Grafting onto Cellulosic Materials

The proper choice of the support matrix is important. The different available functionalized and reactive supports include (a) cellulose as natural organic polymers, (b) PS and PMMA as synthetic polymers, (c) PS grafted onto cellulose as natural-synthetic polymers, and (d) polymer-montmorillonite nanocomposite materials as natural inorganic-orgaific synthetic polymers. 

SMPU is a long polymer chain, and with the exception of some special cases, its molecular weight is generally larger than 10 000. It is impossible for such a large chain to penetrate into the cellulose stmcture and react with the inner part of the cellulose fibers. Therefore, SMPU must be coated or grafted onto textile materials. 

Superabsorbent polymeric materials can be synthesized by polymerizing a variety of mainly hydrophilic monomers with minor amounts of crosslinking agents or by grafting these hydrophilic polymers onto cellulosic materials. The hydrophilicity is due to the presence of water compatible groups such as -OH, -COOH, -CONH2, -CONH- and -SO3H. 

Grafting reactions alter the physical and mechanical properties of the polymer used as a substrate. Grafting differs from normal chemical modification (e.g., functionalization of polymers) in the possibility of tailoring material properties to a specific end use. For example, cellulose derivatization improves various properties of the original cellulose, but these derivatives cannot compete with many of the petrochemically derived synthetic polymers. Thus, in order to provide a better market position for cellulose derivatives, there is little doubt that further chemical modification is required. Accordingly, grafting of vinyl monomers onto cellulose or cellulose derivatives may improve the intrinsic properties of these polymers. 

Narayan, R. and Shay, M. (1986). Graft polymerization onto cellulose acetate and wood using anionic polymerisation. In Renewable Resource Materials, Carraher, E. and Springer, L.H. (Eds.). Plenum Publishing Corporation, pp. 137-146. 

Vinyl monomers that can be grafted to cellulose to achieve adhesive properties are acrylic acid, acrylonitrile, methyl methacrylate, and many others. Graft copolymers of cellulose derivatives have also found use as adhesives. For example, vinylacetate-grafted hydroxyethylcellulose can be used as an adhesive for packaging and tile ( ). Grafting of vinyl monomers onto lignocellulosic materials can convert them into suitable adhesive materials (0). 

Low-substituted cellulose carbamate301 and partially carboxymethylated or cyanoethylated cotton31,321 also proved highly accessible to grafting with in monomer the presence of an initiator. Grafting onto low-substituted acetate- and allyl cellulose is, however, less efficient because these materials only swell poorly in aqueous solutions or emulsions of the monomer32 331. 

Also within this category of application is the field of radiation grafting onto pre-existing polymeric substrates. E-beam or gamma sources can be used to initiate grafting onto a range of materials, for example poly(olefin)s, fluoropolymers, and cellulosics. The biocompatibility of poly(olefin)s can be greatly... 

IR spectroscopy is a popnilar method for characterizing polymers. This spectroscopy may used to identify the composition of polymers, to monitor polymerization processes, to characterize polymer structure, to examine polymer surface, and to investigate polymer degradation processes. There are several reports of use of IR spectroscopy to evaluate grafting of acrylic monomers onto natural materials as carboxymethyl cellulose (CMC) and chicken feathers (CF) (Martinez et al, 2003, 2005, Vasile et al, 2004, Zohuriann-Mehr et al, 2005, Joshi and Sinha, 2006). 

Further EC microcapsules were grafted onto hydroxyl groups of cellulose via BTCA using DCC as a catalyst. Spectrum b in Fig 6 indicates that some ester groups were formed even when textile material was treated at room temperature. 

Cross-linked PVP is applied as a semipermeable membrane [492]. Furthermore, PVP can be used for the encapsulation of hydrophobic material [492]. Poly(iV-vinylpyrrolidone-co-styrene) was found to be an extraordinary catalyst in two-phase reactions [532]. For special applications one can design copolymers of NVP with different olefins and diolefins, or it is possible to graft NVP onto cellulose, polyolefins, keratin, collagen, and others, or to graft PVP with olefins [492,533-542]. 

Desirable and targeted properties for cellulose fibers can be obtained through graft copolymerization, in order to meet the requirements of specialized applications. Graft copolymerization is one of the best methods recommended for modif5dng the properties of cellulose fibers. Different binary vinyl monomers and their mixtures have been graft copolymerized onto ceUulosic materials for modifying the properties of numerous polymer backbones (Kaith et al. 2005 Kalia et al. 2009). 

Grafting of synthetic polymers onto cellulose and cellulose derivatives is a useful method to improve the qualities of both materials and to expand the range of their applications. Cellulose acetate grafting (initiated by free-radical, ionic processes or by gamma-irradiation) aims at the introduction of some branches of synthetic polymers into the main chain, to confer specific additional properties to the substrate itself without destroying its intrinsic characteristics. Thus, literature presents [138] ... 

Condensation reactions between hydroxyethyl cellulose or carboxy methyl hydroxy-ethyl cellulose provides potentially useful textile sizing resins.Starch materials have been treated with MA to obtain starch with maleate half-ester residues, with a substitution degree of 0.01-3.00. Styrene monomer is grafted onto the maleate/fumarate residues, with high efficiency, using standard free-radical initiators. 

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