Evaluating pulp stiffness from fibre bundles by ultrasound

A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The develope...

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Bibliographic Details
Published in:Measurement science & technology 2012-06, Vol.23 (6), p.65603-1-7
Main Authors: Karppinen, Timo, Montonen, Risto, Määttänen, Marjo, Ekman, Axel, Myllys, Markko, Timonen, Jussi, Hæggström, Edward
Format: Article
Language:English
Subjects:
Bundles
Bundling
cellulose
Estimating
Fibre
fibres
Kraft pulp
measurement
pulp
Stiffness
testing
Transducers
Ultrasonic testing
ultrasound
wood
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Summary:A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The developed tester employs (933 ± 15) kHz tweezer-like ultrasonic transducers and time-of-flight measurement through (9.0 ± 2.5) mm long and (0.8 ± 0.1) mm thick fibre bundles kept at (19.1 ± 0.4) °C and (62 ± 1)% RH. We determined the stiffness of soft wood pulps produced by three kraft pulping modifications: standard kraft pulp, (5.2 ± 0.4) GPa, prehydrolysis kraft pulp, (4.3 ± 0.4) GPa, and alkali extracted prehydrolysis kraft pulp, (3.3 ± 0.4) GPa. Prehydrolysis and alkali extraction processes mainly lowered the hemicellulose content of the pulps, which essentially decreased the fibre-wall stiffness hence impairing the stiffness of the fibre networks. Our results indicate that the method allows ranking of pulps according to their stiffness determined from bundle-like samples taken at an early phase of the papermaking process.
ISSN:0957-0233
1361-6501
DOI:10.1088/0957-0233/23/6/065603