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chem unit 1 > ch 8- polymers > Flashcards

ch 8- polymers Flashcards

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1
Q

addition polymerisation

A

chemical reaction between monomers resulting in the formation of a polymer

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2
Q

alkene

A

hydrocarbon with at least one double carbon to carbon bond

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3
Q

alkyne

A

hydrocarbon with at least one triple carbon to carbon bond

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4
Q

condensation polymerisation

A

chemical reaction between monomers resulting in the formation of a polymer and water

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5
Q

cross link

A

covalent bond between polymer chains

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6
Q

thermosetting-cross linked polymers

A

polymer with covalent bonds/cross links that degrade or char when heated

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7
Q

elastomers

A

polymer that forms occasional cross links and is elastic

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8
Q

functional group

A

specific groups of atoms within a compound that affect the properties of the compound

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9
Q

high density polyethene HDPE

A

tightly packed polymers produced at lower pressures

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10
Q

linear- thermoplastic polymers

A

polymer with no cross links that can be remoulded when haeted

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11
Q

low density polyethene LDPE

A

branched polymer produced at high pressures

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12
Q

monomers

A

molecules that can react with other molecules to form larger molecules

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13
Q

plastic

A

molecule produced synthetically from monomers bonded together

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14
Q

polymer

A

molecule produced naturally or synthetically from monomers bonded together

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15
Q

general formula for addition polymerisation

A

[C=C + C=C]n
->
-[-C-C-C-C-]-n

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16
Q

general formula for condensation polymerisaiton

A

let R= any group where a carbon or hydrogen is attached to the rest
R-A-H + R-B-OH
->
R-A-B-R + H2O

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17
Q

how does addition polymerisation work

A

the C to C double or triple bond is broken, allowing carbon atoms to form bonds with adjascent monomers

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18
Q

how does condensation polymerisation work

A

two functional groupds react to form a bond between monomers- forming a polymer and water

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19
Q

general formula for the formation of polyesters

A

(n+1) R(OH)2 + n R’(COOH)2 → HO[ROOCR’COO]nROH + 2n H2O

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20
Q

polymer properties

A

light and strong
durable
highly versatile and modifiable
flammable
chemically resistant- particularly against acids
effective thermal and electrical insulators

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21
Q

polar vs non polar polymers

A

non polar monomer are only held together by dispersion forces but when a polymer

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22
Q

non polar polymer- tetrafluoroethene

A

polytetrafluroethene has strong dispersion forces between chains and other substances making it non stick

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23
Q

polar polymer- polyacrylonitrile

A

make materials like carbon fibre which is found in tennis raquets and fishing rods.
the carbon nitrogen bond in acrylonitrile- the monomer, creates permanent dipole-dipole interaction between chains, giving them a high tensile strength and stiffness

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24
Q

what determines the properties of a polymer

A

the monomer itself
the size and branching - the greater the chain length, the stronger the inermolecular forces due to greater surface material ( the strong intermolecular forces make the material tough)
polarity- physical properties of polymers as it creates certain attractions

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25
Q

how is low density polyethene produced

A

when polymerisation occurs at high temperatures and high pressures, polymers are unable to form linear chains
LDPE has many branches that extend from the parent chain

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26
Q

how do the branches prevent LDPE from becoming dense

A

the branches prevent them from packing close together, leading to weakened dispersion forces

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27
Q

LDPE properties

A
  • Lower density (relative to DPE)
  • Relatively soft
  • Lower melting point (105115 C) (relative to DPE)
  • Good chemical resistance
  • generally opaque
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28
Q

how is high density polyethene produced

A

HDPE is produced under lower temperature and pressure conditions
little brancing and the polymer chains can pack together tightlyp

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29
Q

HDPE properties

A

higher density (relative to LDPE)
* hard
* higher melting point (120180 C) (relative to LDPE)
* Weatherproof and cold-resistant
* Good chemical resistance
* Allows light to pass through
* Insulator of electricity

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30
Q

polypropene- type of polymerisation

A

addition

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31
Q

polypropene- properties and applications

A

durable and cheap making it good for artificial turf and rope

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32
Q

polyvinylidene chloride- type of polymerisation

A

addition

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33
Q

polyvinylidene chloride- properties and applications

A

sticks to itself, making it good for food wrap

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34
Q

polyamide/nylon- type of polymerisation

A

condensation

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35
Q

polystyrene- type of polymerisation

A

addition

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36
Q

polystyrene- properties and applications

A

can be solid or foamed and can be used in cups, insulation foam or bean bags filling

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37
Q

linear polymers properties

A

when heated, they soften enabling them to be reshaped or remoulded
commonly sold as pellets that are heated then moulded to make a variety of plastics
intramolecular bonds of linear polymers are much stronger than the intermolecular forces holding the chains together
sufficient exposure to heat, individual chains become mobile and the plastic can be reshaped

