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Two different nanosized mineral fillers (nano calcium carbonate and nanoclay) were used in the high density poly(ethylene) (HDPE) composites pilot plant production. Structural and mechanical properties of the prepared composites were examined in this study. The homogenous filler distribution was confirmed in the tested samples by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy analyses. The fillers' fortifying effect on polymer composites' mechanical performance was confirmed as indicated by the increased elastic modulus and indentation modulus. Additionally, the possible modulation of the plastic-elastic mechanical behavior was confirmed by the type of the filler as well as its concentration used in the final composites testing articles., Palacky University in Olomouc [IGA_PrF_2021_031]; Tomas Bata University in Zlin [IGA/FT/2021/004, IGA/FT/2021/005]; Faculty of Science, Palacky University in Olomouc, Univerzita Palackého v Olomouci: IGA_PrF_2021_031; Univerzita Tomáše Bati ve Zlíně: IGA/FT/2021/004, IGA/FT/2021/005

A strong difference in the physico-chemical properties of the plastic lubricants studied was found in this study through pressure drop, thermal analysis, vibration damping, texture hardness and rheological measurements. Oxidation aging of the lubricant sample containing rapeseed oil additive was proposed. Its higher thermal sensitivity was simultaneously confirmed by frequency dependent complex shear modulus of elasticity measurements as well as by rheological testing. Rapeseed oil modified lubricant showed a higher decrease in both storage and moduli losses due to a temperature increase from 16 to 26 ° C compared to the rapeseed oil free sample. Simultaneously, the flow curves were shifted to the higher shear stresses (for plastic lubricant without rapeseed oil additive) typical for rheopectic fluids. For the rapeseed oil modified lubricant, the flow curves were shifted to the lower shear stresses, indicating its thixotropic fluid behaviour. The synthetic lubricant without rapeseed oil additive exhibited higher dissipative rheological behaviour as reflected by decreasing first resonance frequency peak position compared to the rapeseed oil modified lubricant as obtained from vibration damping measurements. It was found that the synthetic lubricant exhibited better vibration damping properties and mechanical energy dissipation into heat due to its higher viscous friction than the rapeseed oil modified lubricant under experimental conditions.

This article deals with the characterization of the thermal-induced aging of soft polyurethane (PU) foams. There are studied thermal and mechanical properties by means of thermal analysis, tensile, compression and dynamic mechanical vibration testing. It was found in this study, that the increasing relative humidity of the surrounding atmosphere leads to the initiation of the degradation processes. This is reflected in the observed decreased mechanical stiffness. It is attributed to the plasticization of the PU foams wall material. It is in agreement with the observed increase of the permanent deformation accompanied simultaneously with the decrease of Young's modulus of elasticity. The latter phenomenon is studied by the novel non-destructive forced oscillations vibration-damping testing, which is confirmed by observed lower mechanical stiffness thus indicating the loss of the elasticity induced by samples conditioning. In parallel, observed decreasing of the matrix hardness is confirming the loss of elastic mechanical performance as well. The effect of conditioning leads to the significant loss of the PU foam's thermal stability., European Regional Development Fund in Research Centre of Advanced Mechatronic Systems project within Operational Programme Research, Development and Education [CZ.02.1.01/0.0/0.0/16_019/0000867]; Internal Grant of Palacky University in Olomouc [IGA_PrF_2021_031], CZ.02.1.01/0.0/0.0/16_019/0000867; Univerzita Palackého v Olomouci: IGA_PrF_2021_031

This article deals with the characterization of the thermal-induced aging of soft polyurethane (PU) foams. There are studied thermal and mechanical properties by means of thermal analysis, tensile, compression and dynamic mechanical vibration testing. It was found in this study, that the increasing relative humidity of the surrounding atmosphere leads to the initiation of the degradation processes. This is reflected in the observed decreased mechanical stiffness. It is attributed to the plasticization of the PU foams wall material. It is in agreement with the observed increase of the permanent deformation accompanied simultaneously with the decrease of Young’s modulus of elasticity. The latter phenomenon is studied by the novel non-destructive forced oscillations vibration-damping testing, which is confirmed by observed lower mechanical stiffness thus indicating the loss of the elasticity induced by samples conditioning. In parallel, observed decreasing of the matrix hardness is confirming the loss of elastic mechanical performance as well. The effect of conditioning leads to the significant loss of the PU foam’s thermal stability.

