Silane treatment, natural fiber

The use of silane treated carbon fibers and silane treated silica fume led to increases in tensile strength of cement paste by 56% and modulus and ductility by 39% [30], as compared to the values obtained for cement paste with either as-received carbon fibers or as-received silica fume. Silane treatment of fibers and silica fume contributed about equally to the strengthening. Silane treatment of fibers and silica fume also decreased the air void content. The strengthening and reduction in air void content were less when the fiber treatment involved the use of K2Cr20v instead of silane, and even less when the treatment involved the use of O3. The effectiveness of silane is due to its hydrophilic nature. 

After NaOH treatment, natural fibers of interest are normally washed or rinsed sufficiently with tap or distilled water in order to remove the excess of NaOH or unreacted NaOH for neutraUzation and then dried before use [8, 16, 19]. A large number of studies [12, 40-50] on the effect of alkaU treatment on the properties of biocomposites consisting of various natural fibers and polymer matrices have been extensively performed by many research groups. Some papers [51-53] explored the combination effect of alkali treatment and silane treatment to improve the mechanical properties through the interfacial modification between natural fibers and polymer matrix. 

Analog-to-glass fibers silanes are used as coupling agents for natural fiber polymer composites. For example, the treatment of wood fibers with product A-175 improves wood dimensional stability [53]. In contrast, a decrease of mechanical properties was observed for coir-UP composites after a fiber modification with di-chloromethylvinyl silane [54]. The treatment of mercer-... 

Sometimes, degree of adhesion between fiber and matrix achieved through various primary processing of biocomposites is weak which results in poor performance of developed composites. Natural fibers comprise of waxy and fatty materials on their surface which causes improper bonding between fiber and matrix. There are various chemical treatment techniques (such as alkali-treatment, silane treatment, Benzoylation, Acetylation, etc.) which can be applied to natural fibers before primary processing to condition the surface and consequently improve the fiber matrix adhesion to develop high performance biocomposites. 

Silane treatment of nattnal fibers is highly effective and widely used chemical treatment technique. Silanes act as coupling agents dxuing modification of natual fiber sxir-faces. Silones react with cellxilose hydroxyl group of the natural fibers due to which... 

Figure 23.4 Scheme for silane treatment of natural fiber. 

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. 

Natural fibers are hydrophilic and do not tend to be easily wetted or bond well with many matrix materials, particularly the commodity thermoplastics. Coupling agents, such as maleated polyolefins, silanes, and isocyanates, are often necessary for adequate performance. A wide variety of coupling agents, fiber surface modifications, and treatments has been investigated for use in natural fiber plastic composites and are reviewed elsewhere [22]. 

Silanization Silane treatment or silanization is used to decrease hydrophilicity of natural fibers and as a coupling agent to form strong bonds between the fiber and the matrix. In one of the earliest studies of this kind, it was shown that treated sisal fibers... 

Since both glass fibers and natural fibers have reactive hydroxyl groups, extensive research efforts on silane coupHng agents for processing composites have been performed [18, 57-66]. Additional silane treatment done to the fiber after aUcaH... 

By silane treatment under proper experimental conditions, natural fibers, which are normally hydrophilic or hygroscopic, can be converted into hydrophobic fibers for nonpolar polymer matrices [28], reducing the water absorption rate. Silane treatment of natural fibers may more or less increase the thermal stability of natural fibers depending on the treatment conditions. Silane treatment normally does not damage the natural fibers because no fiber-damaging elements such as an acidic catalyst are present in the silane solution and high temperature treatment... 

Silane treatment normally does not damage the natural fibers because fiberdamaging elements such as an acidic catalyst are not present in the silane solution nor is high temperature treatment used, as mentioned above. Therefore, it is noted that the tensile strength of natural fibers should be little affected by the silane itself [36]. MAPP treatment may slightly increase the fiber strength due to the deposition of MAPP copolymer on the fiber surfaces, leading to more or less uniform and smooth surfaces [86]... 

The superior mechanical properties of biocomposites with appropriate alkali-treated natural fibers are ascribed to the increased fiber-matrix adhesion on removing the natural and artificial impurities, thereby forming roughened surfaces. As described earher, alkali treatment may lead to fiber fibrillation, resulting in the increase surface area contactable with the polymer. Such surface roughness and increased aspect ratio by fibrillation offer better natural fiber-polymer matrix bonds [4]. In another paper [143], the effect of the addition of silane-treated- and untreated talc as filler on the mechanical properties of PLA/recycled newspaper cellulose fiber/talc hybrid composites was evaluated. 

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