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19 Cards in this Set
- Front
- Back
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What are wood fibres held together by? |
Lignin |
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Which fibres offer greater strength. Soft or hardwood fibres? |
Softwood fibres |
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What are the three methods of making pulp? |
Mechanical, chemical, and waste. |
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What are the main stages of making pulp using the mechanical method? |
The wood from coniferous trees is de-barked and then saturated with water.
The saturated wood is then ground down which softens the fibres. The product is called 'groundwood pulp'.
The pulp is then bleached and fed into a fourdrinier machine. |
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What are the main stages of making pulp using the chemical method? |
The hard and softwood is debarked and the logs are cut into 2cm chips.
The chips are pounded and then are treated with either an acid or an alkali.
The treated pulp is then fed into a fourdrinier machine. |
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What are the main stages of making pulp using the waste paper method? |
The waste paper is mixed with a variety of pulps and is processed with bonding agents and bleach to help it retain its strength and colour. |
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Advantages of mechanical pulping: |
90% Yield.
Lower investment costs than for other types of mill/factory.
Good for bulk production.
Can be bleached for higher quality. |
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Advantages of chemical pulping: |
Produces high quality wood pulp.
Produces chlorine free disposable products.
Waste lignin can be burnt as fuel. |
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Advantages of waste pulping: |
Makes use of recycled papers which are a sustainable resource.
Well suited for bulk production. |
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Disadvantages of mechanical pulping: |
Lower strength than softwood chemical pulps.
paper can appear yellow when exposed to bright lights due to high lignin content. |
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Disadvantages for chemical pulping: |
Lower yield due to the lignin being completely separated from the fibres.
No chemical pulp is produced in the UK, meaning it must be imported. |
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Disadvantages for waste pulping: |
Cannot be recycled infinitely as pulp loses strength and quality.
Does not save energy and actually uses the same amount as the other processes.
Requires a lot of processing additives to produce a high quality paper. |
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What are the three parts of a fourdrinier machine? |
The press section, the drying section, and the calendar stack. |
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What is the function of the wet end? |
The function of the wet end is to get rid of excess water. This is done by running the pulp along a vibrating conveyor belt which shakes the water off. |
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What is the function of the press section? |
It uses a system of nip presses or rollers that wring out the remaining excess water from the pulp and makes it a rough paper. |
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What is the function of the drying section? |
It uses a series of steam heated rollers to dry out the paper by removing moisture and can be used to add starch and sizing agents. The produced paper has a water content of 4-6%. |
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What is the function of the calendar stack? |
The calendar stack is a series of rollers which the paper is fed through to smooth it out and give it a uniform thickness. |
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How heavy are:
Layout paper
Tracing paper
Copier paper
Cartridge paper |
Layout paper = 50gsm
Tracing paper = 60 - 90gsm
Copier paper = 80gsm
Cartridge paper = 120 - 150gsm |
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How heavy are:
Bond papers
Coated papers |
Bond papers = greater than 50gsm
Coated papers = 70 - 300gsm |