International audience; Polymeric materials play a vital role in our daily life, but the growing concern for the environment demands economical and natural biopolymers that can be cross-linked to create technologically innovative lightweight materials. Their cellular matrix with extreme flexibility makes them highly acceptable for application prospects in material science, engineering, and biomedical applications. Furthermore, their biocompatibility, mechanical properties, and structural diversity provide a gateway to research them to form technologically important materials. In the light of the same, the review covers cellulose derivatives. The first section of the study covers the general properties and applications of cellulose and its derivatives. Then, the biopolymers are characterised based on their dielectric properties, crystallinity, rheology, and mechanical properties. An in-depth analysis of the diffuse process of swelling and dissolution followed by a brief discussion on diffusion and diffusion of crosslinking has been done. The review also covers a section on swelling and swelling kinetics of carboxymethyl cellulose (CMC) and hydroxyethyl cellulose (HEC). The examination of all the aforementioned parameters gives an insight into the future aspects of the biopolymers. Lastly, the study briefly covers some preferred choices of cross-linking agents and their effect on the biopolymers.

It was found in this study that both fillers (mica and wollastonite) trigger an increase in Young's modulus of elasticity with increasing filler concentration in a HDPE composites matrix. In the case of HDPE/mica the same improvement was also found for the upper yield point vs. filler concentration dependencies indicating higher stiffness. However, for the HDPE/wollastonite composites the opposite trend was observed, i.e. a decrease of the upper yield point and strain at break. These findings were also confirmed by mechanical vibration damping testing where there was found a more intense shift of the first resonance frequency peak position to higher frequencies with increasing filler concentrations for HDPE/mica in comparison to HDPE/wollastonite composites. Both composites exhibited decreasing strain at break with increasing filler concentration indicating a more brittle mechanical behavior in comparison to the virgin HDPE polymer matrix. However, for HDPE/wollastonite composites at 5 w. % filler concentration a 15% increase in the magnitude of the strain at break was found indicating an increase in ductility at 50 mm/min deformation rate. Fracture toughness measurements show, that both studied fillers function as the stress concentrators in the HDPE polymer matrix, which was reflected in the exponentially decreasing dependencies of the fracture toughness vs. filler concentrations. SEM analysis of the fracture surfaces show typical elongation bands of high plasticity deformation regions characteristic of typical shearing bands, interpenetrated with cavities created around filler particles. Thermal analysis data showed for HDPE/mica a strong increase of the crystallinity with increasing filler concentration, however in the case of HDPE/wollastonite the opposite effect of a higher amorphous polymer phase content was found.

In this study it was found that the complex microstructure of chocolate was modified by the addition of whey into original milk chocolate. A decreasing particle size diameter of the dispersed cocoa fat particles with increasing whey content followed by dynamic light scattering measurements was confirmed. Changes of the chocolate fat crystallinity through disrupting the highly ordered cocoa fat dense crystal aggregates to the less developed ones deformed by the inclusion of whey particles into the complex chocolate mass were simultaneously confirmed. These morphology changes affected the thermal and rheological behaviour of the studied samples by decreasing the melting peak temperature as well as Casson's plastic viscosity with increasing whey content. Furthermore, a gradual decrease of the hardness, thus reflecting the plasticising effect of the whey particles on the complex crystalline structure of the chocolate, was observed. The latter fact was also confirmed by the decreased acoustic emissions during chocolate breakage, thus indicating the change of the fracture process from brittle to more ductile.

