Ivan Labaj

This study presents the design, fabrication, and experimental validation of a passive visual displacement sensor manufactured using FDM (Fused Deposition Modeling) 3D printing technology. The operating principle of the proposed sensor is based on the mechanical perforation of pigment-filled capsules triggered by the relative displacement of monitored structural elements. The released pigment is subsequently transferred onto a cellulose substrate, enabling permanent, clear, and easily interpretable visual registration of the displacement. To identify the most suitable construction material, the mechanical properties and resistance to accelerated aging of PLA, PETG, and ABS filaments were investigated. In addition, the samples were exposed to artificial weathering in a QUV/SE chamber under UV irradiation at 50 °C and an irradiance of 1.55 W/m²/nm. Among the evaluated materials, PETG exhibited the highest tensile strength (66 MPa), the greatest elongation at break (4.4%), and the highest stability following environmental exposure, making it the preferred material for the fabrication of the sensor prototype. Functional testing confirmed the effectiveness, reliability, and practical applicability of the developed sensor for displacement monitoring applications.

This study deals with the treatment of cellulose (CEL) as a filler through physical and mechanical methods. The effect of filler treatment on the properties of elastomeric composites based on natural rubber (NR) and cellulose was analyzed. The mechanical treatment involved pressing cellulose at different time intervals (2 min ‐ 6 min) at a temperature of 110 °C. For physical treatment, a plasma discharge was applied. The treated cellulose, in an amount of 45 phr, was incorporated into natural rubber‐based elastomeric composites. The rheological, mechanical properties and cure characteristics of the prepared natural rubber/cellulose composites were examined to assess the impact of filler treatment on these properties. This study aims to determine the optimal combination of physical and mechanical treatment parameters for cellulose as a primary filler in elastomeric composites, comparing the results with composites containing untreated cellulose.

This study examines the effect of accelerated weathering on the mechanical and viscoelastic properties of thermoplastics produced by fused filament fabrication (FFF). Three polymers, acrylonitrile styrene acrylate (ASA), polyethylene terephtha...

An innovative sliding element for use in pipeline conveyor belt systems was developed based on a rubber compound. The aim of the work was to reduce friction and noise emissions compared to traditional steel rollers, as well as to minimize dynamic damage to the conveyor belt. The results of dynamic mechanical analysis (DMA) conducted for two rubber compounds (AFC, AFEG) were presented. The storage modulus (E′), loss modulus (E″), and loss factor (tanδ) were determined over a frequency range of 1 to 50 Hz. The results indicated differences in the viscoelastic behavior of the two compounds, with AFEG compound exhibiting higher stiffness and lower thermal sensitivity, making it a better candidate for structural use in friction-reducing support components.

Effect of recycled thermoplastic vulcanizate (r-PP/EPDM) on the properties of rubber compounds based on natural rubber (NR) was investigated. Compounds containing various amounts of r-PP/EPDM (0, 27.6, and 55 phr) were analyzed. Parameters such as curing characteristics and crosslinking density were assessed. SEM showed limited compatibility of the blends depending on the amount of r-PP/EPDM, which correlated with reduced crosslinking density and increased swelling degree.

Alternative fillers were used to produce rubber compounds intended for use in pipe conveyors: (i) energogypsum (EG) – a byproduct of flue gas desulfurization in the energy industry; (ii) carbon-based filler (CAF) – a product of the pyrolysis of used car tires and other used rubber products, as a partial or complete replacement for carbon black. Effect of the type and content of alternative fillers on the hardness and tensile properties of selected rubber compounds was examined. The best properties were obtained using energogypsum (47.32 phr) and carbon black (30 phr) as fillers.

This study focuses on the possibility of substituting the conventional carbon black filler N339 in a rubber compound, which also contains an energy-gypsum filler obtained as an industrial by-product, with an alternative carbon filler produced by pyrolysis of rubber waste. The proposed basic rubber compound recipe demonstrated excellent mechanical properties, which were also verified through industrial tests. Practical application in transport systems confirmed the reliability, durability, and robustness of the compound ensuring long-term functionality even in demanding operating conditions. From an ecological point of view, the substitution of conventional fillers with pyrolytic carbon materials is being pursued to reduce the environmental burden of the material. The rheological and vulcanization characteristics of the compounds were subject to minimal changes of up to 8%. The increase in the scorch time value of the compounds can be positively assessed given that the optimal vulcanization time has decreased, which leads to a faster course of the vulcanization process. The most significant effect was a 56% reduction in tensile strength without significant effect on elongation at break. These results document the potential for complete replacement of traditional fillers in rubber systems while maintaining several functional parameters.

Effect of physical modification of cellulose microfibers on the adhesion at the interface of rubber compounds was investigated. Cellulose modification was carried out using a pressure process (2 bar) at 121℃ in an autoclave or a non-pressure process in a water bath at 100℃. The interactions at the fiber-polymer matrix interface were assessed based on tensile mechanical properties and scanning electron microscopy (SEM) analysis. Cellulose microfibers modified by the autoclave-assisted process exhibited a more developed surface without fiber structural degradation, resulting in a slight increase in tensile strength and a smaller fracture surface compared to the water-bath treated fibers.

Instead of conventional carbon black (N550), an alternative carbon-based filler (AFC) - ash from the incineration of industrial waste - was used to obtain rubber compounds. The effect of this type of filler on the mixing and vulcanization process of rubber compounds was investigated. The addition of AFC reduced the maximum torque and real temperature of the compound. Compounds with a high AFC content were characterized by greater stiffness in the uncured state and significantly longer scorch times, while maintaining optimal vulcanization times. The obtained results indicate that AFC can partially or completely replace N550 in rubber compounds for conveyor belts without negatively impacting key processing parameters.

The effect of filler type and quantity (30, 40 phr), i.e., walnut shell powder (WS) and cellulose (CEL), on the tensile properties and hardness of natural rubber was investigated. Additionally, resistance to thermo-oxidative aging and its effect on mechanical properties was assessed. Both WS and CEL significantly improve the mechanical properties of natural rubber, while also providing an environmentally friendly and economical alternative to traditional fillers.