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TAPPI T 262 Mechanical pulp prep






Preparation of mechanical pulps for testing


TAPPI T 262 describes a procedure for the preparation of mechanical pulps prior to physical testing.

It is for use with pressure groundwood, refiner mechanical, chemimechanical, thermomechanical, and chemithermomechanical pulps. It may also be used on any pulp sample taken downstream of the refiners (i.e., screens, cleaners, reject refiners, etc.). The purpose of this practice is to remove latency (curl) from pulp fibers.

Hot disintegration of pulps containing lignin may lead to significant loss of brightness. Since brightness is not significantly changed by the presence of latency in the pulp, this procedure is not recommended for pulps that will be formed into brightness measuring sheets.


This standard practice involves recirculating stock at about 2% consistency and at 90–95°C for two minutes using a centrifugal pump connected to a container as a means of processing the fiber prior to physical testing to allow lessening or removal of the pulp’s latency.


In the production of mechanical pulps with refiners or on grinding stones under pressure, a phenomenon referred to as “latency” is introduced into the pulp. The action of the refiner twists and rolls the fibers into balls or nodules of a highly strained state that are not removed by means of conventional disintegration. When disintegration is done in cold water in accordance with TAPPI T 205 “Forming Handsheets for Physical Tests of Pulp,” subsequent testing will not show the full development of the strength properties of the pulp. Disintegrating the pulp at elevated temperatures and low consistency relaxes the fibers, removing the latency (fiber twists, rolls, and nodules). With hot disintegration, the pulp shows complete development of strength properties without further treatment. The “latency” removal ensures full development of pulp strength properties.


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SGS-IPS cannot sell or otherwise provide standards, specifications, or test procedures to third parties.