MATERIALS • PROCESSES
high-wear, abrasion and impact applications: cast polyurethanes. Cast polyurethanes, also broadly referred to as
A
urethanes, are tough, elastic materials that combine many of the performance advantages of high-tech plastics, metals and ceramics along with the resiliency and flexibility of rubber parts. Unlike their closest counterpart, rubber, which is
prepared as sheets or loaves before being moulded in a high-pressure press, urethanes can be poured as a liquid mixture into less expensive, low pressure moulds. Using this technique, complex mould cavities can be filled without high-pressure moulds and presses. This provides a multitude of advantages, not least of which are lower tooling and production costs than both rubber and plastic moulding, and lower material cost than metals and ceramics. In terms of performance, cast polyurethane parts
are often lighter in weight than ceramics or metal alternatives and are not brittle and will not crack like plastics under stress or extreme temperatures. Cast polyurethane parts are not new. Nonetheless,
awareness of the potential for this type of material has largely remained under the radar. This can be attributed to several factors, the primary one being a general lack of understanding of the options and formulations. One does not simply specify a polyurethane part,
for example. There are many formulations – some proprietary – that can be used to manipulate a range of variables such as hardness, resilience, spring rate and chemical resistance. For this reason, design engineers interested in a possible switch to polyurethane from plastics, steel, ceramic or rubber parts are often best served by seeking out the assistance and guidance of experts in urethane formulation.
Double L Global uses proprietary urethane for a component designed to sweep product off a conveyor path
CUSTOMISED PARTS IN ACTION In a recent case study that showcases the merits of these parts, when a Dutch ship-builder required a new slipway liner that could absorb the impact and abrasion of a speedboat exiting and entering its offshore patrol vessel through a rear bay, it selected a specially formulated polyurethane from Argonics, one of the USA’s largest producers of wear-resistant urethane products. The urethane liner replaced a nylon plastic liner,
which tended to damage speedboats because it was too hard, according to Lars Muller, owner of Muller- Beltex, a Netherland-based parts distributor to various industries, who was involved with the project. “The liner had to resist impact, abrasion, seawater and UV exposure yet allow the speedboat to slide in and out of
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lthough design engineers have traditionally specified parts made of rubber, plastic or steel when durability is required, many are now considering an alternative for the most demanding,
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