Термометричні дослідження полімеризації 2-гідроксіетилметакрилату в присутності полівінілпіролідону з одночасним відновленням йонів нікелю

The kinetics of heat release during the processes of 2-hydroxyethyl methacrylate (HEMA) polymerization in the presence of polyvinylpyrrolidone (PVP) and the copolymerization of HEMA with PVP with simultaneous reduction of Ni2+ has been investigated. Nickel sulphate/sodium hypophosphite redox system in alkaline medium was used for Ni2+ reduction. The kinetic regularities of polymerization have been evaluated by thermometric method. The temperature change of the reaction medium during polymerization has been investigated by means of developed equipment, based on the reactor with properties like adiabatic one. The characteristic parameters that correspond to the time of gel formation, the time of exothermic maximum temperature reach, the range of gel effect and maximum temperature of the exotherm are identified on the obtained thermometric curves. It is determined that in the case of HEMA/PVP compositions, polymerization in the presence of benzoyl peroxide occurs with high rate already at 50 °C. The time of the gel effect start and maximum exothermic temperature mainly depend on the initial composition formula, solvent content, initial polymerization temperature, and also the simultaneous reduction of Ni2+ in the polymerization process. The presence of even a small content of oxidizing agent and reducing agent causes an increase of the time of gel formation start, time of maximum exothermic temperature reach and a decrease of the maximum exothermic temperature. It is determined that use of benzoyl peroxide in combination with iron (II) sulfate for initiating of HEMA copolymerization with PVP enables the process to be performed at room temperature and with a maximum exothermic temperature, which provides chemical reduction of Ni2+. The time and temperature parameters of polymerization determined in the work, as well as the main factors on which these parameters depend, will provide an opportunity to substantiate the technological parameters of metal-filled HEMA/PVP copolymers obtaining.За допомогою термометричного методу досліджено кінетику виділення тепла під час полімеризації композицій на основі 2-гідроксіетилметакрилату (ГЕМА) та полівінілпіролідону (ПВП), ініційованої пероксидом бензоїлу з одночасним відновленням Ni2+. Для відновлення Ni2+ використано окисно-відновну систему нікелю сульфат натрію гіпофосфіт у лужному середовищі. Оцінено вплив складу вихідної композиції, вмісту розчинника, початкової температури полімеризації, концентрації окисника та відновника на кінетичні параметри полімеризації – час початку гелеутворення, час досягнення максимальної температури екзотермії, область гель-ефекту та максимальну температуру екзотермії. Встановлено, що у випадку ГЕМА/ПВП композицій полімеризація у присутності пероксиду бензоїлу відбувається з високою швидкістю вже за температури 50°С. Доведено, що використання комплексного ініціатора, який складається з сульфату заліза (ІІ) та пероксиду бензоїлу, дає можливість здійснювати полімеризацію ГЕМА/ПВП композицій за кімнатної температури та з максимальною температурою екзотермії, яка забезпечує хімічне осадження металу. Виявлено, що температура, до якої нагрівається реакційне середовище, може бути достатньою для перебігу хімічної реакції відновлення Ni2+

Effect of magnetic field on the structure formation and properties of hydroxyethylmethacrylate / polyvinylpyrrolidone copolymers

The effect of a permanent magnetic field on the polymerization kinetics and structural parameters of a hydrogel network on the basis of 2-hydroxyethylmethacrylate with polyvinylpyrrolidone compositions has been investigated. It has been shown that the magnetic field activates matrix polymerization of mentioned compositions and assists in the structure formation of copolymers with a smaller crosslink density. The efficiency of the developed polymeric materials for production of ultrathin contact lenses "Glipox" has been confirmed

Formation and properties of hydrogel membranes based on cross-linked copolymers of methacrylates and water-soluble polymers

Experimental results concerning the effect of composition, nature of polymeric matrix, monomer and solvent on the structure, physico-mechanical and selective-transport characteristics of hydrogel membranes based on cross-linked grafted copolymers of methacrylates and water-soluble polymers (polyvinyl-pyrrolidone, polyvinyl alcohol) have been presented. Methods of high-penetrating hydrogel membranes formation have been developed and capability of directional control of their structure and operational characteristics has been determined

Thermogravimetric Research Into Composites Based on the Mixtures of Polypropylene and Modified Polyamide

We established in the present work the regularities for obtaining homogeneous nanocomposites based on the mixture of PP/PA-6 with montmorillonite modified using PVP. In these nanocomposites, PA-6 and MMT contribute to the increase in thermal resistance of the material, while PVP improves compatibility between polar PA-6 and hydrophobic PP.The goal of the present work was to investigate by applying the methods of thermogravimetric analysis a correlation between thermal characteristics of the newly-created nanocomposites based on the mixture of PE/PA-6 with montmorillonite, modified using PVP, and to determine the optimal composition of a nanocomposite with enhanced thermal resistance and a wide temperature interval of the viscous-fluid state.On the basis of experimental data, it was found that the mixtures of polypropylene with polyamide modified by the montmorillonite-polyvinylpyrrolidone mixture are distinguished by the higher thermal resistance compared with the starting PP. It is established that at a content of the modified polyamide in the mixtures with polypropylene within 30 % by weight, samples of the composite are characterized by the highest thermal resistance ‒ weight loss of such composites in a temperature range of 218‒322 ºC is only 7.1 %, temperature of the onset of thermo-oxidation destruction is 300 ºC. It is shown that the developed nanocomposites have wider temperature intervals of the viscous-fluid state – 126–300 ºC. This makes it possible, by changing the modes of processing, to influence the structure and properties of products, especially taking into account the difference in crystallization of the material depending on the conditions and the method of processing. It is established that the most suitable for application and processing is the mixture of polypropylene with modified polyamide in the ratio 70:30 % by weight, respectivel