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DT THEORY - Mr Simmons > POLYMERS > Flashcards

POLYMERS Flashcards

1
Q

Describe the formation of THERMOSETS

A

Long chain with cross-links
Rigid and cannot be heated or reshaped.

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2
Q

Describe the formation of THERMOPLASTICS

A

Can be repeatedly reheated and remoulded
Shape has no cross links
Long chain of molecules

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3
Q

What is the natural source of Polymers

A

crude oil

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4
Q

Examples of THERMOSETS

A

MF (formaldehyde)
UF(urea)
Epoxy resin

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5
Q

Examples of THERMOPLASTICS

A

PMMA(acrylic)
LDPE(low density poly ethylene)
PVC(polyvinyl chloride)
HDPE(high density poly ethylene)
ABS(impact resistant)

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6
Q

What are the properties of THERMOPLASTICS

A

They are more common
Easier to recycle due to the lack of cross links, so when heated it can return to its original form.
Plastic will harden when cooled
Available in - powders for dip coating, granules for moulding, rods and blocks.

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7
Q

What are the properties of THERMOSETS

A

Harder to recycle as they have strong cross links
When reheated their cross links soften and deform
Individual monomers are joined together to form a massive polymer
Commonly found in resin or powder forms for compression moulding

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8
Q

Properties of everyday polymers

A

Brittle, good plasticity(when heated), Durable, low melting point, good strength to weight ratio, insulator, malleable, pigment

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9
Q

Describe deforming

Types of redistribution of polymers

A

Changing the shape of a material without changing the state i.e the material remains solid throughout the shaping process even when subjecting to heat

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10
Q

Describe reforming

Types of redistribution of polymers

A

Changing the shape of a material as well as changing the state i.e the material is purchased in stock form and changes shape.

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11
Q

What are the main polymer stock forms

A

Sheets
Granules
Rolls
Rods
Powder form

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12
Q

What object does blow moulding create

A

Forms hollow, plastic items with one open end e.g bottles

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13
Q

What object does extrusion moulding create

A

Creates objects with a uniform cross-section profile e.g long thin items like poles

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14
Q

What object does injection
moulding create

A

Used to make detailed objects e.g bottle lids and screw caps

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15
Q

What object does vacuum forming create

A

Used to make simple repeated products that have a specific shape where the opening is wider than the rest of the shape e.g yogurt pots

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16
Q

What object does rotation moulding create

A

Used to make hollow plastic items with up to 6mm wall thickness

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17
Q

What object does compression moulding create

A

Mostly used for thermosets
creates items that consists of a lower and upper half.
e.g electrical sockets

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18
Q

What object does calendaring produce

A

Thin sheets of product

19
Q

Explain line bending

A

A process which involves heating a small area of plastic sheet so it can be folded or bent like paper (usually done around a form)

20
Q

What is an elastomer

A

A material which at room temperature can be deformed under pressure and then upon release of the pressure, will return to their original shape.
As the material is distorted the molecules also distort.

21
Q

Natural rubber properties

examples of elastomers

A

malleable, good elasticity, good tensile strength, high impact strength, waterproof, insulator, good cold resistant

22
Q

Polybutadine properties

examples of elastomers

A

Tough, durable, wear resistant, good heat resistance, water resistant, flexible, good tensile strength
used for tires

23
Q

Polyrethane properties

examples of elastomers

A

good abrasion resistance, good elasticity, can be pigmented, flexible lightweight
used for varnishes and lycra

24
Q

Neoprene properties

examples of elastomers

A

thermal resistant, tough, chemical resistant, weather resistant, abrasion resistant, good insulator
used for wetsuit and laptop cases

25
Q

silicone properties

examples of elastomers

A

high plasticity, flexible, temp resistant, lubrictaing qualities, returns to form, forms a watertight seal, poor abrasion resistance

26
Q

Definition of biopolymers

A

come from renewable raw materials such as starch based polymers from wheat, corn and potatoes.
categorised into natural and synthetic

