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By using low-pressure gas-phase catalysis technology, two new high-density polyethylene (HDPE) grades reportedly provide improved cold-temperature impact and environmental stress cracking resistance for custom rotational molders.

PlasticsToday Staff

September 1, 2009

2 Min Read
Two HDPE rotomolding grades launched

By using low-pressure gas-phase catalysis technology, two new high-density polyethylene (HDPE) grades reportedly provide improved cold-temperature impact and environmental stress cracking resistance for custom rotational molders. Lupolen GX 5002 and Lupolen GX 5003 from LyondellBasell Industries (Rotterdam, Netherlands) utilize that company’s Lupotech G technology to produce HDPE grades suitable for industrial storage tanks, containers, intermediate bulk containers, furniture, and playground and sporting equipment. The company says the materials offer a good balance of impact resistance and stiffness, with low-temperature impact performance down to -30°C, allowing its use in applications that must withstand harsh transport conditions in cold weather. In terms of environmental stress-cracking resistance, LyondellBasell reports that Full Notch Creep Test (FNCT) results showed that Lupolen GX 5002 resins outperformed competitive resins and maintained mechanical properties, with a relatively high melt-flow rate (MFR) of 7.5 g/10 min. The MFR gives the materials design flexibility for more complex applications like containers, crates, marine equipment, outdoor furniture, and leisure and playground equipment.

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Rotomolder Promens applied LyondellBasell’s new Lupolen HDPE grades, with high melt flow rates and good impact resistance, for this storage container.

In a release, Cees Besems, technical manager of industrial packaging for LyondellBasell, said it is important to balance the melt-flow rate against mechanical properties, pointing out that typically, high melt flow and cold-temperature impact can be mutually exclusive. By optimizing each without detriment to the other, LyondellBasell says higher melt-flow rate and improved stiffness could enable converters to tackle thin-wall design and lightweight part requirements. In addition, the increased density combined with a high environmental stress-cracking resistance can boost the creep resistance, which is important for large rotomolded containers and tank applications that are exposed to internal pressure during storage. The company also states that Lupolen grades have a wide processing window, with cooking time—one of the determining factors of cycle time in rotomolding technology—being shorter, and thereby reducing the overall cycle.

LyondellBasell’s existing rotomolding offerings include the range of Microthene HDPE, low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE) powders, as well as Petrothene HDPE and LLDPE resin pellets. The Microthene HDPE comes in three grades ranging in density from .942 to .945 with melt indexes from 1.7 to 5.0. —[email protected]

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