Mechanical properties of glass fiber composites with an epoxy resin modified by a liquid crystalline epoxy

The effect of liquid crystalline networks on epoxy + glass fiber composites is investigated. The matrix obtained from in‐situ curing of liquid crystalline (LC) diglycidyl ether of 4,4‐dihydroxybiphenol (DGE‐DHBP) with diglycidyl ether of bisphenol F (DGEBP‐F) by anhydride curing agent was used as the matrix for polymer composites. Impact, tensile, and flexural testing results are compared between the unmodified and modified systems. The interlaminar fracture toughness of commposites in the shear mode was determined by end notch flexure (ENF) tests. Scanning electron microscopy is used to study the fracture surfaces to understand the mechanism of fracture and interphase formation between the fiber and the matrix.     

Brittleness of materials: implications for composites and a relation to impact strength

Brittleness of materials—whether it occurs naturally or with aging—affects significantly performance and manifests itself in various properties. In the past, brittleness was defined qualitatively, but now a definition of brittleness for viscoelastic materials exists, enabling analysis of all types of polymer-based materials. The quantity brittleness, B, has been evaluated for neat thermoplastics, but here composites and metal alloys are also assessed. The physical significance of brittleness is connected to the dimensional stability of materials. The connections of brittleness to tensile elongation and to fatigue are explored while its relationship to surface properties—specifically wear by repetitive scratching—is examined more closely. The economic impact of wear results in monetary loss associated with failure and reduced service life of plastic parts—thus its connection to brittleness finds use across a broad spectrum of industrial applications which utilize plastics for manufacturing, processing, etc. We also demonstrate a correspondence between impact strength (Charpy or Izod) and brittleness of polymers. It is shown that the assumption hardness is equivalent to brittleness is inaccurate; this fact has important implications for interpreting the results of mechanical testing of viscoelastic materials.     

An application of scanning electron microscopy combined with roentgen microanalysis (SEM-EDS) in canine urolithiasis

Urolithiasis is a common diagnostic and therapeutic problem in small-animal veterinary practice. The traditional diagnostic approach usually consists of clinical, radiological and ultrasonographic examination of the patient. The main diagnostic material is still urine sediment, ignoring the fact that presence of crystalluria is not always of pathological significance. In order to establish the most effective therapeutic and preventative strategies, especially in the case of multicomponent stone, it is crucial to define the exact elemental composition of the given stone including crystallization nidus chemical contents. In the course of the research, the usefulness of scanning electron microscopy combined with X-ray-dispersive spectrometry in analysis of canine mixed and compound stones was investigated. The obtained results indicated that the tested method allows one to trace the dynamics of the crystallization process, including crystallization nucleus detection, and concurrently and quantitatively assess the elemental composition of the given urinary concrement. Moreover, the conducted research showed epidemiological data of urolithiasis occurrence in a population of dogs coming from the southern part of Poland.     

In vitro availability of minerals from oat products

The content of macroelements P, Mg and Ca and microelements Mn, Fe, Zn and Cu was determined in 10 commercially sold oat products made by different technological processes (dehulling, instantinising, extrusion, flaking). Phosphorus was the most prevalent of the macroelements (from 240.8 ± 2.2 to 845.5 ± 8.1 mg per 100 g), followed by magnesium (from 73.2 ± 0.7 to 271.9 ± 2.7 mg per 100 g) and calcium (from 30.69 ± 0.01 to 112.7 ± 0.3 mg per 100 g). The Ca/P ratio ranged from 1:5.3 in crushed oat to 1:8.2 in oat flakes. Regarding the microelements, manganese was present at the highest concentrations (from 2.62 ± 0.02 to 8.69 ± 0.01 mg per 100 g). The content of iron was similar and that of zinc not much lower, whereas the amount of copper was considerably smaller (from 0.23 ± 0.002 to 0.59 ± 0.002 mg per 100 g). The highest concentrations of mineral elements were found in instant oat bran flakes and the lowest in extruded oat and corn crisps containing 50% corn grouts. Samples of the products analysed were subjected to in vitro enzymatic digestion, simulating the digestive process occurring in the human alimentary tract. The supernatants thus obtained were analysed for their content of the previously determined mineral components; the percentage of minerals released from the products was calculated. The following sequence of mineral components released was observed: Cu (57.2–95.6%) > P (39.7–60.9%) > Ca (18.2–39.5%) > Mg (16.4–39.8%) > Mn (6.4–24.7%) > Fe (6.5–29%) > Zn (11–17.2%). The Ca/P ratio in the supernatant worsened from 1:8.2 in crushed oat to 1:23.3 in extruded oat and corn crisps. Crushed oat released the highest amounts of mineral elements during enzymatic hydrolysis, with oat grouts coming second. As regards the other products, it is difficult to establish their relative sequence in the release of minerals. © 2002 Society of Chemical Industry     

