Marek Szostak

Two-dimensional spectral–spatial EPR imaging with the rapid scan and modulated magnetic field gradient

A new method for fast spectral-spatial electron paramagnetic resonance imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradients, whose amplitude is modulated at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The spectral-spatial images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to acquire the spectral-spatial image with 800 projections at 200ms.

Development and Characterization of the Injection-Molded Polymer Composites Made from Bicomponent Fibers

The results of this study are related to the implementation of the concept of self-reinforced composites. The input materials in preparation process were the bicomponent fibers. The studies were carried out on three types of fibers, HDPE/PP, cPP/PP, LPET/PET. In each case, the matrix material was a low melting polymer, and the core was made of a higher melting point polymer. The research was conducted for the materials shaped by an injection-molding technique. The analyses confirmed the two-component structure. Properties of the resulting composites confirmed the applicability of bicomponent fibers in the preparation of self-reinforced composites. GRAPHICAL ABSTRACT

Molecular dynamics of poly(ethylene 2,6-naphthalate)-polycarbonate composite by nuclear magnetic resonance

The aim of the work was to examine molecular dynamics of a series of poly(ethylene 2,6-naphthalate)-polycarbonate blends with changing weight ratio of copolymers by off-resonance nuclear magnetic resonance technique. It was shown that this technique provides information about the correlation times of the internal motions. The spectral density function amplitudes were estimated on the basis of the dispersion of the spin-lattice relaxation time off-resonanceTlpoff. The measurements were performed for two series of blends which had been injection moulded with and without compatibilizer. The new polymer materials were also characterized using differential scanning calorimetry. Samples obtained after injection moulding and annealing became amorphous, which indicates that a reaction of transesterification process between the two polymers occurred.

Two-dimensional EPR imaging with the rapid scan and rotated magnetic field gradient

A new method for fast 2D Electron Paramagnetic Resonance Imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradient, whose orientation is changed at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to reduce the image acquisition time up to 10 ms for 2D EPRI, and to detect the sinogram with infinitesimal angular step between projections.

Polyethylene green composites modified with post agricultural waste filler: thermo-mechanical and damping properties

Abstract The aim of the study was to determine thermo-mechanical properties and applicability of sunflower husk waste as a filler for ultra low density polyethylene composites. The post agricultural waste filler was milled and chemically treated with (3-aminopropyl)triethoxysilane (3-APS). The amount of filler used was 5, 10 and 20 wt%. The mechanical and thermal properties of the composites containing unmodified and modified natural fillers were determined in the course of static tensile test, rebound resilience by Schob method, and dynamic mechanic thermal analysis. The influence of filler loading and chemical modification of the filler on the morphology of natural composites was evaluated by SEM analysis.

The influence of processing conditions on the mechanical properties and structure of poly(ethylene terephthalate) self-reinforced composites

The self-reinforced composites based on poly(ethylene terephthalate) (PET) are relatively new materials, competitive to composites based on polymers from the group of polyolefins. The use of PET as a base material should be another step forward for this technology, taking into account the properties, price, and the recycling possibility of proposed composites. In this research work, the main subject was to assess the impact of processing conditions on the final properties of the PET self-reinforced composites (srPET). The examined samples were prepared by hot-compaction technique under variable thermal conditions. The input material was composed of PET resin and low-melting copolymer (LPET). The high tenacity PET fibers were used as reinforcement for PET copolymer matrix. Initially both materials were in the form of continuous fiber; they were woven into a hybrid yarn wherein the proportion of PET and LPET fibers was 50/50. The properties of this hybrid yarn were investigated by differential scanning calorimetry (DSC) analysis, where the hot-compaction process conditions were simulated. Composite samples were investigated using the dynamic mechanical analysis (DMA) and static tension tests. The structure of the composite was observed using the optical microscope. The obtained mechanical properties of such a composite are not comparable to commercially made composite sheets, in which overall properties are mostly higher.

