Fiber degradation

This reduces pulp tensile strength but improves tear strength not because of fiber degradation but because the hemiceUuloses bond chemically to give added tensile strength in the final paper product. To overcome this loss in hemiceUulose polymers, starch is added on the wet end of the paper machine as a dry strength additive. 

The choice of a particular mining method depends on a number of parameters, typically the physical properties of the host matrix, the fiber content of the ore, the amount of sterile materials, the presence of contaminants, and the extent of potential fiber degradation during the various mining operations (33). However, most of the asbestos mining operations are of the open pit type, using bench drilling techniques. 

Metal Complex Dyes. The 1 1 metal—dye complexes caimot be used on nylon because the low pH values needed cause fiber degradation. 

Moheno-Perez, J.A., Almeida-Domingues, H.D., and Sema-Saldivar, S.O. 1999. Effect of fiber degrading enzymes on wet milling and starch properties of different type of sorghums and maize. Starch/Stdrke 51, 16-20. 

Fiber degradation should be monitored after every ten sample runs (see Critical Parameters). 

The degree of the fiber degradation and mineralization of the Seip materials made them difficult to sample and also limited the degree of visual examination that was ethically justifiable without destruction of the textiles. 

One of the more recent studies on cotton, polyester, and nylon (24) demonstrated that cotton was superior to the synthetics in outdoor performance in areas of low air pollution but that its performance was reduced considerably in areas of high air pollution. Specific effects of air pollutants are discussed later under chemical agents causing fiber degradation. 

Figure 13. Fracture tip surface of a typical cotton fiber degraded by exposure to a 100-Mraa dose of high-voltage electrons...

Changes in the fiber and fiber/cement interfacial region due to environmental interactions can affect the long-term performance of cement-based composites reinforced with natural fibers. A significant mechanism of changes in composite properties is pulp fiber degradation... 

The experimental reaction conditions that must be met in order for a given reaction to take place is another important consideration. The temperature required for complete reaction must be low enough that there is little or no fiber degradation, i.e., less than 150°C. The reaction must also have a relatively fast rate of reaction with the cell wall components. It is important to get as fast a reaction as possible at the lowest temperature without lignocellulosic degradation. 

Effect of Fiber Degradation on the Corrosion Solution. Hydrolysis and oxidation of protein and cellulose have been described in the literature primarily with the focus on degradation in industrial processing conditions. In alkaline conditions, amino acids are released from silk in a chain unzipping mechanism in acidic conditions, the scissions are random (8,9). As the polymer deteriorates, free carboxyl and amine end groups are formed. Tyrosine oxidizes to a quinone this reaction gives aged silk its yellow coloration. Amorphous areas of the fiber are attacked first. 

Effect of Metal Corrosion on Fiber Degradation. The effect of the corrosion solution of copper on the progress of protein and cellulosic... 

Because protein and cellulosic fibers are buried in contact with copper metal objects, a chemical microsystem is established whereby the degradation of the fiber and the corrosion of the metal interact physically and chemically. As the corrosion solution impregnates and swells the fibers, polymer molecules in amorphous areas are spread apart but are prevented from complete dissolution by the resistant crystalline segments. Copper ion from the corrosion solution is bound to the polymers (Figure 5). As the fiber degrades and more end groups are formed, more copper is bound. Polymers expand further apart as interchain forces are reduced. 

Fiber degradation, dissolution of degradation products, and oxidation of metallic copper alter the Eh and pH of the corrosion solution so that bound (and also free) copper ions will react with H20 and available HCQr to form one or more copper minerals. These minerals will precipitate in situ within the template of the fiber internal structure. In this manner, the shape of the fiber will be retained, although the size of the pseudomorph can become larger than that of the original fiber. 

C and 37 % RH for an additional 73 d. The increase in temperature to 60°C and decrease in relative humidity to 37 % was intended to accelerate the kinetics of fiber degradation by increasing the temperature while maintaining the same absolute water content in the environment. 

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