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138 15 Black or Brown Specks
15.3.4.1 Material: Contamination
In processing material can be contaminated with a variety of substances including
other plastics, dirt, cardboard, etc. These contaminants can create black specks
either by simply being a dark contaminant or by burning up at the required melt
temperatures. Material contamination can occur in many circumstances including
bad regrind, mixed material, improper cleaning of hoppers or loaders, poor plant
cleanliness, etc. Many of the issues with material contamination can be fixed by
having clear standards and procedures for activities such as cleaning hoppers or
always using lids on gaylords (see Figure 15.6). Figure 15.5 shows black contami-
nation in natural regrind.
Figure 15.5 Contaminated regrind
Figure 15.6 Gaylord without lid
