scholarly journals Highly Stable Organic Bisradicals Protected by Mechanical Bonds

2020 ◽  
Vol 142 (15) ◽  
pp. 7190-7197 ◽  
Author(s):  
Kang Cai ◽  
Haochuan Mao ◽  
Wei-Guang Liu ◽  
Yunyan Qiu ◽  
Yi Shi ◽  
...  
Keyword(s):  
Mechanical Bonds

Mechanical bonds and dynamic covalent bonds

2020 ◽  
Vol 4 (6) ◽  
pp. 1553-1553
Author(s):  
Jishan Wu ◽  
J. Fraser Stoddart
Keyword(s):  
Materials Chemistry ◽  
Covalent Bonds ◽  
Mechanical Bonds

Jishan Wu and Fraser Stoddart introduce the Materials Chemistry Frontiers themed collection on mechanical bonds and dynamic covalent bonds.

scholarly journals Effect of Laundering Hydroentangled Cotton Nonwoven Fabrics

2012 ◽  
Vol 7 (3) ◽  
pp. 155892501200700
Author(s):  
Paul Sawhney ◽  
Michael Reynolds ◽  
Chuck Allen ◽  
Ryan Slopek ◽  
Sunghyun Nam ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Mechanical Energy ◽  
Fiber Quality ◽  
Physical And Mechanical Properties ◽  
Water Jet ◽  
Structural Deformation ◽  
Machine Direction ◽  
Sem Images ◽  
Significant Drop ◽  
Mechanical Bonds

To study the effect of household machine laundering on hydroentangled cotton nonwoven developmental fabrics, several sets of such fabrics, uniformly made with cottons of different fiber quality characteristics, were sequentially laundered repeatedly for their performance evaluation after one washing and drying cycle (1 W), 5 W, 10 W, and 20 W, using a standard AATCC method for washing. The control greige fabrics (i.e., before any wash) and their respective versions after the 1 W, 5 W, 10 W and 20 W were examined for their physical and mechanical properties. The laundering results showed that the fabrics, even after 20 wash cycles, had held up unexpectedly well. Nonwovens generally are not considered wash-durable, and more than a third of nonwovens today are used in durable applications that necessarily do not require laundering since most nonwovens inherently are considered “disposable” after one end-use application. At any rate, all the researched fabrics, irrespective of their fiber quality origin, showed a significant drop in tensile strength, mainly after the first wash. The drop was more severe in the machine direction (MD) than in the cross direction (CD). To primarily investigate the cause of the declined fabric tensile strength due to washing, SEM images of the fabrics before and after the washing(s) were studied for any structural deformation. The SEM images clearly showed that the fabrics before the wash had symmetrical, almost uniformly spaced clusters of well-defined fiber entanglements (corresponding to the geometric locations of the orifices in the water jet-strip). After the first wash, those entanglements somewhat appeared to have been considerably “loosened,” disintegrated, and even lost. It seemed that the washing affected the fabric structure mostly in the (hydroentangling) MD. A possible reason for this phenomenon could be the fact that the cotton card used in preparing the native batt for hydroentanglement had aligned and stressed the fibers mostly in the machine direction. The subsequent crosslapping operation to some extent had been altered (randomized), and the fiber orientation in its web output was subjected to the hydroentangling, water jet forces that also stressed the fibers mostly in the MD. Upon washing the hydroentangled fabric in water, the stressed fibers, as expected, somewhat relaxed by releasing some of the stored mechanical energy that originally had held the fibrous structure together by creating strong inter-fiber cohesion or frictional or mechanical bonds. In other words, the washing basically loosened or broke up some of the “mechanical entanglements” and, consequently, their (MD) frictional bonds that had been created by the forceful water jets of the fabric formation process. Research has been planned to stabilize these mechanical bonds by means of special finishing, such as blending cotton with fusible/bonding fibers, resin finishing, and/or even layered fabric-film reinforced composites.

scholarly journals Mechanostereochemistry and the mechanical bond

2012 ◽  
Vol 468 (2146) ◽  
pp. 2849-2880 ◽  
Author(s):  
Gokhan Barin ◽  
Ross S. Forgan ◽  
J. Fraser Stoddart
Keyword(s):  
Self Assembly ◽  
Rapid Development ◽  
Synthetic Methods ◽  
Interlocked Molecules ◽  
Fair Game ◽  
Mechanical Bond ◽  
Covalently Linked ◽  
Mechanical Bonds ◽  
Molecular Compounds ◽  
Knots And Links

The chemistry of mechanically interlocked molecules (MIMs), in which two or more covalently linked components are held together by mechanical bonds , has led to the coining of the term mechanostereochemistry to describe a new field of chemistry that embraces many aspects of MIMs, including their syntheses, properties, topologies where relevant and functions where operative. During the rapid development and emergence of the field, the synthesis of MIMs has witnessed the forsaking of the early and grossly inefficient statistical approaches for template-directed protocols, aided and abetted by molecular recognition processes and the tenets of self-assembly. The resounding success of these synthetic protocols, based on templation, has facilitated the design and construction of artificial molecular switches and machines, resulting more and more in the creation of integrated functional systems. This review highlights (i) the range of template-directed synthetic methods being used currently in the preparation of MIMs; (ii) the syntheses of topologically complex knots and links in the form of stable molecular compounds; and (iii) the incorporation of bistable MIMs into many different device settings associated with surfaces, nanoparticles and solid-state materials in response to the needs of particular applications that are perceived to be fair game for mechanostereochemistry.

