Thermoplastic Material Selection

A Practical Guide

Eric R. Larson

• Publisher: William Andrew
• Year: 2015
• ISBN:
  9780323312653
• Topic: Tecnologia e ingegneria
• Subtopic: Scienza dei materiali

Thermoplastic Material Selection: A Practical Guide presents current information on how proper material selection is a critical component of any manufactured product. The text is a practical guide to a difficult process, giving the reader a fundamental grounding in thermoplastic materials and providing the tools they need to save time, money, and frustration.

The book provides an overview of the most commonly used thermoplastic materials, including discussions of the different chemical families, plastics categories, and material grades - and the implications of these differences on the material selection process. It provides fresh insights on the traditional methods of material selection based on performance and cost, and also discusses the use of non-traditional methods based on subjective evaluation.

Subsequent sections include references on tools that can be used to conduct further exploration, how to accurately select the most suitable material, writing an effective material specification, and working with material suppliers and distributors.

• Presents current information on how proper thermoplastics material selection is a critical component of any manufactured product
• A practical guide to a difficult process, giving the reader a fundamental grounding in thermoplastics material selection and providing the tools they need to save time, money, and frustration
• Delivers insights on the traditional methods of material selection based on performance and cost, and introduces nontraditional methods based on size, form, appearance, and feel

1

Introduction

Abstract

Whether tools, weapons, clothing, shelter, jewelry, or even toys, humans have always made things. One might even argue that the meaning of the word human is to make. The materials used to make things have changed throughout history, from found to extracted to synthesized. In the process, knowledge about how to use these materials has been passed along from generation to generation, from culture to culture, from continent to continent. This knowledge comes in a variety of forms, ranging from common sense, to tribal knowledge, to sage wisdom, to trade secrets and intellectual property.

Keywords

The Plastic Age; Plastics technology; Materials science; Synthetic; Ulfberht swords

Whether tools, weapons, clothing, shelter, jewelry, or even toys, humans have always made things. One might even argue that the meaning of the word human is to make.

The materials used to make things have changed throughout history, from found to extracted to synthesized. In the process, knowledge about how to use these materials has been passed along from generation to generation, from culture to culture, from continent to continent. This knowledge comes in a variety of forms, ranging from common sense, to tribal knowledge, to sage wisdom, to trade secrets and intellectual property.

Today, many of the things that humans make are made from plastics. We use plastics to protect our children, to preserve our food, to entertain us, and to communicate and connect with other people. Our health and happiness in our day-to-day lives—and, one might even argue, the very future of our species—depends on our effective use of these materials.

Plastics are unique materials, with unusual properties and performance characteristics. They range from simple compounds similar to beeswax, to highly engineered, specialty materials like Teflon^®, whose properties seem to defy the laws of physics. After all, if Teflon is such a resilient, repellant, and nonstick material—how does it stick to the pan?

There are many books about plastics technology, including some that try to help users select an appropriate plastic material for a given application. Sadly, most of these books are written from the perspective of a polymer chemist, and they fail to provide the user with any guidance on how to evaluate plastic materials in a practical, hands-on manner.

This book is meant to be a guide in the process of plastics material selection. It is based on the simple premise that we all make things, and that we have a fundamental understanding of how to use materials—based on our heritage as human beings.

Let us begin our journey into the world of plastics by taking a quick look at human history. You may find that you know more about materials—and about plastics—than you think.

1.1. The Stone Age

Paleoanthropology—the study of ancient hominid fossils—has shown that humans have always made things. The oldest stone tools, found in Ethiopia, date back to about 3.4 million years ago, and could have been used by any of the several varieties of hominid, perhaps even by the ancestors of our species, Homo sapiens [1]. Less than a million years ago, Neanderthals, a not-so-distant cousin (and perhaps a subspecies of H. sapiens), left behind musical instruments made out of bones, along with stone tools and flint blades. They used these blades to make wooden spears, hand-axes, and to skin animal hides for clothing and shelter. Historical records of our species, H. sapiens, date back to about 200,000 years ago. It is now known that H. sapiens interacted with Neanderthals, resulting in some genetic exchange, and probably some material culture sharing, too [2–4] (Figure 1.1).

Regardless of the species, all of the earliest hominids used naturally occurring materials, such as plants, bones, feathers, skins, and tendons. Humans found and modified shells, antlers, and horns for functional and decorative purposes. Shells coated in red ochre clay and used as beads for jewelry, found in what is now eastern Morocco, date back to 82,000 years ago. Excavations in the Sibudu Cave alongside the Tongati River in South Africa reveal shells that were used as containers—not just for water or other goods, but for paint (see Ref. [5]). Layers of sediment preserving years of occupation dating from 50,000 to 80,000 years ago contain needles, animal traps, bone arrowheads, some stone tools, and a type of binder or glue made of ochre clay [6]. Much later, stone was used to make massive buildings and, around the time the wheel was invented, the first roads.

