This document provides information on various types of plastics, their properties, and common uses. It discusses thermoplastics such as polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polypropylene, and polyamide. It also covers thermosetting plastics including epoxy, bakelite, and melamine. For each plastic, the key properties and typical applications are outlined.

1. Geometrical and Mechanical Engineering
Drawing: Unit 2 Module 2
Plastics
A plasticmaterial of a wide range of synthetic/semi-syntheticorganicsolidsthatare mouldable.They
are typicallyorganicpolymersof highmolecularmassbutusuallycontainother substances.Mostare
syntheticandcommonlyderivedfrompetrochemicals.
Properties
Low cost,ease of manufacture,versatility,imperviousnesstowater,usuallylow meltingpoint,electrical
insulator(exceptstretch-orientedpolyacetylene).Some maydecomposetotoxicsubstanceswhen
heated.
Thermoplastics
A thermoplastic, also called a thermo-softening plastic is a plastic which becomes pliable or
mouldable above a specific temperature and returns to a solid state upon cooling.
Most thermoplastics have a high molecular weight. More aesthetically pleasing, expensive
forming process, less resistance to mechanical creep, not suitable for use in EXTREMELY
temperatures, little to no cross-linking in microstructure, eco-friendly forming process.
Polyvinyl Chloride (PVC)
PVCcomesintwo forms,rigid(forconstructioninpipe andindoorsand windows) andare made more
flexible byadditionof plasticizers(phthalates).[Addease ofwork, usedfor cables,lowersglass
transition temperature,increasedflexibility anddurability]
Properties
Highhardness,highmoduli of elasticity(rigid-type),verylow moduliof elasticity(flexible),poorheat
stability,small expansioncoefficient,goodflameretarding,electrical insulator
Uses
PVCpipes,electriccable insulation,uPVCinplace of wood,signs,clothing,furniture
Polytetrafluoroethylene (PTFE)
PTFE isa fluorocarbonsolidwhichcannotbe wetbywater
Properties
Highstrength,toughnessandself-lubricatingdownto5K.Good flexibilityabove194K,highlycorrosion
resistant,thirdlowestcoefficientof friction,subjecttocreep,electrical insulator

2. Uses
Wiringinaerospace andcomputing,printedcircuitboards,TEFLON,plainbearings,gears
Polyethylene
The most commonplastic,mixture of organiccompounds.
Properties
Relativelylowmeltingpoint,corrosionresistant(fromacidsandbases),burnsslowlywithablue flame
High-Density Polyethylene(HDPE)
Density>= 0.941g/cm3
, Low degree of branchinglow tensile strength,usedinmilkjugs,detergent
bottles, garbage containersandwaterpipes.
Medium-Density Polyethylene(MDPE)
Density0.926-0.940g/cm3
Goodshock anddrop resistance,lessnotchsensitive thanHDPE,stress
cracking resistance alsobetter.Usedingaspipesandfittings,sacks,shrinkfilmand carrierbags.
Low-Density Polyethylene(LDPE)
Density0.910-0.940g/cm3
, lowertensile strength,increasedductility,usedforrigidcontainersand
plasticfilmapplications.
Polystyrene (PS)
Syntheticaromaticpolymer,canbe rigidorfoamed.
Properties
Clear,hard,brittle,lowmeltingpoint,poorbarriertooxygenandwater,glassyatRTP, can be cast into
mouldsforfine detail,slowtobiodegrade
Uses
Protective packaging,containers,lids,bottled,trays,napalm-B
Polypropylene
Properties
Tough,flexible,usedasanengineeringplasticwhencopolymerizedwithethylene,goodresistance to
fatigue,chaindegradationdue tosunlight,corrosionresistant,resilienttoimpactandfreezing,canbe
joinedbyheatfusion,heatresistant,lightweight,durable
Uses
Plastichinges,asa dielectric,kettles,foodcontainers,carpets,rugs,ropes,PVCalternative,electrical
cables,plasticmouldings(bottle tops,bottles,andfittings),clothing,andEPPtoyaircraft.

3. Polyamide - Nylon
Macromolecule withrepeatingunits,artificial andnatural.
Properties
Veryelastic,strong,highcrystallinity,hightensile strengthwhendrawnusingheatedrollsathigh
speeds,clear,colourlessormilky,easilydyed,goodelectrical insulator.
Polymethylmethacrylate (Perspex)
Shatterresistantwhichisalsocalledacrylicglass
Properties
Moderate strength,easyhandlingandprocessing,low cost,brittle whenloaded,prone toscratching,
varietiesblockvisible lightwhile allowingtransmissiononIRlight
Uses
Transparentglasssubstitute (submersibles,aircraft,riotcontrol,aquariums),daylightradiation,
implants,acrylicpaint
Thermo-Setting Plastics
A thermosettingresin(a.k.a.athermoset) isapetrochemical thatirreversiblycuresbyheat,chemical
reactionor suitable irradiation.More complex formingprocedure,more resistance tocreep/chemical
erosion,heavilycross-linked.
Epoxy
An epoxyisthe endcuredproductof an epoxy-resin,typicallytworesinsthatneedtobe mixedtogether
before use.
Bakelite
Properties
Heat resistant,electrical insulator,brittle,complexityof production,hard,dense,tendtowellinareasof
perpetual dampness
Uses
Wire insulation,brake pads,whistles,cameras,gun-grips,table-topgames,heat-shields
Melamine
Properties

4. Fire retardant,
Uses
Kitchenutensilsandplates,high-pressurelaminates,countertops,cabinetsandfurniture making