Additives of PC:
1. Functional Additives
2. Fillers
3. Reinforcements
Functional Additives:
1. UV absorbers are the only effective UV stabilizers
2. Colorants
3. Blowing Agents
Fillers:
1. Graphite, MoS2 and PTFE are successfully used in PC to minimize abrasion and wear moldings.
2. Aluminum powder is used to increase the thermal and electrical conductivity.This provides protection against electromagnetic interference (EMI) in, for examples, data processing installations.
Reinforcements:
1. The preferred reinforcement for PC as for many other plastics, glass fiber.
2. PC occupies third place amongst GF reinforced thermoplastics PA and PP.
3. The glass content varies between 10 and 40%. Chopped strand alkali-free E-glass surface-treated with silanes to promote adhesion is the main reinforcement.
4. A PC reinforced with 30% w/w glass fiber can compete in mechanical terms with non-ferrous metals or thermosets.
5. Wollastonite is used very occasionally to improve the stiffness of moldings.
Grades of PC:
PC is available in the following grades.
1. Injection grades
2. Extrusion grades
3. Blow grades
4. Thermoforming grades
In addition to that they are available in the following special grades,
1. Transparent grades
2. Tinted grades
3. Unmodified grades
4. Flame retardant grades
Processing considerations of PC:
1. Drying in hopper dryer or in trays in an over for four hours at 120°C - 140°C will reduce the moisture level in the PC below 0.02%.
2. The apparent melt viscosity is also less dependent on the rate of shear than usual with thermoplastics. Because of high melt viscosities flow path ratio are in the range of 30:1 to 70:1 which is substantially less than for many more general purpose thermoplastics.
3. Processing temperatures are high at which thermal degradation occurs quite rapidly. Normally it is in the range of 280°C - 320°C
4. Polycarbonate adhere strongly to metal and if allowed to cool in an injection cylinder or extrusion barrel may on shrinkage, pull pieces of metal from the wall. It is therefore necessary to purge all equipment free of the resin with a polymer such as PE, after processing.
Processing techniques:
1. Injection Moulding
2. Extrusion
3. Blow molding
4. Thermoforming
Casting process is also used for making films. Like metals, polycarbonate can be cold formed by punching and cold rolling.
Surface Finishing of PC:
1. PC can be easily polished to a high gloss. Only alkali-free polishing pastes should be used so as not to damage the surface.
2. Suitable products are available for printing ,coating, hot embossing etc.
3. PC moldings can also be vacuum metallized.
Machineability of PC:
Machining can be possible in PC with much precaution because it has stress-cracking tendency.
Weldings:
1. Moldings and semi-finished products can be joined by vibration, friction, heated tool and hot gas welding in recent years, welding and riveting with ultrasonics have been preferred.
2. Heated tool welding is preferable to heated gas welding.
3. The tool temperature is 400 C while air temperatures of 450 to 500 C are required for hot gas welding.
Bonding:
1. Suitable adhesives are solvents such as methylene chloride which dissolve the surfaces of the parts to be joined.
2. Two pack adhesives based on epoxide and silicone resins and polyurethane adhesives are suitable for joining PC to PC and other materials.
3. The adhesives must be free of component which are incompatible with PC.
Applications of PC:
1. Appliances
2. Automotive
3. Electrical & Electronics
4. Food contact articles
5. Medical
6. Optical
7. Miscellaneous
Applications of PC in appliances:
Coffee filters, shaver housings, chocolate moulds, blenders, tablewares, kitchen mixer bowls, grinder bowls, housing for ball point and fountain pens, rim heater grills, motor bracket and housing, camera, binocular casings, housings for hair dryers and coffee makers, water tank for steam iron, films for labels and memory switches, fruits juicer parts, high impact vacuum sweeper housing, mixers and power tools, bobbins for textile industries, baby feeding bottles and cutlery
Applications of PC in Automotive:
Wind screen wiper brackets, car interior moulded trims, instruments glazing, indicator lamps, wind shields for two wheelers, door handles, tail and side marker lights, PC blends in instruments, panels as well as bumpers, wheel cover and body panels protective hoods, fan wheels, components for sewing machines, chaises, levers, valves, control cams, directional signs, heating grill, ventilators and radiator grills, overrides, fuse box & covers and housing for automobile & aerial motors.
Applications of PC in Electrical & Electronics:
Wiring devices, insulators panels, plugs and socket terminal blocks, coil formers, Slater enclosures, housing and cover for distributor boxes. Panel light covers, battery boxes fuses, electric meter covers, connectors, breaker boxes, gears, printers housings, slide window,, telephone housing for mining operations, telephone dails, coil formers and housings, winding supports, switch plates, fuse boxes, housing for computers, calculation machine and magnetic disk packs.
Applications of PC in Food Control articles:
Mineral water bottles, microwave oven wares, beermugs table wares and food storage containers.
Applications of PC in Medical:
Blood bottles, dispensers for inhalers, sterilisable lab-wares, tissue culture dishes, posts for IV fluids, sterilizable container and packaging materials, surgical lighting, disposable, diagnostic cardio-vascular and intravenous devices, drug delivery systems and housings for blood cleaning filters.
Applications of PC in Optical:
Diffusers, lenses for lighting, vacuum metallised reflectors, housing for steel lamps and traffic signals, lamp holders, bulk heads, light fixture, lenses and safety glasses, window panels ( for out door lighting) sunglasses, ski goggles and face protective wires, audio compact discs, film and slide cassettes
Miscellaneous Applications of PC:
Sporting goods, stencils, ink ducts, slide rules components and rulers.
Blends of PC:
PC-ABS
- Alloys of a Bisphenol A poly carbonates with ABS and MBS resins have been known for many years.
- These alloys retain their impact strength down to -50 C .They are non-splintering .
- The hardness of the alloys is comparable to that of PC.
- Because of the above properties, ability to mould to close dimensional tolerances , low warpage , low shrinkage, surface finish, PC ABS alloys are widely used in automotive industry for electrical application and for housings of domestics and business equipments.
PC-PBT
This is particularly notable for its high levels of toughens and resistance to petrols and oils.
PC-PET
This is recently introduced for incorporating advantages of both resin in the alloys.
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