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The Effect of Temperature on Wet Web Strength Properties.

1993; Japan Technical Association of the Pulp and Paper Industry; Volume: 47; Issue: 6 Linguagem: Inglês

10.2524/jtappij.47.702

1881-1000

Ernst L. Back, L. Andersson,

Advanced Cellulose Research Studies

Wet web strength properties are presented up to 60°C in the range of 30% to 50% solids content for three furnishes, one newsprint, one unbleached and one bleached softwood kraft at several levels of refining. They refer to MD stress-strain measurements in a cabinet supplied with saturated water vapour of the desired temperature on oriented laboratory sheets pressed in static or dynamic nips with subsequent partial drying. They cover the tensile strength, the breaking elongation, the modulus (or tensile stiffness index) and the rupture energy absorption. They also are presented as a rupture envelope.At solids contents of 40% to 50% the drop in tensile strength with increasing temperature is about 1% per °C. This relative drop in strength is characteristic for paper webs above the glass transition of their cellulose and hemicellulose polymers. It is larger than that for water-free, sheets below their glass-transition temperature and is interpreted as a reduction in the inter-polymer and inter-fiber hydrogen bond strength. At solids contents below and around 30% the drop in tensile strength with increasing temperature is much less and in proportion to the surface tension forces which there dominate interfiber bonding.In an open draw sensitive to web breakage an increasing wet web temperature thus has to be compensated for, e. g. by increasing solids content.