Permissible Color Mix Levels, Percent Color Flint Amber Green Other
Flint (clear) 97 to 100 0 to 3 0 to 1 0 to 3 Amber (brown) 0 to 5 95 to 100 0 to 5 0 to 5 Green 0 to 10 0 to 15 85 to 100 0 to 10
Source: American Society for Testing and Materials (ASTM), 1989, Standard specifications for waste glass as a raw material for the manufacture of glass containers, 1989 Annual book of standards, Vol. 11.04 (Phila.: ASTM), 299-300.
ponents to produce a clean generic polymer. Clean PET is sold as flakes but most HDPE is made into pellets. The HDPE flakes are fed into an extruder and are compressed as they are carried toward the extrusion die. The combined heat from flow friction and supplemental heating bands causes the resin to melt, and volatile contaminants are vented from the mixture. Immediately before the die, the melted mixture passes through a fine screen that removes any remaining solid impurities. As the melt passes through the orifice, a rotating knife chops the strand into short segments, which fall into a water bath where they are cooled. The pellets are dried to a moisture content of about 0.5% and are packaged for shipment to the end user.
Glass used for new bottles and containers must be sorted by color and must not contain contaminants such as dirt, rocks, ceramics, and high-temperature glass cook-
ware. These materials, known as refractory materials, have higher melting temperatures than container glass and form a solid inclusion in the finished product. Table 10.7.2 gives the material specifications for color-sorted glass. The specifications in the Rotterdam glass processing plant limit the maximum amount of ceramics to 100g per ton of crushed glass; the same limit for aluminum is only 6 g per ton.
Trade groups representing manufacturers and processors have established specifications for recycled plastics. These specifications are extensive and beyond the scope of this chapter. In general, buyers require postconsumer plastics to be well sorted, reasonably free of foreign material, and baled within a specified size and weight range.
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