Synthesis Methods of Polyaniline Based Composites

Polymer composites synthesized in the present work have been studied extensively. Polymer composites are investigated using sophisticated analytical tools. Electron microscopy was used to study the surface morphology by SEM/FESEM and dispersion of nanoparticles in the polymer matrix by HRTEM. The structural details, i.e., crystallite size, crystallinity, types of nano structure were studied by X-ray diffraction. H1-NMR, ESI-MS and FTIR have been used to elucidate chemical structure of synthesised monomers. The conformational variations in the polymeric materials have been studied using vibrational spectroscopy employing Fourier Transform Infrared (FTIR) spectroscopy. The UV-Visible absorption spectroscopy was used to study the optical properties of the monomers, and as-prepared polymeric samples. The DC conductivity measurement was carried out to study the electronic properties and charge transport mechanisms of the prepared polymeric samples. The gas sensing response was found by electrical measurement. Thermal study has been used to study the stability of prepared materials.

Linear Viscoelasticity: Review of Theory and Applications in Atomic Force Microscopy

Recently, much research has been performed involving the mechanical analysis of biological and polymeric samples with the use of Atomic Force Microscopy (AFM). Such materials require careful treatments which consider the rate-dependence of their viscoelastic response. Here, we review the fundamental theories of linear viscoelasticity, as well as their application to the analysis of AFM spectroscopy data. An outline of general viscoelastic mechanical phenomena is initially given, followed by a brief outline of AFM techniques. Then, an extensive outline of linear viscoelastic material models, as well as contact mechanics descriptions of AFM systems, are presented.

Extension of the Equivalent Material Concept to Compressive Loading: Combination with LEFM Criteria for Fracture Prediction of Keyhole Notched Polymeric Samples

This work analyzes, both theoretically and experimentally, the fracture process of square specimens weakened by keyhole notches and subjected to compressive stresses. Two materials are covered: general-purpose polystyrene (GPPS) and poly(methyl methacrylate) (PMMA). Firstly, the load-carrying capacity (LCC) of the specimens is determined experimentally. Then, by using the equivalent material concept (EMC) for compressive conditions coupled with the maximum tangential stress (MTS) and the mean stress (MS) criteria, the LCC of the notched specimens is predicted. The results show that by using the approach proposed in the present investigation, not only can the critical loads in the keyhole notched polymeric specimens be precisely predicted, but also the corresponding compressive critical stress of the two mentioned polymers can be successfully estimated.

Ductile failure analysis of epoxy resin plates containing multiple circular arc cracks by means of the equivalent material concept

Ductile failure of polymeric samples weakened by circular arc cracks is studied theoretically and experimentally in this research. Various arrangements of cracks with different arc angles are considered in the specimens such that crack tips experienced the mixed mode I/II loading conditions. Fracture tests are conducted on the multi-cracked specimens and their fracture loads are achieved. To provide the results, the equivalent material concept (EMC) is used in conjunction of dislocation method and a brittle fracture criterion such that there is no necessity for performing complex and time-consuming elastic-plastic damage analyses. Theoretical and experimental stress intensity factors are computed and compared with each other by employing the fracture curves which demonstrate the appropriate efficiency of proposed method to predict the tests results.

TO THE APPLICATION ASSESSMENT OF MASSTRANSFER ANALYTICAL CORRELATIONS TO DEFINE SORPTION CONSTANTS IN SPRM POLYMERIC MATERIALS

The use of analytical solutions for Frick`s diffusion equation to define the main sorption constants leading to the necessity to solve the united problem is shown. To be more exact this is the application assessment of analytical solutions for more often used experimental results and the determination of the representative sample dimensions in the experiments which are need to construct the sorption/desorption curves. By numerical experiments it is established that the most exact values of masstransfer constants are determined for small and middle values of diffuser absorption temporary process with the help of analytical solutions. Because of the difference in real sample dimensions and structural models used for analytical solutions which as a rule are presented in the form of semi-infinite plates it is necessary to minimize the influence of side surfaces in real samples on the accuracy of masstransfer parameters determination. The numerical-analytic study according to the geometry of polymeric samples from the point of view their representation to define diffusion, solubility and swelling coefficients is conducted. Herewith it is brought out that to obtain the values of masstransfer constants to an accuracy of not more 3 %, the sample geometric features must be chosen with relative dimensions L/h >10 (L – width, h – height of sample, accordingly) – the conditions of plane omnidirectional absorption of the diffuser into the right-angle-formed plates. To obtain the diffusion, solubility and swelling coefficients to an accuracy of not more 3 % the cylinder samples with relative dimensions D/h >15 (D – diameter, h – height, accordingly) should be preferably used. The algorithm of masstransfer constants determination when jointly use the sorption curves and the numerical method of diffusion analysis – finite element method is proposed. Herewith the advantages of such approach removing the sample size and shape limits are shown in comparison with the analytical methods of diffusion analysis.

