Download - Overal equation:
New Way Chemistry for Hong Kong A-Level 3B1
n (CH2)6 NN
H
H
H
H + n (CH2)4 CC
O
Cl
O
Cl
(CH2)6 N
H
C
O
N
H
(CH2)4 C
O
n
+ (2n - 1)HCl
Overal equation:
Nylon 6,6
6C
6C
New Way Chemistry for Hong Kong A-Level 3B2
Preparation of nylon-6,6 in the laboratory
35.3 Synthetic Polymers (SB p.171)
Preparation of nylon-6,6 in the laboratory
Reaction occurs at the boundary
New Way Chemistry for Hong Kong A-Level 3B3
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• Kevlar is an aromatic polyamide
• The structure of Kevlar is similar to nylon-6,6
New Way Chemistry for Hong Kong A-Level 3B4
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• The two monomers of Kevlar are benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene
water molecules are eliminated
New Way Chemistry for Hong Kong A-Level 3B5
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• Part of a polymer chain of Kevlar is shown below:
Polyamide : Polymer with repeating units held by amide linkages
New Way Chemistry for Hong Kong A-Level 3B6
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• The repeating unit of Kevlar is:
New Way Chemistry for Hong Kong A-Level 3B7
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• Kevlar is a very strong material
used for reinforcing car tyres
• Used to make ropes
20 times as strong as steel ropes of the same weight
• Used for making reinforced aircraft wings and bullet-proof vests
New Way Chemistry for Hong Kong A-Level 3B8
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
The bullet-proof vest is made of Kevlar
New Way Chemistry for Hong Kong A-Level 3B9
35.3 Synthetic Polymers (SB p.171)
2. 2. KevlarKevlar
• What is the main weakness of kevlar ?
Kevlar undergoes alkaline hydrolysis
New Way Chemistry for Hong Kong A-Level 3B10
35.3 Synthetic Polymers (SB p.172)
3. 3. DacronDacron
• Dacron is the DuPont trade mark for the polyester
Polyethylene terephthalate
(PET, PETE, PETP)• Sometimes called Terylene
New Way Chemistry for Hong Kong A-Level 3B11
Poly(ethylene terephthalate) (PET)Poly(ethylene terephthalate) (PET)
PET is a condensation polymer formed between a dioic acid and a diol.
monomer 1:
C
O
OH
O
HO C
a dioic acid
monomer 2:
CH2 CH2 OHHO
a diolbenzene-1,4-dioic acid benzene-1,4-dioic acid (( 對苯二甲對苯二甲
酸酸 ) ) terephthalic acidterephthalic acidethane-1,2-diolethane-1,2-diol
bifunctional
New Way Chemistry for Hong Kong A-Level 3B12
terephthalic acid ethane-1,2-diol
250C, H+ catalyst
Esterification(condensation)
Ester linkage
New Way Chemistry for Hong Kong A-Level 3B13
the ester molecule formed still has unreacted functional groups at both ends
Repeated condensations
(Polyester)
New Way Chemistry for Hong Kong A-Level 3B14
Overal equation:
Terylene (in UK) or
Dacron (in USA)
Terephthalate ethylene
New Way Chemistry for Hong Kong A-Level 3B15
PET
Polymer:
Repeating unit:
New Way Chemistry for Hong Kong A-Level 3B16
Properties and usesProperties and uses
strong tough smooth resistant to water and chemicals
The ester linkages are polar.
Polymer chains are held together by strong dipole-dipole interaction.
New Way Chemistry for Hong Kong A-Level 3B17
Clothes made of 100% polyester.
resistant to wrinkle
can be dried easily
New Way Chemistry for Hong Kong A-Level 3B18
Clothes made of 100% cotton.
soft, comfortable, absorb sweat quickly
New Way Chemistry for Hong Kong A-Level 3B19
Clothes made of 35% polyester and 65% cotton.
Strong and comfortable to wear
New Way Chemistry for Hong Kong A-Level 3B20
Properties and usesProperties and uses
resistant to chemicals
Non-toxic easily washed
PET is commonly usedfor making food containers and bottles.
New Way Chemistry for Hong Kong A-Level 3B21
4. Urea-methanal4. Urea-methanalUrea-methanal is a polyamide, which is a condensation polymer formed from the following two monomers:
methanalurea
bifunctional bifunctional?
