Introduction to Plastics Engineering

251 Pages·2018·19.221 MB·English

by  Anshuman Shrivastava

Introduction to Plastics Engineering
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Introduction to Plastics Engineering
Anshuman Shrivastava
PlasticsAdvisoryBoard, UMass-Lowell; Geon Molding Technology,
PolyOne Corporation; Society ofPlasticsEngineer (SPE)
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Preface
Plastics engineering is a vast topic that covers plastic materials, their
properties, processing, part design, product development, manufactur-
ing, applications, end of use, and disposal of plastic products. There are
many ways to apply the knowledge of plastics engineering such as new
product development, improving existing applications, failure analysis,
manufacturing optimization, quality control and scrap reduction, recy-
cling, and compliance to environmental laws and regulations. This book
presents technology and engineering essentials in this field and intro-
duces the readers to plastic engineering.
This book intends to provide training to readers new to plastics as
well be a refresher to plastics practitioners. It is recommended that
those readers interested in learning more refer to the sources cited at the
end of each chapter.
The book is divided into seven chapters. Chapter 1, Introduction to
Plastics Engineering, discusses plastics engineering as a whole and
introduces the topic of macromolecules and polymers. These polymers
could be naturally occurring or synthetically produced. They are classi-
fied as thermoplastic or thermoset and could have semicrystalline or
amorphous morphology. Polymers properties tend to be dependent on
temperature and they are capable of exhibiting rigid or flexible behav-
ior. Plastics are divided into commodity or engineering plastic groups.
Chapter 2, Polymerization, elaborates on the topic of preparation of
plastics by polymerization processes. It includes various polymerization
mechanisms used to produce different types of polymers. This chapter
introduces the readers to different structures of polymers at macro- and
microscopic scales. The chapter also includes a brief discussion of
copolymers, their arrangements and the manner they combine dissimilar
properties to benefit the end application. The readers will also learn
how elastomers allow considerable segmental motion, stereochemistry,
and tacticity. The significance of polymer molecular weight and meth-
ods to measure it are described. The chapter also contains nomenclature
systems that are globally accepted as naming conventions of various
polymers and their families.
xiii
xiv PREFACE
Plastic properties play a critical role in selecting a polymeric material
for a specific end use. It is thus important to understand the material
properties and their significance to applications. Chapter 3, Plastic
Properties and Testing, includes a brief introduction and discusses meth-
ods to screen polymers. It then discusses properties that are classified
into 11 categorizes as physical, mechanical, friction and wear, polymer
rheology, thermal behavior, flammability, chemical resistance, electrical
properties, optical properties, acoustics, and radiation resistance. The
chapter presents principles that influence the processing behavior of
plastic materials. Toward the end of the chapter, list of many commonly
accepted testing standards are tabulated for reference.
While we explore plastic properties, their significance and testing
methods, it is imperative to understand that some of the properties of
polymeric materials could be altered. Polymers are often combined with
other materials known as fillers and additives aimed at modifying their
properties as required by end uses. Both colorants that are used to
change plastic’s aesthetics and other additives that alter functional prop-
erties are discussed. Chapter 4, Additives for Plastics, explains the use
of additives and fillers and their impacts on properties and cost of mate-
rials. Fillers, reinforcement agents along with processing aids all play
unique roles in enhancing one or the other features of plastic materials.
Their influence on cost, processability, and applicability are described
in this chapter.
Plastic material in combination with additives and fillers are required
to be processed in a specified manner to produce usable end products.
Chapter 5, Plastics Processing, reviews primary plastic processing tech-
niques including extrusion, injection molding, blow molding, compres-
sion molding, and thermoforming. In addition, the chapter also provides
insights on transfer molding, rotational molding, calendering, coating,
foaming, and pultrusion methods. Significance and use of process moni-
toring procedures are discussed. Rapid prototyping is briefly touched
upon in this chapter.
Plastic parts require intricate designs for successful end us applica-
tion. Plastic part design is a step-to-step process which requires input
from a variety of sources. Chapter 6, Plastics Part Design and
Application, reviews part design along with safety considerations, pro-
cess selection, and specific design features. All plastic parts are not
always ready for use as end products. The parts may require additional
work such as assembly and joining. There are many joining techniques
that engineers can select from. This chapter not only elaborates on
PREFACE xv
joining plastic parts but also describes rapid prototyping including rapid
tooling and the benefits associated with it.
Millions of tons of plastics are consumed each year to produce parts
that are expected to have good performance over their life spans.
Consumption of large volumes of plastic materials impacts the environ-
