Polymer Dictionary

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	Gas phase reactor Type of reactor to polymerise in the gas phase (i.e. all monomers are in the gaseous form); different designs are possible. In processes for the production of polyolefins, often fluidised bed reactors are used. Other constructions involve stirred or slow-flowing beds in different reactor geometries.
	Gloss Brightness or luster of a plastic resulting from a smooth surface. Gloss is determined by measuring the amount of light reflected from a surface, where the position and strength of the illumination has to be defined as well as the reflection angle covered by the measurement (normally 20°).
	Gel A heterogeneity in the polymer that appear as local thickness increase in films or thin-walled articles. Gels are caused by inclusion of high molecular weight particles with a higher viscosity than the surrounding, in some instances also including cross-linked molecules; normally the melting point is also higher than the surrounding. In some instances one also refer to contamination as gels, as examples can be mentioned fibre gels or dirt particles. The cause of this can be badly dispersed additives (agglomeration, dispersion) or other substances. This is not actually a gel, but sometimes called so for simplicity.