Some degree of compromise is almost always necessary in designing plastic parts. Arriving at the best compromise usually requires satisfying the mechanical, thermal, and electrical requirements of the part, utilizing the most economical resin or compound that will perform satisfactorily and be attractive, and choosing a manufacturing process compatible with the part design and material choice. Setting realistic requirements for each of these areas is of utmost importance. Probably no plastic will provide 100% of the requirements for the desired performance, appearance, processibility, and price. Selecting the best qualified material is not based simply on comparing numbers on published data sheets; such values can be grossly misleading. For example, choosing the most economical material for a part by comparing the cost per pound of various plastics is a mistake. Some plastics weigh twice as much per cubic inch as others and so would require twice as much to fill a given cavity and cost twice as much to ship. A more meaningful comparison is cost per cubic inch. But since most expensive plastics are far stronger than the cheaper ones, cost/strength values should be analyzed as well. Paying more per pound or per cubic inch is often more economical if less material can do the job. There is an attractive simplicity in deciding on the material with the highest ASTM test values as listed in manufacturers' data sheets. Unfortunately, this method seldom results in the best choice. First, the choice of any material should be based on the best combination of properties, not only on one property. An ideal material will have a value for each strength property just sufficient to perform properly and safely in a given application and no higher. The best material choice usually represents a trade-off among satisfactory properties, ease of processing, and cost. It is seldom
Products & Services
Heat exchangers are commonly used in a wide variety of industrial, chemical, and electronics processes to transfer energy and provide required heating or cooling.
Abrasive files are small stick or stone made of bonded abrasives or superabrasive coatings for deburring, finishing, lapping and polishing in hard to reach places and recesses.
Centrifugal pumps consist of a set of rotating vanes, enclosed within a housing or casing, that are used to impart energy to a fluid through centrifugal force.
Liquid Handling Pumps
Industrial liquid handling pumps are classified in many different ways, and are distinguished by the media pumped and the fluid motive mechanism (dynamic or displacement).
Topics of Interest
The heart of the control valve is the trim, especially the mating parts that throttle the stream to the demands of the controller. These valve parts are subjected to the most taxing service, and...
18.1 Mechanical Properties of Polymers
In the past, results of standard tests such as tensile strength, Izod impact strength, and softening point have been given major emphasis in plastic technical...
The Conversion Factors table shows the user how to multiple density, pressure, flow, and heating value by various constants to obtain values in different units of measure. This table also provides...
This chapter will help you understand the units used in pressure measurements and become familiar with the most common methods of using the various pressure measurement standards.
Plastics Machining: Understanding the Basics Knowing the issues unique to machining plastic components enables designers and engineers to make better choices and develop better devices. While the...