Leather grains

Anlass-farbe, /. (Steel) temper color (Leather) graining color, -harte,/. tempering hardness, -hartung,/. temper hardening. 

I uzit. m. (Min.) leucite. levoBtierea, v.t. (Leather), grain, levant. levoBtisch. a. Levantine, levigieren, v.t. levigate. 

Narben, m. (Leather, etc.) grain, -bildung, /. scar formation, cicatrization pitting, -bin-degewebe, -gewebe, n. scar tissue, -leder, n. grain leather. -Si, n. (Leather) grain oil. 

Narben-schleim, m. (Biol.) stigniatic mucus, -schmiere,/. (Leather) grain dubbing, -seite, /. grain side. 

An important advantage of the plastic is that in thermal processing the finish on the surface of the tool—whether it be matt, leather grain, jazzy pattern, or what you will—can be transferred directly to the workpieces. One proviso when a design is applied in this way is that the tool should not wear quickly (which will result in loss of definition of the decoration) or, worse, that it be scratched or damaged so that the unwanted mark is carried over to the products. 

For some types of finish, such as leather grains, the surface of a shell may be subjected to shot-blasting before chromium plating. Alternatively, slightly thicker plating may be applied, and shot-blasted afterwards. The second approach may be preferable, bearing in mind that a surface can be renewed by shot-blasting several times before it becomes necessary to remove and re-plate it. 

Surface structures (in aluminum casting molds) like wood structures, linen structures, and leather grain structures can be taken over into the model. An example of aluminum molds for the production of anatomical visual models made from PVC is shown Figure 1.183. 

Fine contours of the model surface are accurately transferred to the galvanized mold inserts through electroplating, such as genuine leather grains, skin texture, fine diamond cuts as used in micro-reflectors, high-gloss polish, etc. 

For instrument panel and door trim skins, technical grains having a geometric (e.g., diamond or square) pattern were introduced in the late 1990s as a substitute for imitation leather grains that have dominated interior skin surfaces for 30 years. 

Splitting. In most modem large tanneries that make upholstery leather, and in some that make shoe uppers leather, the hides are spHt in the lime condition. In splitting the hides are cut to the desired thickness with a horizontal belt knife. The hides are fed into the machine grain up. The clearance between the grain and the blade is maintained by a series of narrow rollers supported by a mbber roUer underneath the spacing roUers. The grain layer is then cut to the thickness desired to an accuracy of about 0.1 mm. 

The chrome-tanned leather is removed from the dmm and wmng to remove the absorbed tanning solution. The leather is then inspected for quaUty of the grain and other characteristics of importance for the leather being made. In large tanneries where very uniform hides are worked, the leather may be trimmed and spHt to the desired thickness. Hides spHt before tanning need no splitting at this point. 

Buffiag may be only to remove surface blemishes such as iasect bites or minor healed scratches, or the buffing may be to make a suede surface. Newbuck is a light suedeiag of the grain of catde hide leather. Sheepskin suede is usually buffed on the flesh side of the skin. SpHts may be buffed to make buck shoe leather or heavy garment leather, often called ranch hide. The variations depend on the desires of the customer. 

Leather finishes penetrate to a greater or lesser extent and have a profound effect on the grain or wrinkle characteristics of the leather. Penetration of the resia into the leather tightens the grain but may produce a surface stiffness and a tendency toward grain cracking upon flexing. The development of leather finish resins and the appHcation of these finishes is done by specialty houses. 

Such a unique hierarchical stmcture gives leather several advantages (/) transformabiUty into any desired shape, (2) resistance to penetration of wind, water, and other materials, (3) breathabiUty (water vapor and air permeabiUty, and water absorption), (4) flexibiUty, and (5) processibiUty into finished forms having a grain or suede surface. 

Vinyl-Coated Fabrics. Leather substitutes are designed to imitate the appearance of leather with its grain surface. This requirement has been accomphshed by coating substances that are capable of forming a uniform film, and was first met by plasticized poly(vinyl chloride) (PVC). A leather-like material termed vinyl-coated fabric was developed in the 1930s in the United States and Germany. Shortages of leather after World War 11 spurred the expansion of this material. 

Significant improvement in the fiber stmctuie of leather is finally achieved by using microfibers as fine as 0.001—0.0001 tex (0.01—0.001 den). With this microfiber, a man-made grain leather Sofrina (Kuraray Co., Ltd.) with a thin surface layer (Fig. 7), and a man-made suede Suedemark (Kuraray Co., Ltd.) with a fine nap (Fig. 8) were first developed for clothing, and have expanded their uses. Ultrasuede (Toray Industries, Inc.) also uses microfibers with a rather thick fineness of 0.01 tex (0.1 den). Contemporary (1995) man-made leathers employ microfibers of not mote than 0.03 tex (0.3 den) to obtain excellent properties and appearance resembling leather. 

The properties of leather-like materials depend on the polymer used for substrate and coating layer. Feel, hand, and resistance to grain break are affected by the constmction. The polymers and constmctions of leather-like materials are shown in Table 1. Physical properties of leather and leather-like materials are shown in Table 2. 

Water-Vapor Permeability. Water-vapor permeabiUty depends on the polymer used for the coating layer and its stmcture. Vinyl-coated fabrics have Httie water-vapor permeabiUty due to the coating layer. Although polyurethane polymer is water-vapor permeable, urethane-coated fabrics also have low permeabiUty values due to their soHd layer stmcture. On the other hand, man-made leathers have good permeabiUty values as high as that of leather due to their porous layer stmcture. The permeabiUty of grain-type is lower than that of suede-type, influenced by finishing method. 

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