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38
Q

how does the presence of cross links impact a molecule

A

it greatly restricts the movement of a molecule, making it more rigid and heat resistant

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39
Q

do thermoplastics have cross links

A

no

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40
Q

forces between chains in thermoplastics

A

weak intermolecular

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41
Q

thermoplastics- response to heat

A

softens/melts

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42
Q

thermoplastics- hardness

A

varies

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43
Q

elastomers- cross links

A

a few giving them elasticity

44
Q

elastomers- forces between chains

A

weak intermolecular forces and occasional strong covalent bonds

45
Q

elastomers- response to heat

A

varies- stretch and return to original shape

46
Q

elastomers- hardness

A

varies

47
Q

thermosets- cross links

A

larger number

48
Q

thermosets- forces between chains

A

strong covalent bonds

49
Q

thermosets- response to heat

A

degradation and decomposition

50
Q

thermosets- hardness

A

generally hard

51
Q

biodegradable

not to be confused with compostable

A

ability to decompose in the environment

within a given time frame (~80 years is a good ballpark)

52
Q

bioplastics

A

plastics produced from biomass

53
Q

carbon negative

A

describes a process that absorbs more carbon dioxide than it produces

54
Q

chemolysis

A

the use of solely chemical substances to decompose organic substances into simpler ones

55
Q

circular economy

A

A continuous cycle that focuses on the optimal use and re-use of resources from the extraction of raw materials through to production of new materials, followed by the consumption and re-purposing of unused and waste materials

56
Q

compostable

A

Describes a polymer that can be at least 90% decomposed after 180 days in a composting environment

57
Q

dehydrate

A

To remove H₂O from a molecule or ion

58
Q

dehydrogenate

A

To remove a hydrogen atom or atoms from a molecule or ion

59
Q

feedstock

A

raw material used for producing another product

60
Q

greenhouse gases

A

molecules that absorb infrared radiation from the sun

61
Q

humus

A

dark, nutrient-rich, organic material produced from composting

62
Q

linear economy

A

Operates on a ‘take-make-dispose’ model, making use of resources to produce products that will be discarded after use

63
Q

plastic dissolution

A

dissolving plastic to extract polymers and separate them from their additives

64
Q

pyrolysis

A

decomposition brought about by high temperatures

65
Q

steam cracking

A

The breaking down of larger saturated hydrocarbons into smaller, often unsaturated ones

66
Q

how is ethene produced

A

via steam cracking- larger hydrocarbons extracted from crude oil, are mixed with steam and heated in the absence of oxygen to produce small, unsaturated hydrocarbons.

67
Q

what is HDPE used in

A

milk jugs, detergent bottles, outdoor furniture

68
Q

what is LDPE used for

A

plastic bags, food wraps

69
Q

PVC

A

aka vinyl
widely used plastic made up of chloroethene/vinyl chloride monomers
chloroethene monomers are synthesised by reacting chlorine gas with ethene which is produced from crude oil in steam cracking

70
Q

what is PVC used for

A

pipes, electrical cable insulation, vinyl records

71
Q

PP

A

plastic composed of propene monomers that are produced via steam cracking

72
Q

PP applications

A

flexible, rigid packaging, rugs, bags, cars

73
Q

PS

A

distinctive plastic made of styrene monomers
ethyl benzene is dehydrogenated and then polymerised

74
Q

PS application

A

as it is soft and lightweight, it is suitable for usage in packaging, polystyrene cups and insulated boxes

75
Q

PLA

A

polylactic acid is a condensation polymer produced from fermented plant starch from crops like sugarcane or corn

76
Q

PLA properties

A

low melting point
high strength
good adhesivity
most widely used filament plastic in 3d printing- also used in disposable cutlery

77
Q

bio PE

A

bio polyethene/renewable polyethene has the same formula as HDPE and LDPE but is deribed from plants

78
Q

how is bio PE produced

A

crops are fermented to produce ethanol which is then dehydrated to form ethene and polymerised and can be produced as LDPE or HDPE

79
Q

bio PE environmental impacts

A

crops used to produce bio PE like wheat and sugar cane, absorb carbon dioxide making its production carbon negative, reducing greenhoue gas emissions
howver, it requires a large area and rapid harvesting can cause land degradation

80
Q

bio PP

A

bio polypropene is primarily produced from crops or vegetable oils

81
Q

production of bio pp from crops

A

fermentation (methylpropan-1-ol)
dehydration (methyl propene)
various methods (propene)
addition polymerisation (polypropene)
same manufacturing equipment can be used

