Substantiation of Polymer Materials for the Use in Plow Constructions

The purpose of the work is to study and determine material "TEKRONE" belonging to the group of polymers, substantiate such a polymer composite material (PCM) in the modernization of the plow blade, which is not inferior to the "TEKRONE" composite and is much cheaper. This requires the study of the physical and mechanical properties of the material. The following studies of the physical and mechanical properties of the "TEKRONE" material have been conducted: density, heat endurance, and tensile strength. It has been found out that when heated over an open flame, the polymer softens with subsequent melting. There is no charring, destruction in the solid state. Therefore, the TEKRONE material is a thermoplastic. After pyrolytic decomposition 0.5… 0.7% of the initial sample weight remains. PCM TEKRONE density is 954 kg/m3. The value of this parameter coincides with the polyethylene density, which, depending on the brand, varies from 910 to 980 kg/m3. The tensile strength stress of the investigated samples of PCM TEKRONE is 17.9 MPa, which is very close to the values of polyethylene (14.8-17.0 MPa). The laboratory studies have shown that TEKRONE polymer-composite material in its properties corresponds to the materials based on polyethylene. It is determined that the closest in properties are PE 500 and PE 1000 polyethylene. It is advisable to recommend the use of PE 500 and PE 1000 polyethylene as a basis for the manufacture of plow blade of PLN type.

FROST WEATHERING OF SELECTED ROCKS FROM THE TATRA MOUNTAINS

The paper summarises the progress of a frost weathering simulation experiment involving a range of rocks after more than 300 gelation cycles. Samples of granite, conglomerate, sandstone, dolomite, limestone and amphibolite were sourced in the Chochołowska Valley, Tatra Mts. The simulation project, which continues at the Low Temperature Laboratory of the Jagiellonian University, Cracow, is set to quantify the resistance of the rocks to frost weathering by measuring the number of gelation cycles after which the samples are damaged. At the end of the project, the degree of damage will be assessed using the percentage loss of the initial sample weight and a frost weathering indicator. So far, little damage has been recorded overall, with the dolomite samples losing the highest percentage of their initial weight at nearly 6%. The paper also presents results of physical tests of the rocks, including their strength, porosity and density, which provide a useful insight into the interpretation of differences in frost weathering resistance.

COMPARISON OF TUMBLERS USED TO REMOVE DEBRIS FROM CELLS OF THE ALFALFA LEAFCUTTER BEE, MEGACHILE ROTUNDATA (HYMENOPTERA: MEGACHILIDAE)

Tumblers used to remove debris-feeding insects, predators of the leafcutter bee, excess leaf pieces, debris, and plant foliar molds from cells of the alfalfa leafcutter bee were compared. A hand-cranked tumbler removed significantly more material than did five motor-driven tumblers. It also removed more debris as the initial sample weight increased.