RESEARCH | ODOUR AND EMISSIONS
Research work carried out in Spain and the UK is addressing the challenge of removing odour using modified compounding processes. Peter Mapleston learns more
Identification and process key to eliminating odour
Unwanted odours and emissions can be a chal- lenge in all compounding applications, but especially so when handling recycled feedstocks. Identifying the presence of a bad odour can be pretty easy; understanding how and why such a volatile component is present and developing an appropriate processing solution to reduce or eliminate it can be a lot more difficult. “Besides screw profile, melt sealing, applied
vacuum, and machine-related topics, sometimes we don’t know if we generate volatiles because of high temperatures or we don’t remove them because of low temperatures, but the result is the same: a high level of volatiles in our compound,” says Luis Roca, leader of Compounding at Spanish research organisation Aimplas. “Understanding the origin of volatiles is key to designing an appropri- ate set up for devolatilisation.” To evaluate at which temperatures and what vola-
tiles are released Aimplas uses coupled FTIR-ther- mogravimetry, a technique that allows the identifi- cation of gases released directly from the sample during a thermal treatment. This simulates behav- iour within the extruder and gives references on what melt temperatures should not be exceeded.
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The use of recycled plastics in the automotive industry has been always a challenge, says Roca. Problems with obtaining the right mechanical prop- erties, colours, rheology, together with issues over volatiles and odours have been traditionally put the brakes on growth. But circular economy policies and new consumer perceptions over environmen- tal issues mean the foot is coming off the pedal. Roca highlights various examples of recycled plastics being used by major OEMs: wheel covers (Chrysler), bumpers (Honda, Ford, Nissan), and radiator covers (General Motors). But there are very few examples in interior applications – he cites seat cushions made from recycled polyurethane foam (Chrysler) and fibres for upholstery (Ford, Nissan). “The main reason is that OEMs have strict
restrictions on the quality of materials used in the vehicle interior. Most of the published standards refer to virgin materials and the requirements are the same for virgin and recycled materials,” he says.
Recycling methodology To address this, Aimplas has developed a methodol- ogy to improve the recyclability and recovery of PP waste for incorporation into interior components,
March 2022 | COMPOUNDING WORLD 67
Main image: Removing volatile odour components from recycled plastics is key to upcycling in automotive interior parts
IMAGE: SHUTTERSTOCK
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