Thermal analysis, texture profile analysis, water holding capacity and dynamic mechanical testing methods were used for study of the physico-chemical and mechanical properties of the model chicken meat batters modified by the addition of amaranth flour. It was found that the addition of the amaranth effectively modified and improved their textural and nutritional properties. Further, the addition of calcium dihydrogen phosphate to the complex meat batter was shown to enhance formation of the creation of the three dimensional gel networks during protein denaturation, which resulted in increased tenderness of the product, as was demonstrated by decreased hardness, toughness and gumminess of the chicken batters with the increase of amaranth concentration. These findings were supported by dynamic mechanical vibration testing experiments and by increased water holding capacity. After amaranth flour addition, the observed frequency dependence of the measured damping transfer function of the tested samples showed typical viscoelastic behaviour rather than pure elastic behaviour. The first resonance peak frequency shifted from 200 Hz for unmodified chicken batter to 120 Hz for batter with 1 wt% amaranth concentration and 0.45 wt% calcium dihydrogen phosphate. Formation of a hydrocolloid gel structure was confirmed by thermal analysis experiments, which showed decreased DTA protein denaturation temperature peak position from 101.3 °C for the unmodified batter to 90.6 °C for batter with 2 wt% amaranth. Interestingly, after addition of a Ca2+ crosslinking agent into the matrix, thermal resistance of the gel phase increased, which was reflected by the increased latter denaturation peak position from 93.7 °C (for 1.5 wt% amaranth concentration chicken meat batters without calcium dihydrogen phosphate) to 108.8 °C for 0.45 wt% crosslinking agent calcium dihydrogen phosphate and 1.5 wt% amaranth concentration chicken meat batters.

Observed data in this study indicated creation of the combined plastic elastic mechanical behavior when spherical hollow sphere CaCO3 particles were used as a HDPE polymer matrix filler. It was found that with increasing filler concentration the corresponding increase of the Young's modulus of elasticity was accompanied with corresponding decrease of the upper yield point and elongation at break. Dynamic mechanical testing of the studied composites performed by means of the frequency dependent transfer damping function indicated lower stiffness of the filled HDPE composites in comparison to the neat polymer matrix. This founding corresponded with the strong effect of the filler particles on lowering the creation of the higher molecular conformational structures of the crystalline regions of the HDPE in favor to the amorphous parts. SEM analysis of the fracture surfaces showed typical elongation bands of high plasticity deformation regions characteristic with a typical shearing bands interpenetrated with clear cavities created around filler particles. Thermal analysis data showed minor change of the crystallinity with increasing filler particles content in the polymer composite matrix in such a way, that the higher amorphous phase content was found with increasing filler concentration. Creep behavior of the tested specimens indicated higher plasticity of the nanocomposites matrix in comparison with the virgin HDPE.

The aim of this study was to evaluate water binding capacity of selected varieties of rice flours as prospective processing parameter for manufacturing gluten-free products. Water retention capability was determined by measuring the effective diffusivity coefficient, DSC, water absorption index and water solubility index. It was found that with decreasing particles size of flour the water binding capacity was increasing. This phenomenon was dependent also on the saccharides and proteins content of individual materials. There was measured gelatinization temperature and enthalpy of fusion. It was found to be 2.08 J/g for black and 5.8 J/g for fine rice flour. Effective moisture diffusivities of 6.167 × 10−10 m2 s−1 for black and of 5.030 × 10−10 m2 s−1 for fine rice flours were found. The latter were of the lowest magnitudes from the set of the studied samples, indicating their highest ability to retain water in their microstructure. There was confirmed structural binding of water based on rheological testing.

