Preparation and Comparative Study of Aerogels Based on Cellulose Nanocrystals and Nanofibers from Eucalyptus Pulp

Nanocellulose-based materials have attracted significant attention because of their attractive advantages. Particularly, aerogel, a porous nanocellulose material, have been used in diverse applications owing to their unique properties. In this study, short rod-like cellulose nanocrystals (CNCs) and long filament-like cellulose nanofibers (CNFs) were isolated from a eucalyptus pulp source using acidolysis and oxidation/mechanical methods, respectively. Subsequently, two different aerogels were prepared from the CNCs and CNFs using the sol-gel method and their properties were compared. The morphology, chemical structure, chemical composition, shrinkage rate, internal structure, thermal degradation, biophysical properties, and mechanical properties of the as-prepared aerogels were compared. Furthermore, the shrinkage of the CNC and CNF aerogels was effectively controlled using a supercritical CO2 drying process. Additionally, three decomposition regions were observed in the thermogravimetric analysis curves of the aerogels; however, the CNF aerogels exhibited enhanced thermal stability than the CNC aerogels. Further, the CNC and CNF aerogels exhibited a mesoporous structure, and the compressive strength of the CNC and CNF aerogels under 85% strain was 269.5 and 299.5 KPa, respectively. This study provides fundamental knowledge on the fabrication of CNCs, CNFs, and corresponding aerogels from lignocellulosic biomass, and their characteristics.

Beating of Eucalyptus Pulp Fibers under Neutral and Alkaline Conditions – A Valley Beater Study

Beating is one of the most important and complicated processes that influences paper production and paper quality from both a process and a paper property standpoint. With increasing costs, environmental regulations and competitiveness in the today’s global market, paper and board producers revisit existing production process to decrease production costs. New approached with additives such as new developed in-situ precipitated paper fillers materials have the potential to reduce production cost and increase profit margins. For this research bleached eucalyptus Kraft pulp adjusted to a pH of 7.5, 11.0 and 12.3, and laboratory manufactured in-situ precipitated calcium carbonate with a filler level based on oven dry fiber content of 20.9% and 41.7% and a pH of 7.5, and commercial produced precipitated calcium carbonate filler of 10% and 20%. All pulp suspensions were beaten for 80 minutes with samples taken at the unbeaten level and 20 minutes increments. The beating curve over 80 minutes beating time show that pulp suspensions with in-situ produced filer material have a higher dewatering ability with increasing filler content compared to the pulps with commercial PCC and different pH values. Viscosity slightly decreases for pulp suspension with commercial and in-situ produced filler content. Pulp suspension at a pH of 12.3 showed a significant decrease in viscosity over the 80 minutes beating time, superseding the filler containing pulp suspensions. Basis weight decreased over beating time for all pulp suspensions, which can be explained with an increased fines production during beating and lower fiber retention during handsheet forming. The breaking length index increase for all pulp suspensions till 40 minutes of beating time for the filler containing pulp suspensions. Tear index and burst index curves based on beating time are similar for all pulp suspensions with a maximum at 40 minutes beating for the tear index and 60 minutes beating for the burst index. High filler containing pulp suspension showed the lowest tear index.

Investigation of pulp flow helicity in rotating and non-rotating grooves

Numerical simulation of pulp flow in rotating and non-rotating grooves is carried out to investigate the effect of pulp rheological properties and groove geometry on the rotational motion of the pulp flow. The eucalyptus pulp suspension is considered as a working fluid in the present study whose apparent viscosity correlation is available from the experimental measurements reported in the literature. The simulations are carried out with OpenFoam for different values of pulp material, fiber concentrations, and groove cross-section. Helicity is introduced to measure the turnover rate of pulp flow in the groove due to the importance of such motion on the final properties of the pulp flow. A measurement of helicity magnitude and its distribution along the groove revealed that a change in the pulp material would significantly affect the flow structures within the groove. Further investigation on the effects of fiber concentration, c, showed that this parameter does not have a significant effect on the averaged helicity magnitude for c = 2.0 and 2.5, whereas the helicity distribution over the groove cross-section changes clearly for c = 1.5. The results showed that the helicity level is negligible for almost half of the cavity cross-section in the non-rotating groove simulations, which can be considered as a shortcoming of the original geometry of the groove. Therefore, a smaller cross-section for the groove is considered through which an enhancement in the helicity magnitude is observed.

