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Unlike Engineered materials, wood, a biological matter, exhibits variability in morphological, physical and chemical properties. This variability is in fact an important attribute without which the papermaker would not have the flexibility to economically create the large variety of papers and paper products required to meet world-wide end-use needs. In the past, the misconception that short-fibre species, hardwoods, are weed species of low commercial value particularly for mechanical pulping, has been rejected with the advance of new technologies such as alkaline peroxide mechanical pulping [1]. Nowadays, a high-quality mechanical pulp can be produced from aspen [2].
In addition to the technological edge in mechanical pulping, a thorough understanding of the rather complicated relationships between wood properties and those of the resulting pulp and paper' is particularly important to maximize the potential use of all species at our disposal. For the past two decades or so, efforts have been made at our research laboratory, as well as at other research institutes, to improve the use of the underused species [3-6]. Satisfactory results could be obtained in pulping optimum mixtures of different species. In view of improving the utilisation rate of the hardwood resource, a better understanding of the influence of fibre morphology on hardwood mechanical pulps is needed. This paper deals with the influence of blending hardwood species of different fibre morphology on the papermaking properties of chemithermomechanical pulps (CTMP).
Experimental
Materials: Three common Canadian hardwood species representing different levels of basic wood density were investigated in the study. They were trembling aspen (Populus tremuloides Michx.), white birch (Betula papyrifera Marsh.) and sugar maple (Acer chaccharum Marsh.). Chips for refining were produced from freshly cut mature logs.
Microtomed sections 20-[Symbol Not Transcribed]m thick were prepared from green wood blocks. Cross-sectional dimensions such as cell diameter and cell wall thickness were measured using a Zeiss Photomicroscope III equipped with a camera. Other fibre characteristics such as fibre length distribution, mean fibre length, fibre coarseness and fines (cells <0.2 mm) content were determined using a Fibre Quality Analyser (OpTest Equipment Inc.).
Chemithermomechanical pulping: Pulping was done using a Sunds Defibrator CD300 pilot plant unit. The chips were pre-steamed at atmospheric pressure for 10 min and fed by means of a plug-screw feeder (compression ratio 2:1) into an...