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7) Ultra High Molecular Weight Polyethylene (UHMWPE):
has extremely long chains, with molecular weight numbering in the millions (usually
2 to 6 million), at least 10 times of HDPE. High MW leads to high degree of physical
entanglements above Tmelt (130 C or 266F), the material behaves in a rubber-like
molecule rather than fluid-like manner causing processing troubles due to extremely
high viscosities. Thus is processed by ram extrusion and compression moulding.
Density 0.928 - 0.941 g/cm 3
Max / Min continuous Service temperature 67 - 82 °C / - 30 °C
Strength: Excellent abrasion resistance and toughness, high impact strength,
ESCR and chemical resistance with the low coefficient of friction, Gamma / UV Light
resistance, UHMWPE yields a self-lubricating, non-stick surface.
Limitations: Not melt processable, higher cost than PE
Applications: Used in variety of applications like Pump parts, seals, lining of
bunkers, silos, chemical tanks, chemical handling equipment, Truck bed linings,
Bearings, Belt wipers, Star wheels, Timing screws, prosthetic wear surfaces, gears,
Guide rails, Chain guides, Hopper/chute linings, Bumpers, Bushings, Wear plates,
Sprockets, butcher-block cutting surfaces, other industrial applications.
8) Polypropylene (PP):
Is an economical material that offers a combination of outstanding physical,
chemical, mechanical, thermal and electrical properties which is not found in any
other thermoplastic.
Density 0.90 - 0.91cm 3
Melting Temperature 165 °C
Glass transition temperature -10 °C
Max / Min continuous Service temperature 100 - 110 °C / -20 To -10 °C
Processing Temperature 190 - 300 °C
Polypropylenes are available either as homopolymers or block co-polymers.
Homopolymers are high strength and stiff but become brittle at low temperatures.
Block co-polymers have ethylene blended-in to improve the low temperature
performance but they have less clarity and gloss. The higher the ethylene content
the softer and tougher the material becomes.
Random copolymers with lower ethylene content and a slightly different structure
exhibit lower melting point, greater flexibility or enhanced clarity (transparency)
The properties of polypropylene can be altered by the addition of fillers like talc or
glass fibres. The addition of talc provides improved rigidity but results in lower
impact strength and reduced resistance to long term heat ageing. Glass fibres
provide good rigidity, improved impact resistance, a good resistance to creep and
better environmental stress cracking resistance.
Strength: Low Cost, Processable by all methods, Excellent aesthetic properties,
easy to fabricate, Low coefficient of friction, stiff, light weight with good tensile,
flexural impact strength, Excellent electrical insulation, Good fatigue resistance,
Excellent moisture resistance, Excellent strength, Autoclavable, Very good
chemical resistance, low moisture absorption, Because of its inherent flexibility it is
ideally suited to integral hinges used for flip flop closures, compass box.

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