The aim of the present study was characterisation of selected varieties of still wines produced in Slovak Republic in vintage year 2013 and one 2012. There were tested ten samples of nine varieties of wines originated from Malokarpatská "Lesser Carpathian" and Južnoslovenská "Southern Slovakia" wine regions of Slovak Republic, Dornfelder, Frankovka modrá, Svätovarinecké, Zweigeltrebe, Müller Thurgau, Veltlínské zelené, Rizling rýnsky, Rizling vlašský and Sauvignon wines. There were studied selected physico-chemical properties of tested wines as a total contents of anthocyanins and polyphenols by means of spectrophotometry, titratable acidity, density and chromatic characteristics. The highest content of anthocyanins (TAC) was found in red wine Frankovka modrá, 183 mg.L-1 and the lowest for sample rose wine St. Laurent 19 mg.L-1. The content of total phenolic compounds as a gallic acid was in range 2833 to 1961 mg.L-1 for red wines, 1016 and 1013 mg.L-1 for rose wines, 1085 to 549 mg.L-1for white wines. Total acidy was average 6.3 ±0.3 g.L-1 only for Ryzling rýnský, 8.2 g.L-1 and Sauvignon rose 8.0 g.L-1 and was expressed as the amount of tartaric acid. Quality of wines can be expressed by colour intensity too. Was evaluated and compared intensity of colour in wines by CIE Lab method and the total differences between red, rose and white wine DE* was calculated. The most differences was found for Svätovarinecké a Frankovka modrá (2.5) - red wines ("clearly perceptible") and 4.9 for Veltlýnské zelené and Müller Thurgau - white wine ("moderating effect").

The blends of gelatin and shear-thinning hydrocolloids (guar gum, kappa-carrageenan and xanthan gum) were examined to determine the effect of the conformational change on the functional properties of the solutions. The polyelectrolyte complexes of 0.5% gelatin/0.5% polysaccharide in 70 mM KCl or 70 mM NaCl were investigated by the laboratory rheometer and conductivity meter in the temperature range 25 - 45 °C. The rheological data were fitted by the power-law and Herschel-Bulkley model to obtain the flow parameters. The functional properties of the samples were substantially affected by the conformational change of the polysaccharide, as well as by the type of the hydrocolloid and salt solution. There was an evident change of viscosity and conductivity of the solutions upon heating, corresponding to the helix-coil transition of the polysaccharide at temperature about 35 °C. The type of the salt solvent had an effect on the gelation properties of the samples. Gelatin/kappa-carrageenan blend in NaCl provided a gel of high consistency at ambient temperature (20 - 25 °C), whereas the blend in KCl did not gel in the studied temperature range. The potential stability of the blends was determined by zeta-potential analysis. The low values of ζ-potential indicate that the gelatin/polysaccharide blends are electrically unstable systems which tend to coagulate. The mixtures of gelatin/polysaccharide electrostatic complexes may have a great potential in many food applications. © 2017 Potravinarstvo Slovak Journal of Food Sciences.

There were studied four types of powder filler materials for polyolefin composite parts production for automotive and aerospace industry. There was confirmed, that the particle shape has a strong effect on the acoustic and mechanical properties of the powder bed as influenced by the varying packing density. The calcium carbonate spherical hollow particles exhibited the best aerodynamic performance when aerated and were completely fluidised. Simultaneously they were exhibiting the easy flowing behaviour as reflected in the observed flowability of 4.71. In contrary to this, the flat lamellar geometry of the precipitated calcium carbonate resulted in the worst fluidisation behaviour, as the aeration energy was 2.5× higher in comparison to the spherical particles. Remaining samples under study, i.e. flash calcined kaolin and dolomite powder, exhibited cohesive rheological behaviour as reflected in the observed flowability. There was found a clear correlation between powder rheological and electrostatic charge data with the observed acoustic performance as reflected in the frequency dependence of the normal incident sound damping coefficient. This was demonstrated by a relatively high increase in the damping efficiency with increasing porosity of the powder bed as reflected in the decreasing packing density. However the best fit was found between the absolute value of the electrostatic charge values and the sound damping properties.

The general theory of electrokinetic phenomena strictly applies to ideal and rigid surfaces or particles. However, many interfaces are non-ideal with respect to both the surface smoothness and surface homogeneity. Detailed knowledge and understanding of the interface structure is often required for proper analysis of electrokinetic measurements. In this study, we investigate the option of studying surface heterogeneity using powder polycrystalline active pharmaceutical ingredients (APIs) as our model systems. We characterized these by a combination of physicochemical techniques, i.e. inverse gas chromatography surface energy analysis, SEM, thermal analysis and powder rheology, to assess the surface interface structure, topology, roughness, chemical heterogeneity and cooperative macroscopic behaviour. The latter characteristics are reflected in the three dimensional packing, which, in turn, affects the porosity and rigidity of the obtained powder bed. Such information is also of paramount interest for realizing proper fluid transport and dispersing or tableting API substances in the pharmaceutical industry. Notably, the 3D packing is affected not only by geometrical characteristics of the powders but also by the polarity and surface charge distribution. These characteristics can be correlated with surface energy data by means of surface energy profiles and surface energy distribution plots.

