RESEARCH IN THE FIELD OF GLASS FORMATION IN THE ASS-ERS SYSTEM

In order to determine the region of glass formation between the AsS and ErS compounds, we studied the methods of physicochemical analysis: differential thermal (DTA), X-ray phase (XRD), microstructural (MCA), as well as by measuring microhardness and density. The eutectic composition between the AsS and ErS compounds is 10 mol. % ErS and temperature 280oC. At a cooling rate v = 102 K / min, the glass transition region based on AsS reaches 10 mol. % ErS. Some physicochemical properties of alloys from the region of glass formation have been investigated. The area of homogeneity based on AsS reaches up to 1.5 mol. % ErS.

Characteristics of 3D Printable Bronze PLA-Based Filament Composites for Gaskets

Composite materials can be tailored for various properties, but the manufacturing process can be quite lengthy depending on the complexity of the final product. Instead, we focused our attention on the relatively new technology of additive manufacturing (3D printing) that can produce complex geometries for a limited number of samples. Due to the weak bond between successive printed layers, these objects will have weaker mechanical properties in relation to cast or sintered materials. Thus, the orientation of the printed layers can make a huge difference in the behavior of the products. In this paper, a 3D printed composite made from bronze-filled PLA is mechanically characterized in order to be used as a substitute for sintered compacted bronze products for compression loads. Thus, cylindrical samples grown with the base horizontally and vertically were subjected to compression loads to determine their stress-strain curves at room temperature as well as in the glass transition region. Due to a lack of published research in this area, this study offers an insight into the usability of bronze-filled PLA for gaskets or other objects subjected to compression loads.

Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

Buckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

Composition dependence of thermo-dynamical and thermo-mechanical properties in SeTeSnGe chalcogenide glasses (ChGs)

In this endeavor, we have synthesized novel quaternary glassy Se78-xTe20Sn2Gex (0 ≤ x ≤ 6) alloys by the well-known rapid cooling of melt under quenching technique, to study the effect of Germanium on thermodynamic and thermo-mechanical properties. In particular, we employed Differential Scanning Calorimetry (DSC) technique for the investigation of thermodynamic parameters (e.g., specific heat Cp and enthalpy ΔH) in the glass-transition-region (GTR). Differential Scanning Calorimetry (DSC) experiment was run under non-isothermal conditions. The thermo-mechanical parameters i.e., micro-hardness, micro-void volume, the energy of creation of micro-void, elasticity, density, compactness, and molar volume are also calculated. It was observed that there is a large increment in Cp values in the GTR. Further analysis shows that the Cp values above the GTR (i.e., Cp = Cpe equilibrium specific heat) and below the GTR (i.e., Cp = Cpg glass specific heat) are vastly composition dependent. The increment in specific heat value after Ge incorporation is explained in terms of molar volume.

Quantitative and qualitative analysis of segmental dielectric relaxations and space charge by TSDC in nanocomposites of natural rubber/clay

The effect of adding three different layered clays, a sodium montmorillonite and two commercial modified montmorillonites, on the morphology and molecular dynamics of natural rubber characterized by Transmission Electron Microscopy and Thermally Stimulated Depolarization Currents (TSDC) was studied. Carbon black was employed as reinforcing filler in a standard compound prepared and used for comparison purposes. The morphological results revealed that the sample with Cloisite\circledR 15A displays the highest degree of exfoliation, which suggests a stronger compatibility between the organic and inorganic phases. When the dispersion degree increases, a decrease of the activation energy was found from the quantitative analysis of the space charge dielectric relaxations. From the qualitative analysis of the dipolar dielectric relaxations around $T_{g}$, changes in the dielectric relaxation profile and in the peak localization were attributed to probable interactions between the nanofillers and the elastomer in the glass transition region of the NR.

Method for determining the temperature characteristics of the glass-transition region of polymeric materials using dielectric analysis. Part 2. Testing.

The paper presents specifi c features and experimental results of the procedure proposed in Part 1 (N3-4/2019) to determine temperature characterstics of glass-transition region of polymers and polymer composites using dielectric analysis.

Method for determination of temperature characteristics of the glass transition region of polymeric materials using dielectric analysis. Part 1. Description

A method for determining the temperature characteristics of the glass transition region of polymer and polymer composite materials using dielectric analysis is proposed. The method is based on the similarity of the dielectric analysis with dynamic mechanical analysis.

Conetworks on the base of polystyrene with poly(methyl methacrylate) paired polymers

It is found that forced (reactive) blending of polystyrene (PS) with polymethylmethacrylate (PMMA) involves the covalent binding of heterogeneous macromolecules to afford the paired polymers. For this purpose, the “anchor” N-H unsubstituted tetrazole or oxirane functional groups are preliminarily introduced in the structure of both polymers in a small amount that leads to a covalent binding of the heterogeneous macromolecules. The reaction between the modified PS and PMMA is carried out in dimethylformamide (DMF), toluene and dichloroethane (DCE) at a high total concentration of polymers (10-20 g dL-1). The process is accompanied by gel-formation to deliver cross-linked paired polymers It is established that the highest rate of the paired polymer is attained in the DCE medium, while the lowest rate is observed in DMF. For paired polymers synthesized in DMF, two glass transition temperatures (Tg) of 92°C and 104°C correspond to the original PS and PMMA, respectively. The products of forced blending of PS and PMMA in toluene have one averaged Tg value (99°C), whereas those obtained in DCE show no pronounced glass transition region at 90 ÷ 115°C. In toluene or DCE, the paired polymers are formed, which represent single-phase systems having one glass transition region.

The Dynamic Constants of Unidirectional Fibrous Composites at the Glass Transition Region as Obtained from the Interphase Concept

Dynamic mechanical analysis (DMA) is a versatile technique that complements the information given by the more traditional thermal analysis techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal mechanical analysis (TMA). Dynamic constants such as storage modulus, loss modulus, and loss factor are temperature dependent and provide information about interfacial bonding between reinforced fibre and polymer matrix of composite material. To study the above mentioned properties at the glass transition region, for unidirectional fibrous composites reinforced with continuous fibers a reliable model was applied. In particular, the composite material was considered as composed of three phases with the intermediate phase between matrix and fibres, the interphase, to have variable properties depending on those of main phases and the mode of preparation of the overall material. The glass transition temperature is defined as the point at which the specific volume versus temperature curve changes abruptly slope marking the region between rubbery polymer and glassy polymer nature. Hence, the behaviour of unidirectional fibrous composites was investigated at this region. Examination of the glass transition temperature, which constitutes an upper limit for the structurally important glassy region through the loss factor, was performed by its consideration as a combination of glass transition temperature of matrix and interphase.