Search

A wide range of elastomers allows to manufacture products that meet high demands of consumers. They are prepared from a mixture of several rubbers, rubber chemicals, additives and reinforcing materials (fibres), which allows you to obtain the desired properties of the products. The other components of rubber compounds are fillers, carbon blacks and plasticizers. Rubber chemicals supplement the mixture in small quantities of related products, which affect vulcanization and regulate their properties, so they have an irreplaceable role in the preparation of rubber products. The aim of experimental part is to assess the properties of the degradation environment on samples of rubber composites to change their properties. The result of the performed mechanical tests to evaluate and compare the obtained values of mechanical properties of rubber compounds and to predict the possibility of biological degradation of the tested material.

The application possibilities of austenitic stainless steels in high friction, abrasion, and sliding wear conditions are limited by their inadequate hardness and tribological characteristics. In order to improve these properties, the thermochemical treatment of their surface by plasma nitriding is suitable. This article is focused on the corrosion resistance of conventionally plasma-nitrided AISI 304 stainless steel (530 °C, 24 h) in 0.05 M and 0.5 M sodium chloride solutions at room temperature (20 ± 3 °C), tested by potentiodynamic polarization and electrochemical impedance spectroscopy. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are used for nitrided layer characterization. The experiment results confirmed the plasma-nitrided layer formation of increased micro-hardness related to the presence of Cr2N chromium nitrides and higher surface roughness compared to the as-received state. Both of the performed independent electrochemical corrosion tests point to a significant reduction in corrosion resistance after the performed plasma nitriding, even in a solution with a very low chloride concentration (0.05 mol/L). [ABSTRACT FROM AUTHOR]

Temperature is considered a complicated external factor of the susceptibility of stainless steels to the pitting. This paper deals with the corrosion behaviour of AISI 316Ti stainless steel in temperature range 22 - 80°C in aggressive chloride environments (3 and 5% FeCl3 solutions). The corrosion resistance of tested steel is evaluated on the base of results of exposure immersion tests and cyclic potentiodynamic tests. According to the obtained results the resistance of AISI 316Ti to the pitting is markedly affected by temperature changes in the range 22 – 80°C. Intensity of corrosion attack increases with the rise of Cl− concentration. Gentle changes of temperature and Cl− concentration cause significant differences in character of local damage. The appearance of pitted surfaces changes with the rise of the temperature (a density of pitting increases, a size of pits decreases). The strongest change in appearance is observed between 40 and 50ºC.

Cr-Ni-Mo stainless steels are susceptible to the pitting in aggressive chloride environments. One of the possible ways for the influence of their corrosion behavior is the use of inhibitors as the chemical modification of the environment. The resistance of AISI 316Ti stainless steel to the pitting with/without the inorganic inhibitor was tested by two independent corrosion tests: 24-hours exposure immersion and potentiodynamic polarization test. Both tests were carried out in 1M chloride acidic solution with/without 0.1M molybdate inhibitor at room temperature. Results of immersion tests were evaluated by the corrosion rates calculated from corrosion losses and by the morphology of the pitting. Potentiodynamic polarization curves were evaluated by the pitting potentials. [ABSTRACT FROM AUTHOR]

Currently, research on materials containing magnetic magnetic particles give opportunity to the prepare and study of composites with interesting magnetic features. One possibility for producing such materials is the use of fillers with magnetic properties. The final properties of such composites depend mainly on characteristic polymer matrix. However, the addition of magnetic materials arose use of new technologies. Such builders include the magnetic ferrites. Metal hexaferrites represent well researched group of magnetic materials (Mallick, 1993). Their high values of magnetocrystalline anisotropy and saturation magnetization enable widespread application of these materials as permanent magnets. Low price and excellent chemical stability with suitable magnetic characteristics classified ferrites to one of the most important magnetic materials (Rigbi, 1988). The experimental material used was a composite formed by combining a polymer matrix (linear polyethylene HDPE), and the hard-magnetic strontium ferrite labeled FD 160S as a filler. Composites with different filler contents were prepared from the starting materials. The dependence of viscosity on the content of ferrite filler was determined by rheological measurements. [ABSTRACT FROM AUTHOR]

