Nanomaterials 2023 , 13 , 2536
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amount of these fibers that remain after HPH, as shown by the yield and transmittance values (Table 6), resulting in increased aspect ratio values. This effect on thickness is not observed in pretreated pulp, because it is the result of the combined effects of hydrolysis and HPH. The internal nanofibrillation caused by the enzyme favors the deconstruction of fiber in nanofibers during HPH. This effect is also observed in Figure 5, in which the D2 increases with the severity of HPH, which indicates the formation of microfibrils around the main structures with the main treatment. On the other hand, the orange color of Enz-80 and Enz-240 CNFs in Figure 6, which is even darker than Mec CNFs, could be due to the degradation products from enzymatic hydrolysis, which can produce oligosaccharides from the amorphous part of the cellulose chains decreasing the polymerization degree of cellulose [48].
Figure 3. Optical microscopy images of CNFs (scale bar: 500 μ m).
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