Mechanical Changes of Natural Fibers

In many studies, it has been reported that alkali treatment may decrease the mechanical properties of many natural fibers [44, 86, 134]. On the contrary, in some cases, it has been noted that alkali treatment may increase the mechanical properties depending on the NaOH concentration and treatment time [135, 136]. A decrease of the fiber strength may be due to cellulose degradation during the treatment. More likely, alkali treatment may cause an increase of surface roughness, including striations and the structural defects, resulting in an increase of stress 

It has been reported that NaOH/Naj SOj treatment resulted in increased strength and modulus of hemp fiber than the untreated counterpart [134]. In addition, there was a paper reporting that a combined alkah and fungi treatment increased about 32% of tensile strength of hemp, compared to the untreated [44]. 

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] 

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