Mechanostereochemistry

2010 ◽  
Vol 82 (8) ◽  
pp. 1569-1574 ◽  
Author(s):  
Mark A. Olson ◽  
Youssry Y. Botros ◽  
J. Fraser Stoddart
Keyword(s):  
Mechanical Bond ◽  
Mechanical Bonds ◽  
Noncovalent Bonding ◽  
Configuration And Conformation

Stereochemistry—in both its static and dynamic variants—has progressed apace now for more than a century to incorporate all aspects of covalent, coordinative, and noncovalent bonding at levels of structure which encompass constitution, configuration, and conformation. The advent of the mechanical bond in more recent times is now providing opportunities for the emergence of new stereochemical tenets and concepts, some of which bear close analogies with those of days gone by in chemistry. Since terminology helps to define and disseminate a discipline, we advocate that the term “mechanostereochemistry” be used to describe the chemistry of molecules with mechanical bonds.

scholarly journals STUDY OF THE DEFORMED STATE CONNECTION OF THE PISTON WITH THE ROD OF THE UNREGULATED PISTON PUMP

2020 ◽  
pp. 95-103
Author(s):  
Vasyl Muzychuk
Keyword(s):  
Plastic Deformation ◽  
Shape Change ◽  
Rolling Process ◽  
Piston Pump ◽  
Connecting Rod ◽  
Maximum Value ◽  
Deformed State ◽  
Metal Products ◽  
Mechanical Bonds ◽  
Favorable Conditions

The technological processes of cold rolling of precision workpieces and ring parts, rolling of pipes, rolling of piston-connecting rod axial-rotor piston pump, which are a kind of processing of metals by pressure and contain changes in the shape of workpieces according to performing relative to the axis of the workpiece radial rotational motion. The workpiece can remain stationary or rotate. It is shown that by means of technological process of rolling of pipes, unrolling of preparations various hollow axisymmetric metal products receive, the specified processes are combined by the mechanism of deformation, namely: at them two deformations of compression and one - tension are realized. This mechanical deformation scheme creates favorable conditions for plastic deformation, because intercrystalline displacements are difficult, leading to the violation of mechanical bonds, and plastic deformation occurs mainly due to intracrystalline displacements. It is shown that in the process of connecting the piston-connecting rod in compliance with the process parameters (output supply pressure, feed rate, leaving time) the value of the specified gap either exceeds the maximum value or decreases to the value at which the next operation of the piston-connecting rod spell. The deformed state in the technological operation of rolling the piston-connecting rod pair at different stages of shape change is studied, the process control mechanism is revealed, which prevents the defect in the form of deviation from the regulated gap after rolling between the piston and the connecting rod. The used resource of plasticity at different stages of rolling is calculated, the deformability of the piston workpiece in the rolling process is estimated.

Investigation of Interfaces Between Steel and Vapor Phase Deposited Tungsten by Optical and Electron Microscopy and by Electron Probe Microanalysis

1968 ◽  
Vol 26 ◽  
pp. 394-395
Author(s):  
Karl H. Meyer ◽  
Klemens Stulpe ◽  
John P. Lehner
Keyword(s):  
Vapor Phase ◽  
Erosion Resistance ◽  
High Temperature Strength ◽  
Tungsten Coating ◽  
Thermal Expansion Coefficients ◽  
Operational Life ◽  
Expansion Coefficients ◽  
Pre Treatment ◽  
Mechanical Bonds ◽  
Treatment Procedures

Specific materials requirements such as high temperature strength in combination with corrosion and erosion resistance and limitations in cost and weight often can only be satisfied when a composite material is utilized. A typical example is shown in the form of a thin tungsten layer deposited by the vapor phase process onto the bore of gun barrels to increase their operational life. Initial attempts to plate 4140 steel resulted in flaking-off of the tungsten coating from the substrate but after development of proper pre-treatment procedures of the substrate and of specified deposition temperature, flow ratios and flow rates, firm mechanical bonds between tungsten and substrate were obtained. Requirements for firm bonds are the absence of surface oxide films, small differences in thermal expansion coefficients, interdiffusion of the two metals into each other and other factors.

ChemInform Abstract: New Homocalixarenes and Catenanes. From Molecular Recognition to Mechanical Bonds

ChemInform ◽  
2010 ◽  
Vol 28 (8) ◽  
pp. no-no
Author(s):  
S. MEIER ◽  
S. OTTENS-HILDEBRANDT ◽  
G. BRODESSER ◽  
F. VOEGTLE
Keyword(s):  
Molecular Recognition ◽  
Mechanical Bonds
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