82
Q

recycling codes

A

1- PETE
2- HDPE
3- PVC
4- LDPE
5- PP
6- PS
7- other

83
Q

mechanical recycling process

A

collection
sorting
cleaning
shredding
melting
reforming
repurposing

84
Q

can thermosets be recycled

A

in general they can’t but all thermoplastics can be mechanically recucled

85
Q

products of mechanical recycling

A

usually only used for lower grade plastic products due to hte risk of toxic contamination and some plastics like PVC are more difficult and resource intensive to recycle than others and so not all recycling facilities consider recycling worthwhile

86
Q

chemical recycling

A

aka advanced or feedstock recycling involves converting plastics back into either constituent polymers, monomers or organic chemicals

87
Q

how can chemical recycling occur

A

plastic dissolution- heating plastics with solvents to produce a solution of polymers and additives that can be separated
chemolysis- depolymerising plastics breaking it up into its constituent monomers- only used for condensation plymers
pyrolysis- convert plastics to raw organic chemicals which can then be used as fuels to produce energy- prohibitvely expensive

88
Q

chemical recycling methods and products- conversion

A

methods: conversion
- gasification, pyrolysis, hydrothermal, hydrocracking
products
- refined hydrocarbons give you petrochemicals or fuels -> monomers -> polymers -> plastic products

89
Q

chemical recycling methods and products- polymerisation

A

methods:
enzymolysis
chemolysis
solvolysis

products
monomers -> polymers -> plastic products

90
Q

chemical recycling methods and products- purification

A

method:
dissolution

products
polymers -> plastic products

91
Q

compostable plastics

A

biodegradable in a short time period without leaving any toxic residue or microplastics only nutrients

92
Q

process of degrading compostable plastics

A

bacteria in a composter struggles to break down the polymer chains- so it is first shredded
reacted with water at high temperatures to break it down into its constituent monomers
bacteria decompose the monomers to produce water vapour and CO2- released into environment as well as humus
high temperature environments of an industrial composter to break down rapidly - in these composting environments, moistre, oxygen and heat levels are carefully controleld to ensure maximal breakdown rate

93
Q

examples of compostable bioplstics

A

PLA and PHB (polyhydroxylbutyrate)- produced when microorganisms are stressed
PHB can be used for internal stitches as it is non toxic

94
Q

fossil fuel based plastic that is compostable

A

PBAT- polybutylene adipate terephthalate is tough and flexible that can be used to make cling wrap

95
Q

current barriers to plastic recycling

A

25%- of thermoset plastics cant be recycled
recycling is expensive and buyers of recycled plastics are hard to find
insufficient recycling facilites- shipped overseas prior but this is now banned
incineration is cheaper- produces toxic emissions
only 9% is actually recycled

96
Q

potential circularity of chemical recycling

A

monomers
polymerisation
high grade plastic
chemical recycling
monomers

97
Q

condensation polymerisation

A

chemical reaction between monomers resulting in the formation of a polymer and water

98
Q

hydrolysis

A

reaction involving the cleavafe of bonds using water to break up polymers into monomers

99
Q

innovation

A

introduction of new methods, procedures or products to traditional industries

100
Q

in condensation polymerisation what reacts

A

alcohol with another functional group, often a carboxylic acid to form a covalent bond bewteen molecules, simultaneously releasing a water molecule

101
Q

uses of PLA

A

as it can be degraded into lactic acid, it is useful in the construction of medical implants like screws or plates as it can remain intact for up to 2 years during a healing process before being broken down and naturally removed

102
Q

condensation polymerisation for PBS- polybutylene succinate

A

monomer succinic acid (COOH functional group) + monomer 1,4 butanediol (OH functional group)
-> polybutylene succinate + water

103
Q

what makes polymers biodegradable

A

as condensation reactions produce water, due to he rearrangement of oxygen and hydrogen atoms from functional groups into water molecules- the functional groups are left in a reactive state
when water is reintroduced to the polymer system- the reaction occurs in reverse, through hydrolysis

104
Q

polymer circular economy

A

renewable resource
industrial processing plant
biodegradable polymer product
biowaste bin
specific biowaste collection
biowaste treatment composting plant
fertiliser
back to a renewable source

105
Q

how does stronger intermolecular forces impact the properties of the polymer

A

increase hardness and rigidity of the polymer
increase melting point or density as they are held together tightly

106
Q

3 ways bioplastics can be recycled

A

chemical- polymer to monomers to raw chemicals
mechanical- shred, melt, reform
organic- composters

107
Q

difference between natural and synthetic polymers

A

Natural polymers are created in the environment, for example, by plants or animals.
synthetic polymers are man-made through manufacturing processes.

chem unit 1 (9 decks)

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