Composites polymer/cellulose fiber

U.S. Pat. No. 4,376,144 (March 8, 1983). L.A. Goettler. Treated fibers and bonded composites of cellulose fibers in vinyl chloride polymer characterized by an isocyanate bonding agent. 

Composites utilizing cellulose fibers have been prepared with many different materials, especially polymers. It has been well demonstrated that these fibers help to alter and in general enhance the physical properties of polymeric composites [140, 149-157]. Additionally, their bio-degradability and biocompatibility enables cellulose-reinforced materials to be suitable for bio-scaffolding in medical applications, if the polymeric component is also biocompatible [140, 158]. Some surface modifications have been performed on cellulose to add selected characteristics, such as antimicrobial properties to polymeric matrixes [140,159]. 

The fiber-matrix interfacial bond strength is expected to be very poor in composites of cellulosic fiber, which is hydrophilic, and thermoplastic polymer, which are hydrophobic in nature. Several treatments have been developed for the above system to improve interface bonding, which improves the mechanical properties and dimensional stability of cellulosic fiber of sisal-LDPE composites [58,59,117]. 

Reinforcement of thermoplastic and thermosetting composites with cellulose fibers is increasingly regarded as an alternative to glass fiber reinforcement. The enviromnental issues in combination with their low cost have recently generated considerable interest in cellulose fibers such as isora, jute, flax, hemp, kenaf, pineapple leaf, and man-made cellulose fibers as fillers for polymer matrices-based composites. 

S.D. Genieva, S.Ch. Furmanova, and L.T. Vlaev, Utihzation of rice husks and the products of its thermal degradation as fillers in S. Kalia, B.S. Kaith and I. Kaur eds.. Polymer composites in Cellulose fibers Bio- and nano-polymer composites, green chemistry and technology, Springer, Germany, pp. 345-376,2011. 

Electric discharge methods are known [31] to be very effective for nonactive polymer substrates such as polystyrene, polyethylene, polypropylene, etc. They are successfully used for cellulose-fiber modification to decrease the melt viscosity of cellulose-polyethylene composites [32] and to improve the mechanical properties of cellulose-polypropylene composites [28]. 

The mechanical properties of composites reinforced with wood fibers and PVC or PS as resin can be improved by an isocyanate treatment of those cellulose fibers [41,50] or the polymer matrix [50]. Polymethylene-polyphenyl-isocianate (PMPPIC) in pure state or solution in plasticizer can be used. PMPPIC is chemically linked to the cellulose matrix through strong covalent bonds (Fig. 8). 

Extruded composites of plasticized PVC and short cellulose fibers have been investigated by Goettler [103]. Pronounced increases in tensile modulus, yield, and ultimate tensile strength are observed. Single step processing of reinforcement and polymer with good product performance are key characteristics of the material whose field of application lies in the vinyl hose industry. 

Felix, J.M. and Gatenhobn, P. (1991). The nature of adhesion in composites of modified cellulose fibers and polypropylene. Journal of Applied Polymer Science, 42(3), 609-620. 

Ito, H., Kumari, R., Takatani, M., Okamoto, T., Hattori, H., and Fujiyoshi, I., Viscoelastic Evaluation of Effects of Fiber Size and Composition on Cellulose-Polypropylene Composite of High Filler Content, Polym. Eng. Set, 48, 415 (2008)... 

Membranes and composites from cellulose and cellulose esters are important domains in the development and application of these polymer materials. The most important segment by volume in the chemical processing of cellulose contains regenerated cellulose fibers, films, and membranes, hi the case of the cellulose esters mainly cellulose nitrate and cellulose acetate as well as novel high-performance materials created therefrom are widely used as laminates, composites, optical/photographic films and membranes, or other separation media, as reviewed in [1], The previously specified nanocelluloses from bacteria and wood tie in with these important potentials and open novel fields of application. 

Macromolecular properties of grafted cellulosic fibers usually measured are differential solubility in either polymeric or cellulosic solvents, mechanical or physical properties, and abrasion resistances. The molecular weights of the grafted or block polymers and of cellulose, both before and after formation of macrocellulosic radicals, have been determined. The number of grafted or block polymer molecules per cellulose molecule calculated has usually been much less than one. Grafted cellulosic fibers exhibit second order transition temperatures, dependent on the composition of the grafted polymer (3, 4). 

Stock composition, kinetics of adsorption and hydrodynamic shear dictate the point at which a cationic polymer is added to a papermaking furnish in order to induce flocculation. Flocculation of cellulose fibers in turbulent flow proceeds very rapidly and is completed in less than two seconds.120-123 Flocks form due to charge interactions through a patch-type or a bridging-type mechanism. However, these flocks will be sensitive to shear force and deflocculation and reflocculation might occur. 

Sachinvala, N. D., et al., Use of Sucrose-based Epoxy Formulations and Cellulosic Fibers in the Design, Preparation and Screening of New Composite Insulation Materials, Polymers for Advanced Technologies, 13, 66-79 (2002). 

Doherty [4] prepared water compatible hydrophobic polymers such as poly (acrylamide-co-t-octylacrylamide), (11), that were used as components in cellulosic fiber compositions. 

Various reports are present in the literature on the usage of cellulose fibers in the preparation of composites. Cellulose fibers like banana, sisal, oil palm, jute, pine apple leaf fiber were found to have a very good reinforcing effect on polymer matrices [38 2]. The mechanical properties and water absorption were found to be dependent on the amount of micro-fibrils. 

Cellulosic fiber reinforced polymeric composites find applications in many fields ranging from the construction industry to the automotive industry. The reinforcing efficiency of natural fiber is related to the namre of cellulose and its crystallinity. The main components of natural fibers are cellulose (a-cellulose), hemicelluloses, lignin, pectins, and waxes. For example, biopolymers or synthetic polymers reinforced with natural or biofibers (termed biocomposites) are a viable alternative to glass fiber composites. The term biocomposite is now being applied to a staggering range of materials derived wholly or in part from renewable biomass resources [23]. 

Fibers having an aspect ratio of above 10, such as glass fibers, asbestos, wollastonite, cellulose fibers, carbon fibers, and whiskers, act as reinforcing agents. Composites may be classified into four groups, as shown in Table II. In modern composites, such as in the case of epoxy resins reinforced with carbon fibers (51). the polymer matrix has only a secondary function to separate the individual fibers from one another and to transfer energy to the fiber surface the fibers almost completely withstand the mechanical load. 

U.S. Pat. No. 5,288,775 [22] describes moldable thermoset acrylic polymer composites containing 3-15% of cellulose fibers, fillers, and water the composite is a hard, high molecular crosslinking type that requires a chemical hardener. 

Another method of improving the dispersibility of cellulose fibers in a thermoplastic matrix is described in U.S. Pat. No. 4,414,267 [36], according to which cellulose fibers (hardwood kraft, from 1 to 40% by weight of the final composite) are pretreated by slurrying them in water, contacting them with an aqueous suspension of a mixture of a vinyl chloride polymer and a plasticizer, and drying the thus-treated fibers. 

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