Wood pulp Flashcards
1
Q
What is wood pulp?
Soft wood fibres?
Hard wood fibres?
A
Is where wood fibres are separated to form a mass of individual fibres
Soft wood fibres are longer giving better strength
Hard wood fibres are shorter giving smoother opaque finish
2
Q
What is mechanical pulp?
Uses?
A
Wood is: Saturated Debarked Ground down- softens lignin Screened to 2mm chips Bleached to improve quality Uses: Low grade newspaper Packaging
3
Q
Advantages of mechanical?
Disadvantages of mechanical?
A
Advantages: Paper mills are low coat 90% yield from log- little waste Bleached Suited to bulk grade papers Disadvantages: Turns yellow when exposed to light Low strength despite using coniferous fibres
4
Q
What is chemical pulp
A
Debarked Cut into 2cm chips Pounded into fragments Stored Treated with alkali/ acid- breaks down lignin Uses
5
Q
Advantages of chemical?
Disadvantages of chemical?
A
Advantages: Longer stronger fibres Produces chlorine free paper Waste lignin burnt to produce fuel Disadvantages: Has to be imported Lower yield
6
Q
What is recycled pulp?
A
Mixed with virgin fibres
Bonding agents and colouring pigments used to improve quality- consistent colour and better bonding of fibres
7
Q
Advantages of recycled pulp?
Disadvantages of recycled pulp?
A
Advantages: Makes use of waste paper Suitable for bulk grades of paper Disadvantages: Cannot be recycled forever Virgin fibres have to be added Lots of additives have to be added Same energy requirement as chemical/ mechanical
