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A Nanocomposite Based on a Styrene-Acrylate Copolymer and Organically Modified Montmorillonite. 2. Barrier and Thermal Properties
No full textThe results of an investigation into the barrier and thermal properties of polymer nanocomposites prepared by blending a styrene-acrylate copolymer solution with a suspension of organically modified montmorillonite are presented. The influence of organomontmorillonite content on the barrier properties of the nanocomposite is investigated with the example of water vapor permeability. The experimental values of the permeability coefficient are compared with those calculated by using a model taking into account the increased path of diffusing water molecules caused by the shielding effect of plate like particles. The thermograms of differential scanning calorimetry in the temperature range from −40 to 130°C are presented. The results of a thermogravimetric analysis for specimens heated in air to 800°C are also reported
Experimental Research of Dynamic Damping of Transversal Vibrations of Beams
No full textВ данной работе исследуется пассивный инерционный динамический гаситель пружинного типа. Объектом гашения являются поперечные колебания жесткого бруса, шарнирно закрепленного на конце и удерживаемого в горизонтальном положении при помощи линейной пружины растяжения - сжатия. Инерционный элемент соединяется с объектом защиты от вибрации с помощью нелинейной конической винтовой пружины. Эксперименты выполнялись на универсальный лабораьорной системе ТМ 150, предназначенной для исследования широкого спектра вибраций
A Nanocomposite Based on a Styrene-Acrlate Copolymer and Native Montmorillonite Clay. 2. Modeling the Elastic Properties
No full textA variant of stepwise determination of the elastic characteristics of quasi-isotropic polymer-silicate nanocomposites with randomly oriented platelike filler particles is considered. First, the elastic constants of transversely isotropic structural elements with coplanarly placed filler particles are obtained, and then they are averaged over all spatial directions by using the orientational averaging method. The characteristic features of the hierarchical structure of exfoliated and intercalated nanocomposites are also considered. The concentration dependences of elastic constants of a nanocomposite based on a styrene-acrylate copolymer and native montmorillonite clay are modeled, and the results obtained are compared with experimental data
Results of Living-Room Microclimate Parameter Measures in Multi-Apartment Buildings before Renovation
No full textPrevious experience shows that renovation of ventilation systems is not a typical component of renovation of multi-apartment buildings (MAB) in Latvia. The typical solution for ventilation of the existing MAB – with natural exhaust channels from the toilet facilities and kitchen premises, and air inflow through gaps between the window frame and window carcass – does not ensure return of heat from the exhaust air and cannot ensure a maintenance of room microclimate that would be independent of weather conditions and would correspond to the human comfort requirements.
As a consequence, rooms are not ventilated enough and indoor air quality (IAQ) is
reduced. This, in turn, leads to progression of the so called sick building syndrome
(SBS).
IAQ measures within energy audit inspections in13 unrenovated MAB shows that CO2 concentration level in 19 of the examined 30 apartments was ≥1000, indicating insufficient ventilation. Reduced temperature on the sourface of building constructions create enable environment for a mold growth.
The results of measures and inspections affirm necessity to realize only complex renovation activities in existing MAB to enhance energy efficiency and indoor microclimate of buildings
Development of the Porous Bioceramics via Highly Viscous Mass Foaming
No full textIn current research a new method for manufacturing of porous hydroxyapatite ceramics using highly viscous mass foaming was created.
In this research hydroxyapatite synthesized by wet precipitation reaction between calcium hydroxide and phosphoric acid was used. Powder was mixed with an organic additive (polyol) to attain a highly viscous/plastic mixture. H4NHCO3 was added to the plastic mass as pore forming agent. Samples were heated by increasing temperature for proceeding the foaming process and particular release of organic additive from the sample. It was established that by varying amount of pore forming agent in the plastic mass from 0,56wt% to 1,68wt%, it is possible to achieve the porosity in range from 52 to 61% after sintering. The porosity was determined using Archimedes method. The morphology of the obtained ceramics was examined by scanning electron microscopy and phase composition was determined by X-ray diffractometry
Effect of the Impact Damage to Strength of Fibrous Composite
No full textContact strength of the GFRC was investigated theoretically and experimentally. The sizes of contact spot and indention of spherical and cylindrical body were defined by iterations repeating the procedure of finite element analysis. The use of the general and special criteria of destruction can give the sufficient information for the approximate prediction of kind of partial destructions in a material and the sizes of a zone of damage. Results of microscopic researches of a surface of a cut in a zone of impact confirm the described shape of destruction of fiberglass at impact with rather small energy