Introduction

This book provides information on the behavior of plastics that influence the application of practical and complex engineering equations and analysis in the design of products. For over a century plastics with its versatility and vast array of inherent plastic properties as well as high-speed/low-energy processing techniques have resulted in designing and producing many millions of cost-effective products used worldwide. The profound worldwide benefits of plastics in economics and modern living standards have been brought about by the intelligent application of logic with modern chemistry and engineering principle.

Today's plastics industry is comprised of both mature practical and theoretical technology. Improved understanding and control of materials and manufacturing processes have significandy increased product performances and reduced their variability. Performance requirements for these products can be characterized in many different ways. Examples meeting different commercial and industrial market requirements worldwide include:

1. light weight,

2. flexible to high strength,

3. provide packaging aesthetics and performances,

4. excellent appearance and surface characteristics without using secondary operations,

5. degradation resistance in different environments,

6. performance in all kinds of environments,

7. adapt well to mass production methods,

8. wide range of color and appearance,

9. high impact to tear resistance,

10. decorative to industrial load bearing structures,

11. short to very long service life, degradable to non-degradable,

12. process virgin with recycled plastics or recycled alone,

13. simple to complex shapes including many that are difficult or impossible to form with other materials,

14. breathable film for use in horticulture,

15. heat and ablative resistance,

There is a plastic for practically any product requirements, particularly when not including cost for a few products. One can say that if plastics were not to be used it would be catastrophic worldwide for people, products, communications, and so on with a major economic crisis because much more expensive materials and processes would be used.

Materials can be blended or compounded to achieve practically any desired property or combination of properties. The final product performance is affected by interrelating the plastic with its design and processing method. The designer's knowledge of all these variables is required otherwise it can profoundly affect the ultimate success or failure of a consumer or industrial product. When required the designer makes use of others to ensure product success.

Plastic plays a crucial and important role in the development of our society worldwide. With properties ranges that can be widely adjusted and ease of processing, plastics can be designed to produce simple to highly integrated conventional and customized products. While it is mature, the plastics industry is far from having exhausted its product design potential. The worldwide plastics industry offers continuous innovations in plastic materials, process engineering, and mechanical engineering design approaches that will make it possible to respond to ever more demanding product applications (Fig. 1.1).

Innovation trends emerging in plastics engineering designs are essentially combinations and improvements of different processes, combinations and improvements of different materials, integration of a wide range of functions within a single product, reduced material consumption, and recyclability of the materials employed. At the same time, rising requirements are being placed on design efficiency, product quality, production quality, and part precision, while costs are expected to be reduced wherever possible. This combination of objectives is achievable by factors such as process-engineering innovations that reduce the number of process steps.

The basic and essential design exercise in product innovation lies in predicting performances. This includes the process of devising a product that fulfills the total requirements of the end user and satisfies

Flow-chart from raw materials to products (Courtesy of Plastics FALLO)

NATURAL GAS PETROLEUM COAL AGRICULTURE

ETHANE PROPANE BENZENE NAPHTA BUTENE

ETHYLENE STYRENE FORMALDEHYDE POLYOL ADIPATE PROPYLENE VINYL CHLORIDE CUMENE ACRYLIC

POLYETHYLENE POLYSTYRENE ACETAL POLCARBONATE POLYPROPYLENE POLYVINYLCHLORIDE NYLON

EXTRUSION INJECTION BLOW CALENDAR COATING

BUILDING PACKAGING TRANSPORTATION RECREATION ELECTRICAL CONSUMER INDUSTRIAL

PIPE APPLIANCE PACKAGING LUGGAGE MARINE SIGN TOY SIDING COMMUNICATION ELECTRICAL MEDICAL AUTO TOOL

the needs of the producer in terms of a good return on investment (ROI). The product designer must be knowledgeable about all aspects of plastics such as behavioral responses, processing, and mechanical and environmental load stresses. Product loads range from short-time static, such as tensile, flexural, torsion, etc., to long time dynamic, such as creep, fatigue, high speed loading, motion control, and so on. In this book, plastics design concepts are presented that can be applied to designing products for a range of behaviors.

An inspired idea alone will not result in a successful design. Designing is, to a high degree, intuitive and creative, but at the same time empirical and technically influenced. Experience plays an important part that requires keeping up to date on the endless new developments in materials and processes. An understanding of one's materials and a ready acquaintance with the relevant processing technologies are essential for converting an idea to an actual product. In addition, certain basic tools are needed, such as those for computation and measurement and for testing of prototypes and/or fabricated products to ensure that product performance requirement are met. A single individual designer may not have all of these capabilities so inputs from many reliable people and/or sources are required.

Inputs from many disciplines, both engineering and non-engineering, may be required when designing a product such as a toy, flexible package, rigid container, medical device, car, boat, underwater device, spring, pipe, building, aircraft, missile, or spacecraft. The conception of such products usually requires coordinated inputs from different specialists. Input may involve concepts of man-machine interfaces (ergonomics), shape, texture, and color (aesthetics). Unless these are in balance, the product may fail in the market place. The successful integrated product is the result of properly collecting all of the required design inputs.

While plastic product design can be challenging, many products seen in everyday life may require only a practical, rather than rigorous approach. They are not required to undergo sophisticated design analysis because they are not required to withstand high static and dynamic loads (Chapter 2). Their design may require only the materials information in conventional data sheets from plastic material suppliers. Examples include containers, cups, toys, boxes, housings for computers, radios, televisions, electric irons, recreational products, and nonstructural or secondary structural products of various kinds like the interiors in buildings, automobiles, and aircraft. The design engineer will need to know when to use the practical approach, the rigorous approach, or a combination approach.

Plastics do not only have advantages but also have disadvantages or limitations. Other materials (steel, wood, etc.) also suffer with disadvantages or limitations. Unfortunately there is no one material (plastic, steel, etc.) that can meet all requirements thus these limitations or faults are sometimes referred to incorrectly as disadvantages. Note that the faults of materials known and utilized for hundreds of years are often overlooked; the faults of the new materials are often overemphasized.

Iron and steel are attacked by the elements of weather and fire [815°C (1500°F)] but the common practice includes applying protective coatings (plastic, cement, etc.) and then forgetting their susceptibility to attack is all too prevalent. Wood is a useful material yet who has not seen a rotted board, wood on fire, etc. There is cracked concrete and so on. Regardless of these and many other disadvantages, lack of perfection does not mean that any steel, wood, or concrete should not be used. The same reasoning should apply to plastics. In many respects, the gains made with plastics in a short span of time far outdistance the advances made in these other materials.

Recognize that modern design engineering has links with virtually every technical area; material, mechanical, electrical, thermal, processing, and packaging to name a few. Any attempt to explain engineering by referring to the special rules for each area would mean that the engineer would need to have a thorough knowledge of each special field. This is not possible in the current state of technology. It is the case, however, that there are certain common concepts behind these specialized areas. Similar features exist among many consumer and industrial products. These features can be described by using a standard procedure, and the fundamental laws of engineering apply to all products, irrespective of the different forms of materials and equipment involved. Proper applications are required.

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