Design Considerations

Materials

Materials must be selected with the correct properties to meet design, economic, and service conditions.

You should be cautious when using manufacturers data sheets and their matrix of performance for much of this data is obtained in laboratory settings and evaluation. This data can be used for screening of a usable material but further testing is necessary. With computer simulations the evaluation of materials has become simpler. Computer models can predict the ways materials can fail and how they will act in an injection situation.

Plastic materials must be selected with care, keeping the final application in mind.  The properties of plastics depend more on temperature than other materials. Plastic is more sensitive to changes in environment therefore many plastics may be eliminated from potential applications.  Bee Jay Molding will help you in the material selection based on our experience and knowledge of alternative plastics. 

Environment

When designing a plastic product you must take into consideration the environment that the material will be subjected to. The physical, chemical, and thermal environments are the most important to keep in mind. The useful temperature range of most plastics seldom exceeds 390 °F. Many plastic materials face degradation from radiant and ultraviolet energy, this is typically destructive to the surface, causing brittleness, and eventually mechanical failure.

In addition to extremes of temperature, humidity, radiation, abrasives, and other environmental factors, you must also take into consideration the fire resistance factor. There are no fully fire resistant plastics. If you have any questions about the selection of your material when dealing with difficult environmental applications please contact us and we will help you.

Electrical

All plastics have useful electrical insulation characteristics. The selection of plastics is usually based on mechanical, thermal, and chemical properties, yet the majority of plastic pioneering was driven by the need for better  electrical insulation. . .

Chemical

The chemical and electrical natures of plastics are closely related because of molecular makeup. There is no general rule for chemical resistance. You must test each plastic for the chemical environment to which it will be subjected.

Some plastics react as semipermeable membranes. These plastics will allow selected molecules to pass while blocking others. This is a useful characteristic when utilizing plastics for filtering applications. 

Mechanical

The mechanical factors of fatigue, tensile, flexural, impact and compressive strengths, hardness, damping, cold flow, thermal expansion and dimensional stability should all be considered when selecting a plastic for a specific application.

The most critical factor will usually be the dimensional stability of the selected material. In many cases a filler can add to the stability of the material. The type and orientation of the reinforcements will greatly influence the properties of stability enhanced materials.

Economics

Although it may be tempting to eliminate the more expensive materials during preliminary selections this is not always the wises choice. There are many other factors that must be evaluated before making a final choice. These factors include processing parameters, assembly methods and desired finish service environment.

Economics must also include the method of production and design limitations of the product. Some materials will work better for some designs while others will not work at all. Yet some designs will require more expensive operations at the same time saving money by decreasing processing time.

The cost of material for tooling along with the processing cost of that material can lead to finding a different plastic that will allow for a more economical process. The final cost will result in the culmination of many factors, thus it is important to evaluate all options when deciding on not only a material of choice put a process as well.  We can help you with these decisions as you move forward in developing you new product or redesigning your current offering.