5 ways to select the right plastic raw material

.1. Look beyond the data sheet
Instead of regarding data sheets as a definitive source of information, engineers should think of them as resumes. Use the information sheets for screening and comparing materials only - and perhaps inputting the values into simple, back-end calculations. "Data sheet properties can give you a quick feel for the material's ability to meet deflection, impact and processing requirements, but only in a comparative sense." [quote Andrew Poslinski from GE Plastics] Engineers should keep in mind that information on data sheets is based on lab tests conducted under ideal (not real-world) conditions using test specimens that are dissimilar to real-world parts. And they contain the averages from several tests, not the spread of data.

.2. Do some digging
To access multipoint information, engineers just have to search a little deeper - not much deeper in many cases. In fact, some information is readily available on the Web. For example, the CAMPUS database provides standardized materials data from dozens of suppliers and much of that information is multipoint. From this source, engineers can get the creep data for many materials in tension in at least three temperatures and four stress levels. Also, material suppliers themselves can provide multipoint information on their websites.

.3. Consult materials suppliers
If researching doesn't yield all the necessary information, then it's time to ask materials suppliers for help. Their expertise is valuable, as they have gathered a wealth of data on impact, creep and acceptable design values - information they provide to customers or prospective customers. And while they may not have data, say, in one-degree increments at a range of strain rates, they can usually propose a good alternative grade for which there is such data.

.4. Pay extra attention to five basic properties
According to materials experts, engineers should heed five basic properties in order to avoid many design errors and even facilitate the more advanced work of later design phases. These properties include impact resistance, moduli, creep, thermal properties and anisotropy. Engineers should be careful to look beyond data derived from common tests for these properties, as such tests often do not reflect end-use conditions.

.5. Perform some testing yourself
Unfortunately, obtaining extra information early in the design cycle won't attend to all of the more complicated concerns that come up later on. Thermal issues, high-rate impact and fatigue, to name just a few, often demand sophisticated computer simulations and thorough testing. According to David Boch, a materials engineering supervisor for Delphi, they moulded the most promising eight material candidates into sample parts and then cut test strips from matching locations from each sample to account for any localized deviations in mechanical properties. They then conducted bench tests on the pieces, hanging weights on them at room and elevated temperatures for about 10 days. They chose the best-performing material and achieved 43% in resin-cost savings.