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Several trends are strongly influencing appliance design today, and though diverse, these trends share something in common: they can be leveraged using thermoplastic elastomers (TPEs).
These versatile elastomeric materials combine the functionality and performance of thermoset rubber with the processability and design freedom of thermoplastics. TPEs are being used to solve a range of design challenges thanks to their colorability, soft-touch feel, broad range of hardnesses, ability to be overmolded (bonded) to other materials, processing versatility, and the ability to be formulated using “green” components.
Today’s appliance designers must create new products that are more environmentally responsible, that meet the needs of an aging and fragile population, and that provide new color and aesthetic choices. TPEs can make it easier to accomplish all of these design objectives.
Environmental MandatesOne of the major environmental challenges for appliances is end-of-life disposal-in particular, keeping these items out of overtaxed landfills. While recycling appliances is a desirable solution, the practical aspects can be daunting due to the wide variety of materials used and disparities in their recyclability. Disassembly can be cost-prohibitive and complicated. TPEs can help solve this problem.
For applications requiring bonding or overmolding of a TPE onto an engineering resin, elastomeric grades can be developed with exceptional compatibility to the engineering resin. As a result, the two materials do not have to be separated prior to being recycled or repurposed. This can simplify the disposal process by lowering the need to disassemble or remove the TPE from the engineering resin.
Often, TPEs can replace thermoset materials that cannot be recycled, helping to make an appliance more sustainable. For example, a wet-vacuum cleaner made by Vacman Internacional in Mexico uses five different seals made from a recyclable styrenic block copolymer (TPE-S) instead of vulcanized neoprene rubber, which is not recyclable. The elastomer also delivers excellent sealing properties and mechanical strength, ease of processing and greater design freedom.
Another important environmental benefit of select TPEs is the ability to be formulated without the use of hazardous substances, such as halogens that are restricted by current legislation, including the European Union Restriction of Hazardous Substances (RoHS) directive. Gaskets, seals, wiring and other appliance parts made from these TPEs also are easier to recycle than components made from traditional materials because they do not require special handling at end of life.
For example, halogen-free, flame-retardant TPEs based on styrene-ethylene butylene-styrene (SEBS) technology can help appliance makers meet current and upcoming environmental regulations. They can replace traditional halogen-containing vinyl materials used in cable jacketing and insulation to support regulatory compliance and promote recyclability.
There are even new halogen-free TPE grades formulated without phthalates that address an increasing concern among consumers and environmentalists. Applications capable of utilizing these elastomers include internal power distribution and electrical cords.
Ergonomic Design for an Aging PopulationIt is no secret that the U.S. population is aging and that demographic is having a profound impact on all types of consumer goods. Designers are rushing to modify products or create new ones that meet the needs of older people-many with chronic conditions such as arthritis or osteoporosis. Ease of use, comfort and safety-which are so important to older or disabled individuals-are key benefits of designing appliances with TPEs.
Ergonomic designs for handles, knobs and buttons can benefit significantly from the use of TPEs. These soft, tactile materials offer a high coefficient of friction that creates a confident, “grippy” feel when overmolded onto appliance handles, controls and other parts that must be grasped firmly by the user. People with arthritis and other conditions benefit in two ways: less force is required to manipulate a part covered with these materials and greater comfort is provided from its soft cushioning.
TPEs can be overmolded onto critical surfaces with a wide variety of geometries and configurations to provide this combination of grip and softness. There are high-flow, low-viscosity grades available that support overmolding of thin, yet durable layers. For example, closures for over-the-counter medications are currently using a layer of TPE to make it easier for seniors to open and securely reclose the bottle.
Importantly, TPEs retain their grip, feel, and other desirable properties even after repeated exposure to hot water and detergents. Overall, TPEs can deliver long service life without performance degradation.
New Aesthetics for Consumer AppealThe days of white-only washers, ranges and refrigerators are long gone. Consumers enjoy a wide choice of colors, textures and effects in both large and small appliances. In today’s market, where aesthetics are now a critical differentiator, TPEs can add significant value to design, thanks to their ability to be easily colored and molded with different textures.
For example, elastomers can provide unique surfaces ranging from silky to ribbed to gel-soft to meet different usage needs. Special color effects can include metallics, pearlescents, thermochromics (heat- activated effects) and geometric metamerism, an effect that changes depending upon the viewing angle.
TPEs can be formulated to have water-white clarity that makes special effects and tints stand out. For example, a clear TPE overmolded onto a patterned or colored substrate can create visual depth. TPEs also deliver outstanding color consistency.
Designers can use elastomers to match or contrast with substrate materials on grips and handles, creating unique effects for product differentiation and helping consumers to see functional parts more easily.
TPEs for AppliancesBecause TPEs are available in a wide range of formulations and hardnesses, they are appropriate for a variety of appliance components, including:
Ice cube dispenser components
TPEs can be injection molded, overmolded (two-component injection molding), extruded, coextruded, blow molded and thermoformed. The ability to be overmolded or coextruded with an underlying rigid product provides a secure bonded interface between the elastomer and the rigid substrate. Eliminating a mechanical interlock design can help ensure final product consistency and enhance product quality as a result. Applications that can benefit from this quality are door seals, drawer stops and handle grips.
Design ImplicationsAppliance designers need to be more knowledgeable than ever about the materials that are selected for their products-particularly about how they can support and enhance sustainability. It’s important to look beyond product creation and everyday use to the full life cycle of the appliance. Materials that provide longer useful life, avoid hazardous substances and are easily recycled, can make a significant environmental impact.
TPEs can play a key role in a sustainability strategy, while also giving designers greater flexibility to innovate and provide aesthetic differentiation.