Assessment of the Quality of Pulp Fibers By Short Span Tensile Analysis

摘要

Fiber strength is an important factor in paper strength, but despite its importance fiber strength is rarely assessed as it involves the tedious and time consuming testing of single fibers. In the recycling of paper, especially of the abundant low grades of waste paper, the question of fiber quality always arises. The inability to monitor fiber quality of recycled pulp, especially from low grade waste paper has led to the practice of utilizing this pulp only for low grade papers regardless of the actual quality of the pulp fibers. Unfortunately, there is a limited demand for low grade papers. Increased utilization of low grade waste paper could be enhanced if the fiber quality of the recycled pulps could be monitored routinely. As the strength of fibers is affected by defects that are randomly distributed among and within fibers it appeared a short span tensile test might provide a means for assessing fiber quality. In short span tensile testing of fibrous webs the load at the break declines as the span increases. The rate of decline is partly controlled by the fiber length distribution. Since the probability of locating defects in fibers increases with increasing span lengths the rate of decline in web strength with increasing span lengths should be a function of fiber quality for a specific fiber length distribution, all things being equal. The results of this investigation indicate that the rate of decline in web strength with increasing span length is indeed a function of fiber quality. It appears that the test method could be used to monitor fiber quality routinely.