New Way Chemistry for Hong Kong A-Level 3B22
−H2Orepeatedcondensations
Stage One : repeated condensations
Conc. H2SO4 as catalyst
New Way Chemistry for Hong Kong A-Level 3B23
−H2Ofurthercondensations
Stage Two : Formation of
cross-links
Cross-links
Strong covalent bonds
New Way Chemistry for Hong Kong A-Level 3B24
−H2Ofurthercondensations
Stage Two : Formation of
cross-linksFor cross-links
to form, one of the monomers must have more than two reactive sites
New Way Chemistry for Hong Kong A-Level 3B25
For cross-links to form, one of the monomers must have more than two reactive sites
urea
New Way Chemistry for Hong Kong A-Level 3B26
−H2Ofurthercondensations
Stage Two : Formation of
cross-links
hard, rigid three-dimensional giant network
Strong covalent bonds
New Way Chemistry for Hong Kong A-Level 3B27
4. Urea-methanal
Polymer: Repeating unit:
New Way Chemistry for Hong Kong A-Level 3B28
conc.sulphuricacid
solution ofurea andmethanal
whiteviscousliquid
stir
white solidof urea-methanal
after further stirring
Laboratory preparation of urea-methanal.
New Way Chemistry for Hong Kong A-Level 3B29
PropertiesProperties
white in colour hard and rigid excellent electrical and heat insulator resistant to chemical attack insoluble in any solvent upon heating, it does not change in shap
e or melt under strong heating, it decomposes
New Way Chemistry for Hong Kong A-Level 3B30
Light coloured electrical switches, plugs, sockets and casings for electrical appliances
UsesUses
New Way Chemistry for Hong Kong A-Level 3B31
Ashtrays and handles of frying pans
UsesUses
New Way Chemistry for Hong Kong A-Level 3B32
35.3 Synthetic Polymers (SB p.175)
4. Urea-methanal
• Urea-methanal is a thermosetting plastic
once set hard
cannot be softened or melted again by heating
New Way Chemistry for Hong Kong A-Level 3B33
Production of plastic productsProduction of plastic products
b) stabilizers — to give stability to the plastics as well as to the colour dyes and pigments;
a) dyes — to give colour;
Two steps are involvedTwo steps are involved
1. Addition of additives
c) plasticizers — to make the plastics more flexible;
d) fillers — to make the products stronger and opaque.
New Way Chemistry for Hong Kong A-Level 3B34
Production of plastic productsProduction of plastic productsTwo steps are involvedTwo steps are involved
2. Mouldinga) Injection moulding
b) Compression moulding
c) Blow moulding
New Way Chemistry for Hong Kong A-Level 3B35
Almost all thermoplastics are moulded by injection moulding.
Injection moulding( 注射成型 )
New Way Chemistry for Hong Kong A-Level 3B36
+ dye / stabilizer / plasticizer / filler+ dye / stabilizer / plasticizer / filler
Injection moulding( 注射成型 )
New Way Chemistry for Hong Kong A-Level 3B37
The material is melted as the plunger moves backwards.
The melted plastic is then forced into the mould as the plunger moves forwards. The plastic sets in the shape of the mould as it cools.
Injection moulding( 注射成型 )
New Way Chemistry for Hong Kong A-Level 3B38
A mark can be found at the bottomA mark can be found at the bottom
Injection moulding( 注射成型 )
New Way Chemistry for Hong Kong A-Level 3B39
Compression moulding is used to mould thermosetting plastics.
Compression moulding(壓縮成型 )
New Way Chemistry for Hong Kong A-Level 3B40
As the powder softens, lower the upper half of the mould to compress the melted plastic into shape.
Cross-linking occurs on further heating and the plastic sets.
Compression moulding(壓縮成型 )
New Way Chemistry for Hong Kong A-Level 3B41
Suitable for making hollow containers.
Blow moulding
Molten plastic tube
New Way Chemistry for Hong Kong A-Level 3B42
35.3 Synthetic Polymers (SB p.170)
There is another kind of nylon called nylon-6. It is similar to nylon-6,6 except that it has one monomer only. What is the structure of the monomer of nylon-6?
http://en.wikipedia.org/wiki/Nylon_6
caprolactam
New Way Chemistry for Hong Kong A-Level 3B43
35.3 Synthetic Polymers (SB p.170)
There is another kind of nylon called nylon-6. It is similar to nylon-6,6 except that it has one
monomer only. What is the structure of the monomer of nylon-6?
New Way Chemistry for Hong Kong A-Level 3B44
35.3 Synthetic Polymers (SB p.170)
Back
N-H and C=O groups point in opposite directions to allow formation of H-bonds with polymer chains from both sides
C
N
N
C
C
N
O
H
O H
O H
N
C N
C N
H
O H
O
Nylon 6
Nylon 6,6
New Way Chemistry for Hong Kong A-Level 3B45
35.3 Synthetic Polymers (SB p.173)
Why would a hole appear when a dilute alkali is spilt
on a fabric made of polyester?
Polyesters undergoes alkaline hydrolysis leaving a hole on the fabric.
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