In this work, a sustainable method to prepare functional cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) using formic acid (FA) (a recoverable organic acid) was established. After FA hydrolysis, the obtained CNCs could be well dispersed in DMAC. Thus, the CNC products and fibrous cellulosic solid residue (FCSR) in DMAC could be easily separated by a conventional centrifugal process, and the collected FCSR could be further fibrillated to CNFs with relatively low-intensity mechanical fibrillation process. The isolated CNC products showed high crystallinity index (about 75%) and excellent thermal stability (with onset thermal degradation temperature of 325 ℃). Both the resultant CNCs and CNFs showed better dispersibility in DMSO, DMF and DMAC respectively because of the introduction of ester groups on the surface of the products. The presence of surface ester groups could increase the interface compatibility of nanocelluloses with polymeric matrices and enable their applications in reinforcing polymeric matrix materials (e.g. the composite films like PHVB+CNFs).

Cellulase treatment is a promising technology to improve the properties of dissolving pulp in an environmental friendly way. Increasing the cellulase treatment efficiency is of practical interest. In the present study, the concept of using cationic polyacrylamide (CPAM) to enhance the cellulase treatment efficiency was demonstrated. The hypothesis was that the CPAM would attribute to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism. Results showed that the viscosity decrease was improved with the addition of 250 ppm of CPAM under the same conditions as those of the control. Degraded cellulose content was increased based on the alkaline solubility analysis, while alpha-cellulose content kept constant. The CPAM-assisted cellulase treatment concept may provide a practical alternative method for upgrading dissolving pulp.

In this study, a hemicellulose recovery process was integrated with a cold caustic extraction (CCE) process in upgrading paper-grade bleached kraft pulp to dissolving grade. Under the conditions of 15% NaOH, 10% pulp consistency, 30℃ and 1 h, a paper-grade softwood bleached kraft pulp was purified to a dissolving-grade pulp with 97.57% α-cellulose and 1.67% pentosan contents. The spent liquor from the cold caustic extraction process was sequentially extracted with ethanol to precipitate and recover the dissolved hemicelluloses, followed by evaporation to recover the ethanol. After the recovery of hemicelluloses and ethanol, the spent liquor can be reused as the caustic solution for the CCE process without compromising the resulting pulp properties. The results demonstrated that it is feasible to integrate hemicellulose production with the cold caustic extraction process of dissolving pulp production, based on the concept of biorefinery.

Dhaincha (Sesbania bispinosa (Jacq.) Wight) is a crop generally cultivated for improving soil quality. Due to the lack of forest worldwide, alternative source of raw materials for cellulose industries is the main concern today. In this investigation, dhaincha samples of 21 accessions were collected from different districts of Bangladesh in order to study the variation of chemical characteristics and its pulpability. The lignin, pentosan and α-cellulose content were varied from 21 to 23%, 16 to 18% and 38 to 43%, respectively. The highest and lowest α-cellulose contents were found in two location of Mymensingh district. There was no correlation was found among the districts. Therefore, pulping of dhaincha from selected seven districts was carried out in kraft process at the conditions of 18% active alkali at 170o C for 2 h. But the pulping properties did not show any mentionable distinction for place variation. Average pulp yield is 42.9% with kappa number 11. The highest brightness 85% was reached with D₀E_pD₁bleaching. The papermaking properties were very close to the conventional raw materials used in Bangladesh. Therefore, dhaincha can be used as a raw material for pulp production in Bangladesh.

Ammonium polyphosphate-diatomite composite filler (APP-diatomite composite filler) was modified with silane coupling agent KH550 to improve the flame retardancy of filled paper. Cone calorimeter was used to analyze the heat and smoke releasing rates, as well as smoke toxicity of the filled paper. The distribution of the composite filler particles in paper and the morphology of the charred residues after combustion were investigated by scanning electron microscope (SEM), and the chemical structure of the charred residues was studied with fourier transform infrared spectroscopy (FTIR). Results show that the peak heat releasing rate (PHRR), total heat release (THR) and peak mass loss rate (PMLR) of the filled paper with the modified APP-diatomite decreased markedly, compared with those for the control paper, while the charred residue after combustion increased. In addition, the filled paper had an increased peak rate of smoke release (RSR) and increased total smoke release (TSR) and peak CO production rates, but a decreased peak CO₂ production rate. It was also found that part of the carbon element in the charred residue of the paper loaded with the modified APP-diatomite was in the forms of C=C=C, C≡C and C≡N, and the charred residue had a relatively more intact structure without apparent fiber breakage and longitudinal cracks.

Interaction of unmodified starch with guest molecules or ligands (e.g., fatty acids) as a basis for the formation of starch-encapsulated mineral filler particles is an effective process for mitigating the negative impact of filler addition on the strength properties of cellulosic networks. As unmodified starch is essentially nonionic, the interaction of starch-engineered fillers with negatively charged cellulosic fibers is somehow limited. Here, the concept of substituting unmodified starch with a minor amount of cationic starch in filler engineering with starch inclusion complexes was proposed. It was hypothesized that filler-fiber interaction would be enhanced by cationic-anionic attraction. Encouragingly, the effectiveness of this concept was demonstrated to be very pronounced. For instance, at a cationic starch percentage of 3% (relevant to the weight of total starch), filler retention and filler bondability with cellulosic fibers were significantly improved, leading to further mitigated negative impact of filler addition on tensile strength. Basically, this easily scalable concept may shed light on greener, more efficient use of filler technologies on the basis of starch inclusion complex formation, opening up new possibilities for real commercial applications.