Oxygen Barrier and Thermomechanical Properties of Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Biocomposites Reinforced with Calcium Carbonate Particles.

This study aimed to prepare poly (3-hydroxybutyrate-co-3-hydroxyvalerate), biocomposites with incorporating various percentages of calcium carbonate using extrusion processing. Calcium carbonate was synthesized in the absence and presence of poly(vinyl sulfonic acid). The polymorph and morphology of calcium carbonate chanced with the introduction of poly(vinyl sulfonic acid). The rhombohedral calcite was obtained in the absence of poly(vinyl sulfonic acid). Rhombohedral calcite transformed into spherical vaterite with the addition of poly(vinyl sulfonic acid). The influence of filler contents on the properties of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) composites was studied. The structure and properties of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/ calcium carbonate biocomposites were investigated by XRD, FTIR, TGA, DSC, SEM, OTR and DMA. The nucleation effect of the calcium carbonate on the crystallization of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) was observed in the DSC and XRD measurements by increasing crystallinity of poly (3-hydroxybutyrate-co-3-hydroxyvalerate). It was shown that the variation of the barrier properties of biocomposites was influenced by polymorph and morphology of calcium carbonate. The addition of 0.5 wt% of the rhombohedral calcite and spherical vaterite increased the barrier properties by 25% and 12%, respectively compared to neat polymer. The dynamic mechanical properties of composites based on rhombohedral calcite and spherical vaterite in poly (3-hydroxybutyrate-co-3-hydroxyvalerate) matrix were investigated. The storage modulus increases by adding both particles in the composites over a wide range of temperature (-30 to 150 °C) where the reinforcing effect of calcite and vaterite was confirmed. At the same loading level, rhombohedral calcite led to more increase in the storage modulus, while less increase in storage modulus was observed in the presence of spherical vaterite particles.

The inhibitory effects of carboxymethyl inulin on the seeded growth of calcium carbonate.

Kinetics of precipitation of calcite (CaCO(3)) from aqueous solution in the presence of carboxymethyl inulin (CMI) was investigated under strictly controlled temperature, pH, supersaturation ratio (S=4.8) and ionic strength (I=0.1M). The highly reproducible constant composition technique was used to study the influence of biopolymers of crystal growth of CaCO(3), on CaCO(3) seed crystals at pH 8.5 and 25°C. The crystal growth of calcium carbonate (CaCO(3)) was inhibited in the presence of CMI at low concentration (2.5×10(-9) to 25×10(-9)mol/L). The larger number of negatively charged functional groups exhibited a 95% growth rate inhibition at a concentration of 15×10(-9)mol/L. The higher inhibition efficiency is related to the maximum surface charge density due to adsorbed polymer.

The role of vinyl sulfonic acid homopolymer in calcium oxalate crystallization.

In this study, the effect of water soluble homopolymer of vinylsulfonic acid on spontaneous crystallization of calcium oxalate (CaOx) was investigated. CaOx crystals exhibiting different shapes and phase structures were produced in the presence of polymer. While the crystal growth of calcium oxalate was inhibited by homopolymer, the morphology of calcium oxalate transformed from monohydrate to dihydrate. Inhibition of calcium oxalate crystallization was provided by adsorption of homopolymer onto the active growth sites of crystals on account of the charge and hydrophilic effects. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface.