New developments in materials, processes and machinery were introduced at an annual meeting of Association of Rotational Molders (ARM).
Nova Chemicals introduced an octane based HDPE copolymer with a balance of processability & stiffness, with 3.5 MFR and 0.941 density. In applications such as chemical and water tanks, cycle time is reduced by 10-15% as compared with a comparable 2 MFR grade. It can fill complex parts as well as a 5 MFR hexene copolymer. Very low catalyst residues are said to provide superior whiteness and easy demolding. Other applications include marine equipment and waste containers.
ICO Polymers has introduced the first crosslinkable semi-conductive PE compounds for rotomolding. It provides high flame resistance and toughness for demanding static-sensitive applications. Non-crosslinkable semi-conductive LLDPE that is stiffer than previous grades is another new compound developed by ICO Polymers.
A new nucleating agent from Milliken Chemicals is used in MDPE rotomolding grades. Already commercialized in packaging film, Hyperform HPN20E is said to provide faster cooling without warpage. The additive helps PE crystallize faster, reducing cooling time. The first commercial use is a rotomolded water tank in Latin America, which boasts a 30-40% productivity improvement.
New labeling approaches are emerging to help rotomolders meet growing customer demand for product traceability, name-brand recognition and decorative quality. The latest from New Zealand 's Polymer Systems International Ltd., is a new in-mold labeling (IML) system which eliminates many of the limitations associated with applying graphics to already molded parts. The olefin-based opaque label is compatible with PE and is placed manually in the mold, which can be at virtually any temperature. This enables molders to keep cycle times to a minimum by not requiring longer cooling times to bring molds within a low temperature range. No spray adhesive is required because the label carries its own. For applications where IML is not practical, the label can be rolled onto a reheated part in a post-mold operation.
Winners of the ARM parts competition included the Cosmo container, claimed to be the industry's first plastic collapsible container for the portable storage and moving market. The 700-lb, 8x5x8 ft PE container, developed by Nova Chemicals, collapses to less than one-third of its height when empty. The prototype design, slated for commercial production early this year, replaces wood and metal storage boxes.
Another innovative application was the industry's first rotomolded fence from SimTek Fence, Utah . The simulated rock privacy fence is designed to fill a gap between extruded PVC and real stone. It consists of foam-filled posts and rotomolded hollow panels that are steel-reinforced at the top and bottom. The 6x6 ft panels include 120 hidden kiss-offs for structural integrity. Tongue-and-groove assembly accommodates thermal expansion.