Glossary PP
This glossary contains an overview of the most used terms in the polypropylenes business.
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| S |
| Scratch resistance |
Resistance of a polymer surface against damage scratching.
The higher the scratch resistance, the lower the abrasion of a material. Scratch hardness is measured by determining the width of a scratch made by a scriber that is drawn across the surface under a specified pressure.
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| Sealing |
Joining pieces of easily fusible material (plastics) by the application of heat.
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| Shore Hardness |
Resistance of a (polymer) surface to deformation. The different hardness measures applied for characterising polymers are: a) Shore hardness (two scales, A for softer and D for harder materials). B) Ball indentation hardness.
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| Shrinkage |
The differences between film dimensions at ambient temperature and at a higher temperature (e.g. 120°C).
Process: A prestretched plastic film will shrink when heated to the temperature of which the material was stretched, because the oriented molecules will return to the state of the highest possible entropy.
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| Slip |
The phenomenon of 2 plastic objects (films) gliding along each other; this is promoted by surface smoothness and e.g. lubricants.
Slip is an important property of a plastic film with regard to confectioning on a high speed packaging line, e.g. for the stacking of (empty) sacks immediately after they have been produced.
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| Slit Film Yarn |
Yarn produced from slitted tape, drawn and twisted. Main applications: ropes and twines.
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| Staple Fibres |
Fibres with a defined diameter and cut to a defined length from endlessly spun filaments. After drawing, the filaments are crimped and receive a curling effect and are cut.
Main applications are: in non woven fabric for needlepunched carpets and geo textile application, hygienic applications like feminin care and diapers.
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| Stiffness / rigidity |
Stiffness is the resistance of a material to deformation.
Stiff materials have a high modulus of elasticity: a high tensile stress is needed to stretch a specimen.
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| Strapping |
Strips, extruded from plate and cut to a defined width or extruded by a single die gate, drawn and pressed with a diamond pattern.
Application: packaging band.
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| Stress |
Force divided by original cross-sectional area of specimen (e.g. of a plastic rod).
Stress is the intensity at a point in a body of the internal (components of) forces that act on a give plane through the point. It is expressed in force per unit area. The stress is calculated on the basis of the original cross-section of the specimen, and is derived from the force, in Newtons, recorded in a tensile test.
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