Lower density (0.90 versus a typical density of 0.98 for compounded PP) and therefore lower weight relative to compounds found in automotive interiors

You can download data sheets (like this one) but beware, test methods vary from vendor to vendor. It is not straightforward to conduct a true “apples to apples” comparison, particularly for cold-temperature impact testing. Therefore, a real-world test is where the proverbial rubber meets the road: Get pellets into the hands of suppliers and molders, and have them produce test parts to see how well the material performs.

PP impact copolymers (ICPs) are widely used for many of these applications due to the need for excellent impact resistance. The question has been though: “Should I select a compounded or a neat ICP for my part design?”

Achieve Advanced PP8285E1 holds promise for automakers and their Tier 1 partners who have searched for a suitable PP to broaden usage in interior trim and door panel applications. It enables automakers to take advantage of weight-saving opportunities and addresses challenges, such as ductility.

The history of automakers’ efforts to use neat ICPs for lightweighting large and complex parts has historically had mixed success. Some early efforts were abandoned in favor of compounded PP, while others returned to the material for value-oriented vehicles. Today, automakers are scattered across both camps. However, this new ICP has made an enormous difference in the industry and more door panels are indeed rolling off production lines using this higher performing material.

Plastics, therefore, remain front and center in the search for new and better lightweighting solutions. Today, plastics represent about 50 percent of the volume of a vehicle but only account for 10 percent of total weight, according to the American Chemistry Council. Even after decades of innovation however, there remain new challenges and new frontiers to cross. Polypropylene (PP) resins, whether used in compounds or “neat” (i.e. no fillers added), provide a prime example of these new solutions and frontiers.

Designers have been searching for ways to reduce the weight of a vehicle without sacrificing performance. The interior of a car is the perfect place to look at providing weight savings, with so many parts produced from PP:  instrument panels, door panels, pillars, quarter trim panels and lift gates.

Until then, click to view a video case study on Achieve Advanced PP8285E1. A large, global manufacturer highlighted the benefits of this new ICP including quality, consistency, overall performance, and reduced molding cycle times. The manufacturer also mentioned reducing weight and increasing impact resistance at low temperatures when using this material.

Brian Dujardin, Customer Application Development with ExxonMobil Product Solutions Company, has been with the company for 23 years. His experience includes OEM and supplier support, problem-solving, and process optimization; assembling multi-lot certifications for polypropylene and polyethylene materials; and injection molding prototyping, mold making, and production.

Portugal has a storied moldmaking tradition that dates back to the beginning of the 20th century, when companies in the town of Marinha Grande, about 95 miles north of Lisbon, started manufacturing molds for glassware rather than importing them. After World War II, plastic injection molds gained a foothold and, with the inevitable ups and downs, that has continued ever since. Automotive OEMs have been reliable customers; medical device manufacturers, not so much. Muroplás, located in Muro-Trofa, about 130 miles north of Marinha Grande, is the exception that proves the rule.

The US auto industry sold nearly 15 million cars and light trucks in 2020, according to Statistica. Imagine the improved vehicle efficiency if neat ICPs were used in all viable interior trim applications.

Muroplás is always attuned to the needs of its customers and continues to invest in the necessary resources to produce complex molds and optimize production, says Baptista, and that is the simple secret of its ongoing success. "R&D is an obsession at Muroplás," says Baptista. "We exist for our customers, and we are proud to have forged a relationship based on quality."

Portugal has a storied moldmaking tradition that dates back to the beginning of the 20th century, when companies in the town of Marinha Grande, about 95 miles north of Lisbon, started manufacturing molds for glassware rather than importing them. After World War II, plastic injection molds gained a foothold and, with the inevitable ups and downs, that has continued ever since. Automotive OEMs have been reliable customers; medical device manufacturers, not so much. Muroplás, located in Muro-Trofa, about 130 miles north of Marinha Grande, is the exception that proves the rule.

This is changing with the development of an ICP with greater ductility and an excellent balance of properties. Achieve™ Advanced PP8285E1 is enabling automakers to use neat ICPs in the interior of the car and take advantage of the lowest density materials in the market. This material was originally developed for use in PP compounds, but it is now finding opportunities in neat applications as automakers continue their push for weight savings.

