BC fibrils

Fig. 3 Model of initially hydrated BC fibrils. Reprinted with permission from [ 1 ]...

Biosynthesis is a simple approach that incorporates the supplement material into the BC fibril network [23]. A schematic diagram is provided in Fig. 14.2a. At the start of the BC synthesis, the supplement is directly added into the BC culture medium. 

The intermolecular interaction between the carbonyl group of BC and the amino group of aloe vera was evidenced by the presence of two new peaks (1574 and 1542 cm ] in the FTIR spectra. For the supplement of 30-50% (v/v) aloe vera, the gel could adhere and form intermolecular bonds to BC fibrils [26]. 

The BC-aloe vera composite synthesized with 5-30% (v/v) of aloe vera gel displayed a quite homogeneous and uniform structure in which aloe vera was well incorporated within BC fibrils (Fig. 14.5). However, a higher volume ratio of aioe vera (e.g., 50% v/v) created a less uniform network structure and led to excessive gel on the film surface. The increase of aloe vera gel... 

A reduction crystallinity index [Cl] of the BC-chitosan composite synthesized with the impregnation method was observed when the chitosan content was increased the reduction also corresponded with an increased immersion time [71]. With the incorporation of chitosan in BC fibrils, BC hydrogen bonding was disturbed by the interaction between chitosan and BC [71]. Moreover, it suggested that because of this interaction, BC chains were difficult to move, resulting in the reduction of Cl [72]. 

According to the impregnation approach, the BC pellicle was immersed in the chitosan solution for different periods of time. It was found that chitosan molecules would not only coat the BC surface but also penetrate through the BC fibrils. Chitosan was well incorporated with nanofibrils, resulting in a denser and more... 

Using the biosynthesis approach, a higher tensile strength, and Young s modulus of BC-chitosan composite were obtained by increasing the MW and concentration of chitosan. Because the fibrils became thicker, they could resist a stronger force than pure BC fibrils [19]. 

During the impregnation technique, chitosan incorporating with BC fibrils could also enhance the WAC of the BC-chitosan composite because of the hydrophilicity of chitosan [71]. However,... 

PVA could penetrate into the BC structure and enwrapped the BC fibrils. From the SEM images, it could be observed that the diameter of the composite fibrils was larger than that of unmodified BC [84]. However, the overall structure of BC and BC-PVA composite, fiber thickness, fiber distribution and three-dimensional orientations were quite similar [85]. The SEM examination of BC and BC-PVA revealed that interpenetrated networks could be formed by integrating PVA fiber into the original BC pellicle [85]. The drying method and conditions also have significant effects on the composite structure. The BC-PVA composites dehydrated by freeze-drying process [84] had a structure that was different from those dried in an incubator oven [85]. When PVA fibers are heated, they contract [86]. 

To synthesize the BC-PVA composite by blending method, the homogenized BC was mixed with PVA solution. Then the films were prepared by casting the mixture on Teflon coated tray [87]. It was found that PVA coated the BC fibrils, leading to a denser structure and more transparency with increasing PVA content. 

The small dimensions of BC fibrils enable them a direct contact between cellulose and matrix polymers, allowing for a large contact surface and thus excellent adhesion. BC films present a good reinforcement for cellulose acetate butyrate (CAB) composites. These composites exhibit phenomena such as stiffening after straining in tension this is widely observed in plant tissues, emphasizing the usefulness of BC-reinforced composites as easily controllable and well-defined model systems for cellulosic composites. Composites reinforced with BC may also find practical application where special properties such as biodegradabitity are desired [175]. 

A recent model of the BC structure in the never-dried state was given by Fink et al. [13]. Anhydrous nano-fibrils in the range 7 x 13nm appear hydrated as a whole and are aggregated to flat microfibrils with a width of 70-150 nm. This means that the water is outside of the crystalline cellulose nano-units and between these elements. A shell of noncrystalline cellulose chains passes around neighboring microfibrils to produce a microfibril band... 

In contrast to BC, cellulose from wood is composed of fibers that are about one hundred times thicker [17] (Fig. 4a). Because of the complex and expensive cultivation of BC (sophisticated medium and long cultivation time), it is also a challenge to produce nano-fibrillated celluloses from wood. The substructures of wood are only accessible by chemical treatment [16] and mechanical disintegration procedures. 

Although PPerAcr fibrils formed after SVA in the device of BC 16, the best performance was obtained after simple processing of both block copolymers from chlorobenzene. A possible reason for the lower performance of devices subjected... 

With the addition of the chitosan solution into the culture medium for BC production, the BC-chitosan composite films were homogeneous with noticeably denser fibrils and smaller pore sizes compared with those of BC film [Fig. 14.6). A smaller pore size was obtained by increasing the MW of chitosan [19,73]. 

BC is pure cellulose made by bacterial fabrication via biochemical steps and self-assembling of the secreted cellulose fibrils in the medium. Shaping of BC materials in the culture medium can be controlled by the type of cultivation and kind of bioreactor and then it obtained BC hydrogel or BC in dry state by methods like freeze-drying [1]. 

Calcofluor White ST -Morphology of BC is changed by preventing assembly of fibrils prohibiting crystallization, but BC is crystalline when dried... 

Gluconacetobacter xylinus) produces a three-dimensional network of bundles of cellulose fibrils. Pure sheets of bacterial cellulose (BC) can be used in composites without any further disintegration [25]. 

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