Extrusion International 1-2026

30 Extrusion International 1/2026 EXTRUDER TECHNOLOGY – CASE STUDY Twin Screw Extruder Sets New Standards in Expandable Polystyrene Production NexKemia Petrochemicals Inc., a leading firm in manufacturing expandable polystyrene (EPS), has relied on ZSK twin screw extruders from Coperion since 2020. Focusing on innovative manufacturing processes and sustainability, NexKemia provides products for the packaging industry and as well as for building insulation. Along with white EPS, NexKemia also produces EPS mixed with graphite, known as GPS (polystyrene mixed with graphite-enhanced polystyrene), as well as products containing up to 30% recyclate. For manufacturing and product development, NexKemia uses Coperion ZSK twin screw extruders, which enable an environmentally friendly production and gentle product handling of white and gray EPS as well as the integration of recycled materials on a single production line. Twin screw technology simplifies production process Conventionally, white expand- able polystyrene (EPS) is manufac - tured discontinuously within the scope of suspension polymeriza- tion, whereby the monomer styrene is polymerized in a batch process. Alternatively, continuous manu- facturing processes exist whereby processing occurs with the feeding of additives and pentane in several successive process steps. Various combinations of twin screw extrud- ers, single screw extruders or static cooling mixers are used. Coperion, in contrast, offers a technology for manufacturing EPS in a very simple, single-step process, using the ZSK twin screw extruder. Particularly in the case of suspen- sion polymerization, the chemical balance during the reaction must be maintained, as even minimal im- purities or foreign materials can dis- rupt the balance and destabilize the process. As no reaction takes place in the extruder, but rather the sub- stances are mixed, this does not pose a challenge to this manufacturing process. All ingredients are fed into the Coperion ZSK extruder via high- accuracy Coperion K-Tron feeders and processed into a homogeneous mass using precisely modified shear introduction and short residence time. This ensures a low thermal stress upon the material. Micropellet manufacturing takes place in an un- derwater pelletizer following the ex- truder, generating very small pellets (≤ 1 mm) with a very narrow particle size distribution. Economical and sustainable manufacturing of innovative EPS products Along with the novelty of single- step EPS manufacturing, the ZSK extruder also enables production of graphite-enhanced polystyrene (GPS) as well as products containing recycled material. When manufac- turing GPS, free graphite, among other ingredients, is added to the product which reflects the heat ra - diation and thus offers higher heat insulation than white EPS. NexKe- mia's GPS products demonstrate a very low lambda value, represent- ing a lower heat conductivity and thus very good insulating capacity. NexKemia has succeeded, togeth- er with Coperion, in integrating re- cycled material into EPS manufac- turing – on just one production line. The purified and compacted regrind can be fed directly into the ZSK ex- truder. Depending upon quality re- quirements, micropellets, and avail- ability of the discharge material, recycling content of up to 30% or greater can be realized. The final Focusing on innovative manufacturing processes and sustainability, NexKemia provides products for the packaging industry and as well as for building insulation: white EPS, EPS mixed with graphite, as well as products containing up to 30% recyclate (Photos: NexKemia Petrochemicals Inc., Mansonville, Québec/Canada)