Contrary to common belief, the major reason suppliers of injection molding services incorporate moldmaking and mold repair into their portfolio typically is not a matter of economics but delivery time, according to Delcam. Time and reputation is lost when a company has to wait for a mold to be repaired or parts shipment is delayed because molds have not been delivered within the planned timeframe. Being able to implement small changes or improvements to the mold on site also improves customer service, and intellectual property ceases to be an issue when molds are built in house, says the company.

Founded in 1989, Muroplás initially produced precision parts for the automotive industry. Shortly after setting up shop, however, "domestic companies that needed components for infusion systems challenged us to produce parts," says Dinis Baptista, International Sales/Information Systems. The company never looked back, and has been a national pioneer in plastic injection molding for medical device OEMs since the 1990s. Medical technology applications now represent 90% of the company's business, and it has cemented its reputation by investing in R&D and new technologies, and embracing change.

This new advanced ICP can help engineers design large, lighter-weight panels that perform well, and in a cost-effective manner versus compounded PP. Features include:

Unlike many molding companies in Portugal, which historically have tended to specialize in specific activities—tooling design, polishing, the fabrication of precision molds, and so forth—Muroplás chose to invest in its own machining department and build molds as well as provide injection molding services.

"We believe that combining the conception and manufacture of molds with injection molding of precision plastic parts offers our customers unique benefits," Dinis Baptista, International Sales/Information Systems, told PlasticsToday. "The use of high-speed machining technology and a dedication to improving the form, function, and manufacturability of molds has allowed us to provide medical device manufacturers with the best of both worlds: accuracy and precision at less cost," adds Baptista.

Lightweighting is an ongoing need in the automotive industry, and plastics continue to play a key role for innovations in internal combustion engine (ICE) vehicles as well as electric vehicles (EVs). Whether the goal is to improve ICE fuel economy or to extend EV range, reduction of vehicle weight is a key enabler.

Factors such as material performance, manufacturing/machinability, look-and-feel of the part, cost, and more all must be balanced to select the right material. Even though neat PP, as the lowest density option, provides the greatest weight savings, it hasn’t always been able to meet the demands of these more challenging applications. This has led designers to select compounded PP materials, typically with talc, which increases the density and therefore the weight of the part.

Consider how these attributes may finally open new applications for door panel lightweighting. Switching from a compounded PP for a 4-pound door panel on a sedan to this ICP would total around 1.5 pounds of weight savings per vehicle. That weight reduction becomes 150,000 pounds per 100,000 vehicles.

Editor in chief of PlasticsToday since 2015, Norbert Sparrow has more than 30 years of editorial experience in business-to-business media. He studied journalism at the Centre Universitaire d'Etudes du Journalisme in Strasbourg, France, where he earned a master's degree.

Using this same approach, many applications in the interior of the vehicle besides door panels can use neat ICP instead of compounded PP. This volume has been estimated at 65 pounds per vehicle based on a recent vehicle launch in North America. Using Achieve Advanced PP8285E1 instead of a compounded PP is saving the automaker approximately 5.5 pounds per vehicle.

Enhanced molding due to a higher melt index of thirty (i.e., melt-flow rate flow rate of 30 g/10 min) vs. the industry standard of twenty - this allows lower pressures, reducing injection molding machine tonnage requirements, and can reduce parting line flash for higher finished product quality

Automotive design engineers have achieved lightweighting success with polypropylene for decades, but large interior panels present ongoing challenges. A new PP impact copolymer from ExxonMobil with greater ductility, high flow, and scratch resistance presents a solution.

Higher ductility versus standard ICPs, which allows the door panel and interior trim parts to pass airbag deployment and other real-world impact testing performed by automakers

The company operates Class 7 cleanrooms on site for the production of infusion, transfusion, and hemodialysis kits. It runs Krauss Maffei and Negri Bossi molding systems in its 4500-sq-m production space. Muroplás also has developed an IT system to help maximize the production of precision parts for medical applications. One investment that has contributed to its success is the purchase early on of PowerMILL CAM software from Delcam plc (Birmingham, UK), which it has used to develop its own range of medical devices. Muroplás carries on a tradition, in fact: Back in 1983, a Portuguese company was the first European moldmaker to install CAD/CAM technology, according to industry association Cefamol.