Chemical company Sabic, headquartered in Riyadh, Saudi Arabia, recently launched a range of polypropylene (PP) compounds for foam injection molding (FIM). According to the company, its mineral-reinforced PPc F9005, PPc F9007 and PPc F9015 grades could help improve the aesthetics of visible automotive interior parts with complex geometries, such as door panels and trim, seat and trunk cladding, A/B/C/D pillar covers and center consoles.
Unlike mainstream FIM materials, which typically exhibit surface defects, the new PP compounds have a more uniformly high surface quality, similar to solid injection molded parts, the company says. Moreover, when compared to solid components, foamed parts made with the PP compounds can offer weight savings that could, in turn, help cut emissions. According to a cradle-to-grave life cycle assessment study carried out by Sabic, the advanced new materials can help OEMs lower carbon dioxide (CO2) emissions by as much as 15%.
“The automotive industry continues to look for new weight-out strategies that can advance energy efficiency and sustainability goals,” said Abdullah Al-Otaibi, general manager. “Although foam injection molding produces desirable lightweight parts, manufacturers have been forced to sacrifice aesthetics, until now. We applied our extensive expertise in foaming technology to develop these new compounds to help resolve the issue of surface quality and open new application opportunities for foamed parts.”
FIM aesthetics
Previously, the FIM process was essentially limited to non-visible parts, restricting its usefulness in automotive applications, the company explains. Foaming can underperform in surface aesthetics, and silver streaking, swirl lines and dimples are common defects. The PP compounds for foamed interior parts have low-gloss textured (grained) surfaces that help eliminate streaking and swirling. Talc filler in these grades acts as a nucleator that promotes the generation of finer bubbles, which contribute to a consistent surface appearance. For improved aesthetics, these grades are currently available in selected automotive interior colors with custom coloring also available, Sabic says.
Weight benefits
Weight reduction depends on several factors, including the type of FIM technique used. Short-shot molding, which uses the same tooling as an injection molded part, can reduce weight by up to 10%. The company’s PPc 9007 is formulated for short-shot FIM and low-impact applications. Core-back molding, which requires part redesign and new tooling, can lower weight by as much as 30%, and both Sabic PPc 9005 and PPc 9015 grades are formulated for core-back molding and deliver medium stiffness and impact.
The choice between the short-shot and core-back techniques, with their different tooling requirements, also helps to determine whether using FIM with Sabic PP compounds is cost neutral or could offer cost savings. Additional cost savings could be possible, such as cycle time reductions and flow improvements.
Another consideration is the foaming process, which can use chemical or physical agents. The PP compounds can be used with chemical blowing agents, which are typically preferred for visible foamed parts. These agents are introduced to the molding machine in the form of a masterbatch, along with the plastic pellets, and activate during the melt phase to release gases for foaming.
The PP compounds have launched in Europe, with upcoming availability in the Americas and Asia/Pacific.
Reinforced Plastics asked the company about how the automotive industry could develop over the next few years. “Sustainability and electrification are helping to drive change at an unprecedented pace,” a spokesperson said said. “FIM with Sabic materials can help in both areas – by reducing the CO2 footprint of component and vehicle production; and by reducing the weight of components and systems to support increased EV range.”