Application of Molecular Weight Regulators for the Synthesis of Sodium Polyacrylate Thinners of Mineral Suspensions

The synthesis of additives for thinning mineral suspensions based on sodium polyacrylate was carried out. The effect of molecular weight regulators on the molecular weight characteristics of the polymer and the effect of such polymers on the rheological properties of suspensions was studied. Sodium acrylate polymers are synthesized by free radical polymerization in aqueous solution using molecular weight regulators. The molecular weight characteristics of the polymeric samples were estimated by viscometry using Mark-Houwink-Kuhn-Sakurada (MHKS) equation. Synthesized polymers were used as thinners ceramic slurries, prepared according to the recipe of the enterprises producing ceramic products. The thinning ability of polymer samples with different molecular weights was estimated using an Engler viscometer from the time of the ceramic slurry flow. The influence of the type and amount molecular weight regulator on polyacryates was revealed. It was found that molecular weight synthesized samples was in the range of 21000 - 91000. It was determined that samples with a molecular weight of 28000 - 35000 synthesized using mercaptoethanol (at a dosage of 0.5-1.5% by weight of the monomer) provide optimal fluidity to the ceramic slurry.

ASPECTS REFERRING TO FATIGUE TESTING OF EPOXY POLYMERIC MATERIALS

Concomitant with the development of new technologies in usage of renewable energies and with the necessity of replacing metal, epoxy polymeric materials are becoming more frequently used. Their main advantages are the reduced weight, high mechanical and corrosion resistance, the possibility to recover, recondition and reutilise the components. Thus, they become suitable for various industries, such as: automobile manufacturing, wind turbine blades, naval industry etc. Increased fragility and low resistance in initiating and developing cracks lead to varied fatigue performance. One way of reducing these disadvantages is to test fatigue in order to observe and analyse its manifestation, before projecting components. This paper presents tests carried on cylindrical epoxy polymeric samples. The samples were manufactured through casting in tubular moulds because of great advantages of this method. The manufacturing time is short, the material usage is maximised and after casting, the samples are smooth and don’t have sharp edges. Hence, the risk of unwanted concentrated stress is eliminated. The testing means assessing the samples to variable loading in rotating bending. For a better precision of test results, it is very important that his method could be accurately repeated with samples, preparing them in similar conditions. The results are used to draw Wohler`s curve using stress-number of cycles (S-N) as coordinates, specific to the tested material. Finally, the level of maximum stress of a material that resists fatigue, without having any ulterior damage can be determined.

THE IMPACT OF THE SELECTED PARAMETERS OF FDM MANUFACTURING TECHNOLOGY ON TRIBOLOGICAL PERFORMANCE OF ABS–STEEL PAIR UNDER DRY FRICTION

The paper presents the result of tribological test of ABS and steel samples sliding under dry friction. Polymeric samples were manufactured of ABS material using FDM technology. Testing was carried out in unidirectional sliding in a ring-on-flat contact in a PT-3 tribometer. The scope of tested parameters included volumetric and mass wear, the friction coefficient, and polymeric specimen temperature. Polymeric specimens used in the study were manufactured at various settings of the 3D printing process such as the orientation of the specimen in print with respect to the printer building tray and the thickness of a single layer of the deposited material. Comparisons of the impact of these parameters on tribological performance of the sliding contact were analysed.

Influence of the Chitosan and Rosemary Extract on Fungal Biodegradation of Some Plasticized PLA-Based Materials

The fungal degradation of the complex polymeric systems based on poly(lactic acid) (PLA) and natural bioactive compounds (chitosan and powdered rosemary alcoholic extract) was studied. Two fungal strains, Chaetomium globosum and Phanerochaete chrysosporium were tested. Both fungi characteristics and changes in morphology, structure and thermal properties were monitored. Biochemical parameters as superoxide dismutase, catalase, soluble protein and malondialdehyde have been determined at different time periods of fungal degradation. The fungi extracellular enzyme activities are slightly decreased in the case of composites containing bioactive compounds. The presence of natural compounds in the PLA-based polymeric system determines an acceleration of fungal degradation and probably the chemical hydrolysis, which further helps the attachment of fungi on the surface of polymeric samples. Significant decreases in average molecular mass of the polymeric samples were observed by fungi action; accompanied by structural changes, increase in crystallinity and decrease of thermal properties and the loss of the physical integrity and finally to degradation and integration of fungal degradation products into environmental medium. It was found that both fungi tested are efficient for PLA-based materials degradation, the most active from them being Chaetomium globosum fungus.