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The main objective of this research work was to study the wettability of thermomechanical pulps (TMP) prepared from heart- and sapwood of Scots pine (Pinus sylvestris [L.]). The TMP were prepared at different pulping temperatures (150 °C, 180 °C). Furthermore, thermomechanical (TMP) and chemo-thermomechanical pulps (CTMP) from Norway spruce (Picea abies [Karst.]) were also investigated. In this case both TMP and CTMP were prepared at 140 °C and 180 °C. Sheets of all pulps were prepared according to a method developed by Roffael et al. (2002). Sheets of TMP pulps from pine sapwood showed much better wettability compared with their counterparts from heartwoods. Pulps from heartwood experienced a dramatic decrease in their wettability when increasing the pulping temperature from 150 °C to 180 °C. In contrast increasing the temperature from 150° to 180 °C seems to have no deleterious effect on the wettability of pulps prepared from sapwood. This phenomenon has been explained by the higher extractive content in pine wood. Comparing TMP and CTMP pulps from Norway spruce leads to the result that in general CTMP pulps are of higher wettability. This can be attributed to the high hydrophobic extractive content in TMP pulps on the one hand and to the higher alkalinity of CTMP pulps on the other hand
The main objective of this research work was to study the wettability of thermomechanical pulps (TMP) prepared from heart- and sapwood of Scots pine (Pinus sylvestris [L.]). The TMP were prepared at different pulping temperatures (150 °C, 180 °C). Furthermore, thermomechanical (TMP) and chemo-thermomechanical pulps (CTMP) from Norway spruce (Picea abies [Karst.]) were also investigated. In this case both TMP and CTMP were prepared at 140 °C and 180 °C. Sheets of all pulps were prepared according to a method developed by Roffael et al. (2002). Sheets of TMP pulps from pine sapwood showed much better wettability compared with their counterparts from heartwoods. Pulps from heartwood experienced a dramatic decrease in their wettability when increasing the pulping temperature from 150 °C to 180 °C. In contrast increasing the temperature from 150° to 180 °C seems to have no deleterious effect on the wettability of pulps prepared from sapwood. This phenomenon has been explained by the higher extractive content in pine wood. Comparing TMP and CTMP pulps from Norway spruce leads to the result that in general CTMP pulps are of higher wettability. This can be attributed to the high hydrophobic extractive content in TMP pulps on the one hand and to the higher alkalinity of CTMP pulps on the other hand
Through the use of fluorescently labelled paraffin wax and UF resin, fluorescence microscopy has been used to simultaneously visualise wax and resin components on medium density fibreboard (MDF) fibre. To simulate differing application methods, the wax and resin were applied to fibre either separately or as a mixture. Visualisation on unpressed fibre and in panels suggests the application order can lead to differing wax-resin behaviours and how each interact with fibre. Both qualitative and quantitative analyses of wax and resin distribution on fibre established that the main differences in behaviours were due to wax and occur on pressing. Applying wax first to fibre led to wax droplet agglomeration in panels whereas applying wax after resin or as a mixture appeared to allow wax to be retained as relatively smaller droplets within the resin matrix. This also manifested itself in differences in wax overlap with resin in panels, where a relatively low overlap was observed when applying wax first, despite a substantially higher overlap in unpressed fibre. Application of wax after resin or as a mixture resulted in the wax generally staying with the resin. The observed differences in wax distribution were also correlated with panel cold water soak properties. Wechselbeziehungen zwischen Wachs und UF-Harz in mitteldichten FaserplattenZusammenfassung Mit fluoreszenzmarkiertem Paraffin und UF-Harz wurden Wachs-und Harzkomponenten auf MDF-Fasern mit dem Fluoreszenzmikroskop simultan visualisiert. Um verschiedene Auftragsmethoden zu simulie-W. Grigsby ( ) · A. Thumm Science Leader, Scion, Private Bag 3020, ren, wurden Wachs und Harz entweder einzeln oder als Mischung auf die Fasern aufgetragen. Die Visualisierung auf ungepressten Fasern und in den Platten ergab, dass die Art des Auftrags das Verhalten zwischen Wachs und Harz und deren Verteilung auf der Faser beeinflusst. Sowohl die qualitative als auch die quantitative Untersuchung der Wachsund Harzverteilung auf der Faser zeigten, dass die Hauptunterschiede auf das Wachs zurückzuführen sind und beim Pressen auftreten. Wird Wachs zuerst auf die Faser aufgetragen, führte dies zu einer Tröpfchenagglomeration in den Platten. Umgekehrt, wenn Wachs nach dem Harz oder als Mischung aufgetragen wird, schien sich das Wachs in relativ kleineren Tröpfchen in der Harzmatrix zu verteilen. Dies zeigte sich auch in der unterschiedlichen Vermischung von Wachs und Harz in den Platten, wobei eine relativ geringe Vermischung zu sehen war, wenn das Wachs zuerst aufgetragen wurde, trotz einer wesentlich höheren Vermischung auf den ungepressten Fasern. Wird Wachs nach dem Harz oder als Mischung aufgetragen, blieb das Wachs generell mit dem Harz verbunden. Die beobachteten Unterschiede in der Wachsverteilung korrelierten auch mit dem Verhalten der Platten nach Kaltwasserlagerung.
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