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Complete LFT lines

Coperion, based in Stuttgart, is partnering with fellow German company ProTec Polymer Processing of Bensheim to supply complete installations for the production of long fibre reinforced thermoplastics (LFTs). 

LFT components possess outstanding rigidity with low weight and increased impact resistance. Compared to short-fibre reinforced thermoplastics they also demonstrate improved mechanical and thermic material properties making them suitable for higher stress und more demanding applications.

The production of long fibre reinforced thermoplastics is carried out by pultrusion, with glass, carbon, metal or natural fibres are mixed into a polymer matrix. Through the pultrusion process, the individual fibres of the strands are impregnated for a homogenous bond of carrier polymer and individual fibre r. Melting of the polymers and mixing of additives takes place within the extruder. 


Coperion uses the ZSK Mc18 twin screw extruder or the STS Mc11. The ZSK Mc18 series is used for products with a high torque demand, such as engineering plastics or high-temperature applications, while the STS Mc11 series is used for standard plastics such as polypropylene and polyethylene.

Coperion K-Tron equipment is used for feeding, as it is particularly suitable for raw materials in powder form, including polymers additives and fillers. Following impregnation, the fibre-polymer strands are cooled in a water bath and subsequently pelletized to rod shaped pellets.  The pelletizer is equipped with a special chopping rotor for this task. The final pellet length is usually between 5-12 mm.

Whereas in the past, primarily polypropylene was used as the base polymer, there is now a clear trend toward other polymers such as PA, PEEK or PLA,. Line speeds are up to 50 metres per minute, depending on the polymer.  

The collaboration between Coperion and ProTec brings a number of advantages. The complete line is offered with optimised components to enable the highest quality LFT pellet manufacturing. Among these, along with the ZSK Mc18 or STS Mc11 twin screw extruder series, is a specially designed impregnation die head, developed by ProTec, which cannot clog with filler material.

In addition, roving unwinding with rotating coils and roving pre-warming with individual fibre spreading enable the best possible fibre impregnation.

The complete installation offers one further advantage – different polymers in combination with special additives can be used in the same production line.
Support and development of customer-specific formulations can take place at ProTec’s Testing Center in Bensheim in order to validate components manufactured with LFT pellets. Using twin screw technology and the special impregnation die head, it is also possible to use additional fillers and even regrind material.

The automotive industry is a typical area for the use for LFTs but this technology offers advantages for further application fields in which products are exposed to higher demands and stresses. Coperion and ProTec are currently working on their first joint client project in Europe.