Addition of Fibers

The definition of unshaped refractory products mentioned that these products may contain fibers. The addition of various fibers to these products will be discussed further in the following sections. 

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Addition of fibers tends to balance the difference between inflow and cross-flow shrinkage usually found in crystalline polymers. When a particulate is used to reduce and balance shrinkage, some fiber is needed to offset degradation. 

On the other hand, the addition of fibers may cause undesired properties of the cement [1759]. Fibers can actually increase pore and fracture systems in latex cements. The amount of fibers in a fiber seal cement influences the porosity and permeability while affecting compressive strength. During acid treatment of the formation, the fibers in the cement can be easily dislodged and extracted from the cracks, leaving pore spaces behind. 

Fig. 8.28 shows a broken cylindrical compact that was manufactured during process development with a laboratory punch-and-die press and actual briquettes obtained in an industrial plant. Concerns that, when produced with a roller press, the addition of fibers would prohibit separation into mostly single, handleable pieces (see also Section 6.9.2) were unfounded. 

The dynamic mechanical analysis of virgin PP, untreated sisal/PP composites and MAPP treated sisal PP composites revealed an increase in the storage modulus (E ) in the PP matrix with the addition of fibers and MAPP (Figure 9.5a) [71]. The loss modulus displayed three relaxation peaks at -80°C (y), 8°C (P), and 100°C (a), respectively. The temperature of P relaxation maximum corresponds to the Tg of the matrix, while the a relaxation peak is related to the slip mechanism in the crystallites. The y relaxation peak is due to the... 

PLA has been used as package materials and other products However, the physical properties of PLA such as brittleness limit the application of PLA. A way to improve the mechanical and thermal properties of PLA is the addition of fibers or nanofiller materials. 

A pilot-plant, double-drum dryer modified to produce low-moisture flakes from a wide range of fruit purees has been described [46]. Products with a relatively high fiber content such as apples, guavas, apricots, bananas, papayas, and cranberries could be dried successfully without additives. Purees with a low fiber content such as raspberries, strawberries, and blueberries required the addition of fiber (low methoxyl pectin, up to 1%) to aid in the sheet formation at the doctor blade. The modification consisted of incorporation of variable-speed take-off rolls, cool airflow directed at the doctor blade area, and a ventilation system to remove saturated air from the area beneath the drums. 

In this discussion, specific methods will be dealt with for processing polymers, which have been reinforced mainly by the addition of fibers. One should remember that all thermosets require some sort of reinforcement, but currently many thermoplastics are reinforced, as well, particularly those defined as engineering polymers. 

Homogenous blends of a thermoplast and an elastomer, or two thermoplasts, are produced to plasticize the matrix. On the other hand, heterogenous blends of elastomer particles in a continuous thermplast phase may produce high-impact-strength thermoplasts. Addition of fibers to thermoplasts increases rigidity. Blends can, however, be produced for a variety of other reasons to make polymers more flameproof with additive materials, to make processing easier, etc. 

Phenolics can be physically modified by blending, interpenetrating network formation, and the addition of fibers or fillers. The formation of multicomponent materials opens new directions for tuning of physical properties of polymers. 

The weight loss for the composite material started at 100°C, and for polypropylene started at 300°C. At 400°C, the weight loss increased with fiber content. Table 6.4 shows that the addition of fiber decreased the ultimate thermal stability in comparison to polypropylene alone. 

The peak temperatures for thermal degradation of the composites and the PP matrix occurred at approximately 458°C and 450°C, respectively. Table 6.4 shows that the addition of fibers caused a significant increase in the peak temperature for composite degradation, reaching 466°C for the composites reinforced with 20 wt% fibers treated with hot water. 

There are cases where a suitable process control can even increase the overall performance of the process, especially in production processes working with bottlenecks. Such is the case of a factory that makes cereal bars where the product labels indicate a fiber content of 4 %. Given that the machines at the factory are not well controlled, the addition of fiber has a variability of 2 %. In fact, the machines, programmed to add 4 % fiber, deliver a product that has between 2 and 6 % fiber. Therefore, to ensure that the products comply with the information on the label, 6 % fiber must be added and all bars are expected to have between 4 and 8 % fiber. 

The microcapsules also become stronger following the addition of fibers treated with acetone, 20 wt% S2, 10 wt.% Span 80, and 30 wt.% SI. 

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