Differences in the mineral composition of sound and disordered apple fruits and of sound and pitted tissue

Separation and analyses of sound Cox's Orange Pippin apples and those with disorders, after storage for 18 weeks at 3.3°C, revealed that sound apples had the lowest, apples rotted by Gloeosporium spp slightly higher, apples with bitter pit higher, and apples affected by breakdown even higher proportions of calcium in the residue after extraction with distilled water, although total concentrations of calcium in these samples were in the reverse order. Lower proportions of calcium, magnesium and potassium were extracted by 75% ethanol from fruit with breakdown than from sound apples, and similarly lower proportions of magnesium, and magnesium and potassium were extracted by water from apples with bitter pit and breakdown, respectively. Proportions of phosphorus extracted by either solvent were not obviously related to disorders. The high concentration of magnesium in pitted tissue, in relation to that in adjacent sound tissue, was evenly divided between the fractions soluble and insoluble in water, but that of calcium was mainly in the insoluble fraction.     

Synthesis and characterization of novel alkyd-silicone hyperbranched nanoresins with high solid contents

Hyperbranched alkyd-silicone nanoresins (ASiHBRs) with high solid content were synthesized by etherification reaction between a hyperbranched alkyd resin (HABR) and Z-6018 silicone. ASiHBRs were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and several other techniques. NMR spectra show the presence of aromatic rings, -Si-O and -C-O; grafting was successful. The molar masses of ASiHBRs determined by GPC are higher than that of HABR. The hydroxyl values decrease with increasing silicone content. ASiHBRs have low viscosities what allows easier film formation. Hydrodynamic dimensions, refractive indices, glass transition temperatures, gloss and hardness of ASiHBRs increase with increasing silicone contents. Low contents of volatile organic compounds provide more environmentally friendly coatings.     

Functionality of graphene as a result of its heterogenic growth on SiC nanoparticles on the basis of reversible hydrogen storage

This article presents the results from research related to graphene functionality based on the production of spatial structures provided for the reversible storage of hydrogen. The functionality process was conducted during graphene synthesis onto a liquid metallic support, on a single level, using SiC nanoparticles. Within the scope of research it was proved that heterogenic growth of the domains of polycrystalline graphene onto the SiC nanoparticles is possible. These nanoparticles are in-built into the graphene structure constituting the pillars of the spatial structure. Material produced in such a way constitutes the foundation for creating a spatial 3D structure (through the rolling operation), called GraphRoll, for the reversible storage of hydrogen in order to conduct its sorption and de-sorption. So, independently of the theoretical configuration, deviations or a possible exception from the 2D configuration on the silicon carbide/graphene were discussed. These differences resulted from the difference between the crystallographic structures of the analyzed forms as well as the structure determined to decrease tensions within the structure.     

Bond strength of polymer lightweight aggregate concrete

Bond strength, physical, and mechanical properties of lightweight PC were investigated with inclusion of pumice lightweight aggregate in maximum size of 12 mm. As binder material, epoxy resin‐based polymer was used with its hardener. The binder to aggregate ratio was 30% by weight. In addition, steel fibers were added to lightweight PC mixtures in ratio of 0, 0.5, and 1%. After lightweight PC mixture was prepared, it was poured in the molds with different type of steel‐bars in size of 100 × 100 × 100 mm³. The steel‐bars centered in the cubic molds, and they were in size of Ø12, Ø14, and Ø16. The specimens were cured at 60°C for 2 h. On the hardened polymer lightweight concrete (PLC), pull‐out test for bond strength and compressive strength tests were performed. Moreover, ultrasonic pulse velocity, water absorption by weight, specific porosity, and density experiments were carried out. The relation between physical and mechanical properties showed that PLCs become more durable when using ratio of steel fibers. POLYM. COMPOS., 34:2125–2132, 2013. © 2013 Society of Plastics Engineers     

Infrared-to-visible conversion luminescence of Er ions in lead borate transparent glass-ceramics

Transparent glass-ceramics were successfully prepared during controlled heat treatment of lead borate glasses. The PbF₂ particles were dispersed into a borate glass matrix which was evidenced by X-ray diffraction analysis. The phase identification revealed that crystalline peaks can be related to the orthorhombic PbF₂ phase. Green up-conversion luminescence due to the ⁴S_3/2–⁴I_15/2 transition of Er³⁺ ions was registered. In comparison to the precursor glass the luminescence intensity was considerably higher, whereas the luminescence linewidth slightly decreased in the studied oxyfluoride transparent glass-ceramics. It indicated that a part of the trivalent erbium was incorporated into the PbF₂ crystalline phase.