A broader and quantitative understanding of cell adhesion to two-dimensional carbon-based materials is needed to expand the applications of graphene and graphene oxide (GO) in tissue engineering, prosthetics, biosensing, detection of circulating cancer cells, and (photo)thermal therapy. We therefore studied the detachment kinetics of human cancer cells HeLa adhered on graphene, GO, and glass substrates using stagnation point flow on an impinging jet apparatus. HeLa cells detached easily from graphene at a force of 9.4 nN but adhered very strongly to GO. The presence of hydrophilic functional groups thus apparently enhanced the HeLa cells’ adherence to the GO surface. On graphene, smaller HeLa cells adhered more strongly and detached later than cells with larger projected areas, but the opposite behavior was observed on GO. These findings reveal GO to be a suitable platform for detecting cells or establishing contacts, e.g. between graphene-based circuits/electrodes and tissues. Our experiments also show that the impinging jet method is a powerful tool for studying cellular detachment mechanisms and adhesion strength, and could therefore be very useful for investigating interactions between cells and graphene-based materials.

Two types of nano/micro sized mica powders for polymer composites, muscovite and phlogopite, were tested for their sound absorption capabilities. Acoustical performance was correlated to surface energy analysis and powder rheology testing. Inverse gas chromatography (iGC) was used to determine the surface energy, with the dominant component being the dispersive component. This reflected the non-polar, hydrophobic, character of the micas. The determined yield locus and Mohr's circles indicated that the material with the highest packing density exhibited more free flowing powder characteristics, compared with the lower packing density materials, which exhibited a greater cohesive powder flow behaviour. All tested mica powders were sensitive to aeration and become fluidised. Based on the acoustical measurements the worst sound absorption performance was found for the highest packing density material exhibiting the highest magnitude of the longitudinal elastic coefficient.

Results of inverse gas chromatography adsorption/desorption experiments using selected probes on skimmed milk, whey and demineralised whey powder materials are presented. The dispersive component of surface energy was found to be dominant, indicating a low polarity character. Surface energy profiles of demineralised whey and skimmed milk showed a characteristic steep exponential decrease from approximately 170 mJ/m 2 to 60 mJ/m 2 and 140 mJ/m 2 to 45 mJ/m 2 , respectively, whereas whey powder exhibited a constant (non-exponential) surface energy at approximately 45 mJ/m 2 . The dispersive surface energy of demineralised whey and skimmed milk powder showed a broad distribution ranging from 40 mJ/m 2 to 120 mJ/m 2 and 175 mJ/m 2 , respectively. In contrast, the dispersive surface energy distribution for whey was very narrow, ranging from only 42.8 mJ/m 2 to 45 mJ/m 2 . The determined yield locus and Mohr’s circles indicated that demineralised whey exhibited free flowing powder characteristics, whereas skimmed milk and whey exhibited cohesive powder flow behaviour.

In this study, an impinging jet deposition experiments were performed on synthetic polymer (Zeonor) original and by micro-embossing modified substrates with exactly defined topology as confirmed by AFM and SEM. Deposition experiments were performed at ambient temperature and at selected flow regime of Re = 10. As a particles deposited a polystyrene (PS) 1,1 μm diameter particles (Sigma–Aldrich) were used having negative charge of −20 mV as observed by zeta potential experiments. There was found gradual increase of total number of deposited particles with time reaching steady state number. Obtained kinetic curves were fitted to the theoretical blocking model where characteristic time required to reach the steady state (blocking time) as well as steady state number of deposited particles were calculated.

