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It is very well suited to replace glass where a higher impact strength, lower weight
and/or easier formability are desired. PMMA can be extruded in to sheets, rods,
tubes which are easy to fabricate, bonds well with adhesives and solvents. PMMA
have large thermal coefficients of expansion and contraction so provisions for the
same must be made for very large parts or for use under extremes of temperature.
Strengths: excellent optical properties and UV resistance, Surface hardness, half
the weight of glass, good dimensional stability, Good insulating properties
Limitations: Brittle, Limited heat resistance (80°C), low chemical resistance
attacked by organic solvents, oil, greases, poor wear and abrasion resistance,
flammable, tends to attract dust so antistatic additive be used, poor flow properties,
easily scratched by dust or cleaning
Applications: windows for aircrafts, Boat windshields, skylights , architectural
glazing, domes, Indoor and outdoor signs, Point-of-purchase (POP) displays,
lighting fixtures, road signs, traffic lights, helmet sight, safety glasses, face guards,
lenses for camera's and photocopiers, tail lights on automobiles, Indicators,
aquariums from small to extremely large, sinks, washbasins, room dividers,
medical contact lenses, Blister packaging, plates, salad bowls, toothbrushes, blood
sample tubes, diagnostic dishes, instrument covers, spoilers and mirror housings.
26) Polycarbonate (PC):
Polycarbonate is a transparent amorphous polymer which exhibits combined
properties of metals, glass and plastics.
Density 1.20 - 1.24 g/cm 3
Glass transition temperature (Tg) 150 °C
Max / Min continuous Service temperature 100 - 150 °C / - 60 °C
Polycarbonate exhibits outstanding properties such as high impact strength (almost
unbreakable), water-clear transparency, heat and creep resistance up to 125°C,
hard and scratch resistant, dimensional stability, abrasion resistance, hardness
and rigidity despite its ductility.
Excellent electrical insulation properties, weatherability, biocompatibility, good
chemical resistance at room temperature, low gas permeability in particularly with
CO2 and transparent to microwave radiation, autoclavable and also suitable for
steam sterilisation (max. continuous working temperature 130 °C). PC is flame
retardant, hard to burn but burns with lighting flame with very low smoke development.
PC is available in clear granules but also available in opaque and translucent
reinforced grades (with glass or carbon fibers). Also blends of PC with ABS, ASA,
PET, PBT and others available for improved properties.
Processed by Injection, Blow, Extrusion process and also thermoformed and
Rotational moulded. PC is hygroscopic and needs to be pre dried at 120 °C in the
appropriate dryers to avoid moisture related processing issues.PC can be glued
with solvents, welded with different weld techniques and printable with special
printing inks (tampon, film, silk screen printing)
Limitations: Affected by boiling water, Poor burning behaviour, Poor solvent stress
crack resistance, attacked by alkalis and strong bases, Subject to stress cracking,
fairly high processing temperatures required, degrades upon extended residence
time in processing equipment, chemical resistance is only fair, Aromatic sensitivity,
Not suitable for high load applications like bearings and gear, difficult to machine.

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