Cellulose pulp reinforcement

U.S. Pat. No. 6,743,507 [40] discloses cellulose-fiber-reinforced composites comprising a matrix polymers such as polyethylene, polypropylene, copolymers, terpoly-mers and mixture thereof in an amount ranging from about 25 to 99% by weight, and cellulose pulp having an a-cellulose purity of greater than about 80, 90, or 98% by weight. 

U.S. Pat. No. 6,270,883 [98] describes reinforced composites containing less than 50% by weight of cellulose pulp fibers dispersed in a thermoplastic matrix comprising nylons, such as Nylon 6, Nylon 12, Nylon 66, or mixtures thereof, and the cellulose pulp comprising fibers with a lignin content less than 2% by weight. 

Cellulose nanofibers from different sources have showed remarkable characteristics as reinforcement material for optically transparent composites [160, 161], Iwamoto et al. [160] prepared optically transparent composites of transparent acrylic resin reinforced with cellulose nanofibers extracted from wood pulp fibers by fibrillation process. They showed that cellulose nanofiber-reinforced composites are able to retain the transparency of the matrix resin even at high fiber content (up to70 % wt). The aggregation of cellulose nanofibers also contributes to a significant improvement in the thermal expansion properties of plastics. 

In another study by Sdrobis et al. [57], the effect of modification on cellulose pulp fibers in LDPE was reported. They used unbleached and bleached kraft cellulose pulp fibers modified with oleic acid in cold plasma conditions as reinforcements. The melt-mixed composites contain up to 10 wt% of untreated and modified cellulose pulp fibers with LDPE. They reported that interfacial adhesion between cellulose and matrix could be improved through modification and most of the properties have been improved when the modified pulp fibers were incorporated into composite matrix. Variation of complex viscosity function of angular frequency for composites is shown in Fig. 11.11. 

The employment of natural fibres, such as cellulose pulp, sisal, bamboo, hemp, flax, jute, ramie fibres, etc., is restricted to countries where these fibres are easily available. They are important constituents of structural elements used for construction of inexpensive buildings in developing regions of the world (Coutts, 2005). In Africa, sisal fibre-reinforced concrete has been nsed extensively for making roof tiles, corrugated sheets, pipes, silos, and gas and water tanks. Subrahmanyam (1984) cited the application of elephant grass... 

The problems related to safe and durable roofs for low cost houses are usually more difficult than those for walls and other elements of the house. For that reason, various kinds of low-cost fibre reinforcement are used in regions where cellulose pulp (in Nordic countries) and natural vegetal fibres (in tropical and subtropical countries) are available (cf. Section 5.7). 

Yano HSJ, Nakagaito AN, Nogi M, Matsuura T, Hridta M, Handa K (2005) Optically transparent composites reinforced with networks of bacterial nanofibers. Adv Mater 17 153 Young R (1994) Comparison of the properties of chemical cellulose pulps. Cellulose 1 107-130 Zhao H-P, Feng X-Q,Gao H (2007) Ultrasonic technique for extracting nanofibers from nature materials. Appl Phys Lett 90(7) 073112... 

The most commonly used reinforcement for high pressure decorative and industrial laminates is paper (qv). The strong substrate layers, or filler, are kraft paper. Kraft is a brown paper made from a sulfate pulp process (8). It consists of both short cellulose fibers from hardwoods and long fibers from conifers. The long fibers impart most of the wet strength required for resin saturation processes. 

Cellulose content varies. Virgin fibers produced Irom wood pulp contain 99.6% cellulose and are white. Fibers manufactured from reclaimed materials contain 75% and are gray or brown. Cellulose fibers (especially virgin materials) have a complex morphological structure which facilitates reinforcement (Figure 2.80). 

Zimmermann et al. [134] have used cellulose fibrils obtained from sulphite wood pulp to reinforce water soluble polymers such as polyvinyl alcohol (PVA) and hydroxypropyl cellulose (HPC). The mechanical properties of these nanocomposites were measured by tensile tests showing that the addition of fibrils increase the modulus of elasticity (E) up to three times and the tensile strength up to five times compared to the raw polymer. Zimmermann et al. [135] have determined the E values and the hardness of cellulose/HPC nanocomposites using nanoindentation technique. The results showed that the E values measured by nanoindentation were from two to three times higher than the E values measured by means of tensile tests. Stauss et al. [136] have explained that differences between tensile test and indentation results are due to the fact that they do not test the same material volumes and regions. The large volume used in tensile test includes defects such as pores, cracks and impurities. 

The objective of this work was to use rice straw pulp cellulose fiber to prepare environmental-friendly rice straw fibril and fibril aggregates (RSF) and evaluate the fibril and fibril aggregates as a novel reinforcing material to compound polypropylene (PP)/ RSF nanocomposite. The scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD), laser diameter instrument (LDl) were used to evaluate the characteristics of RSF. The RSF/PP nanocomposite was prepared by novel extrusion process. The interface compatibility and tensile properties of nanocomposite were investigated by FTIR and tensile test, respectively. 

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