This paper deals with the viscometric characterization of sodium hyaluronate aqueous and (1:1) electrolyte (KCl) solutions at defined pH and temperature. The solution properties affected the macromolecular chain coil dimensions by triggering their expansion or contraction. Studied hyaluronate solutions viscosities at temperature range of 25–35 °C reflect conformation transition from a double helix to statistical coil as revealed by a step change of Huggin’ constant at 30 °C. A change in the slope of the observed reduced specific viscosity induced by temperature change was a further indication of the double helix-coil transition. The effects were simultaneously confirmed by fluorescence spectrometry measurements.

The effect of low temperature air plasma treatment on the physico-chemical properties of kaolinite/polyethylene composites was studied. Moreover, the kaolin powder was treated with (3-aminopropyl)triethoxysilane as a coupling agent to improve the interfacial adhesion between powder filler and polymer matrix. The modification of the kaolin resulted in a notable improvement in the mechanical strength and elastic modulus of filled polyethylene composites, compared to the virgin polymers. Observed improvement of the tensile strength became more marked as the filler loading increased, indicating an improved degree of filler/matrix interaction. Simultaneously the improvement of the fracture toughness of prepared HDPE and LLDPE kaolinite composites was confirmed. Moreover, the morphology of the grains distribution and tensile fracture surface was examined by electron microscopy confirming excellent distribution of the filler in the polymer matrix.

There was studied dough made from refined white and brown wheat flours of different granulometry by means of mechanical, thermal analysis and rheological testing. Observed results were confronted with textural properties of breads. Obtained data confirmed that fine refined white flour dough had high ability to elongate and accumulate stress, in contrary, brown fine flour dough exhibited weaker ability to accumulate stress. Observed increase of the complex viscosity associated with the gelatinization was the fastest in coarse dough, where it gained also the highest peak viscosity. The highest water content liberated was found from fine brown flour bread. This triggered lower water availability for hydration of starch granules in the bread during baking process, thus promoting higher moisture loss affecting thus the overall expansion and porosity of the bread matrix. The latter effect was ascribed to the presence of bran particles in brown flour.

g r a p h i c a l a b s t r a c t a b s t r a c t Results of inverse gas chromatography adsorption/desorption experiments of selected probes on sodium hyaluronate powder material are presented. It was found that a dominating was a dispersive surface energy part thus indicating low polarity character of the studied HA powder. For 0% coverage 30 mJ/m 2

It was found in this study that the air plasma treatment of particular kaolinite has led to the change of its wettability, which was reflected in the decreased values of water contact angles of wetting from 88.7° for virgin kaolinite to 86.3° for 30 min air plasma treated one. Plasma treated samples show higher average surface energies in the wide range of coverage regimes in comparison to the virgin samples as determined by inverse gas chromatography. Results of these measurements confirmed our assumption, that air plasma treatment activates surface energy of the crystal planes of the kaolinite as reflected in the broadened dispersive surface energy distribution after 10 min treatment time. However with prolonged 30 min treatment time the dispersive surface energy distribution profile was decreased. We assume, that the latter decrease reflects the distorsion of the crystal lattice of the kaolinite as confirmed by FTIR analysis as reflected in changes of Si–O–Si and Al2O–H characteristic absorption bands. Calculated dispersive surface free energy for 24 % surface coverage was increased from original 35 mJ/m2 to 40.3 and 40.8 mJ/m2 for 10 and 30 min treatment times. There were determined yield locus and flow function dependencies at different stress levels for virgin and different time plasma treated samples (flow index—ffc, effective angle of internal friction—φe, unconfined yield strength—σc). It was found that by plasma treatment the character of the flow was shifting from region of very cohesive (ffc = 2.39) to the cohesive (ffc = 3.19). For untreated samples effective angle of internal friction was decreased with increasing applied consolidation stress, while for plasma treated kaolinite it was increased.

