Volume 6 Issue 1

Bacterial cellulose is a promising source of biodegradable polymers having high purity. The time required to disperse bacterial cellulose wet membranes was studied, along with evaluation by infrared spectroscopy and thermal analysis of the dispersed bacterial fiber and tests of the physical properties of the sheet. The results showed that bacterial cellulose wet membrane can be dispersed well, forming fibers when the dispersing time was 3 minutes at a suitable concentration. FT-IR results showed that the composition of bacterial fiber is similar to that of bleached softwood fibers. Thus, the morphology, thermal performance, and the length of bacterial fibers are significantly different. The sheets’ physical properties show that with the increasing dosage of bacterial fibers (relative to softwood fiber), the properties of tensile index, tear index, burst index, and stiffness greatly improve, while the porosity and the relative water absorption decrease.

Triticum aestivum PBW-343 is grown in most of the regions of India, and it is one of the renewable sources most suitable for papermaking. Anatomical studies illustrate that vascular bundles near the periphery contain a strong sheath of sclerenchyma cells, which constitutes about 80% of the fibers. The total fibers in wheat straw are about 39.20%, and parenchyma and epidermal cells account for 32.10, and 23.56%, respectively, of the total cells. The dimensions of wheat straw fibers are: average fiber length 1.18 mm, fiber width 13.60 µm, lumen diameter 5.68 µm, and cell wall thickness 3.96 µm. The dimensions of non-fibrous cells are: parenchyma 445×124 µm, vessels 96×57 µm, and epidermal cells 390×38 µm, which lie between the corresponding values for rice straw, and bagasse. Flexibility coefficients and Runkel ratio of wheat straw fires are quite comparable to bamboo. The low lignin contents of wheat straw reflect that it requires mild cooking conditions; however, hemicelluloses are on higher side. Addition of AQ under optimum soda cooking conditions improves pulp yield by 0.75%, and lowers kappa number by 26.1%. Optimum strength properties are obtained at 45±1 oSR except tear index, which declines with increased refining. The fine contents are much higher, and relatively comparable to Eucalyptus tereticornis in terms of curl index and kinks per mm.

The sorption of vapors by cellulose samples and by some cellulose derivatives was studied at 25 oC. To describe sorption isotherms, a thermodynamic equation was proposed: A=Ao/[1-(RT/g)lnφ], where Ao is maximal sorption value, φ is relative pressure of vapors, and g is specific thermodynamic potential. Depending on the g -value, this equation can describe isotherms of various shapes that occur for cellulose and its derivatives. Application of the equation makes it possible to calculate such structural characteristics of the polymers as accessible specific surface and crystallinity, as well as the substitution degree of cellulose derivatives. Moreover, amounts of monomolecular and multimolecular fractions of the sorbate can be determined.

A biorefinery using the process of hemicellulose pre-extraction and subsequent pulping provides a promising way for the utilization of straw biomass and resolution of problems related to silicon. In this work, hemicellulose was extracted from depithed corn stover with sodium hydroxide solution before soda-AQ pulping. Components of the extracts were quantified by ion chromatography. The parameters (alkali concentration and temperature) affecting hemicellulose pre-extraction were optimized. The main constituent of hemicellulose in corn stover was xylan, which accounted for 18.1% of the depithed raw material. More than 90% of the xylan can be extracted under the optimal conditions: NaOH concentration of 10%, temperature of 75ºC, and time of 2h. Solid fractions after extraction were subjected to soda-AQ pulping. In comparison with control pulp obtained without extraction, it was found that alkali pre-extraction could improve the brightness and decrease kappa number of the subsequent pulp, causing a slight loss of yield, viscosity, density, and burst strength, but an obvious improvement of tear strength. Moreover, the silicon content was decreased by 79.8% when the extraction conditions were set at 75 ºC with alkali concentration of 8%, suggesting that pre-extraction of hemicellulose is a potential way to solve silicon problems associated with alkaline pulping of stover.

Standard handsheets of bleached bagasse and hardwood pulps were prepared with calcium carbonate filler loading by conventional method and by in-situ precipitation. The handsheets were printed with an IGT printability tester. The effect of filler loading by in-situ precipitation on ink transfer, print density, and print-through was studied. For a given amount of ink on the printing disk or on the paper, the print density was greater and the print-through was less for in-situ precipitation of filler when compared with the conventional filler loading.

