The new generation of PP foam core material can be used for light truck trailer, RV

Several companies around the world have developed new grades of polypropylene (PP) foams designed to improve performance and reduce weight, mainly for injection molding interior parts in the automotive industry. Toray Industries (Japan) has also developed a new crosslinked PP foam core for helmet and buffering applications. But Spur's (Czech Republic) offering is quite different, aiming for sandwich structures using a fiber-reinforced composite skin - something most big plastics companies consider an ancillary or niche market.

According to Spur's business manager, we saw the need for lightweight, high-performance panels that are easy to recycle 5-6 years ago. Therefore, we began to develop what is now Hardex XPP (extruded polypropylene) closed cell foam core.

Is it really easy to recycle? Spur says it has been producing XPP foam for full PP lightweight panels for better shelter refugee housing. Waste from the manufacturing process is being uprecycled into other products at the plant, such as kitchen profiles and furniture side bands. But Spur says it's absolutely possible to recycle the entire panel, even with a fiber-reinforced shell, into extruded grade material, which the company is currently doing internally.

Big market for trucks and cars

Trucks and trailers are in great demand for lightweight materials. Spur has done a lot of testing of the XPP material on the floor and side walls of the truck trailer. More broadly, there is a huge demand in the automotive market for PP foam to replace PVC[polyvinyl chloride] and PET[polyethylene terephthalate] foam for single-material parts that are easier to recycle. Previously, these types of parts were glued together using several different types of materials, so they required separation and were difficult, making recycling more challenging and expensive. Using our materials, you can produce PP sandwich board, which contains PP sandwich board and Hardex XPP foam core, fused together by thermal bonding. Once this is done, you can shred the panel and remake it into an extruded material. That's what's being done now, so it's a proven technology.

By replacing the plywood in these floors with Hardex XPP foam, 300-400 kg can be reduced per truck trailer.

This approach is exactly what Spur is pursuing in truck trailers, where Hardex XPP is foam core and the skin is usually glass fiber reinforced PP. If the customer uses a heated dual tape press with cooling function to connect the outer skin to the core, they can produce these panels at a rate of 4 meters per minute. Currently, truck panels are produced very slowly, in which FRP(fiber-reinforced polymer) skins are bonded to foam and other core materials and vacuum formed, often taking hours to cure. Using the new XPP material, the system can be replaced by thermal laminating. This solution is a great opportunity for customers who are manufacturing panels and components to provide new solutions for the transportation industry.

Can foam core really withstand the abuse of truck trailer floors? So far, we are confident that the panels will resist the load on the truck floor and sidewalls, but this is something Spur is working on as part of various development projects. If more resistance is required, then the panel manufacturer can use another layer of glass /PP tape, or reinforce local areas.

But the main goal is to replace plywood, which is becoming harder to come by, more expensive, and heavy. By replacing plywood with Hardex XPP foam, 300-400 kg of weight can be reduced per truck trailer. And, at the end of their useful lives, these panels can be shredded, re-granulated and extruded from the recycled material to be used as side fairing or truck skirt panels. So this is a real opportunity to build a chain of circular products and processes for these transportation companies.

Another big opportunity is recreational vehicles (RVS). Again, we focused on the side walls and furniture, offering foam core panels that are significantly lighter in weight, non-absorbent and can be recycled into strips already used in RV upholstery and cabinets. We think this lighter furniture structure will also appeal to manufacturers of boats, yachts and other Marine vessels.

The unconventional, extruded PP

There are many types of PP foam, including: Expanded polypropylene (EPP), crosslinked polypropylene and extruded polypropylene foam, also abbreviated XPP. EPP is a low modulus granular foam, which you would see used in better quality bicycle helmets, for example. XPP is extruded foam, not crosslinked. This product is therefore very different from EPP and crosslinked PP because it is a special grade of polymer foam with both high mechanical properties and recyclability. Since the XPP began extensive development in 2017-18, Spur has also developed a unique technology to achieve higher performance than the standard.

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