Effect of the Micronization of Pulp Fibers on the Properties of Green Composites

Green composites, composed of bio-based matrices and natural fibers, are a sustainable alternative for composites based on conventional thermoplastics and glass fibers. In this work, micronized bleached Eucalyptus kraft pulp (BEKP) fibers were used as reinforcement in biopolymeric matrices, namely poly(lactic acid) (PLA) and poly(hydroxybutyrate) (PHB). The influence of the load and aspect ratio of the mechanically treated microfibers on the morphology, water uptake, melt flowability, and mechanical and thermal properties of the green composites were investigated. Increasing fiber loads raised the tensile and flexural moduli as well as the tensile strength of the composites, while decreasing their elongation at the break and melt flow rate. The reduced aspect ratio of the micronized fibers (in the range from 11.0 to 28.9) improved their embedment in the matrices, particularly for PHB, leading to superior mechanical performance and lower water uptake when compared with the composites with non-micronized pulp fibers. The overall results show that micronization is a simple and sustainable alternative for conventional chemical treatments in the manufacturing of entirely bio-based composites.

EFFECT OF ADDITION OF DEINKED PULP TO BLEACHED KRAFT PULP ON TISSUE PAPER PROPERTIES

The influence of addition of deinked pulps with low and high brightness to bleached eucalyptus and pine kraft pulps on functional tissue paper properties was studied. Deinked pulps with low and high brightness had some different functional properties. Deinked pulp with high brightness has higher bulk, porosity, water absorption after immersion, initial water absorption, bulk softness as well as brightness. On the contrary, the difference in relative bonded area and porosity e between deinked pulps with low and high brightness was moderate. The mixed pulps laboratory pulp sheets from bleached eucalyptus kraft pulp or bleached pine kraft pulp with addition of 20, 40 and 80% of deinked pulp with low brightness or deinked pulp with high brightness were prepared. The addition of the deinked pulp with high or low brightness to bleached kraft pulp leads to increasing of bulk, bulk softness as well as high water absorption after immersion and initial water absorption. The tensile index rapidly decreased by the addition of deinked pulps with high brightness to bleached eucalyptus and pine kraft pulps. Similarly, the addition of deinked pulp with low brightness to bleached pine kraft pulp led to rapid decreasing of tensile index. On contrary, with the addition of deinked pulp with low brightness to eucalyptus kraft pulp, the decreasing of tensile index was less pronounced. Mixed pulp from bleached eucalyptus kraft pulp with a small content of deinked pulp with low brightness with functional properties suitable for production of tissue papers was found as optimal.

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.

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.

The Dual Effect of Ionic Liquid Pretreatment on the Eucalyptus Kraft Pulp during Oxygen Delignification Process

Oxygen delignification presents high efficiency but causes damage to cellulose, therefore leading to an undesired loss in pulp strength. The effect of ionic liquid pretreatment of [BMIM][HSO4] and [TEA][HSO4] on oxygen delignification of the eucalyptus kraft pulp was investigated at 10% IL loading and 10% pulp consistency, after which composition analysis, pulp and fiber characterizations, and the mechanism of lignin degradation were carried out. A possible dual effect of enhancing delignification and protecting fibers from oxidation damage occurred simultaneously. The proposed [TEA][HSO4] pretreatment facilitated lignin removal in oxygen delignification and provided fibers with improved DP, fiber length and width, and curl index, resulting in the enhanced physical strength of pulp. Particularly, its folding endurance improved by 110%. An unusual brightness reduction was identified, followed by detailed characterization on the pulps and extracted lignin with FTIR, UV, XPS, and HSQC. It was proposed that [TEA][HSO4] catalyzed the cleavage of β-O-4 bonds in lignin during the oxygen delignification, with the formation of Hibbert’s ketones and quinonoid compounds. The decomposed lignin dissolved and migrated to the fiber surface, where they facilitated the access of the oxidation agent and protected the fiber framework from oxidation damage. Therefore, it was concluded that ionic liquid pretreatment has a dual effect on oxygen delignification.

Adsorption of Cellulases on BHKP Fibers during Pretreatment for MFC Film Preparation

Adsorption of cellulase on fibers is a key factor in determining its efficiency on fiber treatment and microfibrillated cellulose (MFC) preparation. Different adsorption behavior, treatment efficiency and performance of MFC and MFC film were observed due to the different properties of cellulases. Herein, bleached eucalyptus kraft pulp (BHKP) was pretreated by complex cellulase (D cellulase) and endocellulase (R cellulase) with different dosages for MFC preparation. Enzyme activity, adsorption ratio, adsorption kinetics and adsorption thermodynamic of the two cellulases were comprehensively studied, and the impacts of the cellulase pretreatment on the properties of MFC and MFC film were investigated. The results showed that D cellulase possessed higher adsorption ratio than R cellulase, but R cellulase demonstrated higher adsorption rate than D cellulase. High temperature discouraged the adsorption of the two cellulases because of their exothermic natures. The crystallinity index (CrI), specific surface area (SSA) and morphology of MFC were tuned by the combination of two cellulases at different dosages. The CrI of MFC treated by D cellulase and R cellulase increased from 40.45% to 66.50% and 66.67% respectively when the cellulase dosage was 10 U/g. The elongation at break (E) and tensile strength (TS) of MFC film treated by D cellulase were decreased first and then increased slightly, but the MFC film treated by R cellulase decreased continuously. The MFC film prepared by D cellulase possessed the best barrier property at 20 U/g and the corresponding oxygen permeability coefficient was 4.37×10-14 cm3·cm/cm2·s·Pa. However, the oxygen permeability coefficient of MFC film pretreated by R cellulase at a dosage of 10 U/g was 4.13×10-14 cm3·cm/cm2·s·Pa. This work shows that R cellulase was more suitable than D cellulase for BHKP pretreatment to prepare MFC film.