new way chemistry for hong kong a-level 3b 1 overal equation: nylon 6,6 6c

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


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



2. 2. KevlarKevlar

• Kevlar is an aromatic polyamide

• The structure of Kevlar is similar to nylon-6,6



2. 2. KevlarKevlar

• The two monomers of Kevlar are benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene

water molecules are eliminated



2. 2. KevlarKevlar

• Part of a polymer chain of Kevlar is shown below:

Polyamide : Polymer with repeating units held by amide linkages



2. 2. KevlarKevlar

• The repeating unit of Kevlar is:



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



2. 2. KevlarKevlar

The bullet-proof vest is made of Kevlar



2. 2. KevlarKevlar

• What is the main weakness of kevlar ?

Kevlar undergoes alkaline hydrolysis



3. 3. DacronDacron

• Dacron is the DuPont trade mark for the polyester

Polyethylene terephthalate

(PET, PETE, PETP)• Sometimes called Terylene


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


terephthalic acid ethane-1,2-diol

250C, H+ catalyst

Esterification(condensation)

Ester linkage


the ester molecule formed still has unreacted functional groups at both ends

Repeated condensations

(Polyester)


Overal equation:

Terylene (in UK) or

Dacron (in USA)

Terephthalate ethylene


PET

Polymer:

Repeating unit:


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.


Clothes made of 100% polyester.

resistant to wrinkle

can be dried easily


Clothes made of 100% cotton.

soft, comfortable, absorb sweat quickly


Clothes made of 35% polyester and 65% cotton.

Strong and comfortable to wear


Properties and usesProperties and uses

resistant to chemicals

Non-toxic easily washed

PET is commonly usedfor making food containers and bottles.


4. Urea-methanal4. Urea-methanalUrea-methanal is a polyamide, which is a condensation polymer formed from the following two monomers:

methanalurea

bifunctional bifunctional?


−H2Orepeatedcondensations

Stage One : repeated condensations

Conc. H2SO4 as catalyst


−H2Ofurthercondensations

Stage Two : Formation of

cross-links

Cross-links

Strong covalent bonds




cross-linksFor cross-links

to form, one of the monomers must have more than two reactive sites


For cross-links to form, one of the monomers must have more than two reactive sites

urea




cross-links

hard, rigid three-dimensional giant network

Strong covalent bonds


4. Urea-methanal

Polymer: Repeating unit:


conc.sulphuricacid

solution ofurea andmethanal

whiteviscousliquid

stir

white solidof urea-methanal

after further stirring

Laboratory preparation of urea-methanal.


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


Light coloured electrical switches, plugs, sockets and casings for electrical appliances

UsesUses


Ashtrays and handles of frying pans

UsesUses



4. Urea-methanal

• Urea-methanal is a thermosetting plastic

once set hard

cannot be softened or melted again by heating


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.


Production of plastic productsProduction of plastic productsTwo steps are involvedTwo steps are involved

2. Mouldinga) Injection moulding

b) Compression moulding

c) Blow moulding


Almost all thermoplastics are moulded by injection moulding.

Injection moulding( 注射成型 )


+ dye / stabilizer / plasticizer / filler+ dye / stabilizer / plasticizer / filler



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.



A mark can be found at the bottomA mark can be found at the bottom



Compression moulding is used to mould thermosetting plastics.

Compression moulding(壓縮成型 )


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 )


Suitable for making hollow containers.

Blow moulding

Molten plastic tube



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



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?



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



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.

Back

new way chemistry for hong kong a-level 3b 1 overal equation: nylon 6,6 6c

Documents

new way chemistry

hong kong

kevlar slide

kevlar kevlar

c slide

terylene slide

boundary slide

synthetic polymers sb