Fiber spreading

Figure 6-8. Schematic of the electromagnetic fiber spreading technique.

Work at Courtaulds [22,23] in the early 1970s attempted to incorporate carbon fiber in a cement slurry, which was difficult due to the size of the cement particles. They tended to be filtered out by the fiber reinforcement, so a cement with a fine particle size (Swiftcrete, an ultra rapid hardening Portland cement with a maximum diameter of about 45 pm) was used and the fiber spread as thinly as possible, using either an air knife, or a water flume and then held in the spread position by sizing with a water based compatible size such as sodium carboxymethylcellulose [22,23]. These larger particles limit the carbon fiber content to about 5% v/v, but in practice, due to a non-uniform distribution, a value of some 12% v/v was attainable. 

Corrosion Resistant Fiber-Reinforced Plastic (FRP). Fiber glass reinforcement bonded with furfuryl alcohol thermosetting resias provides plastics with unique properties. Excellent resistance to corrosion and heat distortion coupled with low flame spread and low smoke emission are characteristics that make them valuable as laminating resins with fiber glass (75,76). Another valuable property of furan FRP is its strength at elevated temperature. Hand-layup, spray-up, and filament-win ding techniques are employed to produce an array of corrosion-resistant equipment, pipes, tanks, vats, ducts, scmbbers, stacks, and reaction vessels for industrial appHcations throughout the world. 

Dew retting iuvolves the action of dew, sun, and fungi on the plants spread thinly on the ground. Dew retting takes 4—6 weeks, but the action is not uniform and it tends to yield a dark-colored fiber. However, it is far less labor iatensive and less expensive than water retting. It is commonly used iu regions of low water supply and accounts for 85% of the Western European crop, especially iu France, and also iu the former Soviet Union. 

Disposable polypropylene nonwoven fabrics are widely used as the coverstock for disposable baby diapers. The expansion of the disposable diaper market throughout the world has been the primary source of growth in the consumption of polypropylene in the fiber market. In addition, nonwoven polypropylene fabrics are used in a variety of other disposable sanitary products, such as baby wipes, adult incontinence, and feminine hygiene products. Use of polypropylene nonwovens in disposable medical apparel, such as surgical gowns, has increased as a means of reducing the spread of infection. 

Reclaimed mbber, which is widely used in dry mbber, has Htde use in latex compounding. A dispersion or artificial latex of the red aim must be made by a rather expensive process of milling in dispersing agents, eg, soaps and casein, and water. Some reclaim dispersions are used in latex compounds for such things as spread mbber goods and adhesives and fiber binders to reduce cost. However, for most latex compounds, it is not desirable because of the poor physical properties it imparts and the resultant darkening of the compound. 

PVA fibers have found wide spread industrial use in cement as replacement for asbestos in cement products, reinforcement of mbber material such as conveyor belts and hydraulic mbber hoses used in cars, ropes, fishing nets, etc. Only a small amount of fibers is used in the production of textiles. 

Many fluorochemical finishes for fabrics require curing at up to about 175°C. Curing aUows melt-spreading of the fluorochemical to ensure maximum leveling of the finish on the fibers and to promote optimum orientation of the pendant fluorinated portion of the molecules on the fibers. 

The Cardiac Cycle. The heart (Eig. lb) performs its function as a pump as a result of a rhythmical spread of a wave of excitation (depolarization) that excites the atrial and ventricular muscle masses to contract sequentially. Maximum pump efficiency occurs when the atrial or ventricular muscle masses contract synchronously (see Eig. 1). The wave of excitation begins with the generation of electrical impulses within the SA node and spreads through the atria. The SA node is referred to as the pacemaker of the heart and exhibits automaticity, ie, it depolarizes and repolarizes spontaneously. The wave then excites sequentially the AV node the bundle of His, ie, the penetrating portion of the AV node the bundle branches, ie, the branching portions of the AV node the terminal Purkinje fibers and finally the ventricular myocardium. After the wave of excitation depolarizes these various stmetures of the heart, repolarization occurs so that each of the stmetures is ready for the next wave of excitation. Until repolarization occurs the stmetures are said to be refractory to excitation. During repolarization of the atria and ventricles, the muscles relax, allowing the chambers of the heart to fill with blood that is to be expelled with the next wave of excitation and resultant contraction. This process repeats itself 60—100 times or beats per minute... 

Combustible Dusts Dusts are particularly hazardous they have a very high surface area-to-volume ratio. When finely divided as powders or (dusts, solids burn quite differently from the original material in the bulk. Dust and fiber deposits can spread fire across a room or along a ledge or roof beam very quickly. On the other hand, accumulations of dust can smolder slowly for long periods, giving little indication that combustion has started until the fire suddenly flares up, possibly when no one suspects a problem. 

Beside of the viscosity of the glue resin itself also the viscosity of the glue mix plays an important role. A higher dilution of the resin gives a higher volume to be spread and with this a better distribution of the resin on the particles or fibers with hence better bonding strength [173]. This also saves costs. 

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