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Surface Activity of Hydrophobized Modified Starch Hydrolysates in Mixed Systems
The manuscript presents research focusing on the adsorption and emulsion properties of starch hydrolysates modified through acetylation, oxidation, and cross-linking. The techniques used in this study included measurements of equilibrium surface tension (du Noüy ring) dynamic surface tension (drop shape analysis), and the preparation and evaluation of emulsion stability (TURBISCAN). The surface activity of the acetylated starch hydrolysates is affected by the degree of acetylation. The acetylated starch 0.02Ac-H exhibited higher surface activity than the more highly substituted derivative 0.1Ac-H. Furthermore, it was shown that the surface activity of the components increased as the acetylated oxidized starch underwent hydrolysis. The fractions collected after 180 min using a membrane with a low separation capability (8 kDa) revealed the highest capacity for reducing surface tension. In binary systems consisting of starch derivatives and surfactants, synergistic effects in reducing surface tension were particularly noticeable in systems containing ionic surfactants. The addition of a cationic surfactant to the modified starch hydrolysate solution (1:6 mol/mol) resulted in a significantly more efficient saturation of the air/water interface. This study demonstrated that emulsions stabilized with modified starch hydrolysates remained stable over time, even when these hydrolysates constituted up to 60% of the emulsifier mixture.
Dextrins as Green and Biodegradable Modifiers of Physicochemical Properties of Cement Composites
Growing interest in the use of natural organic compounds in the production of green concrete with the use of plasticizers has been particularly noticeable in the literature of recent decades. Starch is an attractive material due to its abundance, the low cost of sourcing it, and its biodegradability, biocompatibility, and susceptibility to modification. The objective of the study was to evaluate the effect of starch hydrolysate additives on the physicochemical properties of cement composites and concrete. Compressive strength tests and cement slurry rheology measurements were carried out for water–cement ratios from 0.40 to 0.50 and for amounts of added dextrin from 0.0 to 0.7% in relation to the cement weight. The dextrins used were characterized in terms of their viscosity, polymerisation degree, and surface activity in air/water systems. Conducted research indicates that even the minimum content of dextrin increases the fluidization of cement mixes (the flow diameter increased by 67.5% compared with the mixture without the admixture), enables the reduction of mixing water, and contributes to the compressive strength of cement mortars. A further decrease in the w/c ratio to the value of 0.40 resulted in an increase in the strength value of up to 67.9 MPa, which provided a 40% increase in strength. The degree of the polymerisation of added dextrin is seen as having an effect on the physical parameters of the cement mortar; the shorter the polymer chain of the studied dextrin, the more packed the adsorbent layer, and the greater the flow diameter of the cement mortar.