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Equipment Description:Stone Groundwood (SGW) and Pressurised Groundwood (PGW) To print this FactSheet click here To return to the FactSheet home page click here

Equipment Description:
Stone Groundwood (SGW) and Pressurised Groundwood (PGW)
Date Added: 26 October 2006 Last updated: 27 October 2006
This Fact Sheet has been viewed: 4958 times.

Distribution...	High yield pulp (92-96% yield) produced mainly in Scandinavia and North America
Fibre Types...	Produced from low density Softwoods (EG. Spruce in Scandinavia and Hemlock in North America) and Hardwoods (EG. Aspen in Scandinavia)
Fibre Properties...	Prepared material forms wood fragments or splinters,rather than fibres. For Softwoods – Typical length 3-4mm; Typical diameter 0.03mm

Typical Pulp Properties...   Groundwood pulp can be either unbleached or bleached to between 60-80% ISO. Bleaching is done with peroxide only. Brightness reversion readily occurs due to the presence of lignin. The key characteristics of all groundwood pulps are, high bulk, opacity and compressibility, but low strength and poor colour permanence. Groundwood pulps are used unrefined and the initial stock freeness is low (IE. High Schopper Reigler). Compared to Stone Groundwood (SGW), Pressurised Groundwood (PGW) is produced at a higher temperature which results in a better fibre separation (less fines), which improves the strength properties. There are slight differences between softwood and hardwood grades. At a similar freeness hardwoods will have a shorter fibre length distribution, weaker strength, but will give higher opacity and initial brightness

Typical Uses...   Groundwood pulps are mostly used in integrated mill operations, although some market pulp is available. This pulp has been used at 15-100% of the furnish, with or without chemical softwood pulp addition, depending on the paper or board grade being made. Typical grades include Newsprint, Directories, Magazine and Catalogue papers, Bulky book papers and Cartonboard. The pulp is also found in the mid plies of Folding boxboard and Chipboard (for bulk) and sometimes in the mid plies of Wallpaper Base.

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