Synthetic Condensation polymers: Dacron & Nylon

6AS Group 3 Kitty Au-Yeung Giselle Ho

Rachel ChuiCici Tam

Angela Tsui

Positive impacts of development of polymers on our society

Plastics have replaced an increasing number of natural substances

Synthetic textile fibers have revolutionized the textile industry

the low cost, light weight, strength and design adaptability of plastics meet a variety of applications

Nylon replaced silk in military applications such as parachute and flak vests, and was used in many types of vehicle tires

A synthetic fiber manufacturing facility occupies a much smaller area of ground than would be needed to produce an equal quantity of natural fibers, such as cotton, wool or silk.

Negative impacts of development of polymers on our society

Birds may eat the plastic scraps mistakenly and dieFishing gear tangles up to form a net and kill sea creatures

Negative impacts of development of polymers on our society

Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, containing hydrogen cyanide

Some plastic contains toxic chemicals such as Phthalates which cause reproductive disorders

Some polymers are non-biodegradable and become solid waste which occupy many spaces in the landfill

The effect of structures on the properties of nylon

Hardness and rigidityable to crystallize mostly because of

strong intermolecular hydrogen bonds through the amide groups and because of Van der waal’s forces between the methylene chains

Crystallinity of nylons can be controlled by nucleation, i.e., seeding the molten polymer to produce uniform sized smaller spherulites

Hardness and rigidityIncrease with crystallinityReason for high crystallinity: 1. Polar planar amide (-CO-NH-)

groups result in multiple hydrogen bonds among adjacent strands of nylon

2. Nylon backbone is regular and symmetrical

Crystal structure of nylon 6 and nylon 6.6

Hardness and rigidityNylon 6.6:Have multiple parallel strands aligned with

their neighbouring peptide bonds at coordinated separations

the chains have no directionalityCarbonyl oxygens and amide hydrogens form

interchain hydrogen bonds repeatedly

Hardness and rigidityNylon 5,10:Have coordinated runs on 5 and 8 carbonsParallel strands participate in an extended, unbroken,

strong and tough super- molecular structureNylon 6:Form uninterrupted hydrogen-bonded sheets with

mixed directionalitiesadjacent chains are anti-parallel and the hydrogen

bonding is between adjacent chains within the same sheet (bisecting the CH2 angles

the chains are parallel and the hydrogen bonding is between chains in adjacent sheets

Hardness and rigidityWhen extruded into fibres…Individual polymer chains align because of

viscous flowFibres align further in the cold drawing

afterwardsCrystallinity is increased and hence hardness

as well as rigidity

Hydrolysis and degradabilityAll nylons are susceptible to hydrolysis(Strong acids

and water at high temperatures)Lower members of the nylons (such as nylon 6) are

affected more than higher members (such as nylon 12)Cannot be used in contact with sulphuric acid for

example, such as the electrolyte used in lead-acid batteries

Must be dried to prevent hydrolysis in the moulding machine barrel

By adding heat stabilizer can allow usage at elevated temperature for long-term performance

By adding carbon black can reduce the radiation degradation

Tensile strengthThe strength of nylon comes from amide groups in its

molecular chainA very regular shapeWell suited to create fabrics designed to stand up to

intense forcesUltra drawing of solidified crystalline material induces a

high degree of chain extension , which leads to very high tensile strength

Major material used in parachutes and ropes during the Second World War

Bullet-proof vests and other hard wearing items now

Model of extended molecule chain in

superdrawing fibre

The End