Eco-friendly waterborne polyurethanes (WPU) find wide application in agriculture as pesticide carriers, which enhances their efficiency. To provide better control of the retention time and capacity of pesticides, WPU can be modified by cyclodextrin derivatives able to form supramolecular assemblies with bioactive substances. Synthesis of WPU containing up to 15 wt.% of covalently bound β-cyclodextrin partial nitrate (CDPN) is reported in this work. Covalent bonding of CDPN to a polyurethane matrix has been proved by IR spectroscopy and size exclusion chromatography. The particle size and viscosity of the WPU dispersion have been determined. The introduction of CDPN affects molecular weight and thermal properties of WPU films. The presence of CDPN in WPU is shown to provide higher average molecular weight, wider molecular weight distribution, and larger average size of dispersed particles, compared with WPU reference samples containing 1,4-butanediol. The analysis of the rheological behavior of the obtained WPU dispersions shows that they can be classified as pseudoplastic liquids. The analysis of the thermal parameters of WPU films indicates that the introduction of 15.0 wt.% CDPN shifts the value of the glass transition temperature from −63 °C to −48 °C compared with reference samples. We believe that the results of the present study are sufficiently encouraging in terms of using CDPN-modified eco-friendly WPU as potential systems for developing the delivering agents of bioactive compounds. The application of such systems will allow the long-term contact of pesticides with the plant surface and minimize the possibility of their release into the environment.
1 January 2015 in Russian Journal of Applied Chemistry
The structure of an active diluent influences the rheological properties of epoxy compounds. The use of a linear alkyl glycidyl ether allows preparation of compounds with the lowest dynamic viscosity. As the active diluent content is increased from 0 to 20%, the period in which the network polymer is formed in the course of curing of epoxy compounds increases from 5 to 30 min because of a decrease in the rate of consumption of epoxy groups in the compound with an increase in the active diluent content. The elastic-strain and thermal properties of epoxy polymer films were studied. When using a linear alkyl glycidyl ether as an active diluent, the ultimate strength and glass transition temperature as functions of the diluent content pass through a minimum. Introduction of monofunctional active diluents into the compound leads to a decrease in the elastic modulus. An increase in their content in the compound from 5 to 20% does not affect the elastic modulus.
23 March 2017 in Protection of Metals and Physical Chemistry of Surfaces
It has been determined that a dopant acid affects the dispersion composition of the prepared coreshell pigments. Anticorrosion properties of the pigments with the polyaniline (PAN) shell have been investigated. Pigments with a PAN shell doped by phosphoric acid possess the highest anticorrosion properties. The dependence of the electrical conductivity on the substrate-to-PAN ratio has been determined. Anticorrosion properties of polymer coatings containing the pigments with PAN shell have been studied.
Core/shell pigments allow for the combination of the active anti-corrosion effect of the shell and the barrier effect of the core. This makes it possible to obtain anti-corrosion pigments, with a high—protective effect and low toxicity. Thus, the need for a comprehensive study of the properties of these pigments grows more urgent, before their application to paints and varnishes. The hiding power of core/shell pigments comes close to the one of pure polyaniline (PANi), when the PANi content in the pigment reaches 50 wt.%, with sulfuric and phosphoric acids used as dopants. This paper, also, shows that the blackness value of core/shell pigments with 10 wt.% PANi is around 35 and constant; for pure PANi, their blackness value is 40. When PANi content is 5 wt.%, kaolin-based pigment shows the lowest blackness, which happens due to a generally higher whiteness of kaolin. However, when the PANi content surpasses 10 wt.%, there seems to be no influence on the blackness of the core/shell pigments. The core/shell pigment with a 20 wt.% PANi is, optically, identical to a black-iron-oxide pigment. An increase in the PANi content of the core/shell pigment leads to an increase in the oil absorption of the samples. It was found that the dispersion process would be the most energy efficient for core/shell pigments, containing kaolin and talc as a core.
1 July 2018 in Russian Journal of Applied Chemistry
Aqueous dispersions of doped polyaniline were synthesized in the presence of mixtures of a carboxylcontaining polymeric surfactant with low- and high-molecular-mass stabilizers. Polyaniline aqueous...