Technical Literature

Comparing Wet Zero Span Tensile Testing with Conventional Laboratory Pulp Evaluation, 1994 Process & Product Quality Conference Proceedings

ABSTRACT: The papermaking quality of bleached kraft softwood, as defined by standard tensile and tear tests done on handsheets from PFI beaten pulp, can be comparably assessed by measuring the wet zero span tensile of fiber aggregates. The rapidity, precision, and low cost of acquiring wet zero span tensile data makes it an appropriate method for reliable and economical monitoring of pulp quality on a lot by lot basis

Testing pulp quality – an alternative to conventional laboratory evaluation TAPPI Journal vol 77 No 10 Oct 1994

ABSTRACT: An alternative method of measuring pulp quality is presented. The method is rapid, reproduceable, and shows a high degree of correlation with tensile strength as measured conventionally in mill laboratories. The method gives pulp mills the option of increasing the frequency of testing, resulting in better quality management.

Annergren, G.

Fundamentals of Pulp Fiber Quality and Paper Properties, 1999 Pulping Conference Proceedings

ABSTRACT: Fundamental aspects of pulp fiber quality and paper properties are discussed on the basis of different levels in a hierarchical structure of paper, the molecular level, the fiber-wall level, the fiber level, and the fiber-network level. Different paper and board grades have different priorities regarding properties of the pulps in the furnish. Strength is only one of several different quality criteria, but a very important one.
The chemical composition of the pulps has a strong influence on the fiber properties. Cellulose is the main strength-giving component, hemicelluloses are softeners in the wet state, and lignin gives wet stiffness and resistance to strength development through refining. The amount of lipophilic extractives in pulp is always rather small but they may still be quite disturbing. Fiber morphology is a dominating factor for pulp quality (both the structure of the fiber wall and the fiber dimensions). Fiber length and coarseness are important quality criteria as is the heterogeneity of the fibrous material. In these respects there is a fundamental difference between softwood and hardwood pulps which determines how they are used.
The determination of mechanical properties of standard paper after mild beating in the laboratory is discussed as is the interpretation of the results. As an indication of potential papermaking properties, they are important for the pulp producer in the control of fiber characteristics, but the results should not be used directly to predict the behavior of the pulp in the paper mill or its impact on final paper properties. For such predictions, data are needed from applied tests in the laboratory, and on a pilot and/or commercial scale.
The lack of simple translations of current test results and often also of a common technical language for communication between pulp producer and papermaker shows that there is a need for better and more relevant test methods. Zero-span and short-span tensile testing, optical measurements and image analyses on individual fibers, and NIR spectral measurements on-line are developments which may meet the need for new methods.

Determination of load-bearing element length in paper using zero/short span tensile testing, Solutions!, August 2003, Vol. 86(8) – 03AUGSO47, TAPPI Journal, August 2003, Vol. 2(8)

ABSTRACT: This study presents an equation developed to estimate, from zero and short-span tensile tests, the average length of load-bearing elements (the distance between serious defects along a fiber length) within a sheet of paper. The equation was used to examine the effect of drying treatment on the average load-bearing element length in paper made from five furnishes: two radiata pine kraft pulps, a Eucalyptus globulus kraft pulp, a eucalypt neutral sulfite semichemical (NSSC) pulp, and a recycled pulp. Of the three sets of handsheets for each pulp, the first used never-dried pulps, the second used reslushed handsheets that had been air-dried under restraint, and the third set was made from reslushed handsheets that had been oven dried. For all five furnishes, the average length of load-bearing element was approximately equal to the optically measured arithmetic average fiber length and did not decrease after the fibers were dried. The results suggest that the reduction in the strength of paper made from previously dried fibers, compared to never-dried fibers, is not due to the introduction of serious defects during drying.
Application: This study helps explain the loss of sheet strength that occurs after paper is made from recycled fibers.

At What Cost Quality? Case Studies of Measurements that Facilitate Optimization of Cost and Quality, 2000 Pulping/Process & Product Conference Proceedings, TAPPI Press

ABSTRACT: Fiber Quality is important in paper quality, as a good quality fiber runs better on the paper machine and produces a good quality product. Due to production costs, however, there is often a trade off between cost and quality. A number of mills have found that measuring the zero and short span tensile strength in the pulping and papermaking process has reduced operational expenses while maintaining or increasing tonnage of high quality sellable paper.
This paper explains the measurement of zero and short span tensile strength. Several case studies are presented to explain how mills are balancing fiber qualities with cost, as well as improving customer satisfaction.

Automated Strength Testing Technology Optimizes Market Pulp Mill’s Output February 1, 1998 (Pulp & Paper Magazine) (Web Site)

ABSTRACT: Zero-span and short-span tests track pulp strength throughout one Pacific Northwest mill and reduce the need to retest bales before shipment.

Some aspects of Using Zero-Span Tensile Index as a measure of Fiber Strength,
Proceedings of the International Paper Physics Conference, Victoria BC 8-11
Sep 2003, pp107-114 STFI Publications

ABSTRACT: The effect of fiber damage in pulping has two aspects in relation to sheet strength. The loss in load-bearing ability of the fibers due to fiber kinks affected tensile stiffness strength. The local loss of fiber tensile strength affected the fracture properties. A good correlation between tear strength at a certain tensile index and the rewetted zero-span tensile index was observed.