The new book “Blown Film
Extrusion, an Introduction” by Kirk
Cantor is a welcome addition to
the extrusion literature. This book
is devoted exclusively to blown
film extrusion, while most film extrusion
books available today cover flat film extrusion as well as blown film extrusion.
It is written for people involved in and concerned with
practical aspects of blown film extrusion and for people
new to the industry. The book does not cover extrusion
theory or mathematical modeling; after all, it is an
introduction. It is written in pleasant, easy to understand
language with clear and abundant full-color illustrations.
This highly visual approach is testimony to the author’s
many years of teaching experience at Pennsylvania College
of Technology as well as at various extrusion companies.
The 165 page book has seven chapters: materials for
blown film, extrusion overview, hardware for blown
film, processing, coextrusion, film properties, and
troubleshooting. It is accompanied by a CD-ROM that
contains a blown film simulator. This software was
developed to teach blown equipment operation and the
processing principles of blown film extrusion. The graphic
interface and operating techniques were designed to
emulate actual blown film extrusion operations. Numerous
blown film simulator exercises are incorporated throughout
the book to complement the information presented in the
book and provide valuable first “hands-on experience” to
the novice.
Chapter 1, Materials for Blown Film, covers the various
plastics and additives used in blown film extrusion, such
as antiblocking agents, antioxidants, antistatic agents,
colorants, lubricants, reinforcements and fillers, stabilizers,
and tackifiers. Chapter 2, Extrusion Overview, is the largest
chapter of the book. It covers extruder hardware as well as
functional zones of the extruder: solids conveying, melting,
melt pumping, mixing, degassing, and die forming. This
chapter will be particularly useful to people involved in any
type plastic extrusion, not just blown film extrusion.
Chapter 3, Hardware for Blown Film, discusses upstream
components, grooved feed extruders, extruder screws,
blown film dies, bubble geometry, bubble cooling, bubble
stabilization, collapsing frames, haul-off, winders, and line
control. Chapter 4, Processing, covers process variables vs.
bubble geometry, characteristic bubble ratios, and process/
structure/property relationships. Chapter 5, Coextrusion,
covers dies and interfacial instability.
Chapter 6, Film Properties, covers tensile strength,
elongation, tear strength, impact resistance, blocking
load, gel count, low temperature brittleness, gloss,
transparency, haze, density, melt index, and viscosity.
Chapter 7, troubleshooting, covers extrusion problems such as surging, high melt temperature, excessive
cooling, and low output as well as film problems such
as melt fracture, thickness variation, die lines, gels, low
mechanical properties, and poor optical properties.
This book will be helpful to any person working in
blown film extrusion, particularly those relatively new
to the industry. Chapter 2 provides a clear overview of
extrusion hardware and provides an excellent description
and explanation of what happens inside the extruder.
This chapter provides the information necessary to
understand how an extruder works, how to successfully
run an extrusion line, and how to set optimum process
conditions. Chapter 4 provides an overview of the
relationship between blown film processing, molecular
structure, and solid-state film properties. This chapter
explains how to achieve specific film properties by proper
choice of the material and processing conditions.
The chapter on troubleshooting is one of the most
important and valuable chapters of the book. After all,
efficient troubleshooting is critical for any successful
industrial blown film extrusion operation. Several bubble instabilities are discussed: draw resonance, helical
instability, frost line oscillation, bubble sag, bubble tears,
bubble flutter, and bubble breathing. Cantor not only
describes practical methods to eliminate the various
types of bubble instability, but also points the reader to
theoretical models of the film blowing process to analyze
bubble instability.
This book is not only a must have for people involved in
blown film extrusion, it is also useful for people involved in
other types of extrusion operations because a substantial
portion of the book covers information useful in all types
of extrusion. The book is well written, technically accurate,
and easy to understand. The simulation software supplied
with the book adds substantial value because it provides
a tool for the reader to practice setting up and running a
blown film extrusion line. The simulator will be particularly
useful in training operators involved in blown film extrusion— it is easier to recover and learn from extrusion problems
created in a computer-based simulator than from real and
costly extrusion problems on the production floor.
Overall: a highly recommended tool to improve any blown
film extrusion operation.