The polymeric composites on the base of the PA+PAI filled by glass fibres are usually used in automotive industry and also exposed to natural atmosphere. The research is focused on resistance study of the mentioned composites in simulated atmospheric conditions. The tested specimens contented 10, 20 and 30 % of the glass fibres and they were exposed in UV box with defined time and intensity of UV radiation and temperature. The mentioned factors have a considerable influence on utility and lifetime of product made of the polymeric composite. The effect of the exposition on the composites behaviour was evaluated microscopically, by rheological measurements and impact tests. By the rheological measurements the changes of visco-elastic parameters (complex viscosity, moduli of elasticity and plasticity) were studied after different times of exposition in the UV box as well as chosen mechanical properties. [ABSTRACT FROM AUTHOR]

The bituminous binders used in road constructions are characterized by empirical tests as penetration, softening point and breaking point without characterizing the elastic-plastic response. This now appears to be inadequate mainly in the case of polymer modified bitumen. The objective of this work was to investigate the rheological properties of non-modified and polymer modified bitumen binders in dynamic shear rheometer by complex shear modulus and phase angle. The complex shear modulus values of non-modified bitumen are lower than the polymer modified bitumen at higher temperatures throughout the frequency range. The phase angle values of non-modified bitumen are significantly higher over the temperature and frequency test range. This is caused by lower elasticity compared to polymer-modified bitumen. Comparison of penetration results with complex shear modulus at 25°C showed that the bitumen is harder, the penetration is lower, and the complex shear modulus is higher. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of surface treatment (grinding, electrochemical polishing) on the corrosion resistance of AISI 316L, a Cr-Ni-Mo low-carbon austenitic surgical stainless steel, in a physiological solution at the temperature of 37 °C. The influence of a surface defect and of sensitization by heat treatment on the corrosion behaviour of electrochemically polished surface is also studied. The evaluation is based on the results of cyclic potentiodynamic polarization tests and on the microscopic observation of specimen surfaces after performed tests. The analysis of cyclic potentiodynamic curves showed the highest pitting corrosion resistance of electrochemically polished specimens regardless of the previous sensitization. The as-received specimen showed the highest susceptibility to pitting, which was microscopically confirmed. Based on the performed experiments we can conclude that electrochemical polishing is an efficient chemical surface treatment to increase the resistance of AISI 316L to pitting corrosion; the resistance to pitting corrosion of electrochemically polished surface can by markedly decreased by the presence of mechanical defects; the as-received surface and the ground surface showed lower resistance to pitting corrosion than electrochemically polished ones; sensitization induced by heat treatment (700 °C/10 hours) does not decrease resistance to pitting corrosion. [ABSTRACT FROM AUTHOR]

The influence of the surface preparation of AISI 316L stainless steel by mechanical grinding, polishing and following passivation was examined by immersion corrosion tests in solution simulating body fluids. Decreasing of the surface roughness by finer preparation resulted in decrease of corrosion rates of AISI 316L stainless steel. Passivation of specimens resulted in decreasing of the corrosion rates and in decreasing of the corrosion process kinetics independently on the roughness of specimens before passivation. Lowest corrosion rates were observed in the case of polished and passivated specimens. However no significant difference in corrosion rates between polished and ground specimens with following passivation was observed. [ABSTRACT FROM AUTHOR]

Bituminous binders are broadly used for asphalt mixtures in construction of roads. They are often modified by synthetic polymers to improve their physical properties (to increase their softening point and decrease their breaking point). This paper deals with comparison of rheological parameters η*, G', G" of selected polymer modified bituminous binders at the temperatures of 60 and 80 °C. [ABSTRACT FROM AUTHOR]

The effect of temperature is important external factor of inclination of stainless steels to pitting. It is held to be very complicated problem connected with many factors (composition of electrolyte, character of metal, experimental conditions). This paper deals with the corrosion behavior of AISI 316Ti stainless steel in temperature range 22 - 80 °C in aggressive chloride environments (3 and 5% FeCl3 solutions). The corrosion resistance of tested steel is evaluated on the base of results of the exposition immersion tests (visual and microscopic observation of failed surfaces, mass losses of specimens) and the cyclic potentiodynamic tests. [ABSTRACT FROM AUTHOR]

Small differences in the chemical composition (chosen elements) of stainless steels can influence their pitting corrosion resistance. The corrosion behavior of stainless steels is characterized by the Pitting Resistance Equivalent Number (PREN), which is derived from the Cr and Mo content. In our work the influence of different sulphur contents in AISI 316Ti steels with similar PRE numbers was analyzed. In the second part of this work the effect of protection by means of nitrate inhibitors at the temperature range 20 - 80°C, was tested and evaluated too. [ABSTRACT FROM AUTHOR]