The successful performance and profitable manufacture of any product depend on the material selected for production. The awesome growth of plastics has occurred over a very large range of load-bearing applications. Most of today’s plastic applications require high and sophisticated performance.

When we speak of design technology, we mean the prediction of performance, including all the characteristics and properties of a material that are essential to the process of material selection. To the designer or product engineer, a property is defined as one that permits calculation of part dimensions from stress analysis, and such properties are obviously the most desirable upon which to base material selection.

The need for systematic material selection has long been recognized. Product reliability is becoming more important.Plastics generally are substantially lower in strength and rigidity, especially at elevated temperatures. Consequently, they are designed close to their allowable limits. It has therefore become increasingly important to know these limits, both quantitatively and under actual environmental conditions.