Web-exclusive: Resin Spec Check: Staying ahead of the curve

If you’re looking to save money by substituting one material for another, there are a few basics to keep in mind.

I’ve noticed a trend with press releases from resin suppliers lately. The headlines are starting to have less and less price increases and more and more “price adjustments” and “price revisions.” No matter what candy coating suppliers apply to the news, raw material prices are getting harder to swallow. Read the last Resin Spec Check article (“What’s really going on with resin pricing?” August 2006 IMM, immnet.com/articles?article=2938) and you’ll see it’s safe to say that resin prices will continue to rise for the foreseeable future. The question should no longer be “How long will this trend continue?” but rather “What can be done to stay ahead of the curve?”

The most obvious solution to an expensive resin is a less expensive resin. This solution is easier said than done. Substituting a less expensive material is not always an option. In some cases OEMs require that a material be approved to an internal specification, as is generally the case with most automotive applications. Some applications require that a resin carry a regulatory approval, such as RoHS, FDA food contact, or USP Class VI. While these issues are important, they do not pose the greatest challenge in specifying an alternative. Is the material easy to process? Are the mechanical, thermal, and/or electrical characteristics on par with the current resin? In other words, how equivalent is the potential alternative material?

For example, recently one of our clients contacted us about finding an offset to Valox 420SE0 from GE-Plastics, a PBT grade the company was processing for a Chrysler automotive application. After conducting an “exhaustive two-week search,” it had narrowed the list of potential resins to two grades from LG Chem and SK Chemicals. When we ran an alternative resins search, the pool of potential resins grew to 143 injection moldable grades with a glass filler of 25-30% available from 31 resin manufacturers in North America, including RTP Co., Clariant Performance Plastics, and Polymer Resources Ltd. (see graph).

Shopping around

If price increases themselves weren’t bad enough, as the cost of producing plastics goes up, less popular grades or product lines may be trimmed to support more profitable materials. In more drastic cases, entire product lines may be discontinued. The biggest example in recent memory of this happening was the discontinuation of Dow Plastics’ Questra line of SPS (syndiotactic polystyrene). In either case, you may be forced to find an alternative material.

If the past few years have taught us anything, it is that agility and adaptability are the keys to survival. Having a variety of time-saving tools at your disposal will help you not only survive, but thrive. When you have to search for an alternative material, here are a few things to remember:

• List and prioritize material requirements, and don’t forget to define acceptable ranges on property values.
• If you need additional information about a material, contact the resin manufacturer; often it has more data than is displayed on a data sheet.
• Remember that compounders can work wonders with materials. If you have a special problem, contact your trusted compounder to see if it can help.
• Shop around by contacting more than one distributor for price quotes.
• Resin distributors and manufacturers may be able to recommend an alternative resin, but it’s up to you to determine if it will work.
• Double-check the density of the new resin. Remember that you buy resin by weight, but sell parts by volume. An equally priced lower-density material will produce less expensive parts.
• Verify mold shrinkage potential of the new resin as expensive tooling changes can eliminate material cost savings. Some testing may be required to get a handle on mold shrinkage for your application.

Ben Howe is an engineer at IDES, a plastic materials information firm based in Laramie, WY. IDES’s primary product is Prospector, a database of materials that provides vertical search capabilities on a variety of resins and materials technical data. Howe can be reached at howeb@ides.com, or (307) 742-9227. Visit IDES at www.ides.com.