Search

The work develops the method of obtaining new composite materials based on novolac phenol-formaldehyde resin with improved adhesion properties and heat resistance. The composites were obtained by chemical modification of phenol-formaldehyde resin by epoxy resin and polyvinylpyrrolidone during the hardening of the composition. The mechanism of resins modification and hardening has been determined. It is shown that due to the modification, the heat resistance and adhesive strength of the obtained enamels and coatings have significantly increased. In particular, with the polyvinylpyrrolidone content from 0.5 to 1 wt% and epoxy resin from 25 to 50 wt%, the adhesive strength of the compositions increases 5-7 times.

The article presents the methodology of using the results of computer simulation of the injection process to assess the suitability of the material for the injection molding. Computer simulation of the basic phenomena occurring during the filling phase, packing, and cooling phase of the injection molding provides a number of different results, containing typical information both on the suggested technological parameters of the process and on the dimensional accuracy of the molded part, but also allows obtaining data on the production efficiency and energy demand of the processing machine. On the basis of this information, it is possible to assess the suitability of the polymer materials used in the simulation, intended for the production of products from a specific industry, taking into account various criteria, mainly of an economic or qualitative nature.

The article presents issues related to the problem of applying biocidal substances to a polyethylene film produced in the blow extrusion process in order to extend the functional properties of the film, while maintaining its existing processing parameters. The aim of the research was to determine how the technology of applying a biocidal preparation to the surface of the plastic film will affect the selected properties of the blow polyethylene film. For this purpose, two methods of applying the preparation to a plastic film have been developed. The first method consisted in spraying the biocidal preparation directly during the extrusion process onto the still hot foil surface. The second method was to spray the biocidal preparation on the cooled polyethylene film in a horizontal position. The uniformity of the preparation application, the coefficient of friction and the surface free energy of the film were tested, and the quality and mechanical strength of the welded joint of the surface-modified film were assessed. The geometrical features of the polyethylene films resulting from the course of blow extrusion process were also determined.

Tento článek popisuje studie mechanických vlastností martenzitické struktury oceli C45 získané jako výsledek tepelného zpracování. Tato ocel byla podrobena vysokému popouštění v rozsahu teplot 500 ÷ 700 °C (každých 50 °C) a pro různé doby expozice, od 15 minut do 23 hodin. Kromě toho byla martenzitická ocel podrobena zkouškám kalením při teplotě 850 °C po dobu 20 minut a poté popouštěním po dobu 1 hodiny v teplotním rozsahu 50 ÷ 800 °C (každých 50 °C). Výsledné vzorky oceli byly podrobeny pevnostním zkouškám, tedy zkouškám tahem a tvrdostí a také zkouškám mikrostruktury. Výsledky těchto studií jsou prezentovány a podrobně diskutovány z hlediska jejich praktické aplikace. This article describes the studies of the mechanical properties of the martensitic structure of C45 steel, obtained as a result of heat treatment. This steel was subjected to high tempering, within the temperature range of 500÷700°C (every 50°C) and for various exposure times, from 15 minutes to 23 hours. Moreover, martensitic steel was sub- jected to tests by quenching at a temperature of 850°C for 20 minutes and then tempering it for 1 hour, within the temperature range of 50÷800°C (every 50°C). The resulting steel samples were subjected to strength tests, that is, to tensile and hardness tests and also to tests on the micro-structure. The results of these studies are presented and discussed, in detail, in terms of their practical application.

As the use of the thermoplastic materials becomes conventional in numerous parts and various applications, incidence of various types of failure becomes inevitable. Failure of injection molded parts can be a cause of economic and legal problems, as well as causing health damage or death. Public perception of plastics is adversely affected by their failures, such as the bad reputation that early plastics earned with toys that broke too easily. As the injection molding process is very complex, finding the cause of failure is very complicated. In industrial mass scale production, determining the cause of failure is key point in customer-supplier relationship. In the presented study, a type of injection molded product from HDPE affected by occurrence of cracks was investigated by mechanical, thermal testing and spectral analysis. Mechanical properties were evaluated by the uniaxial tensile test and the SHORE hardness test. Thermal properties of the samples were evaluated by DSC/TGA analysis and for the spectral analysis a Raman spectroscopy device was used. Obtained results provided information about fluctuating quality of used material, coupled with non/stable molding conditions and small molding window. All those aspects caused molded in stress, which was released in the form of crack during the installation.

This work deals with the development of method for obtaining polyamide and montmorillonite based nanocomposite, which was modified with polyvinylpyrrolidone by mixing in formic acid solution. The structure and thermophysical properties of the obtained nanocomposites were investigated by X-ray, differential-thermal, thermogravimetric and IR spectroscopic analyzes. It has been found that nanomodified polycaproamide has a higher crystallinity and higher thermal stability than the original PA-6, and is characterized by considerably higher melt fluidity. The presence of polyvinylpyrrolidone and exfoliated montmorillonite in the nanocomposite structure was experimentally confirmed.

