Effects of sulfonation on properties of different cell wall layers

Holzforschung, 2011

The morphological and chemical characteristics of cell walls govern the response of wood fibre to mechanical pulping processes and thereby influence the energy efficiency of the process and determine most pulp and paper properties. A study has been carried out at the microstructural/ultrastructural level of fibre cell walls by means of a newly developed Simons’ staining (SS) method and scanning electron microscopy to characterize thermomechanical pulps (TMPs) produced under different refining conditions. The SS method allows assessment and quantification of pulp fibre development during the process in terms of cell wall delamination/internal fibrillation (D/IF) under different process conditions, and the degree of D/IF can be statistically evaluated for different TMP types. In focus was never-dried Norway spruce TMP from primary stage double-disc refining running in a full-scale mill, where specific refining energy was varied at different refining pressure levels. Improved energy ef...

Different electron microscopy techniques including SEM (scanning electron microscopy), FE-SEM (field emission-scanning electron microscopy), TEM (transmission electron microscopy) and Immuno-gold TEM (immuno-gold transmission electron microscopy) were applied in order to gain a better understanding of the influence of the native softwood fibre cell wall ultrastructure including morphology and topochemistry (i.e. lignin and glucomannan distribution) during mechanical pulping. In thermomechanical pulp (TMP) processing, wood fibres undergo structural changes (cell wall delamination and fibrillation) that are regulated by the native fibre micro- and ultrastructure. In addition, novel information was obtained on the fibre cell wall architecture. In contrast, the stoneground wood (SGW) process inflicted severe damage to the fibre structure resulting in transverse and longitudinal fibre breakage. However, juvenile wood SGW fibres showed improved properties (strength and light scattering) c...

In this study the effects of mechanical treatment of kraft pulp fibers, at different temperatures, on pulp and pulp strength properties were investigated. The beating demand increased while the tear index and zero-span tensile strength of treated pulps decreased as the treatment temperature was increased from 100 o C to 170 o C. The carbohydrate compositions measured as monosaccharides after acid hydrolysis of the pulps were the same. The small differences in fiber deformation of the bleached pulps could not explain the severe strength losses at 170 o C. The fracture analysis, together with the results of a fractionation study of treated pulps, indicated that single fiber strength was lost. The results also indicated that the fiber damage resulting from mechanical treatment at high temperature under alkaline cooking conditions led not to a reduction in interfiber bonding ability.

Holzforschung, 2004

The aim of the study was to evaluate the effect of refining on the ultrastructure of spruce pulp fibres. Pulps with different molar masses of cellulose (estimated as intrinsic viscosity) were studied after PFI-refining. The molar masses of the polymers were decreased by increases in alkali concentration during pulping. Fibre surface structures were examined using Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) was used to observe changes in the internal structure of the fibres. Pulps with lower (125 and 329 ml g−1) intrinsic viscosity showed more damaged during refining than pulps with higher (620 and 1120 ml g−1) intrinsic viscosity. Observations showed pulps with lower intrinsic viscosity to have large decreases in fibre length after refining. Fibres with low intrinsic viscosity (i.e., 125 ml g−1) had less primary wall and S1 layer remaining and the external fibrillation and damage of the S2 layer had increased. The S2 wall of fibres...

Holzforschung, 2013

Primary refined softwood was subjected to high-consistency (HC) or low-consistency (LC) secondary refining, and the nature of the development of the internal and external fiber microstructure and ultrastructure has been compared. The primary refining of mixed softwood as a raw material was performed in pilot scale by the advanced thermomechanical pulp process. The study was aiming at the comparative characterization of LC and HC pulps at the fiber level when produced with similar and well-characterized handsheet properties. The formerly described Simons’ staining method was applied. A significant degree of fiber wall delamination/internal fibrillation (D/IF) was observed during both LC and HC refining. Both the energy input and the refining consistency had a significant impact on elevating the degree of fiber wall D/IF. The statistical evaluation of internal fiber development indicated that the fiber populations in LC- and HC-refined pulps had a similar degree of fiber wall D/IF des...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003

The surface properties of thermomechanical pulps (TMP) were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Finnish and French spruce samples representing two different defibration temperatures as well as two different stages of refining were studied. In addition, samples from an RTS process were studied. The XPS results showed that the surface content of non-cellulosic components was higher for Finnish spruce compared with the French pulp samples. Different wood fibre cell wall structures and transition lamellae within the cell walls with characteristic microfibril orientation were identified by AFM. Besides the morphological features, the homogeneity of the surfaces was studied with AFM with respect to adhesion and stiffness. The refining was concluded to result in a cleavage taking place either within the secondary cell wall or at primary/secondary cell wall interface. No randomly oriented microfibrillar network structures typical for the primary cell wall were observed. The RTS process resulted in most homogeneous samples whereas heterogeneous structures with even damaged microfibrils were observed for e.g. the stage-2 refined TMP. #