Main focus of this study was on characterization of surface properties of virgin and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) phospholipid layer coated poly(ethylene terephthalate) (PET) and polycarbonate (PC) planar articles. Surface properties were followed measuring static contact angles of wetting by means of sessile drop method and deposition of negative polystyrene (PS) colloidal particles followed by impinging jet method at defined flow regimes. It was found that phospholipid coating of both studied samples (PET, PC) let to the vigorous increase of the surface free energy. For coated samples major part of the surface free energy was dominated by polar component in contrast to the non-treated materials. Here the dispersive component was dominating. Results of the deposition experiments of polystyrene particles of 3 μm diameter correspond with trends obtained by contact angle measurements, i.e. the surface treated materials exhibited higher surface activity reflected in increased particle deposition rates. Simultaneously there was confirmed the fact, that with increasing magnitude of the Reynolds number of the dispersion flux the higher deposition rates were observed.

This research examines the effect of a microsize/nanosize talc filler on the physicochemical and mechanical properties of filled polypropylene (108MF10 and 33MBTU from Saudi Basic Industries Corp. and HE125MO grade from Borealis) composite matrices. A range of mechanical properties were measured (tensile properties, bending properties, fracture toughness, notched impact strength (at the ambient temperature and � 20 � C), strain at break, and impact strength) along with micro- hardness testing and thermal stability testing from 40 to 600 � C as measured by differential thermal analysis and thermogravimetric analysis. Increasing filler content lead to an increase in the mechanical strength of the composite material with a simultaneous decrease in the fracture toughness. The observed increase in tensile strength ranged from 15 to 25% (the maximum tensile strength at break was found to be 22 MPa). The increase in mechani- cal strength simultaneously led to a higher brittleness, which was reflected in a decrease in the mean impact strength from the initial 18 kJ/m 2 (for the virgin polypro- pylene sample) to 14 kJ/m 2 , that is, a 23% decrease. A similar dependency was also obtained for the samples conditioned at � 20 � C (a decrease of 12.5%). With increas- ing degree of filling of the talc-polypropylene composite matrix, the thermooxidative stability increased; the highest magnitude was obtained for the 20 wt % sample (decom- position temperature ¼ 482 � C, cf. 392 � C for the virgin polymer). V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2742-2747, 2008

Oxidative (oxygen and air) RF-plasma treatment of HDPE was found as an effective tool for improving wettability, as well as for increasing its surface micro-hardness. The latter plasmas generate wide range of reactive species in the system, which undergo consecutive chemical reactions, creating thus several oxygen based functionalities at the interface (carbonyl, carboxyl, ether, peroxide etc.) as were detected by ATR FTIR and XPS analysis. An increased negative surface charge of plasma treated polyethylene (PE) confirms the presence of functional ionogenic groups containing oxygen. Simultaneously, the vigorous increase of the surface roughness was found as a result of the successful plasma etching.

The zeta potentials of kaolin dilute and concentrated suspensions were monitored using the techniques of electrophoresis and electroacoustics, respectively. The effect of addition of salt (KCl), a polymer material (Triton X-100), and an anionic surfactant (sodium dodecyl sulphate, SDS) on the suspension properties was investigated by electrophoresis. Electroacoustics was employed for the measurement of zeta potentials for the highest possible kaolin content in suspension and the effect of dilution. The effect of aging of a freshly prepared sample and kaolin isoelectric point was also studied. Using both techniques it was noted that there was no isoelectric point, just a maximum value in the magnitude of the kaolin suspension zeta potential. These maxima were observed also in the presence of Triton X-100 and SDS. An increase of the concentration of KCl and SDS in suspension shifted the maxima towards more acidic values, while in the presence of Triton X-100 the position of the zeta potential maxima remained constant. Electroacoustic techniques revealed that a freshly prepared concentrated suspension requires about six hours to equilibrate to achieve a steady zeta potential. Diluting the concentrated suspensions led to decrease of the zeta potential as ions bound to the surface desorbed and screened the surface charge. The zeta potential maxima remained unchanged even after heating the powder in an oven at 200°C (to remove any organic material) thereby suggesting that the most likely explanation for the maxima is isomorphic substitution.