Screw length-to-diameter ratio

L/D ratio See screw length-to-diameter ratio, leach To extract a soluble component from a mixture by the process of percolation. See percolation, leachate A contaminated liquid that drains from landfills and must be treated before entering the environment. It can contain decomposed wastes, decomposition byproducts, heavy metals, or bacteria. See geomembrane, lead 1. The distance in an axial direction from the center of an element such as a screw flight at its outside diameter to the center of the same flight. See directional property. 2. A heavy metal, Pb is hazardous to one s health if inhaled or swallowed. Its use is restricted. In plastics it is found in certain products, such as additives. Pb can be used in safe environments since it has excellent performance properties, such as resisting attack by many corrosive chemicals and is impervious to x-ray and gamma radiation. See hazard x-ray. 

Figure 7.5 Morphological evolution along the extruder (L/D, screw length to diameter ratio) of a PA-6/EPM-g-MA blend.

This behaviour tended to occur towards the end of melting and could be prevented by applying screw cooling to freeze the melt film in contact with the screw. Screw cooling had been shown to improve mixing in earlier papers [1, 3] but this was a remedy used more often in the days when extruder screw length to diameter ratios (L/D) were typically 15 1 and the consequential reduced output rate due to the cooling was evidently acceptable. 

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