Hardware for Blown Film

This chapter covers hardware specific to blown film extrusion. It is organized by the order in which material flows through the extrusion line, beginning upstream of the extruder and proceeding through windup. 

Simulator Exercise When the cursor is paused over any hardware component, an identification tag shows its name. 

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Lubricants are used with polymers for two main needs external lubrication and internal lubrication. External lubrication reduces friction between the polymer and the extrusion hardware, such as on the internal flow surfaces of the die. For example, lubricants can help eliminate melt fracture of blown film by reducing stress on the polymer as it passes through the die. Additionally, die drool (or die lip buildup) has been reduced by the use of lubricants. Internal lubrication reduces the friction between flowing polymer molecules, effectively reducing melt viscosity. Use of internal lubricants can reduce the power consumption required for polymers that are difficult to process. Some common lubricants are metal stearates and paraffin waxes. 

This chapter covers two main sections extruder hardware systems and extrusion functional zones. The first section identifies the primary components of the extruder and provides detail into their capabilities and size ranges. The second section describes how the hardware interacts with the material as it passes through the system. In other words, it provides a look at what is happening inside each zone of the extruder. The descriptions here are purposefully brief, serving as a foundation to support later discussions specific to blown film extrusion. If the reader is interested in pursuing this topic further, there are many books devoted entirely to the extruder and extrusion processes. For example. Polymer Extrusion by Rauwendaal [3] provides an excellent in-depth analysis. Other references are listed in the back of this book [4-6]. 

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