Petr Valášek

Thermoset Composite on Basis of Recycled Rubber

The paper describes the mechanical qualities of thermoset – epoxy resin filled with recycled rubber in the form of micro-particles. Such an application of waste can be regarded as material usage which should be preferred to other ways of waste handling. Micro-particles of recycled rubber affect the mechanical qualities of polymer in which they are dispersed. The paper quantifies cohesive and adhesive properties of the filled epoxy resin. Filling polymers – thermosets with waste fillers saves costs, it does not burden the environment, and it is inexpensive. The results described in this paper can lead to enlarging the application areas of recycled rubbers. As the filler, recycled rubber gained by the process of an ecological disposal of tyres by Gumoeko, s.r.o. (private limited company) was used.

Mechanical properties of adhesive bonds reinforced with biological fabric

Abstract The paper deals with the utilization of a biological reinforcement in an area of an adhesive layer. An advantage of the biological reinforcement application is a simplification of following recyclation of adhesive bonds comparing to those with carbon and glass fibre based reinforcements. Biocomposites combining the biological reinforcement with an inorganic adhesive can be used in the area of connecting materials by means of the adhesive bonding technology. This study was focused on the analysis of an adhesive bond strength when the bonds were reinforced with biological fabric such as jute, flax and cotton. It evaluates the quality of the adhesive layer by means of SEM. The aim of this experiment was to describe an influence of the biological reinforcement in the form of fabric on the adhesive bond strength loaded with various loading speeds from 0.5 to 300 mm/min. The experimental part is devoted to the research on the influence of added fabrics of the natural origin on the shear strength of the adhesive bond which is prepared with the polymer adhesive. The experiment results proved a benefit of the reinforcing biological fabric in the layer of the adhesive. The reinforcement of the adhesive bond with the layer of the flax and the cotton showed in the positive way with the increase of the adhesive bond strength up of ca. 50%. The biological reinforcement was not fully wetted with the resin which did not considerably influence the adhesive bond strength.

Recikliranje čestica korunda - abrazivno trošenje između dva tijela od polimernih kompozita na temelju otpada

Original scientific paper Recycling of all materials should be supported by modern society. Material recycling is one of the most important ways of dealing with waste. One of material recycling possibilities is an inclusion of waste into primary matrices. A suitable ratio and a combination of waste particles influence in a positive way mechanical properties of the material in which they are dispersed and they decrease its price. An example of the mentioned material recycling is a dispersion of corundum waste particles in the polymeric matrix. The combination of these types of matrix and filler gives birth to new polymeric particles composite creates a qualitatively brand new material. As most important characteristics of the polymeric particle composites, one often lists resistance to abrasive wear, hardness, impact resistance and strength and, last but not least, their cost. This article deals mostly with the two-body abrasive wear resistance and hardness of polymeric particle composites with the waste Al2O3 as filler and two-component epoxy matrix.

Long-Term Degradation of Composites Exposed to Liquid Environments in Agriculture

Abstract Polymeric particles composites with hard inorganic particles are abrasion resistant materials which can be used in the sphere of agriculture - e.g. for functional areas in renovation or as resistant layers. Silicon carbide waste particles were used in the present experiment, replacing the primary filler with waste without significant changes in the mechanical properties. The present paper describes the effect of immersion of polymeric particles composites with epoxy matrix in liquids on selected mechanical properties. Overall, it explains the change of hardness and resistance of abrasive wear, a typical kind of wear in the sphere of agriculture.

Using Recycled Rubber Particles as Filler of Polymers

One of a way of a material utilization of a rubber waste originated at a recyclation of tyres is its inclusion into polymeric materials. The paper describes chosen mechanical properties of an epoxy adhesive and polyurethane filled with the waste rubber. The waste rubber was gained as one of outputs of a recycling line of a firm Gumoeko, Ltd. The filler presence influences resultant mechanical properties and decreases a price of gained materials. Defining of mechanical properties enables to specify possible application areas.

