Glossary PP
This glossary contains an overview of the most used terms in the polypropylenes business.
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| H |
| Hardness |
The resistance of a material to local plastic deformation.
Method: an indentor of specific size and shape is pressed into a plastic specimen under a specific load. Hardness is expressed as the depth of the resulting deformation. It is usually higher at higher densities. Hardness often is a good indication of the wear properties of a material. A relation exists between the hardness and the toughness of ductile materials. When the MFI and the comonomers of two plastics are the same, the tougher plastic will have a lower hardness.
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| Haze (opacity) |
Impossibillity to see clearly through a plastic film.
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| Heat defelction temperature (HDT) |
Heat deflection temperature (HDT) indicates how loaded material deforms at higher temperatures. Test bars are placed in a heating bath, resisting horizontally on two supports. A constant load is applied in the center of the specimen and the bath temperature is raised at a constant rate. The temperature of the bath at which the flexural deflection of the loading point has reached a predefined level is the heat deflection temperature of the material.
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| Heat stabiliser |
An additive which increases the thermostability of a plastic during end-use: it gives a better resistance to degradation by heat.
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| Homopolymer |
Homopolymer consist only of propylene units; their properties can be regulated via molar mass distribution and the degree of isotacticity (stereoregular structure).
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