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The main goal of this work was to reinforce softwood pulp (SP) with bacterial cellulose (BC) to generate a sustainable biocomposite. BC is a nanocellulose, which was anticipated to increase interfacial adhesion between the cellulosic fibers and BC. The organism used was Gluconacetobacter xylinus, which was incubated in a static Hestrin-Schramm culture at 28°C for 14days. The specimens of BC, SP and the reinforced SP with BC were characterized using X-ray diffraction (XRD), FT-IR, FESEM, and physico-mechanical testing. The crystallinity index was found to be 83 and 54% for BC and SP, respectively. FT-IR spectra showed that the composition of BC was fully different from that of SP fibers. Based on FESEM images, one can conclude that BC and softwood fibers do form a good combination with a nonporous structure. BC fibers fill in among the softwood fibers in the sheet. The physical and mechanical properties showed that as the dosage of BC increased, the properties of tensile index, tear index, and burst index greatly improved, while the porosity and the elongation decreased. The reason for the improved mechanical properties can be attributed to the increase of interfibrillar bonding which reduced porosity. This would be due to the high aspect ratio of BC that is capable of connecting between the cellulosic fibers and BC nanofibers, enhancing a large contact surface and therefore producing excellent coherence. This study suggests that BC could be a promising material for reinforcing composites at low loading.

The aim of this paper was to prepare composites of bacterial cellulose (BC) filled with silica (SiO2) nanoparticles to evaluate the influence of the SiO2 contents (3, 5 and 7wt%) on the thermo-mechanical properties of the composites. BC hydro-gel was immersed in an aqueous solution of silanol derived from tetraethoxysilane (TEOS), the silanol was then converted into SiO2 in the BC matrix by pressing at 120°C and 2MPa. The BC/SiO2 translucent sheets were examined by dynamic-mechanical analysis (DMA), thermo gravimetric analysis (TGA), and scanning electron microscopy (SEM). The temperature dependence of the storage modulus, loss modulus and tan delta was determined by DMA. In general, the results revealed that the increment of storage modulus and thermal stability increased concomitantly with the augmentation of SiO2 content. Therefore, it could be concluded that the mechanical properties of the composites were improved by using high amounts of nano silica. This would be a high aspect ratio of BC capable of connecting the BC matrix and SiO2, thereby enhancing a large contact surface and resulting in excellent coherence. A decrease of the storage modulus was consistent with increasing temperature, resulting from softening of the composites. The storage modulus of the composites increased in the order: BC/S7>BC/S5>BC/S3, while the loss modulus and tan delta decreased. On the other hand, the thermal stabilities of all BC/SiO2 composites were remarkably enhanced as compared to the pristine BC. TGA curves showed that the temperature of decomposition of the pure BC gradually shifted from about 260°C to about 370°C as silica content increased. SEM observations illustrated that the nano-scale SiO2 was embedded between the voids and nano-fibrils of the BC matrix. Overall, the results indicated that the successful synthesis and superior properties of BC/SiO2 advocate its effectiveness for various applications.

The aim of this research was to fabricate multilayer insulator nanocomposites using phenolic resin impregnated bacterial cellulose (BC) handsheets and investigate the relationships between their structural and electro-thermo-mechanical properties. G. xylinus was incubated in a static Hestrin-Schramm culture at 28 °C for 14 days. Then, BC aqueous suspension was added to kraft pulp aqueous suspension. The content of BC that was added to the pulp suspension was as follows: 5, 10 and 15%. The disintegrated BC was turned into handsheets by a vacuum method. Dried handsheets were immersed in phenolic resin. To obtain composites, 5 immersed handsheets from each treatment were laid-up and hot pressed at 150 °C under 100 MPa pressure for 10 min. The specimens were characterized by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) techniques and insulating tests as dielectric loss factor and breakdown voltage. The results of thermal analysis showed an improvement in the thermal stability and an increase in the evaporation enthalpy of prepared samples with higher BC content. The mechanical examinations indicated that by increasing BC content in nanocomposites, the loss modulus and tan delta increased and the storage modulus of specimens decreased. The coefficient of thermal expansion (CTE) of samples diminished with increase of BC content. FE-SEM characterization showed different qualities of resin impregnation of the papers. The results of insulating tests confirmed that dielectric loss tangent and dielectric breakdown voltage increased in the specimens with higher BC content.

The aim of this paper was to prepare composites of bacterial cellulose (BC) filled with silica (SiO

In this study the effects of growth times and culture mediums on the structural characteristics of bacterial cellulose have been investigated. Bacterial cellulose (BC) nanofibers were synthesized by Gluconacetobacter xylinus. BC pellicles were compared using SEM, FT-IR and X-ray diffraction techniques. The crystallinity index (CrI) and crystallite size (CrS) were calculated based on X-ray measurements. Three growth times (7, 14 and 21 days) and three culture mediums (A, B and C) were applied. SEM micrographs showed that increasing growth time up to 7 days improves the microfibril branches crossing to each other and the number of bundles. However, further increase in growth time (21 days) results in decrease in the microfibril network. On the other hand the hydrogen and C–H bonds were developed by the increase in growth time. In conclusion, BC synthesized in medium B for 7 days had superior properties in terms of CrI, CrS and microfibril networks.

The preparation and characterization of bacterial cellulose (BC)/silica nanocomposites are presented in this paper. BC hydro-gel was immersed in an aqueous solution of tetraethoxysilane (TEOS). By pressing the treated BC matrices at 120 °C and 2 MPa, water-free translucent sheets were obtained. TEOS concentration (3, 5 and 7%) and press time (8, 10 and 12 min) were used as variable factors. These materials were characterized by different techniques, namely FE-SEM, FTIR, SEM, tensile strength and Young's modulus. All composites showed good dispersion of the fibers and strong adhesion between the fibers and the matrix. FE-SEM observations showed that the nano-scale silica was embedded between the voids and micro-fibrils of the BC matrix. Reflecting this structure, the maximum Young's modulus and tensile strength of dry BC/silica composites improved to 1.46 GPa and 113 MPa, respectively. The tensile strength and Young's modulus showed 35 and 18-fold increase (with 7% TEOS), respectively, while the same properties were reduced 15 and 10-fold with increase in press time from 8 to 12 min. FTIR results illustrated strong chemical interactions between the cellulose and silica phases. The optimum condition was obtained when the TEOS dosage and press time were 7% and 8 min, respectively.