Mechanical and Thermophysical Properties of Epoxy Nanocomposites with Titanium Dioxide Nanoparticles

The introduction of nanoparticles and their homogeneous distribution in the polymer matrix, as well as their size, can have a significant effect on the mechanical properties of composite materials. In this work, we studied the mechanical characteristics of TiO2/epoxy nanocomposites with different contents and sizes of nanoparticles. The preparation of nanocomposites was carried out by a stepwise curing (at 90 and 160 °C) of ED-20 dianic epoxy resin in the presence of an aromatic hardener with the addition of titanium (IV) dioxide nanoparticles preliminarily synthesized by the plasma-chemical method. Ultrasonic dispersion was used to achieve a uniform distribution of nanoparticles in the polymer matrix. The chemical and phase composition, the structure of the as-synthesized TiO2 nanoparticles, and the resulting epoxy nanocomposites were characterized by elemental analysis, X-ray diffraction, transmission and scanning electron microscopy, and infrared spectroscopy. The mechanical properties of the nanocomposites were determined by the static tensile test, and the impact toughness was determined by the Charpy method. The glass transition temperature and thermal stability of the TiO2/epoxy nanocomposites were studied by thermal analysis methods. The formation of an interfacial layer between the TiO2 nanoparticles and an epoxy matrix has been shown for the first time by spectral methods. It is shown that the mode of curing and ultrasonic dispersion used, as well as varying the content and dispersity of the TiO2 nanoparticles, make it possible to obtain epoxy nanocomposites with simultaneously improved deformation-strength characteristics and impact strength values

Особенности взаимосвязи редокс-метаболизма и структуры растений кальцефитов

Calciphyte species form a systematically and structurally heterogeneous group of plants capable of tolerating highly stressful conditions. Various structural adaptations occur in calciphytes to protect them against excess light (leaf pubescence) and moisture loss (waxy coating). Their shoot structure determines the volume of primary plant production. The present work studied the relationship between the antioxidant status and structural features of some calciphyte species. Redox metabolism in plant leaves was assessed using parameters such as water content, photosynthetic pigments, soluble carbohydrates, water-soluble phenolic compounds, water-soluble and membrane-bound proteins, and lipid peroxidation (LPO) level. The data obtained showed that the contents of the components regulating redox metabolism correlate both with each other and with the structural parameters of plants. In particular, the content of photosynthetic pigments in multi-species communities is lower in taller plants than in low-growing ones. The content of phenolic compounds and the level of LPO in calciphyte leaves are associated with the level of development of wax covering. The plants forming clumps and vigorous shoots exhibit increased LPO activityРастения кальцефитных флор образуют систематически и структурно неоднородную группу растений, способных переносить высокострессовые условия. Кальцефиты реализуют различные структурные адаптации, противодействуя избытку света (опушение), снижая потери влаги (восковой налет). Структура их побегов определяет объем первичной продукции растений. Цель настоящей работы – изучить взаимосвязи антиоксидантного статуса со структурными особенностями некоторых представителей кальцефитной флоры. Редокс-метаболизм оценивали по оводненности листьев, содержанию фотосинтетических пигментов, углеводов, фенольных соединений, водорастворимых и мембранно-связанных белков, интенсивности накопления продуктов перекисного окисления липидов (ПОЛ). Полученные данные показали, что количественное содержание компонентов, регулирующих редокс-метаболизм, демонстрирует наличие корреляционных связей к ак между о тдельными г руппами э тих в еществ, т ак и со структурными показателями растений. В частности, в многовидовых сообществах у более высоких растений содержание фотосинтетических пигментов ниже, чем у низкорослых. Содержание фенольных соединений и уровень ПОЛ в листьях кальцефитов связаны с уровнем развития воскового налета. Растения, формирующие куртины и мощные побеги, характеризуются повышенной активностью ПО