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Machinery and equipment | products Comac reports long-fibre progress

Comac of Italy has expanded its range of equipment for producing glass-reinforced compounds and has reported successes with its existing lines. It now offers a conversion

kit for its conventional twin-screw compounding lines that allows them to also produce long-glass-fibre (LGF) pellets starting from continu- ous filament glass rovings. These are fed from bobbins in a special head. The resulting pellets

typically have a glass content of 20 to 60% and are usually cut to a length of 0.5” (12 mm) for use in injection moulding applications. Pellets with 20 to 40 % glass loadings are intended for direct use, while 60 % glass material is usually used as a masterbatch to be diluted with unreinforced polymer. In addition to the special head, the conversion kit includes the other necessary upstream and downstream equipment. When the kit is removed, the same line can also be used to produce traditional glass fibre rein- forced compounds with chopped strand fed through a side feeder. “This technology provides

compounders with lines capable of making either traditional compounded pellets with chopped fibres or LGF pellets,” says Alberto Lorioli, export manager at Comac. Comac also produces

dedicated co-rotating twin- screw extrusion lines using direct-long-fibre technology (D-LFT) to produce long- fibre-reinforced sheets for

Comac’s D-LFT lines make sheets reinforced with fibres fed into the barrel as continuous rovings

compression moulding. The fibres are supplied in the form of continuous glass filament rovings and are compounded and extruded with the resin, which is typically PP. The long-glass loading in the finished product is usually between 15 and 40%. Lorioli sees growing

demand for D-LFT lines. Comac has installed such equipment in Italy and other countries over the past few years. In January 2012 it started up a new D-LFT line at a Chinese plant owned by the Korean group Hanwha to

produce PP sheet with LGF contents ranging from 15-40%. In a D-LFT line, glass

filament rovings are fed at suitable points along the barrel and are chopped and blended by the screws. The resulting compound is extruded into a sheet, cut into desired lengths and laid on a belt conveyer that carries the sheet to a press for final forming. The process pre- serves fibre length better than conventional compounds that start from chopped strands. Although there is growing

interest in long-fibre technolo-

gies, the majority of the lines that Comac has sold for glass-reinforced compounds still use chopped strands and the company reports continued strong demand in this area. These applications are primarily based on PA6 or PA66, typically with up to 50% glass fibre loading, or based on polyolefins, which typically contain up to 35-40% glass fibre. Some of the chopped

strand lines are used to process reclaimed PA from fibre and filament waste. ❙

In a separate move, Comac has rolled out its new barrel design, which was first seen at K 2010, as standard equipment on all its extruders. Lorioli says a key advantage of the new design is faster maintenance because the barrel sleeves can be changed without tools and with reduced handling of heavy parts. In addition, the modules have built-in alignment for easy reassem- bling. The new design also offers more accurate thermo-regulation because the

temperature probes are positioned very close to the inner surface that is in contact with the material being processed.


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