Modification of poly(lactic acid) (PLA) was performed with the surface modified magnesium hydroxide (mMH) obtained from seawater. Surface modification of MH with different amount of stearic acid (SA) results in chemically bonded SA, stearate as confirmed by Fourier transform infrared spectroscopy (FT-IR). Based on FT-IR and X-ray diffraction (XRD) analysis modified filler with a higher amount of SA was used for the composite preparation. PLA/m10MH composites were prepared using laboratory mixing extruder. Differential scanning calorimetry (DSC) was applied to study thermal properties and crystallinity of PLA/mMH composites, while the thermal stability was performed by thermogravimetric analysis (TG). According to DSC analysis, PLA crystallization is primary influenced by the filler. PLA/m10MH composites degrade in four degradation stages. With an increase of m10MH content in the composites, their thermal degradation becomes more complex and their thermal stability is getting worse. XRD and X-ray microcomputed tomography (XμCT), used to obtain structural and microstructural information about PLA/m10MH composites, revealed that addition of m10MH decreases the crystallinity of PLA, increases the porosity of the composite and produces agglomeration of mMH.

The purpose of this study was to investigate the influence of a rinsing of Mg(OH) 2 precipitated from seawater by substoichiometric precipitation (80% precipitation) and the addition of TiO 2 on microstructural characteristics of the MgO obtained by sintering at low temperature (1400 o C). The results of examination indicate that the method of rinsing of the magnesium hydroxide precipitate in the technological process of obtaining MgO from seawater significantly affects the chemical composition of samples, primarily with regard to the CaO and B 2 O 3 content. The samples were doped with TiO 2 to improve the evaporation of B 2 O 3 and sintering of MgO samples that were characterized by XRD and SEM/EDS. These techniques confirmed the high purity of MgO samples obtained and the formation of secondary compounds in very small quantities that have a positive effect on the densification.

The process of obtaining magnesium hydroxide from seawater involves precipitation of magnesium ions with suitable basic reagents, such as calcined dolomite. The purity of the magnesium hydroxide precipitate depends on dolomite characteristics; therefore, it is necessary to find high purity dolomite with good physical properties. The aim of this study was to characterize the specific dolomite from the location of Đipalo-Sinj (Croatia), its quality, and the favourable conditions for calcination. Certain physical and chemical characteristics were determined by pure chemical analysis, as well as by using TG/DTG-DTA, FTIR and SEM/EDS analysis. Good chemical quality of dolomitic lime (59.03 wt. % CaO, and 40.69 wt. % MgO) with low content of impurities was confirmed with the TG/DTG-DTA thermal analysis. In the atmosphere of air + CO 2 , dolomite decomposes to CaCO 3 and MgO in a temperature area between 415 and 824 °C; thereafter, another reaction begins-the decomposition reaction of calcium carbonate, completed at 897 °C. In air, the simultaneous decomposition of two carbonates occurs between 657-840 °C. The FTIR and EDS analyses confirmed the complete breakdown of carbonates at 950 °C. The main components (Mg, Ca, and O) confirmed the purity of the dolomite lime.

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This study has focused on the favourable effect of the TiO 2 addition (1, 2 and 5 wt%) on the reduction of B 2 O 3 content during activated sintering of magnesium oxide from seawater at temperatures of 1400, 1500 and 1700°C for the duration of 1, 2 and 4 h. A mathematical model of dependence between the B 2 O 3 mass fraction in the sintered sample, the temperature of isothermal sintering, the isothermal sintering time and the mass fraction of TiO 2 added have been proposed. Magnesium oxide was obtained from seawater by substoichiometric precipitation, with the addition of 80% of dolomite lime as the precipitation agent. New phases formed in magnesium oxide samples were examined by the XRD and SEM/EDS analysis. The results indicate that during activated sintering of seawater-derived magnesium oxide with a TiO 2 addition, reactions of formation of Ca 2 B 2 O 5 , CaTiO 3 and Mg 2 TiO 4 took place simultaneously. The thermodynamics analysis of experimental results, based on the Onsager reciprocity relations (symmetry relations), was applied and phenomenological coefficients were calculated to describe the interference of these three irreversible processes. adhana(0123456789().,-volV)FT3 ](0123456789().,-volV)