Surface modification of natural fibers

The strength of the fiber is very important for natural fiber-reinforced composites. Polar natural fibers are inherently incompatible with hydrophobic polymers. Therefore, the surface modification of natural fibers is required to improve its physical and chemical properties. Various chemical treatment methods have been used to modify the surface properties of the natural fibers. Few methods of surface modification are described below  

Alkaline treatment or mercerization is one of the best used chemical treatment for natural fibers. 

Due to alkali treatment there is an increase in the amount of amorphous cellulose at the expense of crystalline cellulose. By this treatment there is a removal of hydrogen bonding in the network structure. Reaction which takes place during this treatment is shown below  

Silane treatment in surface modification of glass fiber composites have been applied by various researchers [42-45]. They have found that Silane coupling agents are effective in modifying natural fiber-polymer matrix interface and increasing the interfacial strength. 

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Native cellulose are commonly modified by physical, chemical, enzymic, or genetic means in order to obtain specific functional properties, and to improve some of the inherent properties that limit their utility in certain application. Physical/surface modification of cellulose are performed in order to clean the fiber surface, chemically modify the surface, stop the moisture absorption process, and increase the surface roughness. " Among the various pretreatment techniques, silylation, mercerization, peroxide, benzoylation, graft copolymerization, and bacterial cellulose treatment are the best methods for surface modification of natural fibers. 

Pommet, M. Juntaro, J. Heng, J.Y.Y. Athanasios, M. AdamF.L. Karen, W. Gerhard, K. Milo, S.P.S. Bismarck, A. Surface modification of natural fibers using bacteria Depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites. Biomacromolecules 2008, 9 (6), 1643-1651. 

A. K. Mohanty, M. Misra and L.T. Drzal, Surface modifications of natural fibers and performance of the resulting biocomposites An overview , Polym Interfaces, 2001, , 313-17. 

Mohanty A, Misraa M, Hinrichsen G (2000) Biofibres, biodegradable polymers and biocomposites an overview. Macromol Mater Eng 276/277(1) 1-24 Mohanty A, Misra M, Drzal L (2001) Surface modifications of natural fibers and praformance of the resulting biocomposites an overview. Compos Interf 8(5) 313-343 Mohanty M, Misra M, Drzal L (2002) Sustainable bio-composites from renewable resources opportunities and challenges in the green materials world. J Polym Environ 10(1/2) 19-26 Morrison W, Akin D (2001) Chemical composition of components comprising bast tissue in flax. J Agric Food Chem 49(5) 2333-2338... 

Reinforcing fibers can be modified by physical and chemical methods. Chemical and physical modifications of natural fibers are usually performed to correct the deficiencies (described above) of these materials, especially to impart bonding and adhesion, dimensional stability, and thermoplasticity. Surface modification of natural fibers can be used to optimize properties of the interface. 

Pommet M et al (2008) Surface modification of natural fibers using bacteria depositing bacterial cellulose onto natural fibers to create hierarchical fiber reinforced nanocomposites. Biomacromolecules 9(6) 1643-1651... 

Based on the literature discussed in this chapter, it seems that surface modification of natural fibers is absolutely necessary to improve their thermal stability, dispersion in the polymer matrix, and compatibility with the polymer matrix. Physical and chemical methods reported have significantly modified the surface properties of the fibers as well as polymer matrices to improve the dispersion of the fibers and hence various properties of the polymers. Use of silane coupling agents and acetylation... 

Mohanty A.K., Misra M., and Drzal L.T. 2001. Surface modification of natural fibers and erfor-mance of the resulting biocomposites. Composite Interfaces 8 313-343. 

Pommet, M Jimtaro, J Heng, JYY Mantalaris, A Lee, AF Wilson, K Kalinka, G Shaffer, MSP Bismarck, A. Surface Modification of Natural Fibers Using Bacteria Depositing Bacterial Cellulose onto Natural Fibers To Create Hierarchical Fiber Reinforced Nanocomposites. Biomacromolecules, 2008, 9, 1643-1651. 

SURFACE MODIFICATION OF NATURAL FIBERS FOR REINFORCEMENT IN POLYMERIC COMPOSITES... 

SURFACE MODIFICATION OF NATURAL FIBER COMPOSITES AND THEIR POTENTIAL APPLICATIONS... 

Interest in natural fibers obtained from different resources to reinforce polymer so as to get the novel composites is growing rapidly because they are renewable, cheap, recyclable, and biodegradable. Research in this field has prompted surface modification of natural fibers in order to improve the compatibility between hydrophilic fibers and hydrophobic matrix [1], Major challenges for polymer scientists in the development of structural natural fiber-reinforced composites are to increase the moisture resistance, dimensional stability with minimized matrix material, and to decrease the manufacture costs of the composite materials. Different researchers have used different surface modification methods, that is, mercerization [2], benzoylation [3], silanation [4], acetylation [5], graft... 

Therefore, a large number of studies on chemical and physical surface treatments of various natural fibers have been devoted not only to increasing the interfacial adhesion between the natural fiber and the polymer matrix but also to enhancing mechanical, thermal, and other properties of biocomposites consisting of different types of natural fibers and polymers [13-20]. Meanwhile, a few excellent papers have reviewed the surface modification of natural fibers for biocomposites [4, 11, 21, 22]. Many research results dealing with surface treatment of natural fibers and characterizing various properties of biocomposites with different modification methods as well as with different natural fibers and polymers have been reported in recent years. 

There are a number of papers reporting the surface treatment of cellulose-based natural fibers and the property improvement of biocomposites through the surface modification of natural fibers by means of plasma treatment [96-99]. 

A few papers have reported that cellulose-based natural fiber surfaces can be modified with corona treatment and that the resulting polymer composites exhibited the improved properties through the surface modification of natural fibers [102,103]. 

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