The effect of grooves number in the feed section and screw length as well as filler nature and content on the productivity of single-screw extruder has been examined. Compositions based on polypropylene with glass fibers, talc and chalk were used for research. It is established that the number of grooves in the feed section and the length of the screw differently affect the productivity of a single screw extruder depending on the nature and content of the filler. This effect is shown to be most significant for polypropylene compositions with mineral powders (talc and chalk).

The structure and thermal characteristics of nanocomposites based on polyvinyl alcohol (PVA) and montmorillonite (MMT) intercalated with polyvinylpyrrolidone were investigated by X-ray diffraction analysis and differential scanning calorimetry. The modification of PVA with intercalated MMT reduces the degree of crystallinity of the resulting nanocomposites but significantly increases their thermal stability. Under ultrasound, the intercalated MMT was completely distributed in a PVA solution and formed a monocrystalline structure. Films based on PVA with modified MMT were cross-linked at 110°C in the presence of 5 wt% acrylic acid and 0.5 wt% Ferrous(II) sulfate as an initiator. The formed films have a homogeneous cross-linked structure.

This paper presents the assumptions of a thermodynamic equation of state for polymers according to the Renner model. The experiments involved extruding a biocomposite based on poly(butylene succinate) that was filled with ground wheat bran with its size not exceeding 200 μm. The biocomposite was produced in pellet form with three different contents by weight of wheat bran, i.e., 10%, 30% and 50%. All specimens were examined for their thermodynamic p-v-T characteristics. Taking advantage of the SimFit module of Cadmould 3D-F, experimental results were used to determine the coefficients of thermodynamic equation of state for the tested biocomposite according to the Renner model. The coefficients were then used to calculate transition temperature and to create diagrams illustrating the relationship between pressure, temperature and specific volume for the tested biocomposite. The obtained results can serve as a basis for assessing the suitability of the biocomposite for injection molding, selecting technological parameters of this process, as well as for analyzing shrinkage and defects of injection-molded parts.

The paper presents the injection shrinkage of composite moldings with mineral filler phenomenon. The definition of shrinkage and shrinkage types are described. The main factors affecting shrinkage value of injection-molded part are discussed. Based on the experimental tests conducted using injection-molded parts made from polypropylene filled with glass fiber and talc, the dependence of injection-molded part shrinkage on filler content and selected parameters of the injection molding process has been determined.

The paper reports the experimental results of a study investigating the effect of different contents of a mineral filler on the rheological properties, p-v-T, of polypropylene. Using the pvT100 apparatus, we measured specific volume under isobaric cooling at different pressures for pure polypropylene and chalk-filled polypropylene (10 wt%, 20 wt% and 30 wt%). Next, we employed computer methods to determine the coefficients of a mathematical model describing the variations in specific volume in a function of temperature and pressure. The model was used in the numerical simulations of injection molding and shrinkage processes.

The effect of small polyamide additives modified with polyvinylpyrrolidone and montmorillonite on polypropylene technological properties and heat resistance has been researched in the work. It has been determined that the melt flow index of the obtained composites increases by more than 2 times in comparing with pure PP. It has been shown that adding to polypropylene a small amount of polyamide which is modified by montmorillonite-polyvinylprolidone mixture significantly increases the heat resistance of the material. The displacement of the beginning of thermal-oxidation destruction and burning samples into the range of higher temperatures on 114-123 oC dependently on the modified polyamide content has been observed.

The publication deals with the measurement and evaluation of roughness parameters by means of laser profiling, and its main task is to determine the effect of selecting the internal gain adjustment (Gain mode) on measured roughness values of the surface treated by the water beam technology. The publication details the software, hardware, and other parts of the device designed to measure the roughness of different types of surfaces. It further describes the behavior of individual parts of the apparatus as a whole and methods of measuring the roughness of the surface along a defined profile section by means of the triangulation principle of laser profiling. The measured sample was cut by a thick (rough) cut at pressure of 380 MPa. As an abrasive, the Australian Grenade with the grain Mesh 50 was used.The experiment was carriedout at the Faculty of Production Technologies in theLaboratory of Roughness Measurement at the Department of technical systems design and monitoring in Prešov. Measurement of surface roughness parameters was performed on an optical measuring system to control surface parameters and the contact roughness meter Mitutyo SJ400.

Manufacturing companies are now placing great emphasis on competitiveness and looking for ways to explore their resources more efficiently. This paper presents optimum efficiency improvement of the automotive transmission assembly production line by using line balancing. To optimize has been selected 3 assembly stations where is waste and where requirements are not met for achieving the production capacity. Several measures have been proposed on the assembly lines concerned to reduce operations by using eliminating unnecessary activities of the assembly processes, reducing the cycle time, and balancing manpower workload using line balancing through Yamazumi chart and Takt time. The results of the proposed measures were compared with the current situation in terms of increasing the efficiency of the production line.

