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The rotomolding process is normally associated with linear low and medium density grades of polyethylene. New polypropylene (PP) micropelletizaton technology developed by compounding company HD Kunststoffe & Kunststofferzeugnisse and rotomolding grades of PP offered by Total Petrochemicals (07.2/D08), however, have opened up potential for penetration of PP into this application, bringing numerous benefits to boot.

October 21, 2013

1 Min Read
K 2013: PP makes a play in rotomolding

"Traditionally, rotomolders wanting to process PP had to resort to powder grades prepared through cryogenic grinding," says Veerle Naets, Business Manager Technical Parts, Durables, Consumer Goods at Total. "This generally meant that PP powders were prohibitively expensive, costing EUR50-55 per kilogram versus EUR18-20 for PE powders." To reduce material pricing to an acceptable level of EUR25-30 per kilogram, Total turned to the micropelletizaton process developed by HD Kunststoffe. The microgranules  have been manufactured since 2o12 in Remscheid, Germany and sold under the HD eco-tech brand. These materials are based on Total's Lumicene impact copolymer impact modified grades.

"Rotomolding with PP enables the excellent surface aspects of PP to come to the fore, such as gloss, brilliance, scratch resistance, and feel," says Naets. "There are also benefits to be had in terms of chemical resistance."

According to HD Kunststoffe, microgranules also offer opportunities for weight reduction through optimization of wall thickness (30-40% less material), while an extremely high impact strength of >64 kJ/m2 at 23°C is attainable. Heat resistance is up to 148°C.

Recent applications of PP rotomolding grades include a chemical container, the waste water tank of a floor cleaner, a kayak, a manhole, a hydraulic tank, a glycol tank, and automotive air duct, and a condenser hood for a heat exchanger. This latter part was processed on one arm a two-arm rotomolding machine, wish an analogous PE part processed on the other arm under the same conditions.

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