Glossary PP
This glossary contains an overview of the most used terms in the polypropylenes business.
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| E |
| Elasticity |
The tendency of a material to show a quick and complete recovery from deformation after removal of the deforming force.
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| Elongation |
The increase in length of a plastic specimen under tension, usually expressed as a percentage of the original length.
Strain is the unit change due to force in the size of a body referred to its original size.
Technical:
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| Embossing |
The process of producing contoured patterns on sheet or film surfaces.
Embossing is used in e.g. disposable nappy film to improve softness. Usually the pattern is engraved on the chill roll (cast film). The material is embossed immediately before it solidifies, so that the pattern is "frozen in" and is maintained during further confectioning.
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| ESCR |
Environment stress crack resistance (ESCR) = the resistance against the formation of tears and cracks under a certain stress in a chemical environment (usually a detergent). This is a physical property.
Mostly, compression moulded plaques are evaluated. The time till break of a nicked specimen loaded in the presence of a detergent, is a measure of the ESCR. It is measured at different temperature/stress combinations. Material with a low degree of branching, and low MFI material usually have a good ESCR.
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| Extruder |
Equipment for melting, pressurising and homogenising plastics by means of a rotating screw. Different configurations are possible; the most simple one being a: - single screw extruder mainly used for conversion processes like cast film extrusion, fibre spinning, film blowing or pipe and profile extrusion. For more demanding applications like compounding of polymer powder before - pelletisation of the mixing of polymers, twin screw extruders are used where the two normally intermeshing screws can be moved in a corotating (same direction) or counterrotating (opposite direction) fashion. These machines normally contain different mixing elements, most important being kneading blocks for the local creation of extentional flow.
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