Wpływ struktury materiałów wierzchnich i wkładek obuwniczych na ich właściwości elektryczne

Protective footwear for occupational use conducts static electricity through the upper, linings, insole and outsole into the ground. Footwear must be made from appropriate material to reduce the possibility of electrocution and other electricity-related incidents.In this study the influence of footwear materials for the upper and lining components’ structure on their electrical properties was investigated. For investigations leather and various textile laminates were chosen. The thickness of leather coating, composition textile laminates, the upper–lining system, and relative humidity of the environment on electrical resistivity changes were evaluated. Leather shows antistatic properties at standard humidity, but its electrical conductivity greatly increases at high humidity due to the presence of polar groups in the leather structure. Textile lining laminates composed of natural and synthetic fibres are insulators, but their systems with leather at high humidity show resistivity values close to antistatic materials. Leather acrylic coating decreases the electrical conductivity of materials.Obuwie ochronne do użytku zawodowego przenosi ładunki elektrostatyczne przez materiał wierzchni, wkładkę i podeszwę w ziemię. Obuwie musi być wykonane z odpowiedniego materiału, tak aby zmniejszyć ryzyko porażenia prądem i innych incydentów związanych z energią elektryczną. W pracy zbadano wpływ struktury materiałów obuwniczych na ich właściwości elektryczne. Do badań wybrano skórę i różne laminaty tekstylne. Oceniano wpływ grubości powłoki skórzanej, rodzaj kompozycji laminatów tekstylnych oraz wilgotności względnej otoczenia na zmiany rezystywności elektrycznej. Skóra wykazuje właściwości antystatyczne przy standardowej wilgotności, ale jej przewodność elektryczna znacznie wzrasta przy wysokiej wilgotności ze względu na obecność grup polarnych w strukturze skóry. Laminaty z włókien tekstylnych składające się z włókien naturalnych i syntetycznych są izolatorami, ale po połączeniu ich ze skórą w wysokiej wilgotności wykazują wartości oporności zbliżone do materiałów antystatycznych. Stwierdzono także, że skóra z powłoką akrylową charakteryzuje się zmniejszoną przewodnością elektryczną materiałów

Phase-Selective Crystallization of Perylene on Monolayer Templates

The planar aromatic hydrocarbon perylene serves as the core unit in many photoconductive and electronic materials. Perylene crystallizes in two polymorphic forms, α and β, which grow concomitantly from many solvents. Crystallization in the presence of a small library of gold–thiol self-assembled monolayers (SAMs) and functionalized siloxanes identified conditions under which phase pure material can be obtained. Au-biphenylthiol SAM templates nucleated phase pure α-perylene with preferred alignment along the α-(100) plane. Siloxanes with terminal amino functionalities proved to be effective templates for the generation of phase pure β-perylene aligned along β-(100). Phase mixtures grew on most other templates examined. Comparison of the morphologies and nucleation densities of crystals grown under various conditions suggests that the phase selectivity observed on these templates is also sensitive to solvent choice and solute concentration

Solvent Effects on the Growth Morphology and Phase Purity of CL-20

The performance and stability of the high energy secondary explosive 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW, also known as CL-20) can be affected by factors including the phase purity of the bulk material, as well as the particle size, morphology, and defect density of the individual crystallites. Slow evaporation crystallization of CL-20 from 16 different single solvent and co-solvent systems was performed. The phase purity of the bulk material obtained was analyzed by powder X-ray diffraction, optical microscopy, and differential scanning calorimetry. These complementary methods confirmed that under most of the slow evaporation conditions examined, a concomitant mixture of two or more crystalline phases was usually obtained. Numerous individual crystal morphologies were determined using single crystal X-ray goniometry and compared against calculated BFDH morphologies. Examination of the packing interactions in the different CL-20 phases via Hirshfeld surface analysis provides some insight into why concomitant polymorphism is so frequently observed

Structural Diversity in 1,3-Bis(<i>m</i>‑cyanophenyl)urea

Hydrogen bonding between 1,3-bis ureas is a commonly used motif in the assembly of supramolecular structures such as gels, capsules and crystals. The title compound, 1,3-bis­(<i>m</i>-cyanophenyl)­urea (<b>mCyPU</b>), has previously been shown to crystallize in both an anhydrous and monohydrate phase (α and H–I). An expanded search for polymorphs and cocrystals of <b>mCyPU</b> revealed a much greater diversity of solid forms including three additional polymorphs (β, δ, ε), a second hydrate (H–II) and two cocrystal phases with dimethyl sulfoxide and triphenylphosphine oxide. Analysis of the single crystal structures obtained in this study shows that the typical 1-dimensional H-bonding between 1,3-bis urea groups is disrupted by the presence of other H-bond acceptors including cyano, water, sulfoxide and phosphine oxide functionalities. Re-examination of <b>α-mCyPU</b> additionally showed both blade and plate-like morphologies could be obtained from different growth solvents, with crystals of the latter morphology exhibiting a grain boundary migration prior to melting

Predicting Cocrystallization Based on Heterodimer Energies: The Case of <i>N</i>,<i>N</i>′‑Diphenylureas and Triphenylphosphine Oxide

Diarylureas frequently assemble into structures with one-dimensional H-bonded chain motifs. Herein, we examine the ability of triphenylphosphine oxide (TPPO) to disrupt the H-bonding motif in 14 different <i>meta</i>-substituted <i>N</i>,<i>N</i>′-diphenylureas (mXPU) and form cocrystals; 1:1 mXPU:TPPO cocrystals were obtained in 9 of 14 cases examined (64% success rate). Cocrystals adopt five different lattice types, all of which show unsymmetrical H-bonded [R₂¹(6)] dimers between the urea hydrogens and the phosphine oxygen. Heterodimer (mXPU···TPPO) and homodimer (mXPU···mXPU) interaction energies, Δ<i>E</i>_int, calculated using density functional theory at the B3LYP/6-31G­(d,p) level were used to rationalize the experimental results. A clear trend was observed in which cocrystals were experimentally realized only in cases in which the differences in heterodimer versus homodimer energy, ΔΔ<i>E</i>_int, were greater than ∼5.3–6 kcal/mol. Although calculated interaction energies are a simplified measure of the system thermodynamics, these results suggest that the relative ΔΔ<i>E</i>_int between heterodimers and homodimers is a good predictor of cocrystal formation in this system