Papermaking Potential Research Articles

Papermaking Potential of Novel Structured PCC Fillers with Enhanced Refractive Index

While much effort has been focused on optical properties imparted by particle size distribution, shape, and packing of inorganic particles, the refractive index contrasts within the paper matrix have received less attention. PCC fillers can be used as tools for increasing the refractive index contrast, which further improves paper optical properties. We studied the papermaking potential of novel PCC fillers with an enhanced refractive index. PCC samples were fabricated by conventional carbonation method in the presence of refractive-index enhancing additives. We had previously found that introduction of ZnO as fine spots, including nano-sized structures, on host PCC surfaces improved the effective refractive index and optical performance of PCC. Now, we have studied the papermaking potential of this approach in experiments with handsheets using moderate Zn modification. In addition to Zn, we studied the effect of Sr as an additive and found that Sr inclusion alters the host particle morphology and crystal structure. We report effects of such modifications on light scattering coefficient, brightness, opacity, tensile strength, bulk, and porosity of paper, both before and after calendering. Our results suggest beneficial optical properties, as well as combination of light scattering with strength properties, especially in the case of Sr modified filler. Zn modified fillers opened the sheet structure, while Sr structuring closed the sheets. Calendering resulted in reduced bulk with all fillers, while optical properties were maintained with the Sr modified PCC, but reduced benefit was observed in the combination of light scattering and strength. Calendering conditions should therefore be optimized for these fillers. A higher modification degree of the fillers should also be considered to achieve a more significant refractive index contrast.

Effect of Eucalyptus globulus wood density on papermaking potential

It is well documented that the characteristics of raw materials determine the papermaking potential of the pulp. The variability of the wood used by the pulp mills is extremely wide. We report on the behavior of three Eucalyptus globulus wood chip samples with basic densities of 0.467, 0.537, and 0.600 g/cm3, in kraft cooking and papermaking. The pulp yield range of 49%–58.7% was attributed to the different wood chemical composition, in particular to the lignin content and relative proportion of cellulose and hemicelluloses. The morphological characteristics of the pulp fibers were also markedly different. The average fiber length is 0.71, 0.80, and 0.85 mm, respectively for the E. globulus of low, intermediate, and high wood basic density. The pulp fibers from the lowest density wood exhibit very high wet fiber flexibility, while those from the highest density wood exhibit rigid behavior. Using this structural property as reference, the corresponding papers are stronger, but exhibit lower light scattering coefficients than those from the lowest density wood

Cynara cardunculus L. alkaline pulps: Alternatives fibres for paper and paperboard production

The pulping of Cynara cardunculus L. (cardoon) was performed under conditions for kraft, kraft-AQ and soda-AQ processes. The best results in terms of delignification degree, expressed as kappa number, pulp viscosity and screened yield, were obtained for the kraft-AQ process with 0.20% of anthraquinone (AQ). The papermaking potential of the selected pulp was studied attending to biometric fibre characterisation, refining aptitude, optical and strength properties. All properties were compared against a Eucalyptus globulus pulp at different refining degrees. The cardoon pulp was also evaluated concerning its potential to board manufacture, alone and in mixtures with pine pulp, giving rise to promising results for liner manufacture.

Characteristics of Pulps and Their Papermaking Potential

This work is a contribution to the characterization of the papermaking potential of wood pulps. Prevision of this potential developed during the drying process is the scope of this study. The VARIDIM© apparatus allows to measure shrinkage for different loads applied on the paper strip samples with constant air-drying conditions. The dried papers are then tested in an extensometer to determine mechanical properties. The main originality of this study lies in the possibility of classifying pulps by the maximum specific energy they are able to develop during drying shrinkage.

Pulp from oil palm fronds by chemical processes

To enhance the use of the abundant biomass generated by the palm oil industry in Malaysia a study was conducted in view of exploring the papermaking potential of this industrial byproduct. Fiber strands from the frond of oil palm trees were examined relative to their physical and chemical characteristics and their response to chemical pulping such as sulfite, soda-sulfite and soda processes. Morphologically, the frond fibers are comparable to those of hardwood. They contain high content of holocellulose but low in lignin. Chemical pulps of 45–50% yield produced either by soda-sulfite or soda process exhibit acceptable papermaking properties comparable to those of hardwood kraft pulps. The study showed that frond pulp might be used as a reinforcement component in newsprint production using softwood thermomechanical fibers.

