Papers by Keyword: Molecular Orientation

Abstract: The use of different process media such as cutting fluids, coolants, honing oil and washing media in typical machining operations exceeds 5,000 m³ per year. These media support critical functions such as lubrication, corrosion protection, cleaning and cooling, and have an enormous effect on the manufacturing performance. The tribological properties of these media are improved by using additive molecules, which are physically or chemically adsorbed on the surface of tools and workpieces. The additive performance is especially important in water lubricated tribosystems, where the environment is highly corrosive. The role of corrosion inhibitors typically applied is to neutralize the pH of contaminants in the fluid. Ethanolamines and ethylamines are known as ligands which can form chelate bonds with metals via their amino, hydroxyl and deprotonated hydroxyl-groups. In tribology they are widely spread, as corrosion inhibitors and detergents especially for water based lubricants. This study inquires the tribological performance of amine-based solutions in two types of tribotesters which apply different contact conditions. The dissimilar behaviour under rolling and sliding contact is explained in terms of the structure of the adsorbed compounds. Understanding the performance of the first chemisorbed layers of additives on the workpiece provides essential information for optimizing lubrication in aqueous solutions.

Abstract: In this work, the spring back, dimensional change, internal structure and morphology of extruded polypropylene were investigated in order to consider the rolling characteristic. It was found that the internal structure, molecular orientation and crystallinity were changed a little by high spring back under low reduction in thickness. Crystal structure was extended along the rolling direction with high reduction in thickness due to the increase of plastic deformation. As a result, molecular orientation increased and crystallinity decreased at over 30% of reduction in thickness. Crystalline structure of surface was similar to the center part in cross-section at 70% reduction in thickness, and molecular orientation was constant.

Abstract: The present work investigated the variation of internal structure, molecular orientation, crystallinity and mechanical characteristics of polypropylene(PP) after rolling process. The materials plate became narrow when rolled from entrance to exit, and the internal crystalline gradually deformed and at last destroyed. Plastic deformation was discovered along the rolling direction. In this direction, the crystallinity and vickers hardness were decreased, and molecular orientation was increased. Moreover, molecular orientation had a sharp increase at the second half part of rolling sample. The tensile stress of rolled samples increased by 80% parallel to rolling direction and decreased by 22% perpendicular to rolling direction.

Abstract: We examined the molecular orientation of paper and mechanical properties of prepared paper yarn by twisting strips of paper made from various ratios of mulberry bast and Manila hemp. The molecular orientation of paper in direction of the strip was highest for paper with a mulberry bast weight ratio of 30 wt% as measured by a microwave molecular orientation analyzer. In contrast, the paper yarn sample with a mulberry bast weight ratio of 100 wt% showed a low molecular orientation of paper in direction of the strip. For mechanical properties, paper yarn with mulberry bast weight ratio of 30 wt% had the highest strength and Young’s modulus and the lowest elongation. These results show that the mechanical properties of the paper yarn depend on the molecular orientation of the paper in direction of strip.

Abstract: The effect of magnetic field on the flow-phase diagram of discotic nematic liquid crystalline polymers (LCPs) is analyzed with the extended Doi theory in which the molecular shape parameter is defined at negative one. The evolution equation for the probability function of the LCP molecules is solved without any closure approximations. The transition among flow-orientation modes, such as tumbling, wagging and aligning defined similar to the rodlike LCPs, are strongly affected by the magnetic fields parallel to the flow direction.

Abstract: Success in surgical joint replacements has resulted in a huge demand amongst patients. Coupled with the lowered average age of patients requiring hip replacements, younger patients are demanding longer life expectancy from such devices. The increasing need and demand for more durable implants have led to new formulations of high performance nanomaterials (materials with basic structural units of 1-100 nm). Nanotubes in particular have shown great promise because they: 1) have sizes that approach biological structures and 2) possess efficient channels for displaying chemistries relevant to living systems at high densities and well-controlled spatial distribution. Helical rosette nanotubes (HRN) are a new class of soft organic nanomaterials composed of a guanine-cytosine building block that self-assembles in aqueous environments into stable nanotubular structures with an inner diameter of ~1.1 nm. HRN can be decorated with biologically active chemical functionalities such as cell attracting peptide fragments. Previously, we have showed that HRN coated Ti can enhance OB attachment. In addition, proteins were seen to interact favorably with HRN networks in a manner favorable toward OB attachment. Furthermore, in the absence of proteins, HRN were seen to play the role of proteins in promoting OB attachment. The studies herein, attempt to understand the role of the lysine clusters on HRN toward OB attachment. Results show that OB do respond to lysine and molecular orientation considerations were shown to be important. Detailed structural considerations from molecular modeling further present the possibility of topographical influences (nanotube network architecture) towards OB attachment.

Abstract: The molecular organization of the phospholipids Langmuir-Blodgett (LB) films on solid substrates has been studied via Fourier Transform Infra Red (FTIR) spectroscopy. In this study, the formation of well organized ultra thin LB films of phospholipid molecules has been performed by depositing the monolayer onto the solid substrates of silicon wafer. The space filling molecular models of two types of phospholipids have been proposed on the basis of the FTIR spectra.

Abstract: A relationship of residual stress distribution and surface molding states on polymeric materials is presented in thin-walled injection molding. The residual stress is computed by computational numerical analysis, observed with stress viewer and birefringence. The residual stress on polymeric parts can allude the surface quality as well as flow paths. The residual stress distribution on polymeric parts is related with thickness, gate layout, and polymer types. Molecular orientation on polymeric parts is also important in thin wall injection molding. The residual stress and molecular orientation are related to the surface molding states intimately. Analysis of the residual stress is validated through photo-elastic method and surface molding states..

Abstract: Residual stress distribution and surface molding state of polymeric materials are presented for thin-walled injection molding. The residual stress is computed by computational numerical analysis, observed with a stress viewer and birefringence. The residual stress on the surface of the polymeric part can indicate the surface quality as well as flow paths. The residual stress distribution of the polymeric part is related with the part’s thickness, the gate layout, and the polymer type. Molecular orientation, affected by flow paths, is simulated and validated by observing the birefringence of the polymeric specimens. The residual stress and molecular orientation are closely related to the surface molding states.