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Views: 3 Author: Site Editor Publish Time: 2026-01-26 Origin: Site
The viscosities of plastics are reduced with increasing temperature. This was explained in Chapter 5. The viscosity of water is 1 cp or 0.01 poise. It is also 1 Pa-sec.
Fig. 13.6 shows the viscosity of several plastics. Polyethylene has the largest viscosity and all of the plastics show shear thinning behavior. This is better explained in a previous chapter.
The head zone follows the end of the screw. Melt flows from the end of the extruder to screen pack and through breaker plate allowing for additional mixing and homogenizing. The screen pack is a collection of wire screens to filter out contaminants. It needs to be changed if it gets clogged, or blinded causing high back pressure. A breaker plate is a disk of sturdy metal with many holes drilled in it, e.g., a coarse screen. Fig. 13.7 shows examples of screen packs and breaker plates.
Fig. 13.7