Figure 1.1 A sample of early stone tools. HeinNouwens/Shutterstock.com.

The materials these early humans left behind have enabled anthropologists to learn about each civilization’s technological and cultural development. The things they made and how they made them—their material culture—can tell us a lot about how they lived, what was important to them, and what motivated them to build and invent new things. Much of the knowledge about materials came from the exchange of ideas and material culture between peoples, as well as apprenticeship, the passing on of knowledge through generations. As it turns out, there was a “materials science” long before the term was ever coined and institutionalized in universities.

As humans developed, so did their use of materials. Many of the materials used in ancient times are still in use today, including stone and animal shells. These materials still have the same qualities that they did back then, including appearance and feel. But the development of metals led to a whole new way of life, made possible by the unique qualities of these materials. While it was once thought that the practice of metallurgy began in one place and diffused around the globe through trade, the latest archaeological evidence indicates that it was more complicated than that. In many cases, people discovered how to use metal independently of one another. This led to a diversity of techniques in metallurgy, some of which led to smelting, as well as the synthesis of new alloys.

1.2. The Age of Metals

Beginning about 8700 BCE, copper with its lustrous sheen and flexible properties attracted the human eye in Mesopotamia, Asia and other sites around the world. People learned how to extract raw metal from ores, and began to use found metals like copper, silver, and gold. Europeans and Asians first used copper to make pigments and jewelry [7]. Smelted copper appeared around 5500 BCE in southeastern Europe—what is now Serbia [8]. The Sumerians and Egyptians also loved copper, crafting religious iconography, jewelry (of course), and even pipes for use in plumbing [9,10]. Copper was used in North and South America, too. Some of the oldest copper artifacts date back to about 6000 BCE in North America. Indigenous Americans did not smelt copper, but hammered it into shapes. Living near the Great Lakes, they had access to a great deal of pure copper, and made knives, awls, spearpoints, and jewelry [11,12] (Figure 1.2).

Figure 1.2 A sample of copper ore. RussellShively/Shutterstock.com.

With the advent of smelting, metals could not only be extracted and purified, but also intentionally combined with other materials while in a molten state. The resulting metal alloy would then be poured into a cast, usually made of clay, and cooled until hardened in the desired shape. Bronze, the first alloy, was primarily made of copper combined with smaller amounts of arsenic or tin. It first appeared as a copper and tin mixture in the Near East, Egypt, and Mesopotamia. The oldest known artifacts were produced by the relatively peaceful Vinča farming culture in what is now Serbia, and included figurines and ornaments [13]. Around the world, bronze became the primary metal for use in toolmaking, as it was much stronger than copper. In China, bronze remained the preferred metal for vessels, art, and utilitarian objects even after iron came into use (Figure 1.3).

Iron developed in a more haphazard way around the world due to the difficulty involved in mining and shaping iron and, in some cases, a cultural preference for the look and feel afforded by bronze. Ancient peoples first used meteoric iron (an alloy containing nickel), hammering it into the desired shape. This alloy is naturally found in meteors, and did not need to be smelted for use, and some people used it without ever having discovered bronze. However, while iron ore is found throughout the world, iron is rarely found in nature in a pure state. Extracting pure iron from iron ore requires smelting. It is during the smelting process that carbon can be introduced to iron, resulting in steel, a harder and stronger material. Since steel was lighter and cheaper than bronze, and in many cases stronger, it became the preferred metal for weapons, armor, containers, and other objects in many parts of the world. Artisans began to depart from the casting methods that were commonly used for bronze, and began utilizing forging and tempering, developing the blacksmith tradition. More advanced metallurgy and smelting at higher temperatures led to the crafting of new kinds of steel, using different amounts of carbon and nickel and other alloying elements. The swords and weaponry of the middle ages were the result of the materials science developed during this period (Figure 1.4).

Figure 1.3 Ancient bronze helmet. Planner/Shutterstock.com.

Ulfberht, the famous Viking sword featured on the PBS NOVA program [14], is the first known example of fine steelmaking. In fact, it predated similar technologies by nearly a thousand years. While most medieval weapons were made from common wrought iron, the Ulfberht swords—so named because the brand was marked in the blade itself—were made from something called crucible steel. At the time, Vikings would most likely have acquired the technology from trade or conquest activities in Central Asia. Fired at a much higher temperature and made liquid, crucible steel absorbed a much larger amount of carbon, while impurities—such as slag and other particulates—were dissolved. Crucible steel was therefore much stronger and more flexible, and made a much finer (and ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Series Editor
• Copyright
• Dedication
• Acknowledgments
• Preface
• 1. Introduction
• 2. Why Use Plastic?
• 3. Understanding Thermoplastics
• 4. An Overview of Thermoplastic Materials
• 5. Material Selection Based on Performance
• 6. Material Selection Based on Cost
• 7. Material Selection Based on Feel
• 8. Bringing It All Together
• Resources
• Index