Preparation and Characterization of Calcium Stearate Powders and Films Prepared by Precipitation and Langmuir−Blodgett Techniques

Abstract

The preparation of calcium stearate (CaSt2) using precipitation and Langmuir−Blodgett techniques was investigated in this study. While sodium stearate and calcium chloride were used in the precipitation process, calcium stearate nanofilms were produced from stearic acid and calcium chloride in sodium borate buffer with the Langmuir−Blodgett technique. Fourier transform infrared (FTIR) spectroscopy indicated carboxylate bands at 1577 and 1543 cm−1 in equal intensity in the powder form, but the films had a higher intensity 1577 cm−1 band than the 1543 cm−1 band. This showed the calcium ions associated with the COO− ions in the monodendate and bidendate structures in powders, and it was mainly in the bidendate structure in films. While characteristic peaks of CaSt2 at 2θ values of 6.40° and 19.58° were obtained in the X-ray diffraction (XRD) pattern of the dried powdered product, no sharp peaks were present in the 13 layer CaSt2 film. From scanning electron microscopy (SEM) micrographs, it was seen that calcium stearate powder had lamellar structure and the average particle size was 600 nm. The AFM picture of the CaSt2 film indicated the surface was not smooth with a peak to valley distance of 6 nm.