Composite roll covers

Two basic composite designs for the functional layer of roll covers are used in the paper industry Composite covers with a fiber reinforced functional layer and composite covers with a cast functional layer (resin covers). 

Structural composites, where the fiber characteristics dominate the mechanical properties, the fiber volume content of the functional layer of roll covers is relatively low. The major physical properties like hardness, compressive modulus or strength of the covers are mainly dominated by the particle fiUed resin matrix. 

The surface of the covers must be as smooth as possible, the wear resistance excellent These properties can be influenced for instance by the modulus of the fibers, particle size distribution and hardness combinations of the fillers and, to a minor extent by the properties of the resin. Temperature resistance and low heat build up of the cover under dynamic load is mainly a function of the resin matrix system. Operating conditions of calenders such as 25 Hz load frequency, 90 °C surface temperature and 50 MPa nip pressure as well as expected load cycles of >10 make the elastic calender covers the most demanding applications of roll covers. Figure 5.13 shows an elastic composite cover in a multi-nip calender. 

Vamac can be calendered and fabricated into roll covers for specialty applications. Compositions for roll covers should be formulated to minimize heat buildup (Table 6.41). 

There is one obvious drawback of high-hysteresis rubber. In normal rolling operation, considerable elastic deformations still take place in the tyre wall, and high-loss tyres will consume fuel and generate considerable heat. The way out is to use a low-loss tyre covered with a high-loss tread - another example of design using composite materials (Fig. 26.9). 

Hose may be hand built using a three roll wrapping machine. The centres of the three rolls form an equilateral triangle. The hose during construction sits on the junction between the two lower rollers and pressure is exerted to consolidate the composite by the upper movable roller. An extruded inner liner, after fitting to a solid inner mandrel, is placed into the machine between the rollers and then the various layers of rubber coated or resorcinol-formaldehyde-latex treated, fabric are applied in a spiral form, with overlap. Once the reinforcement layers have been added the cover rubber is applied and a cloth, usually nylon, is spirally wrapped around the constructed hose using the roller system. The hose is now ready for vulcanisation. 

Typical of the temporary or manufacturing aid coating systems is the RISTON dry film photoresist for printed circuit (PC) board fabrication. This was the first of these systems developed. The RISTON product structure and the basic steps in its use are shown in Figure 2. It consists of a photopolymer sheet laminated between a Mylar cover sheet and a polyolefin separation sheet. It is manufactured as a continuous web (see Coating processes, survey), and is supplied in rolls of varying width and photopolymer composition. 

Viscose rayon if the sample be cotton or acetate rayon. It is then rolled up and placed in a test tube and covered with the appropriate peroxide liquor. The compositions of the liquors and the conditions of the tests are set out in Table 25.1. 

Prior to the invention of screw closures, corks, glass stoppers, pulpboard discs and parchment covers were the main closures. Historically, prethreaded screw closures have consisted of a threaded shell containing a wad or liner and a facing. The wad or liner may be made from cork agglomerate (gelatin or resin bonded), pulpboard, feltboard, plastic or rubber. It provides a resilient backing which receives the compression. In the case of screw closures the compression is due to the application of a controlled torque. Other closures, e.g. roll on, clinch, press on, may achieve this by the simple application of top pressure. Under the normally recommended torques, composition cork compresses by about 50% and pulpboard by approximately 20%. 

The textile with embedded flexible solar cells overcomes the aforementioned technical problems. According to a first aspect, its subject matter is a reliable photovoltaic composite, employed in particular for solar protection, which includes at least one flexible photovoltaic panel and at least one textile panel on the outside face, on which the said photovoltaic panel is laminated by means of a first connecting layer. In a characteristic manner, in the direction transverse to that in which it is to be rolled and at any level of the photovoltaic panel, the said composite is of more-or-less constant thickness, including one or more reduced thickness zones, where the said reduced thickness corresponds to the thickness of the textile panel possibly covered with a film on its inside face. This particular arrangement is used to prevent the formation of folds in the composite, whether during the rolling operation or in the deployed position. 

For lower demand apphcations composite covers with conventional fiber reinforcements (glass or polyester) are used. These covers are for apphcations such as guide rolls or special press positions. 

Chemistry. The composition of Beta-21S is based on the objective of obtaining a cold roUable, strip-producible alloy for economical processing into foil form. The key to processing an alloy to foil form is cold rolling of strip product. If an alloy cannot be cold rolled as strip, a hot process on a hand-mill using cover sheets to form packs for heat retention is the only other viable option. Although the pack process offers the opportunity to crossroll to minimize texture, it is nonetheless labor intensive and inherently a lower yield process. 

Nitrile rubber/phenolic adhesives are also quite useful in adhering rubber to various met-als, " e.g., in the manufacture of rubber covered metal rollers. Huber reported that a nitrile/phenolic adhesive composition provided excellent bonding of rubber to a magnesium roll (Table 20). Other metal bonding applications with nitrile rubber/phenolic adhesives include laminating aluminum foil to paper and then to wood, bonding abrasives to metal, and bonding polyamide to metal. 

The diffusion welding and cold-rolling procedure previously described for the synthesis of the Ni-based membrane has been also applied to the production of a Pd-Ag/Nb/Pd-Ag composite membrane. In this application, two Pd-Ag foils with a thickness of 25 pm were used to cover a Nb plate with a thickness of 1 mm. This composite membrane was rolled down to a thickness of 128 pm (of which about 122 pm was Nb bulk, between two very thin Pd-Ag layers of 3 pm). The permeation tests carried out at 180°C... 

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