A Multi-Scale Approach to Microencapsulation by Interfacial Polymerization

This work applies a multi-scale approach to the microencapsulation by interfacial polymerization. Such microencapsulation is used to produce fertilizers, pesticides and drugs. In this study, variations at three different scales (molecular, microscopic and macroscopic) of product design (i.e., product variables, process variables and properties) are considered simultaneously. We quantify the effect of the formulation, composition and pH change on the microcapsules’ properties. Additionally, the method of measuring the strength of the microcapsules by crushing a sample of microcapsules’ suspension was tested. Results show that the xylene release rate in the microcapsules decreases when the amine functionality is greater due to a stronger crosslinking. Such degree of crosslinking increases the compression force over the microcapsules and improves their appearance. When high levels of amine concentration are used, the initial pH values in the reaction are also high which leads to agglomeration. This study provides a possible explanation to the aggregation based on the kinetic and thermodynamic controls in reactions and shows that the pH measurements account for the polyurea reaction and carbamate formation, which is a reason why this is not a suitable method to study kinetics of polymerization. Finally, the method used to measure the compressive strength of the microcapsules detected differences in formulations and composition with low sensibility.

NEW POLYMERIC COMPOSITES BASED ON EPOXY RESIN WITH TECHOGENIC WASTES

The microstructure of gas silicate wastes is investigated. It is established, differences in particle size distribution affect rheology, abrasivity, abrasion resistance and material strength. The kinetics of polymerization of epoxy binders in the initial and filled samples is investigated: filler particles prevent the crosslinking of polymer molecules, breaking the bulk structure of the polymer matrix. As a result of research, the possibility of directional regulation of the physicomechanical properties of epoxy com-posites due to the introduction of dispersed fillers is shown, giving the binder complexes higher physi-comechanical properties, which expands the areas of their application in most industries. The theoret-ical justification is that the thermal parameters of the filler are much lower than the parameters of the main raw material. At the same time, the porosity of the filler material due to its own pores and heter-ogeneous materials formed during mixing gives the effect of thermal energy absorption, which ulti-mately leads to an increase in the thermal resistance of the samples and a slight decrease in the ther-mal conductivity coefficient.

Kinetics of Alkoxysilanes and Organoalkoxysilanes Polymerization: A Review

Scientists from various different fields use organo-trialkoxysilanes and tetraalkoxysilanes in a number of applications. The silica-based materials are sometimes synthesized without a good understanding of the underlying reaction kinetics. This literature review attempts to be a comprehensive and more technical article in which the kinetics of alkoxysilanes polymerization are discussed. The kinetics of polymerization are controlled by primary factors, such as catalysts, water/silane ratio, pH, and organo-functional groups, while secondary factors, such as temperature, solvent, ionic strength, leaving group, and silane concentration, also have an influence on the reaction rates. Experiments to find correlations between these factors and reaction rates are restricted to certain conditions and most of them disregard the properties of the solvent. In this review, polymerization kinetics are discussed in the first two sections, with the first section covering early stage reactions when the reaction medium is homogenous, and the second section covering when phase separation occurs and the reaction medium becomes heterogeneous. Nuclear magnetic resonance (NMR) spectroscopy and other techniques are discussed in the third section. The last section summarizes the study of reaction mechanisms by using ab initio and Density Functional Theory (DFT) methods alone, and in combination with molecular dynamics (MD) or Monte Carlo (MC) methods.