Degradation Process in Area of Connecting Metal Sheets by Adhesive Bonding Technology in Agrocomplex

From the production essence point of view the necessity to create constructional bonds comes into being. In the sphere of connecting thin metal sheets it is suitable to apply the adhesive bonding technology. A significant branch is an agricultural production which is distinguished for many very degradable environments. The aim of experiment is to study and experimentally verify the degradation processes influence running in the adhesive bonds. The interval of the exposition of the adhesive bonds to the degradation environment was 0, 2, 4, 8, 16 and 32 weeks. Secondarily, the influence of various contaminants on a rise of the corrosion at the constructional carbon steel S235J0 was evaluated. Another aim is to determine by means of statistical methods ANOVA an influence agreement of single liquid contaminants types based on industrial and mineral fertilizers (Ammonium sulphate, NPK, DAM and Slurry).

Influence of Glass Powder Size Sorting on Properties of Composite Systems

Abstract Glass powder ranks among the secondary raw materials, which can be used in the interaction with polymeric materials. In the present experiment the polymeric/epoxy particle composite with different sizes of glass powder particles is described. Such utilization of recyclable materials is environmental-friendly and should be preferred. The size of particles forming the filler of the described composites is one of the key characteristics affecting the mechanical properties. Due to the properties of the systems filled with glass powder, these materials can potentially be used in agriculture (renovations, adhesive bonding, cementing, etc.). In the experiment, glass powder was dimensionally sorted through sieves. Three fractions of glass powder with particles size of 0−30, 30−50, and 50−90 μm were created and utilized, the average particle size being 18.7, 38.7, and 72.6 μm, respectively. The interaction of the 18.7 μm particles did not lead to a statistically significant decrease of shear strength values in the interval 0−20 vol.%. The presence of glass powder, however, in all cases decreased tensile strength.

Effect of active rubber powder on structural two-component epoxy resin and its mechanical properties

Abstract The aim of the research was to investigate a possibility to use active rubber powder (ARP) from a process of tyres recyclation in an area of a filler into a reactoplastics matrix applied in structural adhesive bonds. This study focuses on an analysis of a tensile strength, a shear impact strength and a hardness of the composite mixture itself and further on the interaction with an adhesive bonded material, i.e. it evaluates an influence of different ratio of ARP on the adhesive bond strength. Effects of the cyclic degradation environment combining the decreased temperature −40 °C and the increased temperature 90 °C at the simultaneous acting of the increased moisture up 90% is a part of the research. The tensile strength and the hardness were decreased by adding ARP. The experiment results proved a positive effect of ARP in the area of adhesive bonds exposed to the cyclic degradation at increased and decreased temperatures. Elastic ARP is able to absorb an inner tension in the layer of the adhesive bond.

Influence of the Hardener Proportion on Mechanical Properties of Adhesive Bonds Used in Agriculture

Abstract Joining materials by adhesive bonding is used across all industrial branches. The occurrence of adhesive bonds in machine constructions is still more frequent because of the development of adhesives which are able to meet various requirements of designers. This trend is observable also in agriculture - in the construction of agricultural machines. There even exists a cooperation between the companies developing the adhesives and the agricultural machines producers. The production process of machines and equipment must consider a required production tact. Adhesives and the process of their hardening have to meet these requirements. In the sphere of agriculture, epoxy resins hardening based either on hardeners or heating are used. Mechanical properties of two-component epoxy resins depending on variable amount of the hardener starting crosslinking of these reactoplastics are described.

Measurements of the Friction Coefficient: Discussion on the Results in the Framework of the Time Series Analysis

Tribology studies the interaction between surfaces in relative motion with a particular focus on the principles of friction, wear and lubrication. The measurement of the friction coefficient (COF) is extremely sensitive to experimental friction force fluctuations thus making COF direct measurement not a trivial task. In this manuscript, a novel approach toward the understanding of the friction coefficient behavior during reciprocating tests is proposed. The proposed procedure represents a first approach for a deep investigation about measured COF distribution during tribological tests. It is based on the analysis of COF data measured during the tests in the framework of time series analysis and it was applied to several real tests in dry-friction showed as example of application. Output parameters (i.e., friction, traction force) were investigated to detect trends, connected to running-in period of the tribo-couple, seasonal, connected to the periodicity induced from reciprocating motion, and residual components. After “smoothing” the COF data set by removing the trend and seasonal components, the residual component was analyzed to check the stationary of the COF data set which represents the most characteristic interval in friction measurements.