Structural characteristics of poly(vinyl alcohol) - calcium carbonate composites prepared by sequential method

Composites of poly( vinyl alcohol) (PVA) and calcium carbonate (CaCO3) were prepared by a sequential method involving first in situ synthesis of CaCO3 in PVA solution, then physical crosslinking of synthetic suspension and subsequently washing of resultant elastic gel followed by consolidation. The phase and composition, mechanical properties and microstructure of the composites and possible molecular interactions between both components were evaluated. X-ray diffraction analysis revealed that calcium carbonate was mainly composed of aragonite and calcite. Compression tests confirmed the composites prepared by this sequential method had good mechanical properties and that the compressive strength of the composites increased with higher content of calcium carbonate. PVA formed an interconnected network and needle-like CaCO3 crystals together with some fine grains were well compatible with PVA. In situ synthesis induced a spectral shift of hydroxyl groups and C-O bonds of PVA and the suppression of the characteristic adsorption of calcite was also observed, according to Fourier transform infrared spectroscopy measurements.