Linear abrasion

Tang et al. [39] prepared superomniphobic coatings by spray-casting dispersions of polyurethane and MoS nanoparticles. After the spraying 

Zhou et al. [43] used the same experimental apparatus to evaluate the mechanical performance of cotton fabric that was rendered superhydrophobic by incorporation of polyaniline and fluorinated alkylsilane via a facile vapor phase deposition process. The applied pressure was 3.68 kPa. The authors demonstrated that their surface could maintain water APCAs greater than 150° for 600 abrasion cycles but they did not mention anything about hysteresis values. 

Tenjimbayashi and Shiratori [46] developed superhydrophobic coatings by mixing SiO nanoparticles and ethyl alpha cyanoacrylate polymer in acetone and subsequently spraying them while at the same time the distance between spray source and substrate was continuously changing. The change in the distance between spray and substrate was foxmd to be the 

---

Notoriously, professional or amateur skin divers are exposed to an enormous variety of risks, including skin problems. Staphyloccocal skin infections are relatively frequent and also difficult to treat. Local burns can derive from overheating inside the wet suit. Underwater welding procedures can induce erythemas and telangiectasia. The skin trapped in the folds of the suit can present linear abrasions. 

Subaquatic activities External otitis, intertrigo, staphylococcal infections, burns, linear abrasions from wetsuit folds, pruritus and erythema from decompression, napkin eruption type dermatitis... 

Figure 9.4a depicts a typical experimental setup for performing a linear abrasion test. Usually it consists of a horizontal arm holding a vertical cylinder that reciprocates in a linear direction while the speed and the length can be adjusted. The bottom end of the cylinder can be fitted with various types of abradant materials like cloth, sandpapers, rubbers, papers or hard aluminum oxide which produce different type of mechanical wear. The... 

Figure 9.4 Linear abrasion configurations (a) with motorized arm that moves and rubs the tested sample surface tangentially, and (b) with sample moving on the abradant surface.

Circular abrasion is based on the same concept as linear abrasion and it uses the same experimental apparatus with the only difference being the type of movement that the abradant material performs. In this case the abradant material has the shape of a disk and it performs a rotational motion. The only disadvantage in this case, compared to the linear abrasion, is that different parts of the abradant material move with different speeds. Even if in most of the cases this is not very crucial, we cannot exclude the possibility that this technique can produce diverse surface characteristics in the abraded surfaces. The Martindale method is a common circular abrasion test that is used mainly for evaluating textiles (see also Section 9.5.1). 

Rubbing between two solid surfaces is a common case that can occur in everyday use of liquid repellent materials. However, there are also occasions when surfaces could come into contact with sharper objects (e.g. knives, pens, forks, etc.) that induce much more severe damage. Driven by this problem, a few studies have been published where liquid repellent surfaces undergo blade tests, which are practically linear abrasion tests but instead of a flat abradant material the rubbing is performed by a sharp blade. 

Currently, however, quantitative assessment of the mechanical durability of non-wetting surfaces is difficult due to the diversity of wear testing and characterization methods discussed above. Ideally, the evaluation techniques should be more standardized and possibly reduced in number, as this would be beneficial for focused efforts to develop resilient coatings. From all the techniques that we described above, there seem to be some of them that are more commonly accepted. Linear abrasion, for instance, seems to be a very well accepted and is a common method to evaluate the mechanical durability. Sand, water/jet and gas impact are also good techniques to evaluate the stability of the surfaces for outdoor applications. Nevertheless, the range of possible applications for super hydrophobic surfaces may call for specialized mechanical tests like laundry tests, finger touch, etc. 

A. Steele, B.N. Nayak, A. Davis, M.C. Gupta and E. Loth. Linear abrasion of a titanium superhydrophobic surface prepared by ultrafast laser microtexturing. J. Micromech. Microeng., 23,115012 (2013). 

Taber Industries Linear Abraser can also emulate the physical contact made with various scratch media. The Multi-Mar Attachment allows you to conduct similar tests as the balance beam tester using mar and scratch tools such as a paperclip, loop stylus, needle stylus, Hoffman type stylus and coin. For soft materials, a 1.0mm diameter hemisphere Scratch Tip is suggested. For harder materials, a conical tool such as the Diamond Scratch Kit or Tungsten Carbide Scratch Tips may be used. 

A linear relationship exists between the cohesive energy density of an abrasive (10) and the WoodeU wear resistance values occurring between comndum H = 9) and diamond H = 42.5). The cohesive energy density is a measure of the lattice energy per unit volume. 

The patented system (15) has stationary disks mounted inside a pressure vessel (horizontal vessel, vertical disks) which is mounted on rollers and can rotate slowly about its axis. A screw conveyor is mounted in the stationary center of rotation it conveys the cake, which is blown off the leaves when they pass above the screw, to one end of the vessel where it falls into a vertical chute. The cake discharge system involves two linear sHde valves that sHde the cake through compartments which gradually depressurize it and move it out of the vessel without any significant loss of pressure. The system rehes entirely on the cake falling freely from one compartment to another as the valves move across. This may be an unrealistic assumption, particularly with sticky cakes when combined with lots of sliding contact surfaces which are prone to abrasion and jamming, the practicality of the system is questionable. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

A wide range of polyurethane-type products has become available in recent years for coating applications. These include simple solutions of linear polyurethanes, two-pot alkyd-isocyanate and polyether-isocyanate systems and a variety of prepolymer and adduct systems. The coatings can vary considerably in hardness and flexibility and find use mainly because of their toughness, abrasion resistance and flexibility. Uses include metal finishes in chemical plant, wood finishes for boats and sports equipment, finishes for rubber goods and rain-erosion-resistant coatings for aircraft. One type of coating is potentially competitive with PVC leathercloth. Both alkyd-di-isocyanate and adduct-diisocyanate compositions may be coated on to fabrics from solutions of controlled viscosity and solids content. Such coated fabrics are soft, flexible and, unlike PVC leathercloth, free from plasticisers. 

Sundararajan et al. [131] in 1999 calculated the slurry film thickness and hydrodynamic pressure in CMP by solving the Re5molds equation. The abrasive particles undergo rotational and linear motion in the shear flow. This motion of the abrasive particles enhances the dissolution rate of the surface by facilitating the liquid phase convective mass transfer of the dissolved copper species away from the wafer surface. It is proposed that the enhancement in the polish rate is directly proportional to the product of abrasive concentration and the shear stress on the wafer surface. Hence, the ratio of the polish rate with abrasive to the polish rate without abrasive can be written as... 

Linear regression analysis was performed on the relation of G"(s) versus PICO abrasion index. Figure 16.10 plots the correlation coefficient as a function of strain employed in the measurement of loss modulus. The regression results show poor correlation at low strain with increasing correlations at higher strains. These correlations were performed on 189 data points. 

Even in a homogeneous solid elastic wheel the distortion is complex and requires sophisticated methods to arrive at a precise relation between force and slip. For tires this is even more difficult because of its complex internal structure. Nevertheless, even the simplest possible model produces answers which are reasonably close to reality in describing the force-slip relation in measurable quantities. This model, called the brush model—or often also the Schallamach model [32] when it is associated with tire wear and abrasion—is based on the assumption that the wheel consists of a large, equally spaced number of identical, deformable elements (the fibers of a brush), following the linear deformation law... 

---