Thermoplastics

Question 1

What is a thermoplastic?

Answer 1

A thermoplastic has polymer chains which has no cross links.

Question 2

What are the properties of all thermoplastics?

Answer 2

Remouldable (heat up and remold into something else over and over) Therefore is recyclable. 
Self Coloured (Colour added at start of process)
Self Finishing (Finish added at start of process)

Question 3

Why are thermoplatics not sustainable and how long do that take to biodegrade?

Answer 3

They are nearly all oil based.

Take approximately 100+ years to biodegrade.

Question 4

Give some positives (3) and some negatives (3) of ABS and examples of it in use (3). How is it normally molded?

Answer 4

\+ Durable
\+ Wide range of colours
\+ Can make intricate designs
- Cannot be clear 
- Relatively expensive
- Not flexible
High quality toys (Lego), mobile phones, safety helmet
Injection Molded

Question 5

Give some positives (5) and some negatives (1) of PET and examples of it in use (1). How is it normally molded?

Answer 5

\+ Strong
\+ Clear
\+ Used to make hollow objects
\+ Makes disposable objects
\+ Inexpensive
- Crinkley feel
Plastic water bottles
Blow Molded

Question 6

Give some positives (3) and some negatives (2) of PMMA (Acrylic) and examples of it in use (2). How is it normally molded?

Answer 6

\+ Optically clearer than glass
\+ Variety of bright colours
\+ Almost 100% light transfer
- Scratches very easily
- Unsuitable for industry use
Headlight lenses, Shop signs
Injection Molded

Question 7

Give some positives (3) and some negatives (2) of Polypropylene (PP) and examples of it in use (2). How is it normally molded?

Answer 7

\+ Very tough
\+ Wide variety of colours
\+ Can make integral hinges
- Not clear (partially/milky clear)
- Rather expensive compared to others.
Sandwich boxes, School chairs
Injection Molded

Question 8

Give some positives (3) and some negatives (2) of High Impact Polystyrene (HIPS) and examples of it in use (2). How is it normally molded?

Answer 8

\+ Wide variety of colours
\+ Relatively inexpensive
\+ Clear
- Brittle
- Low quality
Cheap toys, calculator cases
Vacuum formed and injection molded

Question 9

Give some positives (6) of LDPE and examples of it in use (2). How is it normally molded?

Answer 9

\+ Only plastic able to make plastic
\+ Can be strong at very thin thicknesses (0.1mm)
\+ Light
\+ Relatively inexpensive
\+ Stretches 
\+ Can be printed on
Toothpaste tubes, carrier bags
Calendar printing

Question 10

Give some positives (2) and some negatives (1) of HDPE and examples of it in use (3). How is it normally molded?

Answer 10

\+ Disposable / Semi-disposable
\+ Cheaper than P.P
- Not very strong
Washing up bowls, buckets, milk bottles
Injection molded and blow molded

Question 11

Give some positives (4) and some negatives (1) of Expanded Polystyrene and examples of it in use (2). How is it normally molded?

Answer 11

\+ 8x original size when injected with air
\+ White not usually coloured
\+ Buoyant
\+ Relatively inexpensive
- Broken easily
Packaging and insulation
Injection molded

Question 12

Give some positives (3) of Nylon and examples of it in use (2). How is it normally molded?

Answer 12

\+ Can be woven
\+ Be a thread
\+ Self lubricating
Clothes (like tights), bearings and gears.
Woven or injection molded

Question 13

Give some positives (2) of UPVC and examples of it in use (3). How is it normally molded?

Answer 13

+ Hard (plasticized)
+ Relatively inexpensive
Window frames, gutters, pipes
Extrusion

Question 14

Give some positives (1) PVC and examples of it in use (3). How is it normally molded?

Answer 14

+ Can be clear
Electric tape, hose pipes, Clear pencil case
Usually calendared but could be extruded.

Question 15

Give some positives (2) and some negatives (1) of Polystyrene and examples of it in use (1). How is it normally molded?

Answer 15

\+ Disposable
\+ Relatively inexpensive
- Has to have a 5 degree draft angle
Food containers like yogurt pots
Vacuum formed

Question 16

What does Plasticizer do to the plastic?

Answer 16

Plasticizer softens the plastic and therefore changes the natural material properties. Sometimes used to make the material easier to process.

Question 17

What does filler do to the plastic?

Answer 17

Bulks out the plastic to replace polymer and reduce costs.

Question 18

What does stabilizers do to the plastic?

Answer 18

Stops deteriorating over time from heat, UV, biodegradation.

Question 19

What does Bio Batch do to the plastic?

Answer 19

An additive to make thermoplastics biodegrade in less than 5 years.

Question 20

What stock forms do plastics come in?

Answer 20

Sheets, tubes and granules.

Question 21

Describe line bending.

Answer 21

Line bending is lying a sheet over a simple heating element until hot then bend over a mold or jig. Usually used for acrylic.

Question 22

Describe drape moulding.

Answer 22

Heat thermoplastic in an oven until hot (150 degrees, not molten) the drape over basic wooden mould.

Question 23

Describe vacuum forming.

Answer 23

A piece of thermoplastic (like polystyrene) is heated above a wooden mold (usually MDF) in a Vacuum former. When heated the wooden mold is moved level to the plastic and the air is sucked out, causing the plastic to stick to the mold. This sets in the same shape as the mould which is has to have a 5 degree draft angle so the plastic can be removed from the mould.

Question 24

Describe injection moulding.

Answer 24

Plastic granules are poured into a hopper which places them into a tube which pushes them into an archimedean screw. This then takes them though a heater which makes it molten. The plastic is then pushed into a dye of at least two parts. The plastic cools and the dye is taken apart, then ejector pins remove the product.

Question 25

Describe blow moulding.

Answer 25

The same machine as injection and extrusion molding is used to push a plastic tube (parison) into a mold (usually a bottle). Air is then blowed in causing the plastic to surround the inside of the mold therefore taking the shape. The mould is opened and the product is taken out. A blow molded product needs a very big entrance hole.

Question 26

Describe extrusion.

Answer 26

Plastic granules are poured into a hopper which places them into a tube which pushes them into an archimedean screw. This then takes them though a heater which makes it molten. The plastic is extruded though a simple dye. This is an infinite process which is cut to length.

Question 27

Describe rotational moulding.

Answer 27

Plastic granules are placed in a dye which is surrounded by a heater. The dye rotates, and the plastic melts. This continues whilst the plastic cools therefore creates a hollow object.