Thermal Properties of Polymer-Metal Composites

The objectives in this paper are to investigate the effects of the filler content and size on the effective thermal conductivity of the PE/Al; PE/Cu, PE/Fe and PE/bronze composites. The polymer matrix of the polymer/metal composites was two types of polyethylenes: LDPE and HDPE (from Basell Orlen). The following polymer/metal composites obtained by extrusion process containing: 10% by weight of Al, Cu, Fe and bronze powder in LDPE matrix and composites containing 5, 10, 15 and 20% by weight of Al flakes in HDPE polymer were prepared and tested. Adding in the extrusion process 10% by weight of bronze powder into the polyethylene, increased more than five times the thermal diffusivity of produced composite. Use as a filler 20% wt. of aluminum flake increases it by more than twice. The study showed the ability to produce polyethylene matrix composites with the addition of metal powder fillers (Al, Cu, Fe, and bronze). Analyzing the measuring results of thermal diffusivity coefficient by Angstrom method, it can be concluded that with the appropriate filler content, the particles are located close enough to each other to form a continuous conductive path, then the thermal diffusivity of the composite increases significantly.Copyright

Influence of Fill Imbalance on Pressure Drop in Injection Molding

During injection molding process melted polymer is introduced into mold cavity due to the pressure delivered from injection unit. Mold design principles suggests that filling of the cavity should be balanced. It means that the furthest regions of cavity (measured from injection point) should be filled at the same time to avoid problems with differential shrinkage and injection pressure drop. Fill imbalance can lead to the significant increase of pressure drop and needed clamp force, that can be compensated with more powereful injection molding machines. In this paper the relation between fill imbalance and injection pressure needed for cavity filling were investigated with Autodesk Moldflow Insight software. In this research several different shapes with thickness change of analyzed parts were performed to measure the significance of imbalance on injection pressure drop. It was found that it is possible to find a gate location even for geometrically imbalanced part, where significant pressure drop reduction can be obtained. Additionally, It was found that lowering V/P switchover point can provide significant reduction of needed injection pressure even if gate location must be placed in unfavorable location

The structure of isotactic polypropylene in composites filled with lignocellulosic material

ABSTRACT Biodegradability of fillers, interesting physical and mechanical properties of polypropylene/lignocellulosic materials are essential motives for undertaking studies of various properties of such materials. Up to now, there have been no complex investigations defining processing of polypropylene/rapeseed straw composites. This study presents the results of research into finding optimal technological parameters of extrusion and injection molding methods. The structural investigations were done using the wide-angle X-ray scattering method. Crystallization of polypropylene in composites filled with rapeseed straw is connected with interfacial interactions, such as shearing forces at the boundary of phases: polypropylene matrix—mold wall—lignocellulosic filler. The value of the melt flow index (MFR) for polypropylene influences the crystallization structure of the crystallization in the injection molding process. Moreover, various parts of dumbbells have different structure of the matrix, which is caused by shearing forces and cooling conditions during the polypropylene processing.

Wpływ modeli materiałowych na jakość wyników analiz wytrzymałościowych wyrobów z tworzyw sztucznych

Nowadays, more and more elements originally made of metal are replaced with plastic parts. This is due to the low density of polymer materials, their high relative strength, as well as the ease of forming (complicated elements can be produced in one operation). The disadvantages of plastics are low rigidity and very non-linear material properties. To increase rigidity, a glass fiber filler is used above all. Its addition to the polymer allows to increase the rigidity from four to six times (depending on the type and amount of fiber added, in the case of carbon fiber, it is possible to achieve up to 10-fold improvement in rigidity), due to which the manufactured elements have less deformability with a slight increase in basis weight [1, 2]. The disadvantage of using glass fibers is to reduce the maximum elongation of details and their impact strength. In addition, the introduction of glass fibers into the polymer matrix results in the anisotropy of the material depending on the orientation of the fiber, which in turn depends on the method of filling the cavity forming the mold. In addition, it complicates the mathematical description of the phenomenon of deformation under the influence of applied loads.