The paper is dedicated to development of a method for producing structured waterproof films based on polyvinyl alcohol (PVA) and montmorillonite-polyvinylpyrrolidone mixture (MPM) to research the impact of borax, pH-environment and MPM content on the rheological properties PVA solutions and water absorption capacity of films based on them. By experimental studies have been established that the montmorillonite- polyvinylpyrrolidone mixture significantly affects on viscosity the characteristics of the solution polyvinyl alcohol provided their mixing in the ultrasonic field. Composition of traces of sodium tetraborate in the aqueous solution eminent by the highest rates of viscosity. Also, designed compositions considerable influence pH at the viscosity, particularly compositions obtained in weakly alkaline environment with higher values of relative viscosity than compositions obtained in neutral and acidic environments. Simultaneously, is the best water resistance and mechanical properties of films obtained in an acidic environment. The optimum from the standpoint of durability and water resistance is a composition of PVA:MPM = 12:1 and because, depending on the contents of the MPM and pH characteristics films based on PVA can be adjusted over a wide range, which would expand the scope.

The present paper describes the experimental tests undertaken to examine the influence of rotational speeds of two axes of the mould on properties of casts produced in the rotational moulding process. The general principles of this polymer processing technology have been described. The main applications have been introduced, and leading advantages and typical disadvantages of rotational moulding process have been told over. Rotational mould's speed around axes was changed, and a thickness of cast walls has been measured also with average surface concentration of colorant in cast walls. Laboratory test stand, processing properties of polymer, also test program and experimental test methodology have been described.

This paper introduces basic information on the biodegradation of polymers as well as the mechanisms of degradation and factors influencing this process. This paper describes prodegradant additives that induce decomposition of polymers to biodegradable compounds with regard to additives causing oxo-biodegradation. Based on the results of experiments conducted for molded pieces made of polypropylene and extrudates made of low density polyethylene with a d2w prodegradant additive, dependences between prodegradant content and selected properties of the polymer composite, such as tensile strength, hardness and density, were determined. As for polypropylene, a higher content of the oxo-biodegradable compound caused an insignificant decrease in its tensile strength (by approx. 2.5%), while its relative elongation at break increased by approx. 5.7%. However, the hardness and density of polypropylene did not practically change (changes below 1%). With increasing the d2w content, the tensile strength of polyethylene slightly increased (by approx. 4.5%) and its relative elongation at break improved (by approx. 5,2%), while hardness and density did not change to any significant degree (changes below 1%). The average Young modulus of polypropylene slightly increases (by approx. 2.5%), whereas the average Young modulus of polyethylene clearly decreases (by approx. 9.5%).

The basic information characterizes the process of plastic injection molding and questions connected with computer simulation and numerical modeling of the phenomena setting during the injection molding were presented in the article. The results of the numeric simulation of the injection process of the molded part were obtained and analyzed for several models of injection mold cooling systems with different construction. Numerical simulation was conducted in the aim of the optimization of the conditions of the cooling of molded part in dependence from chosen factors connected with the parameters of the injection process and the dimension accuracy.

The development of nanoparticle reinforced polymer composites is presently seen as one of the most promising approaches in the field of future engineering applications. The unique properties of at least some of these nanoparticles (e.g., CNTs or carbon black) and the possibility of combining them with conventional reinforcements (e.g., carbon-, glass-or aramid-fibers) has led to an intense research in the field of nanocomposites. This study presents mechanical properties of two carbon composites made from bisphenol A epoxy resin (E) and 3 layers of 160 g/m2carbon cloth with twill (TC) and plain (PC) weave as a reference and three-composite system that consists from carbon fiber reinforced epoxy matrix and 1% of multi-wall carbon nanotubes dispersed in epoxy resin. Used hardener H507 was based on cycloaliphatic polyamine with absence of nonylphenol. Samples were also tempered at 80 oC (for 12hours) for improvement of their thermal resistance.

This article provides general information about the aging process of polymer plastics. It also reports the experimental results of investigations undertaken to determine changes in the mechanical properties of polypropylene injection-molded samples with the oxo-biodegradable additive d2w which were subjected to natural aging for two years. A decrease of tensile strength and elongation at yield as well as an increase of hardness were observed during the experiment.

This paper presents the result of a study evaluating the influence of alternative path generation strategy on structure and some mechanical properties of parts produced by Fused Deposition Modeling (FDM) technology. Several scientific investigations focused on resolving issues in FDM parts by modifying a path generation strategy to optimize its mechanical properties. In this study, an alternative strategy was proposed with the intention of minimizing internal voids and, thus, to improve mechanical properties. Polycarbonate samples made by this alternative path generation strategy were subjected to tensile strength test and metro-tomography structure evaluation. The results reveal that the structure observed on build models differs from a structure expected from path generation predicted by software Insight 9.1. This difference affected the tensile strength of samples.

Basic information concerning the process of polymers' ageing is given and the methods of investigation of the changes of properties being the results of ageing is characterized. The types of ageing and the phenomena causing this process are presented. The basic problems concerning the resistance of polymers to ageing and comparative indices describing the intensity of ageing were defined. The problems related to forecasting of changes of polymers properties were presented in details, including the basic forecasting methods especially the procedure concerning the polymers and the products made of them. So the following methods used were characterized: Arrhenius equation (Fig. 1), analysis of random variable distribution (Fig. 2), regression equations (Fig. 3 and 4) as well as time series analysis (Fig. 5 and 6), among others exponential equalization.