Sheet surface texture

Plastic Sheet. Poly(methyl methacrylate) plastic sheet is manufactured in a wide variety of types, including cleat and colored transparent, cleat and colored translucent, and colored semiopaque. Various surface textures ate also produced. Additionally, grades with improved weatherabiUty (added uv absorbers), mat resistance, crazing resistance, impact resistance, and flame resistance ate available. Selected physical properties of poly(methyl methacrylate) sheet ate Hsted in Table 12 (102). 

In a calender line, the polymer melt is transformed into films and sheets by squeezing it between pairs of co-rotating high-precision rollers. Calenders are also used to produce certain surface textures which may be required for different applications. Today, calendering lines are used to manufacture PVC sheet, floor covering, rubber sheet, and rubber tires. They are also used to texture or emboss surfaces. When producing PVC sheet and film, calender... 

The physiological properties of SF matrices strongly depend on its molecular conformation and surface texture. SF exhibits at least three crystalline forms silk I, silk II, and alpha-helix. All three conformations can be formed from the appropriate preparation conditions and each is interchangeable under certain conditions. Crystallization of SF involved the conformational transition that can be easily induced by simple physical (thermal), mechanical or chemical treatments. The most common method to convert the distorted conformation (random coil or silk I) of SF into the more stable P-sheet (silk II) conformation is to treat the SF film with an organic solvent. It is well known that organic... 

In its simplest, most highly developed form, the texture of sheet is such that most of the grains are oriented with a certain crystallographic plane hkl) roughly parallel to the sheet surface, and a certain direction [wnv] in that plane roughly parallel to the direction in which the sheet was rolled. Such a texture is described by the shorthand notation hkl) uvw. In an ideal texture of this kind, the grain orientations in the sheet are fixed with respect to axes in the sheet there is none of the rotational freedom of grain orientation possessed by a fiber texture. 

If a coating, such as an electrodeposit, on a flat sheet has a fiber texture with the fiber axis [uvw normal to the sheet, then the hkl) planes normal to [uvw will be parallel, or nearly parallel, to the sheet surface. Unusual diffraction effects can then occur ... 

An electroplated layer of copper on sheet steel is examined in a back-reflection pinhole camera with Cu Ka radiation incident at right angles to the sheet surface. Assume the copper has a fiber texture with the fiber axis [ww] scattered by an angle p in every direction about the sheet normal. How large must p be for the 420 Debye ring (see Table 4-2) to appear on the film if the fiber axis [//yw] is (a) [110], (b) [100] ... 

Fig. 9 Chill roll stack for sheet extrusion (1) sheet die with flow restrictor (2) molten sheet extrudate (3) lower chill roll (all chill rolls temperature controlled) (4) middle chill roll (imparts gloss/surface texture to sheet) (5) upper chill roll and (6) solidified sheet.

Tube and rod concretions are small (0.1-5 cm diameter, 3-50 cm long) horizontal to vertical masses that occur both individually and in groups. They are associated with overbank fines (OF), palaeosol horizons (P), aeolian sand sheet deposits (ES) and interdune (ID) deposits (Table 1 Fig. 6). They often branch, and most thin downwards (Fig. IOC). Some rod concretions have pitted, tubular and grooved surface textures most are smooth. 

Figure 1 Examples of different morphologies, surface textures and sediment cover on lava flows on the northern East Pacific Rise. Digital images were taken from heights of 5-1 Om above the seafloor using the Woods Hole Oceanographic Instution s camera system. The dimensions of the photographs are approximately 4.5 m x 3.0 m. (A) Pillow lava. (B) Hackly or scrambled flow. (C) Lobate lava. (D) Lineated sheet flow. (E) Ropy sheet flow. (F) Collapse structure in lobate flows. (G) A young flow contact on top of older flows. (H) Heavily sediment covered lobate flows with small fissure. Images from Kuras etal. 2000.

Calendering can also be used to produce film and sheet with desired thicknesses and surface textures. In this process, the polymer melt is squeezed between pairs of co-rotating high precision rollers, followed by a series of chilling rolls. Very tight tolerances in film or sheet thickness can be attained. PVC sheet is usually made in this manner. 

Optical parameters, which are properties of the surface, gloss, reflectance, and color, are in principle relevant to all polymer materials, but it is not frequently that rubbers and foams are used where these aesthetic qualities are important. Not that these properties are entirely a matter of appearance, because color and reflectance are important in terms of solar energy reflected and hence the temperature rise in an exposed material. Roofing sheet is a particular example, but generally the color would only need to be approximately matched. Gloss is also important in terms of glare from a surface and would be controlled in such products as artificial sports surfaces. Surface texture will affect gloss and reflectance and how a surface looks, but it is not in itself an optical property. 

Guenard, V., Valentini, R. F and Aebischer, P. (1991), Influence of surface texture of polymeric sheets on peripheral nerve regeneration in a two-compartment guidance system. Biomaterials 12(2) 259-263. 

In sheet extrusion where the molten sheet of polymer is forced through a set of rolls, the surface conditions are strongly determined by the surface texture of the rolls. If the rolls are polished, they will impart a polished surface onto the polymer sheet-this is why these rolls are often called polishing rolls. Obviously, a variety of different textures can be machined into the rolls and, consequently, a number of different textures can be imparted to the extruded sheet. 

Calender Production machine that uses a series of heated rollers to form thin plastic sheets while also producing a specific surface texture. 

Grit or sand-blasted mold surfaces having roughness dimensions of 200-300 i,m are usually acceptable for nonappearance products. Chemically etched surfaces yield texture dimensions to 100 pm or less. Vacuum-formed products usually do not replicate mold surface details of less than about 50 pm. Mold surface texture details as fine as 10 pm can be replicated when the sheet is pressure formed. 

The wetted areas were calculated from the data shown in Figure 2-2. Figure 2-4 illustrates that interfacial area can be increased significantly by promoting spreading of the liquid through design of the surface texture impressed upon the metal sheet. 

With sheet metal structured packings, the ratio of interfacial area to geometric area at low liquid flow rates will vary from 60% to 80% depending on the surface texture, as illustrated in Figure 2-4. This area ratio increases with increasing liquid flow. 

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