27
Q

What are polyactides

biopolymers

A

Used as surgical implants
starch based can be used for creating conventional plastic

28
Q

What is PLA - polyactide

biopolymers

A

found naturally
transparent and is similar to polyethlyene and polypropelene
can be used for bottles, bags, films and disposable nappies

29
Q

PHA - Polyhydroxyalkanoate

biopolymers

A

(Biopol) is grown from bacteria and is used in many medical applications and even for slow release medictaion

30
Q

PHB - Polyhydroxybutrate

biopolymers

A

has similar properties to plolypropylene and can be used for products such as packaging
grown from micro organsims

31
Q

Oxo - degradable polymers

biopolymers

A

have additives that break the polymer down to fine powder with heat, oxygen, moisture, and mechanical stress

32
Q

Photo degradable

biopolmers

A

polymers break down in ultra-violet light
hydrodegradbale polymer
using water usually with heat

33
Q

What is a biopolymer

A

Alternatives to plastic, moulded, cut and shaped the same as plastic, need specific conditions to break down, can leave behind toxic residue eg.methane gas

34
Q

Pros + Cons Potato Pak

Biopolymers

A

Pros
- very sustainable as they are produced from waste potato starch
- can be bio-degradable which reduces environmental impacts

Cons
- requires lots of land, time and money to initailly grow potatoes, let alone harvesting and extracting starch
- although there are many benefits reguarding the environment, there are also concerns as the process of production can be very polluting

35
Q

Pros + Cons Corn starch polymers

Biopolymers

A

Pros
- similar to potatopak, is very sustainable as it can be recycled and comes from naturally occuring resoources
- it does not contain toxins
- 65% less energy is used to make this compared to other polymers
- much safer than usual plastics as no explosives (gasoline) are involved.

Cons
- It is compostable, there are a few sites that can actually form the procedure
- can contaminate the recyling network if not thrown away properly
- moral issues as the corn could be used to feed people who are dying of hunger
- problem with GM crops

36
Q

Pros + Cons Biopol

Biopolymers

A

Pros
- very versatlie with many medical uses
- also has a very high melting point meaning it can withstand lots of heat making it good for products used around hot objects

Cons
- biopol has a low tolerance to acid bases (including bleach)
- it is more expensive to produce than fossil fuel plastics, making it not very cost effective
- is not as impact resistant as fossil fuel plastics, meaning it is not suitable for some apllications.

37
Q

Pros + Cons Polyactide

Biopolymers

A

Pros
- environmentally friendly
- doesnt relsease many harmful fumes
- appealing shiny and smooth apperance

Cons
- less sturdy than ABS
- can deform when exposed to heat

38
Q

Pros + Cons Polydroxyalkanoate

Biopolymers

A

Pros
- can be created from renewable enrgy resources
- biodegradable
- biocompatible, menaing not harmful to living tissue

Cons
- high production costs
- limited functionalities
- poor mechanical properties
- incompatible with conventional thermal processing techniques

39
Q

Why are additives used in polymers

Enhancing polymers

A

Additives are added to polymers when they are being made.
They are designed to improve the properties and characteristics of the material.
Either for performance of the material when it has been made into a product or to improve the material’s capabilites for processing.

40
Q

Use of lubricants

Additives - enhancing polymers

A

Reduces the amount of viscousity of molten polymers, (making them less sticky)
Allows the moulding temp to be lowered, saving energy.
- if too much is added it can affect cooling

41
Q

Use of Antixoxidants

Additives - enhancing polymers

A

Prevents the polymer oxidising or discolouring from exessisve heat during the process

42
Q

Use of pigments

Additives - enhancing polymers

A

Mixed with the molten polymer to give it colour

43
Q

Use of Anti-statics

Additives - enhancing polymers

A

Reduces the likelihood of the polymer building up static charge

44
Q

Use of flame retardants

Additives - enhancing polymers

A

Reduces the likelihood of combustion or the spread of fire

DT THEORY - Mr Simmons (6 decks)

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