The integrated forest biorefinery (IFBR) concept provides a promising opportunity for the development of the pulp and paper industry. One proposed next generation technology for an integrated forest biorefinery is the extraction of hemicelluloses, allowing the co-production of pulp and different hemicellulose-based chemicals. In addition to paper properties, hemicelluloses are known to be important for the function of cationic papermaking additives, because they are the main source of charged groups in fibers. This paper shows that the alkaline extraction of hemicelluloses from bleached kraft pulp decreases both the total and surface charge of the pulps. It was found that the decreased fiber charge leads to increased filler retention with fixed retention aid dosage. The reduction observed in the fiber surface charge for alkali-extracted pulp was mainly attributed to the decrease in the amount of anionic groups located in fines.

Triploid Populus tomentosa Carr. (Salicaceae) is a good alternative to meet the increasing need of the global pulp and paper industry. Meanwhile, the xylem of this species could be a useful bioresource to develop low molecular extractives with significant bioactive potential. In the present work, a phytochemical investigation on aqueous EtOH extractives of Triploid P. tomentosa xylem, by systematical performance of Sephadex LH-20 open column chromatography and Thin Layer Chromatography (TLC), resulted in the isolation of two phenolic acids (ρ-coumaric acid (I) and caffeic acid (II)), two flavonoids (apigenin (III) and luteolin (IV)), and three phenolic glucosides (salicortin (V), salireposide (VI) and populoside (VII)). The structure elucidation and determination of the isolated extractives were based on their spectroscopical data and physiochemical evidences. This was the first time to report the low molecular weight extractives of Triploid P. tomentosa. Various low molecular weight extractives fromTriploid P. tomentosa xylem exhibited significant antioxidative activities by DPPH and hydroxyl radical scavenging assays.

Black liquor alkaline lignin and magnesium lignosulfonate were liquefied at 320 oC. The antioxidant abilities of the liquefaction products were compared with the raw materials. Results showed that the total phenol content and unit antioxidant power of both alkaline lignin liquefaction products (ALLP) and magnesium lignosulfonate liquefaction products (MLLP) were improved, and ALLP had a larger increase than MLLP. The influence of reaction time and temperature on oil yield, total phenol content, and antioxidant power of ALLP was evaluated. The total phenol content was found to have certain relationships with the antioxidant abilities. These results explore a new approach for further studies and applications of liquid antioxidant from lignins.

Binderless fiberboards from enzymatic hydrolysis lignin (EHL) and cotton stalk fibers were prepared under various manufacturing conditions, and their physico-mechanical properties were evaluated. Full factorial experimental design was used to assess the effect of fiber moisture content and pressing temperature on boards’ properties. In addition, differential scanning calorimetry (DSC) was used to obtain the glass transition temperature (Tg) of EHL. We found that both fiber moisture content and pressing temperature had significant effects on binderless fiberboards’ properties. High fiber moisture content and pressing temperature are suggested to contribute to the self-bonding improvement among fibers with lignin-rich surface mainly by thermal softening enzymatic hydrolysis lignin. In this experiment, the optimized pressing temperature applied in binderless fiberboard production should be as high as 190°C in accordance with the EHL Tg value of 189.4°C, and the fiber moisture content should be limited to less than 20% with a higher board density of 950 kg/m3 to avoid the delamination of boards during hot pressing.

Every year, significant amounts of date palm rachises are accumulated in Tunisia. The rational valorisation of this renewable resource is therefore imperative, in order to fulfil the sustainability approach. In this context, this work aims to study the potential use of date palm rachises as a raw material for papermaking and to compare it with other sources of lignocellulosic fibres, such as wood, non-wood species, and agricultural wastes. For this purpose, soda-anthraquinone pulping of date palm rachis was performed giving rise to a yield of 45% (w/w). This value is similar to that obtained by pulping non-wood materials and is higher than that corresponding to the pulping of agricultural residues. The resulting pulps were subsequently refined using a PFI mill refiner at 0, 500, 1500, and 3000 revolutions, screened through a 0.15 mm mesh size sieve and used to produce conventional handsheets. Both pulps and papers were fully characterized in terms of morphological, chemical and physical properties, according to commonly used standards. The physical properties of the prepared handsheets were very similar to those displayed by other papers made of common lignocellulosic fibres. Furthermore, the pulps exhibited a good drainability together with excellent mechanical properties of the ensuing papers. For these reasons, date palm rachises could be considered as a potential source of fibres for papermaking applications.