By Ben Howe, Content Development Lead for UL IDES
Finding alternative plastics has been a hot topic recently, especially after hurricanes Katrina and Rita dealt heavy blows to the petrochemical industry. The resulting supply chain interruptions and price increases have no doubt triggered numerous searches for alternative plastics. Aside from the post-hurricane scrambling, there are other, more common reasons for finding alternative materials that you may encounter from time to time; either your parts need improvement, the material you’ve been using doesn’t exist anymore, or you’ve been asked to cut costs yet again. Whatever the reason, it’s time to start looking for another resin.
Reasons for Finding Alternative Plastics
Reducing Part Cost
The most common reason for finding an alternative plastic is lowering part costs. Reducing part cost doesn’t mean just finding a cheaper resin, because a cheaper resin doesn’t always translate into lower priced parts. Keep in mind that you purchase resin on a per unit weight basis, but you sell parts on a per unit volume basis. A lower-density material will make lower cost parts than an equally priced higher-density material. Additionally, decreasing cycle time by finding a better processing material can translate into cost savings by allowing you to make more parts in the same amount of time.
Part Performance Improvement
If a part you’re molding isn’t performing well enough, search for a similar material with improved properties. Use the existing material as a baseline and adjust the values of the properties that need improvement.
Material Discontinued or Renamed
If the material you’ve been using is no longer available, a call to the resin manufacturer is a good place to start. If the material has been discontinued the resin manufacturer generally has a short list of suitable alternatives. If not, you can use the datasheet from the old grade as a basis for searching for a new grade. Occasionally resin manufacturers change their nomenclature or sell a product line to someone else, so the grade you’re using may just be called something else.
Part Requirements Have Changed
Sometimes the requirements of an existing part change. Recently someone called me for help finding a new plastic. A part he was molding was intended for the domestic appliance market, but he was trying to develop the product for commercial use. During product development he discovered that the part needed to meet the more stringent UL 746 f1 rating than the f2 rating it needed for the domestic market. This requirement change triggered his search for a new material.
Current Supplier Can’t Deliver
Hurricanes aren’t entirely to blame for supply chain woes. A world-wide increase in demand for petroleum is placing further stress on domestic supplies. Sometimes a supplier just can’t make the deliveries it promised, or a business relationship has soured. Whatever the reason, if you just can’t get the pellets you need, you’ll have to look elsewhere.
Obstacles to Finding Alternative Plastics
If you are replacing a material for which you already have tooling for production, one extremely important characteristic to consider is mold shrinkage. Tooling modifications can be very expensive and time-consuming. Make sure the alternative plastic won’t require tooling changes unless you are ready to assume the cost and down-time of having tooling modified. Be aware that some resin manufacturers do not publish mold shrinkage data simply because of liability concerns, but provide the information upon request. Believe it or not some people have cut molds based entirely on a datasheet mold shrinkage value. With molds costing tens or hundreds of thousands of dollars it’s a good idea to use mold shrinkage values as a guideline and not concrete fact.
Sometimes the search for an alternative begins at the start of a project. An OEM may recommend a resin for a part, which may or may not be the most cost effective resin. Sometimes OEMs are open to suggestions and work with the molder to produce quality economical parts. At other times OEMs place restrictions on which materials can be used to produce specific parts. The American auto makers are a good example of this practice. They list certain materials in approvals and then call-out those approvals for parts. These approved resins are the only materials that can be used even if there is a better, more cost effective alternative available. On the flip-side, Japanese auto makers specify part performance and give their part suppliers the ability to select the best resin for the job. If the molded part can meet the OEM’s requirements, then the resin may be used. This flexible practice is how the Japanese have kept costs down, while still getting quality parts.
Finding a supply of resin is always a challenge. Sometimes a material is only available in certain parts of the world or the resin manufacturer isn’t well-known, so finding a distributor is difficult. Even after a supply is secured, there’s production lead-time and shipping delays, not to mention developing a good relationship with a supplier to ensure a steady supply of resin takes a lot of work.
If the resin you need to replace is highly specialized, chances are there aren’t many similar materials to begin with. The more specialized a resin is, the fewer resins there are that can replace it.
Tips for Finding Alternative Plastics
Prospector has a powerful Alternative Plastics Search. With the click of a button you can find a list of possible alternatives. Detailed searches within Prospector that may take 30 minutes to fine tune are finished in a few seconds with the alternative materials search, many times with better results. But, as mentioned earlier, alternative searches sometimes require a slightly different material, so a direct offset is not the goal. In these cases, a more detailed search is required.
The most important thing you can do in preparing for an alternative plastic search is to determine which data available for the existing resin is most important for your application, and what tolerances are allowable. Requirements should be prioritized. It is a good idea to separate requirements into two categories: must-have, and like-to-have. After you generate a requirements list, assign tolerances to each numerical value. Suitable materials may lie at the margins of your original requirements.
With your list in hand it’s time to search for an alternative. Start searching based on your highest priority criteria first. It is important to remember when searching that some properties are more commonly reported by material suppliers than others. If an obscure test is an absolute requirement, it’s best to put it on the back-burner until you’ve got to decide between a few finalists. If the number of search results drops off dramatically when you perform a search, it’s a sign that there isn’t much data available. When you’ve got your short list of possible alternatives, place a call to the resin manufacturers to see if they have the obscure test data before you have the material tested. Many times a resin manufacturer will have additional test data on hand, but have chosen to leave it off the datasheet.
In the article Test Standards: Back to Basics, I mentioned the ability to search multiple properties within the IDES database simultaneously. These test standard spanning properties are found in Prospector under the “Combined Standard” category. These properties are essentially blind to test standards. The data from all related properties have been combined and made searchable through one property. For example, if you’re looking for a resin with a density between 0.95 and 0.98 g/cm³, you don’t really care about the test method, so by using a “Combined Standard” property, you are including all density data in your search. The advantage to performing a search using one of these properties is that you are not excluding any materials based on your selection of search property. If you were to grab Density-Specific Gravity, ASTM D792, and perform a search, you’d automatically exclude both ASTM D1505 and ISO 1183 data.
If the number of potential alternatives is too long to be useful (as is often the case for commodity resins) there are a few things you can do to cut the list down. Filter out materials that don’t meet your regional availability requirements. Check to see if any of the potential alternatives have unnecessary additives and adjust accordingly. Once the list of potential alternatives is manageable, don’t forget to check the density, and double-check the mold shrinkage. If you need help when it is time to source the material, contact us. IDES offers a sourcing service to make it easier to get materials.
About the Author
Content Development Lead
|Ben Howe is the Content Development Lead for UL IDES and is responsible for the management of 83627 unique grades of material datasheets from more than 883 resin suppliers. Ben holds a degree in Mechanical Engineering from the University of Wyoming (2001).|
The views, opinions and technical analyses presented here are those of the author, and are not necessarily those of UL, ULProspector.com or Knowledge.ULProspector.com. While the editors of this site make every effort to verify the accuracy of its content, we assume no responsibility for errors made by the author, editorial staff or any other contributor. All content is subject to copyright and may not be reproduced without prior authorization from Prospector.