In Situ Precipitated Calcium Carbonate in the Presence of Pulp Fibers – A Beating Study

The paper industry around the world is in search for new ways to decrease production costs. New approached with additives such as new developed In Situ precipitated paper fillers materials have the potential to reduce production cost and increase profit margins. In Situ precipitated calcium carbonate filler with 20.9% and 41.7% filler material was produced in a large-scale laboratory unit using a eucalyptus pulp fiber suspension with a 1.7% fiber solids content. Laboratory beating tests were performed with a Valley Beater and APFI Mill using pure eucalyptus pulp with no filler content as the based trial and the two-laboratory manufactured In Situ precipitated filler pulps. Valley Beater and PFI Mill laboratory beating machines show similar differences/trends for the breaking length, tear and burst index. EC-pulp with no filler has the highest strength for breaking length, tear and burst index. With increasing filler level breaking length, tear and burst index decrease. Filler containing pulp shows a decrease in beating time for the same beating level. 20 minutes for the Valley Beater and 15000 revolutions for the PFI mill show highest change in pulp fiber beating level sufficient for paper making operation. Valley Beater and PFI Mill laboratory equipment operate different and an exact comparison of the beating curves is not possible. Based on the amount of pulp fiber needed for experiments the Valley Beater for large amounts and the PFI mill for smaller amounts should be selected. The SEM pictographs of the Valley Beater and PFI Mill beating trials from 0 stage to the high beating stage at 80 minutes for the Valley beater and 60000 revolutions for the PFI Mill show similar results. No damage to the fibers is noticeable at the unbeaten level. With increasing beating level. At a magnification of 430 times the fiber structure shows an increasing dense fiber structure with less visible pores. Magnification of 2500 times reveals increasing damage to the fiber wall and fiber surface.

Effect of Mechanical Treatment of Eucalyptus Pulp on the Production of Nanocrystalline and Microcrystalline Cellulose

This study aimed to assess the effect of mechanical pretreatment on bleached eucalyptus kraft pulp fibers and investigate the influence of reaction time and temperature on the properties and yield of nanocrystalline cellulose (NCC) and microcrystalline cellulose (MCC). Two types of pulps were hydrolyzed, pulp 1 (control, whole fibers) and pulp 2 (mechanically pretreated, disintegrated fibers). NCC and MCC particles were obtained by sulfuric acid hydrolysis (60% w/w) of eucalyptus pulps under different conditions of time (30–120 min) and temperature (45–55 °C). Physical treatment of kraft pulp facilitated acid hydrolysis, resulting in higher NCC yields compared with no pretreatment. The morphologic properties and crystallinity index (CI) of NCC and MCC were little affected by pulp pretreatment. NCC particles obtained from pulps 1 and 2 were needle-shaped, with mean diameters of 6 and 4 nm, mean lengths of 154 and 130 nm, and CI of 74.6 and 76.8%, respectively. MCC particles obtained from pulps 1 and 2 were rod-shaped, with mean diameters of 2.4 and 1.4 µm, mean lengths of 37 and 22 µm, and CI of 73.1 and 74.5%, respectively. Pulps 1 and 2 and their respective NCC and MCC derivatives had a cellulose I crystalline structure.

Small Pilot System for the Manufacture of in Situ Precipitated Calcium Carbonate in the Presence of Pulp Fibers

Paper fillers materials are less expensive than fiber, allowing reduced production costs and improvement of paper properties. A small pilot scale in-situ laboratory calcium carbonate filler precipitation unit was developed and designed with the objective to provide enough pulp fiber containing in-situ precipitated calcium carbonate for a small 12-inch (304 mm) wide laboratory paper machine. The in-situ precipitation system requires the reactants calcium hydroxide and carbon dioxide and was tested with a eucalyptus pulp fiber pulp suspension. The final precipitated in-situ filler content achieved was 38.2%, 55.5% and 66.6% based on initial eucalyptus pulp fiber content. The precipitation time from an initial pH of 12.77, 12.76 and 11.98 to an final pH of 7.29, 7.55, and 7.28 for the 3 kg, 6kg, and 9 kg of calcium hydroxide reactant addition was 45 minutes for the 3 kg and 9 kg calcium hydroxide addition and 40 min. for the 6 kg calcium hydroxide addition.

Optimizing Cellulose Microfibrillation With NaOH Pretreatments for Unbleached Eucalyptus Pulp

This study aimed to assess the effect of drying unbleached Eucalyptus cellulose fibers after the application of pretreatments in order to optimize the microfibrillation process, as well as to evaluate the efficiency of NaOH pretreatments in reducing energy consumption for production of microfibrillated cellulose (MFC). Pretreatments with 0 wt% (untreated), 5 wt% and 10 wt% NaOH were evaluated. The length and width of the fibers pretreated with NaOH decreased significantly, mainly with hasher pretreatments. The removal of hemicellulose from the fiber cell wall was an important factor concerning the degree of fibrillation of the fibers. Pretreating fibers with 5 wt% NaOH for 2 h increased the water retention value (WRV), in addition to presenting the lowest energy consumption for fibrillation, promoting energy savings of up to 48%. Pulps that were not dried after the NaOH pretreatments incurred in easier microfibrillation and lower energy consumption when comparing to the dried pulp, which shows the negative impact of drying on the fibers to obtain the MFC.