Search

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.

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.

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.

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.

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.

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.

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.

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

The aim of this study was to determine the basic rheological parameters of dispersed highly concentrated lignite aqueous suspensions. Typical dilatant behavior was observed, where critical parameters of dilatancy were determined for different size fractions and concentrations. To modify the non-Newtonian behavior of the lignite highly concentrated suspensions, the effect of surfactant addition on the flow parameters of the suspensions was determined.

This presentation examines the effect of the micro/nano-sized talc filler on the physico-chemical and mechanical properties of the filled poly(propylene) (SABIC PP 108MF10, SABIC PP 33 MBTU [Saudi Basic Industries Corporation]) composite matrix. A range of mechanical properties were measured (tensile test, bending test, fracture toughness, notched impact strength (at the ambient temperature and −20°C), strain at break, impact strength), as well as micro-hardness testing and thermal stability from 40° C to 600°C measured by thermal analysis DTA and TGA. It was found that increasing filler content lead to a concomitant increase mechanical strength and toughness. The observed increase in tensile strength ranged from 15% to 25% (maximum tensile strength at break was found to be 22MPa). The increase in strength and toughness simultaneously lead to higher brittleness reflected in the decrease of mean impact strength from the initial 18kJ/m2 (for the virgin PP sample) to 14kJ/m2, i.e. a 23% decrease. Similar dependency was also obtained for the samples conditioned at −20°C (decrease of 12.5%). It was found, that with increasing degree of filling of the talc-PP composite matrix the thermooxidative stability was increased, the highest magnitude was obtained for the sample 20 wt% (482°C decomposition temperature cf. 392°C for virgin polymer).