Characterization of wood fibers using fiber property distributions

The properties of pulp fibers have a strong influence on their papermaking potential. Dimensions and physical properties of fibers vary considerably. The papermaking potential of pulp is currently evaluated solely based on the mean values of fiber properties, for instance fiber length. Property distributions with the same mean value can be totally different and therefore a more suitable approach in determining pulp quality is needed. The distributions of fiber properties are likely to be more important than their mean values in controlling pulp quality, as the heterogeneity of the papermaking material is evident. Various problems associated with mean values are considered. A better understanding of characteristic distributions and their meaning in predicting paper properties can prove a significant aid in improving the quality control of pulp.

Genetic selection within Douglas fir (Pseudotsuga menziesii) in Europe for papermaking uses

The study aims to identify the feasibility and the relevance of a genetic selection for enhancing the pulping potential of the Douglas fir wood. At first, wood predictors for TMP potential are identified through the refining of thirty trees 17-year-old, using a specific procedure on a 12 Andritz refiner. The variations of TMP physical properties are linked with those of anatomical parameters, but also with within ring density related traits. The brightness of the unbleached TMP is negatively correlated with the red chromatic component of wood. Lignin, holocellulose and extractives content on one hand, Kraft fibre morphology on the other hand are considered to evaluate roughly the wood potential for the Kraft process. Then 15 clones out of 200 are non destructively selected within a 24-year-old German test to evaluate the range of the genetic va- riation of the papermaking potential. Chemical analyses give evidence of large variations of the chemical composition ratio between clones (ho- locellulose/lignin ratio). The clone discrimination of the fibre length is weak, but significant differences of fibre coarseness are observed as a consequence of the large variability of the latewood density levels. The industrial selection gain for pulping is discussed on the basis of TMP pi- lot plant tests which show large differences of physical and optical TMP properties between average wood assortments of each clone. This leads to practical recommendations for breeders considering the expectations of both the pulping and the wood industry. wood quality / TMP / Kraft pulp / genetic selection / Pseudotsuga menziesii

Prediction in Repeated-Measures Models with Engineering Applications

This article focuses on the problem of predicting future measurements on a statistical unit given past measurements on the same and other similar units. We introduce a conditional predictor that uses the information contained in previous measurements. The prediction technique is based on the iterative EM algorithm, but a noniterative variant is also provided. We use the sample-reuse methodology to select an appropriate predictor. The technique is illustrated in three engineering applications. The first considers prediction in the context of marketing for bucking in automatic forest harvesters. In fatigue-crack-growth data, the interest is in predicting the future crack-growth development of the test unit, and the third application concerns evaluation of pulp from the point of view of its papermaking potential.

Prediction in Repeated-Measures Models With Engineering Applications

This article focuses on the problem of predicting future measurements on a statistical unit given past measurements on the same and other similar units. We introduce a conditional predictor that uses the information contained in previous measurements. The prediction technique is based on the iterative EM algorithm, but a noniterative variant is also provided. We use the sample-reuse methodology to select an appropriate predictor. The technique is illustrated in three engineering applications. The first considers prediction in the context of marketing for bucking in automatic forest harvesters. In fatigue-crack-growth data, the interest is in predicting the future crack-growth development of the test unit, and the third application concerns evaluation of pulp from the point of view of its papermaking potential.

Structural Changes in Cellulose During Papermaking and Recycling

AbstractRecent advances in understanding the structure of cellulose are used as the basis for analyzing the structural changes that occur in pulp fibers during papermaking, particularly in the drying stage. These changes are responsible for the degradation of papermaking properties, and they must be reversed during recycling if the maximum papermaking potential of the virgin fibers is to be recovered. A number of studies have assessed the structural transformations that can occur in cellulosic fibers upon exposure to elevated temperatures. The researchers have invariably observed that the changes occur at the secondary and tertiary levels of structure, the levels that can have significant effects on the properties of fibers. In addition, some studies have focused specifically on the structural effects of recycling; clear correlations of structural change with changes in paper characteristics have been reported. The results of the various studies point to directions for further investigations into enhancing the recovery of papermaking value from recycled fibers.

Mycelial paper: A potential resource recovery process?

AbstractEleven species of fungi representative of a broad range of cell‐wall compositions were evaluated with respect to their papermaking potential as additives to woodpulp furnishes. Some of these species were also examined for their ability to grow on a spent liquor from the pulp‐and‐paper industry. Handsheets with various levels of incorporated mycelia exhibited a wide range of species‐dependent properties. Behavior of the mycelia in the sheets can be modified to a degree by physical and chemical treatments. The overall results suggest that small amounts (5–10% of the sheet constituents) of mycelia, grown inexpensively on waste effluents, might be incorporated into wood fiber paper without serious deleterious effects on paper strength properties. In some cases improved paper is obtained, and larger quantities of mycelia might be used to impart specific properties to the product.