2016

This article presents the impact of a degree of polymerization on the papermaking potential of paper. Bleached pinewood kraft pulp from one of paper mills was used for research purposes. The main objective of this work was to investigate the influence of a degree of polymerisation of pulp on the properties of fibres such as water retention value (WRV) and the fines content etc. Different degrees of polymerization were obtained as a result of the pulp drying at different temperatures (105 ̊C, 130 ̊C and 150 ̊C) for a period from 1 hour up to 150 hours. During the drying process, a visible decrease in a degree of polymerization of cellulose in hornified fibres occurs. Significant differences in pulp properties can be observed in particular in case of pulps dried at a very high temperature (150°C) and in case of a long drying time (150 h).

Wood and Fiber Science, 2007

Eucaypfus is currently one of the main fibrous raw materials used in the pulp and paper industry in given parts of the world. The objective of the present paper is to optimize the chemimechanical ouloinu conditions for Eucalynfus arandis, evaluate the oulo auality obtained, and draw conclusions-~ ~-. regarding its potential use. The raw material used was Eucalypttrr grandis industrial chips obtained at a Celulosa Areentina mill in Puerto Pirav. Misiones. Areentina. For all the exoeriments. the chemical. . .stage was carried out in a stainless steel digester with a liquor recirculation system. he mechanical stage was canied out in an &in. atmospheric disk refiner. Sodium sulfite and sodium hydroxide were added as chemical reactives. The central composite experimental design used involved five levels for the two variables srualeo (A" tactonal aeslgn + star + central point). Three repetitions of the central point were carried out to check for errors. The variables studied were: initial amount of sodium sulfite in the wood (0.9 to 3.5% oven-dry wood) and reaction temperature (96 to 124 0. Times until maximum temoerature and time at maximum temoerature were. resoectivelv. 20 and 90 minutes. A constant. .. . level of sodium hydroxide was maintained in all the experiments (1.5% oven-dry wood). Pulp evaluation was carried out using the usual characterization techniques. Chemical and physical evaluations, including optical testing, were, for the most part, done in accordance with TAPPI procedures. The results obtainedjndicate that the central point of the design used in our research (1 10 C and 2.5% oven-drv wood sulfite). aooears to reoresent the ootimal conditions for the variables studied for the chemimechanical pulping b~~u c a l y p l~s grandis. g he pulps obtained could be used as furnish in printing and writing paper grades. The positive correlation between sulfonate concentration and water retention value (WRV) suggests that by increasing fiber wall swelling, the number of sites accessible to sulfonation is i n c r e a s e d h e tensile index corrilates positively with the degree of sulfonation and with the water retention value of the oulos. It decreases according to the fraction retained in a 30-.. mesh screen (due to the presence of numerous shives) and increases according to the fraction of fines passing through a 270-mesh screen.

The requirement for high quality pulps which are widely used in paper industries has increased the demand for pulp refining (beating) process. Pulp refining is a promising approach to improve the pulp quality by changing the fiber characteristics. The diversity of research on the effect of refining on fiber properties which is due to the different pulp sources, pulp consistency and refining equipment has interested us to provide a review on the studies over the last decade. In this article, the influence of pulp refining on structural properties i.e., fibrillations, fine formation, fiber length, fiber curl, crystallinity and distribution of surface chemical compositions is reviewed. The effect of pulp refining on electrokinetic properties of fiber e.g., surface and total charges of pulps is discussed. In addition, an overview of different refining theories, refiners as well as some tests for assessing the pulp refining is presented.

Bioresources, 2021

Particles in mechanical pulp show a wide variety but are commonly described using averages and/or collective properties. The authors suggest using distributions of a common bonding factor, BIND (Bonding INDicator), for each particle. The BIND-distribution is based on factor analysis of particle diameter, wall thickness, and external fibrillation of several mechanical pulps measured in an optical analyser. A characteristic BIND-distribution is set in the primary refiner, depending on both wood and process conditions, and remains almost intact along the process. Doubledisc refiners gave flatter distributions and lower amounts of fibres with extreme values than single-disc refiners. More refining increased the differences between fibres with low and high BIND. Hence, it is more difficult to develop fibres with lower BIND. Examples are given of how BIND-distributions may be used to assess energy efficiency, fractionation efficiency, and influence of raw material. Mill scale operations were studied for printing-grade thermomechanical pulp (TMP), and board-grade chemithermomechanical pulp (CTMP), both from spruce.