Wood for Pulp and Paper Production Flashcards
What production is more common, sulphate or sulphite pulping?
Sulphate.
Production in 2022 was about 25X that of sulphite pulp
Examples of softwood trees (long fibres)
Pine
Spruce
Fir
Cedar
Hemlock
Examples of hardwood trees (short fibres)
Birch
Beech
Eucalyptus
Aspen
oak
List some cellulose preparation techniques (pulping processes)
Groundwood
TMP/CTMP
Sulphate/Kraft process
Sulphite
Soda
Organosolv
What is another name for the sulphate pulping process?
Kraft process
What is the general structure of a tree? (3 parts)
1 - Crown - needles/leaves and branches, these are responsible for energy supply via photosynthesis
2 - Stem - responsible for transport
3 - Root system
What is the scientific name for hardwoods? And list a few
Angiosperms
Eucalyptus. Birch. Beech. Aspen. Oaks
What is the scientific name for softwoods? And list a few
Gymnosperms
Pine. Spruce. Fir. Cedar. Hemlock.
What is the cambium of the tree?
The thin layer of cells between bark and inner sapwood where cell growth takes place
How is wood produced?
Not directly through photosynthesis - this creates carbohydrates that aid the process though.
The tree grows though cell divisions in growth points. Then each cells goes through development phases. (enlargement, wall thickening, lignification, death)
Draw a cross section of a tree stem. Label the parts
Outer bark: Protection
Inner bark: Conduction and storage
Cambium: Layer of cells where cell growth occurs
Growth ring: Early wood for conduction and latewood for strength
Heartwood – mechanical support
What is the earlywood’s primary function? (springwood)
Conduction
What is the latewood’s primary function? (Summerwood)
Strength
What is the outer bark for?
Protection
What is sapwood for?
For transporting (conduction) of sap up the stem to the leaves
What is the function of heartwood?
Mechanical support
What is a clear difference in cell structure between hardwoods and softwoods?
Hardwoods contain vessel cells, softwoods do not. Vessel cells are for conduction
What are the 2 broad categories of wood cell?
Prosenchyma cells - long and thin with tapered edges - fibres
Parenchyma cells - rectangular short cells
Fibre length range for softwoods?
2 to 6mm
List the layers of a fibre (7)
Middle lamella - acts as a glue between fibres - mainly lignin
Primary wall
secondary wall - makes bulk of cell there are 3 layers to this
S1 outer layer of secondary wall
S2 main body of the fibre
S3 inner layer of the secondary wall
Lumen - central cavity of the fibre
What are the major cell types? (3 cells) and their function
Trachieds/ Fibres (for support)
Ray cells (for storage or conduction)
Vessel elements (only in hardwoods for conduction)
What are the 3 principal functions of cells and give an example of the cell
Support (fibres)
Conduction (vessel cells in hardwoods and ray trachieds in softwoods)
Storage (ray cells)
What are typical cell types in hardwoods?
Fibres
Vessel elements
Ray and longitudinal parenchyma cells
What is the correlation between wood density and papermaking properties?
A high wood density gives a slower beating response, lower tensile, burst and folding strength. But greater bulk and higher tear strength
What is the benefit of thinner cell walls?
They collapse easier during sheet formation and form good inter fibre bonding surfaces
What properties do thick cell walls give to a paper sheet?
More open absorbent and bulkier sheet
What is the correlation between wood density and papermaking properties
High wood density means lower tensile, burst, and fold. But greater bulk and tear. We also have a slower beating response. Additionally the yield is directly related to the density.
