PLASTIC MATERIALS SELECTION

Getting it right is critical because selecting, testing and qualifying plastic materials are among of the most important product development decisions you will make. Stress Engineering has the expertise to make sure you get it right.

When you make the right materials choices for a new product or package, it rarely attracts notice. The product performs well in the trade and everyone is happy. But when a wrong choice is made, fasten your seat belt, because the unanticipated costs that accompany project delays, warranty claims or recalls can be staggering.

Because material selection is so critical, it is not a decision that should be left to a resin supplier, or based on a molders suggestion, or even to prior experience. The consequences of getting it wrong are just too costly. The decision should be based solidly on data derived from application-relevant testing. Application relevant is key here.

The 45% Failure Rule

About one-half of all failures in plastics result from making the wrong material choice (Figure 1). Product stability tests or short-term material tests for screening candidate materials are often used, but are frequently unreliable for several reasons.

More often than not the failure mechanism is time-dependent where the time scale for failure is longer than the stability test.

The range of "standard" qualification tests does not fully encompass all forces that will be acting on the product in the real world.

The influence of design is not adequately accounted for with respect to the life-limiting characteristics of the particular resin selection.

Stress Engineering Has the Experience

Stress Engineering has decades of experience applying, and where necessary, developing situation-specific product and package test methods to support material selection and qualification. Figure 2 illustrates a recent resin qualification project where seven resins were evaluated to determine whether or not they could be safely used as an alternative in the case of a material shortage, or to exploit a commercial opportunity. The test battery was based on specific features of the product.

Depending on the markets your product sells into, simply knowing whether or not there are other viable materials available may not be sufficient. You may need to compile statistic required for FDA documentation, or to establish a realistic product warranty. Stress Engineering can support these needs as well by developing practical test and analysis methodologies aimed at providing critical data.

No Substitute for Reliable Data

Stress Engineering was asked to help determine if the in-service life of a new product was greater than the three-year industry accepted warranty for this type of product. Stress Engineering devised a range of accelerated, life-limiting tests that simulated both service loads and environment. Failure data generated during the testing were used to calculate the probability of a service failure as a function of reliability requirements (Figure 3).

Our services are organized to provide you the information you need, when you need it. Our plastics engineers can help you comb through thousands of possibilities to identify the best candidate materials. Low-cost screening tests are used early in a project to quickly identify the top few candidates. Depending on your application, a final round of tests may be completed to establish the effects of process variation on as-molded properties.