Pulping qualities of refractory vs. permeable douglas-fir heartwood

Graduation date: 1970Heartwood samples of Pacific Coastal Douglas-fir (Pseudotsuga\ud menziesii var. menziesii) and Rocky Mountain Douglas-fir\ud (Pseudotsuga menziesii var. glauca) were rated for relative liquid\ud permeability, and evaluated for kraft pulping characteristics.\ud Highly impermeable wood of the Rocky Mountain variety was termed\ud "refractory," while the pervious wood of the Pacific Coastal variety\ud was termed "permeable."\ud Under constant pulping conditions, refractory Douglas-fir\ud underwent less delignification than permeable Douglas-fir, giving\ud higher screened rejects and lower screened yields. Pulp made from\ud refractory Douglas-fir required less refining to achieve a given level\ud of Canadian Standard Freeness.\ud Handsheet properties were direct functions of fiber characteristic\ud variations. Paper made from refractory Douglas-fir heartwood\ud had greater sheet density, tensile strength, zero-span tensile\ud strength, stretch, and fold endurance. Paper made from permeable\ud Douglas-fir had greater internal tear resistance and a higher sheet\ud brightness. No significant difference existed between the Mullen\ud strengths of paper made from the two varieties