Glossary / P

Packaging paper
Collective term for papers of different pulp composition and properties, sharing only the application. Selection and mixture of the pulps depend on the demands made on the paper. Important are tear strength, bursting strength, creaseproofness, abrasion resistance as well as elasticity and stiffness. Often also good printability is demanded (packaging as advertising medium). For special purposes packaging paper can be imparted wet strength or water repellent properties or made impermeable for aromas or water vapour. For these purposes either special additives are admixed to the pulp or the paper is coated, impregnated or combined with plastic and/or metal film.

Paper
The name for all kinds of usually vegetable matted or felted sheets of fibre, based on an age old process of dehydration of the cellulose fibres suspended in an aqueous solution then reduced to sheets to be dried. Paper is defined according to the fibrous material used in its composition, the surface finish, the thickness and the weight, expressed in grams per square meter.

Paperboard
Monolayer paperboard is basically thicker paper, frequently used in multilayers.

Paper for bags
Paper used in the manufacturing of bags. Paper used to contain foodstuffs must not contain toxic residues nor contaminants.

Parchment
Animal skin (calf, goat, sheep) soaked in lime and ten stretched on a frame, shaved, cut, and worked until very thin. Used in the Middle Ages as a writing material. The origin of the term is probably associated with the library at Pergamum, which was expanded considerably by Eumene II (2nd century BC), where parchment was used more than elsewhere, and at a time when papyrus was predominant material. The use of parchment for the production of books in the West began to spread in the third and fourth centuries AD and from the fifth to thirteenth centuries it became the sole writing material. The calamus was the only writing instrument. The was a softened reed that varied in thickness depending upon the type of writing, whilst the inks were formulated in various ways: gallic acid, soot, gum and even red lead and cinnabar (for red ink).

Particulates
Airborne solid impurities such as those present in gaseous emissions (sodium sulphate, lime, calcium carbonate, soot).

Peroxide bleaching
Method of bleaching pulp with hydrogen peroxide (H2O2) to remove lignin; reduces or avoids the need for chlorine dioxide in final bleaching.

PGW
See Pressurised groundwood pulp.

Picking
Removal of particles from the paper surface during printing when ink tack is greater than surface strength.

Picking resistance
Ability of a paper surface to resist picking by tacky printing inks.

Pick–up
Roll which lifts the wet paper or board web off the wire before the drying section.

Pigmentizing
Coating of paper with a chemical agent (pigment) to reduce surface porosity and increase opacity.

Plasticizer
Agent mixed into coating colour to give a more flexible coating.

PM (Paper Machine)
Machine for the production of a real of paper from a previously prepared stock.

Polythene paper
Paper coated on one side with a polythene film. The polythene is applied to the paper on reels with an extruder. The weight of the applied polythene ranges from a minimum of 10 to a maximum of 50 gsm . There are many types of wrapping paper than can be polythene coated, including kraft, parchment, glazed paper etc.

Porosity
A structural property of paper reflected by the size distribution of pores.

Postcard board
Postcard board is either slightly mechanical or woodfree and calendered.

Poster paper
Poster paper is a highly mechanical, highly filled, mostly coloured paper that has been made weather resistant by sizing.

Press nip
On a paper machine, a pair of rotating rolls between which the paper web passes.

Pressurised groundwood pulp (PGW)
Mechanical pulp produced by treating logs with steam before defibration against a grindstone under externally applied pressure.

Primary fibre
See Virgin fibre.

Pulp
1) Stock. The acqueous suspension of all the fibrous and other materials required for the making of paper following the beating of the fibres and the halfstuffs, the sizing, and addition of coloured fliers and any other additives.

2) Pulp. The qualitative and quantitative formulation of the fibrous and non-fibrous material that makes up the stock.

Pulper
Unit for defibrating (slushing) pulps and paper machine broke, usually at the wet end of the paper machine.

Puncture resistance
Force acting perpendicular to a paper or board surface needed to puncture the sheet.