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This paper deals with a research focused on utilization of microparticle and short-fiber filler based on cotton post-harvest line residues in an area of polymeric composites. Two different fractions of the biological filler (FCR—reinforced cotton filler) of 20 and 100 µm and the filler with short fibers of a length of 700 µm were used in the research. The aim of the research was to evaluate mechanical characteristics of composites and adhesive bonds for the purpose of gaining new pieces of knowledge which will be applicable in the area of material engineering and assessing application possibilities of residues coming into being from agricultural products processing. Mechanical properties of the composite material produced by a vacuum infusion and tested at temperatures 20, 40, and 60 °C and adhesive bonds which were exposed to a low-cyclic loading, i.e., 1000 cycles at 30% to 70% from reference value of the maximum strength, were evaluated. Composite systems with the FCR adjusted in 5% water solution of NaOH showed higher strength values on average compared to untreated FCR. Unsuitable size of the FCR led to a deterioration of the strength. The filler in the form of 700 FCR microfibers showed itself in a positive way to composite materials, and the particle in the form of 20 FCR did the same to adhesive bonds. Results of adhesive bond cyclic tests at higher stress values (70%) demonstrated viscoelastic behavior of the adhesive layer.

The present study examined the effects of heating and freezing pretreatments on the mechanical, chemical, and spectral characteristics of sunflower seeds and oil under a linear compression process involving a universal compression-testing machine and a pressing vessel of diameter 60 mm with a plunger. The heating temperatures ranged from 40 to 80 °C and freezing temperatures from −2 to −36 °C at constant heating time of 30 min. The pretreated samples of initial height of 80 mm (22.6 × 10−5 m3) were compressed under a preset load of 100 kN and a speed of 5 mm/min. The results showed that oil expression efficiency significantly increased (p < 0.05) with increased heating temperatures but decreased with freezing temperatures. The lowest energy per volume oil of 22.55 ± 0.919 kJ/L was recorded at 80 °C compared to 26.40 ± 0.307 kJ/L noticed at −2 °C and control (25 °C) of 33.93 ± 3.866 kJ/L. The linear regression equations expressing oil expression efficiency, energy per volume oil, peroxide value, and free fatty acid, dependent on heating and freezing temperatures, were described with coefficients of determination between 0.373 and 0.908. Increased heating temperatures increased the UV absorption rate of the oil samples at a wavelength of 350 nm. The study is part of the continuing research on linear compression modeling of all processing factors, whereby the results are intended to be applied to the non-linear process dealing with a mechanical screw press to improve the oil extraction process.

Herák D., Kabutey A., Sedláček A., GŰrdil G., 2012. Mechanical behaviour of several layers of selected plant seeds under compression loading. Res. Agr. Eng., This article is focused on the determination of the mechanical behaviour of several layers of plant seeds namely; garden pea (Pisum sativum L.), common bean (Phaseolus vulgaris L.), common sunflower (Helianthus annuus L.) and jatropha (Jatropha curcas L.) seeds under compression loading. The results from the experiment showed that during compression plant seeds may change their mechanical behaviour that is deformation characteristic ceases to be a function of growing and beginning to resemble that of trigonometric functions and this behaviour is called the "wave effect". Also the strain value at which there is no further change of the mechanical behaviour is actually a local maximum of deformation characteristic and this is called the limit deformation. Exceeding this value can cause vibration of the presser including other negative factors which influences the process of pressing. The amounts of the limit deformation, strain energy and volume energy for jatropha, common bean, common sunflower and garden pea were determined in this experiment. From the calculated amounts of the volume energy, garden pea had the best resistance to change in the mechanical behaviour due to the fact that its change in the mechanical behaviour was not discovered. The other plant seeds; common beans, common sunflower and jatropha with respect to resistance to change in the mechanical behaviour followed in that order of magnitude.Keywords: jatropha; common bean; garden pea; common sunflower; pressing; wave effect In oil extrusion with usual extruders used in industrial practice, there is non-linear compression of pressed mixture incurred during the processing. This means that the compression is combination of translational movement moving and rotational movement. For better understanding of mechanical behaviour of plant seeds under compression loading, it is necessary first to understand mechanical behaviour of one free placed seed and one layer of seeds with limited deformation and also mechanical behaviour of more layers of the seeds. Earlier experiments conducted with plant seeds, namely jatropha, palm oil, sunflower and knotweed, showed that the specific strain energy required for deformation of one free placed seed was much greater than for pressing the same seeds layer (Fomin 1978; Blahovec, Řezníček 1980;Herák et al. 2007). There is a dynamic effect on plant tissue and thus higher cell damage (Addy et al. 1975), which is arising due to radial pressure during pressing, the gradual deformation of seeds, seeds of mutual friction and friction of the seed on the pressing vessel. There is also a required gradient of pressing pressure, and thus if the pressure gradient is inVol. 58, 2012, No. 1: 24-29 Res. Agr. Eng.

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