polymers Flashcards
Define polymers
long chain molecule made by combining repeating similar basic units
What are the three types of polymer. Give 1 example of each type of polymer
- thermoplastic polymer - PVC, nylon
- thermosetting polymer - bakelite, melamine
- elastomers polymer - rubber
state 1 property of elastomers polymer
- can be stretched and return to original shape
- posseses high elasticity properties
Which type of polymer will degrade after being heated and cannot be moulded into different shapes?
- thermosettign polymer
What method can be used to polymerize an alkene?
- addition polymerisation
give examples of polymers produced by addition polymerisation
- polyethene
- polychloroethene
- polypropene
- polystyrene
What type of polymerisation method can be used when combining 2 different monomers.
give and example of polymer produced with this method
- condensation polymerisation
- nylon, terylene
What polymer is used to make toys and textile. State the properties which support its uses
- polypropene
- durable
what are the properties and uses of polyethene
- strong and durable
- plastic bags, plastic containers
in condensation polymerisation, polymer and ____ or _____ is produced
- water or hydrogen chloride
Give 3 properties of synthetic polymers
- lightweight, strong and hard
- inert and chemically unreactive
- good heat and electical insulators
- resistant to heat
What is the monomer for polyisoprene
Isoprene, 2-methylbut-1,3-diene
What causes rubber to oxidize when exposed to air
- presence of carbon-carbon double bond , C=C
Explain 3 characteristics of natural rubber
- elastic: can be stretched and release to original shape
- low resistance toward heat : becomessticky when exposed to high temperature
- good electrical insulator : cannot conduct electricity at all
- reactive to chemicals: can react with acid, base and organic solvent
- waterproof: impermeable to water
- easily oxidised : O2 reacts with double bond
Latex can coagulate naturally when exposed to air or by _____
- adding methanoic acid
Explain coagulation of latex with methanoic acid
- latex is a aqueous suspension of colloidal rubber particles
- the rubber particles are surrounded by a layer of protein membrane
- the layer of protein membrane is negatively charged causing rubber particles to repel against one another thus preventing coagulation
- Methanoic acid ionize to form hydrogen ions
- hydrogen ions will neutralize the negative charges on the protein membrane
- When rubber particles collide, the protein membrane breaks and rubber polymers coagulate
Latex can coagulate when exposed to air due to the presence of ___ which produces ____
- bacteria
- lactic acid
How to prevent coagulation of latex?
- add ammonia
what process is done to make natural rubber more elastic and has better quality?
- vulcanisation of rubber
State the catalyst, substance and condition needed for vulcanisation of rubber with sulphur
Sulphur is heated with natural rubber at 140 oC with zinc oxide as catalyst
Why cant some rubber be vulcanised with sulphur?
- they do not have carbon carbon double bond
How does vulcanisation of rubber can increase quality and elasticity
- sulohur atoms added to carbon carbon double bond of rubber will form sulphur cross links between long polymer chain
Explain the properties of vulcanised rubber in terms of elasticity
- when vulcanised rubber is stretched, the sulphur cross links prevents the polymer chains from slipping past one another
- when the stretched vulcanised rubber is released, the sulphur cross links pull the polymer chains back to its original position
- thus, vulcanised rubber is more elastic
How does vulcanising rubber increases its resistance towards heat?
- addition of sulphur atoms increases molecular mass of rubber
- Van Der Waals foa between rubber molecules become stronger
- more heat energy is needed to overcome the stronger VDW foa between rubber molecules during heating
- melting point of rubber increases
State a use of thiokol (type of synthetuc rubber)
Sealant
What type of rubber can be used to make rubber glover?
- neoprene, nitrile rubber
