Transcript 35.3 - ilc.edu.hk
Overal equation:
n H H N (CH 2 ) 6 H N H + n Cl O C (CH 2 ) 4 O C Cl 1 H N
6C
(CH 2 ) 6 H N O C
6C
(CH 2 ) 4 O C
Nylon 6,6
New Way Chemistry for Hong Kong A-Level 3B n + (2n - 1) HCl
35.3
Synthetic Polymers (SB p.171)
Preparation of nylon-6,6 in the laboratory
2 Preparation of nylon-6,6 in the laboratory Reaction occurs at the boundary New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• Kevlar is an aromatic polyamide • The structure of Kevlar is similar to nylon-6,6 3 New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• The two monomers of Kevlar are benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene 4 water molecules are eliminated New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• Part of a polymer chain of Kevlar is shown below: 5 Polyamide : Polymer with repeating units held by amide linkages New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• The repeating unit of Kevlar is: 6 New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• 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 7 New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
8 The bullet-proof vest is made of Kevlar New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.171)
2. Kevlar
• What is the main weakness of kevlar ?
9 Kevlar undergoes alkaline hydrolysis New Way Chemistry for Hong Kong A-Level 3B
35.3
Synthetic Polymers (SB p.172)
3. Dacron
• Dacron is the DuPont trade mark polyester for the P oly e thylene t er ep hthalate (PET, PETE, PETP) • Sometimes called Terylene 10 New Way Chemistry for Hong Kong A-Level 3B
Poly(ethylene terephthalate) (PET)
PET is a condensation polymer formed between a dioic acid and a diol .
monomer 1: bifunctional monomer 2: O O HO C C OH HO CH 2 CH 2 OH a dioic acid benzene-1,4-dioic acid (對苯二甲酸) terephthalic acid a diol ethane-1,2-diol 11 New Way Chemistry for Hong Kong A-Level 3B
terephthalic acid Esterification (condensation) ethane-1,2-diol 250 C, H + catalyst 12 Ester linkage New Way Chemistry for Hong Kong A-Level 3B
13 the ester molecule formed still has unreacted functional groups at both ends Repeated condensations (Polyester) New Way Chemistry for Hong Kong A-Level 3B
Overal equation:
Tere phthalate ethy lene Terylene (in UK) or Dacron (in USA) 14 New Way Chemistry for Hong Kong A-Level 3B
PET
Polymer: Repeating unit:
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Properties and uses
The ester linkages are polar .
Polymer chains are held together by strong dipole-dipole interaction .
strong tough smooth resistant to water and chemicals 16 New Way Chemistry for Hong Kong A-Level 3B
resistant to wrinkle can be dried easily Clothes made of 100% polyester .
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soft, comfortable, absorb sweat quickly 18 Clothes made of 100% cotton .
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Strong and comfortable to wear Clothes made of 35% polyester and 65% cotton .
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Properties and uses
resistant to chemicals Non-toxic easily washed PET is commonly used for making food containers and bottles.
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4. Urea-methanal
Urea-methanal
is a polyamide, which is a condensation polymer formed from the following two monomers: bifunctional bifunctional?
21 urea methana l New Way Chemistry for Hong Kong A-Level 3B
Stage One : repeated condensations
Conc. H 2 SO 4 as catalyst −H 2 O repeated 22 New Way Chemistry for Hong Kong A-Level 3B
Stage Two : Formation of cross-links
23 Strong covalent bonds Cross-links −H 2 O further New Way Chemistry for Hong Kong A-Level 3B
Stage Two : Formation of cross-links
For cross-links to form, one of the monomers must have more than two reactive sites 24 −H 2 O further New Way Chemistry for Hong Kong A-Level 3B
25 urea For cross-links to form, one of the monomers must have more than two reactive sites New Way Chemistry for Hong Kong A-Level 3B
Stage Two : Formation of cross-links
hard, rigid three-dimensional giant network −H 2 O further Strong covalent bonds 26 New Way Chemistry for Hong Kong A-Level 3B
4. Urea-methanal
Polymer: Repeating unit:
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stir after further stirring
conc.
sulphuric acid solution o f urea and methanal white viscous liquid white solid of urea methanal Laboratory preparation of urea-methanal.
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Properties
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 shape or melt under strong heating, it decomposes 29 New Way Chemistry for Hong Kong A-Level 3B
Uses
Light coloured electrical switches, plugs, sockets and casings for electrical appliances 30 New Way Chemistry for Hong Kong A-Level 3B
Uses
Ashtrays and handles of frying pans 31 New Way Chemistry for Hong Kong A-Level 3B
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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 32 New Way Chemistry for Hong Kong A-Level 3B
Production of plastic products
Two steps are involved 1. Addition of additives
33 a) dyes — to give colour; b) stabilizers — to give stability to the plastics as well as to the colour dyes and pigments; c) plasticizers — to make the plastics more flexible; d) fillers — to make the products stronger and opaque.
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Production of plastic products
Two steps are involved 2. Moulding
a) Injection moulding b) Compression moulding c) Blow moulding 34 New Way Chemistry for Hong Kong A-Level 3B
Injection moulding
(注射成型)
Almost all thermoplastics injection moulding.
are moulded by
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Injection moulding
(注射成型)
+ dye / stabilizer / plasticizer / filler
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Injection moulding
(注射成型) 37
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.
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Injection moulding
(注射成型)
A mark can be found at the bottom
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Compression moulding(
壓縮成型
)
Compression moulding is used to mould thermosetting plastics.
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Compression moulding(
壓縮成型
)
40
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 .
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Blow moulding
Suitable for making hollow containers.
Molten plastic tube 41 New Way Chemistry for Hong Kong A-Level 3B
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 42 caprolactam New Way Chemistry for Hong Kong A-Level 3B
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?
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35.3
Synthetic Polymers (SB p.170) N-H and C=O groups point in opposite directions to allow formation of H-bonds with polymer chains from both sides N H O C Nylon 6 H N C O N C O H N Nylon 6,6 N H O C C O H N
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35.3
Synthetic Polymers (SB p.173) 45 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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