Time Temperature Superposition - Master Curve
A method is explained to characterize polymer properties with respect to their structure and processing behavior during thermoplastic processes such as Injection Molding, Extrusion, Foam Extrusion, Sheet Extrusion and Thermoforming. Using the rheological standard test methods flow curve or frequency sweep, the viscoelastic properties can only be measured within a limited shear rate range. To be able to completely characterize such materials and to achieve satisfactory results about the actual processing behavior it is necessary to obtain data over a rather wide angular frequency or shear rate range. The procedure can be applied in a fast and easy way for most of the standard polymer melts or “thermorheologically” simple materials. Polymers with a high level of crystalline structures and high molar mass such as HDPE do not show significant temperature dependence.
Polystyrene PS shows a long hydrocarbon chain, with phenyl groups attached to carbon atoms. It was discovered by Simon in 1839 and published by Staudinger in 1922.
PS is amorphous with a glass transition point ranging from 75 °C to 105 °C, has a high clarity and a good dimensional stability. Further advantages are: Excellent electrical properties, low water absorption, odorless, tasteless, unlimited colorability, good processability, workability and decorability, good chemical resistance to many acids, bases, low alcohols, salt and salt solutions. It is very easy to recycle.
Some typical applications are: Toys and novelties, rigid packaging, refrigerator trays and boxes, cosmetic packs and costume jewelery, lighting diffusers, audio cassettes and CD cases.
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