Tensile strentgth components of Eucalyptus grandis kraft pulps

AREA, MARIA CRISTINA; BENITEZ J.; FELISSIA, FERNANDO

O PAPEL

ABTCP - Associação Brasileira Técnica de Celulose e Papel

Lugar: Sao Paulo; Año: 2010 vol. 71 p. 48 - 62

0031-1057

The objective of this work is to study the relative effect of the different components of the tensile strength of an industrial Eucalyptus grandis kraft pulp. We studied the components of the tensile strength of a brown pulp subjected to a change of base (to Na and Ca), and after series of treatments O, Op and P, with and without addition of a phosphonated chelating agent. The resulting pulps (M) were subjected to the bleaching sequences: OOpP and OQOpP, with or without the addition of the chelating agent at each stage, generating 20 pulps: 10 in Na base and 10 in Ca base. The relative bonded area (RBA) of brown pulps and bleached pulps was calculated from the light scattering coefficient (S), as (S0-S) / S0, where S0 is the light scattering coefficient of unbonded fibers. For doing this, 15 handsheets of each pulp were subjected at three different pressures (20, 50 and 90 psi) and then they were tested. The RBA of the O and Op pulps was obtained from a value of S0 resulting from a regression equation involving the sodium and magnesium content of pulps (R2= 98.0). Bond strength per unit of bonded area values were calculated using the Page equation. This work shows that there are differences in the bond strength per unit of bonded area values that are due to the type and content of cations in the fibers. Since RBA and fiber strength (represented by ZI) tend to increase with bleaching, the large decrease in bond strength per unit of bonded area would be responsible for the decrease in tensile strength of TCF bleached pulp.