ment. In discussing environmental aspects of plastics, two topics cov-
ered in Chapter 7, Environmental Aspects of Plastics, are (1) the effects
of environment on plastic properties and part performance and (2) the
overall effects of using plastic materials on environment. Both topics
are fairly broad and involved. This chapter focuses on introducing the
reader to environmental aspects of plastics, which is why both topics
are only briefly covered. Sources have been included in the references
section for further reading.
To make the most from this book, it is recommended that readers
explore the chapters in the recommended manner as the chapters are
sequenced and outlined. Those with a working knowledge of plastics
engineering or interested in a specific topic, may go directly to the sec-
tion of interest.
1 Introduction to Plastics
Engineering
1.1 Introduction to Plastics
Plastic products have become significant part of our daily life. The
clothes we wear, the toothbrush we clean our teeth with, the storage
containers we carry and heat our food in, the cars we drive, the elec-
tronic devices we use to communicate, the credit cards to make pay-
ments, and several such products have become essential to everyday
living. These products are typically made from different types of plastic
materials.
The word plastic or plastics is derived from Ancient Greek word plas-
tikos meaning “fit for molding” and from Latin word plasticus meaning
“of molding” [1]. Both words indicate forming shapes or molding by
heating. Thus, shaping of plastics using heat and pressure creates the
foundation of almost all plastic manufacturing processes. Typical to these
manufacturing and technological processes, the plastic materials are usu-
ally made soft by applying heat [2]. The softened plastic is then given a
desired shape to fit the application. Once it attains the shape, the material
is then cooled to let it harden and retain the shape.
Plastic products are widely accepted primarily due to their lower cost
and lighter weight. Ease of processability, resilience, recyclability, and
versatility add to the benefits of adapting to plastics. During the last
century, the development and acceptance to plastics have raised the
comfort and standard of living. In absence of plastic products, today’s
clean water, food distribution, healthcare, apparel, automobiles, aircraft,
agriculture, and consumer goods would be unimaginable.
Plastics entered large-scale applications after the Second World War
and quickly began to revolutionize daily life by replacing expensive and
scarcely available metallic counter parts. Millions of plastic products
offering unique functions and conveniences are routinely used. The end
uses of plastic vary from simple economical commodity merchandize to
expensive complex products for application in aerospace, automobiles,
medical drug delivery devices, prosthetics, grafts, and others. To under-
stand the growing diversity and complexity of plastic products, it
becomes imperative to explore “plastics engineering” as a scientific field.
IntroductiontoPlasticsEngineering.
DOI:https://doi.org/10.1016/B978-0-323-39500-7.00001-0
©2018ElsevierInc.Allrightsreserved. 1
2 INTRODUCTION TO PLASTICS ENGINEERING
1.2 Plastics Engineering
Plastics engineering as a field focuses on designing, developing, and
manufacturing of plastic parts that satisfy the requirements of the
intended application. This means that each plastic product that is
designed for specific application has to satisfy the three “F’s” as form,
fit, and function for that application.
As we review examples of wearable safety, it would be clearer how
form, fit, and function alter with application. In discussing “wearable
safety for eye protection,” the form would be to produce rigid structure
in the form of wearable safety glasses, fit would be to develop the shape
and size that comfortably fit the user typically around the eyes and ears,
and the function would be the ability of selected material to safeguard
against foreign objects as a protective barrier, without interfering with
user’s normal vision.
Similarly, reviewing “wearable safety for body armor,” the form
would be to produce a flexible vest that could be worn around the chest
and shoulders, the fit would be to develop sizes that are able to fit dif-
ferent body types, and function would be the ability of the selected
material to protect against bullets and other such fast-moving objects at
close range, yet remain lightweight for the user’s comfort.
The examples of “wearable safety” demonstrates how engineering a
plastic product incorporates the knowledge of various interdisciplinary
fields in designing of form, fit, and function for a product. Fig. 1.1 illus-
trates plastics engineering as an interdisciplinary field that relies on var-
ious scientific and technical disciplines. Plastics engineering not only
combines the concepts of form, fit, and function, which involves design
principles, but also encompasses the knowledge of various scientific
and engineering fields that requires a good understanding of materials,
their properties, processing methods, design principles, functional
requirements, and the application.
Understanding the engineering of plastics is necessary for developing
innovative, safe, economical, and convenient solutions to meet the
expanding demands universally. To learn about plastics engineering,
one needs to develop a basic understanding of its fundamental princi-
ples, design techniques, processing methods, material properties, and
governing regulations. One of the first steps to grasp the fundamentals
of polymer engineering is to understand the macromolecules and poly-
mers that make the backbone of all plastic materials.