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issue: April 2005 APPLIANCE Magazine
Designing with Plastics
Improving Dryer Longevity |
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To improve the performance of its compact clothes dryer, Electrolux turned to Santoprene™ rubber from Advanced Elastomer Systems, an affiliate of ExxonMobil Chemical Company. |
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By constructing its dryer roller with Santoprene™ 8201-80HT, a non-hygroscopic vulcanizate (TPV) rubber, Electrolux was able to improve the durability of its compact tumble dryer.
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The Santoprene rubber 8201-80HT is said to provide both the stability and flexibility required to keep the dryer drum in line and quietly rotating. The material is a soft, colorable, non-hygroscopic vulcanizate (TPV) in the thermoplastic elastomer (TPE) family that is said to offer enhanced tensile, tear, and abrasion properties, along with improved processability and finished part appearance. For these and other reasons, Electrolux decided to construct its dryer roller with the rubber. Installed in the front of the dryer cabinet, the 17-mm diam roller supports the drum axle in the horizontal axis while keeping the rotation of the drum smooth.
Material Benefits
Prior to the change, a urethane material was used to form the roller’s outside ring. The change came when Electrolux wanted to increase the life of the component and reduce part cost. The Santoprene 8201-80HT rubber also proved to have a better balance of abrasion and compression set.
Luigi Arreghini, Electrolux tumble dryer manager, explains: “The core of the part is a metal insert consisting of a sleeve for the axle inside a ball bearing collar. Surrounding this is a ring of glass-filled polypropylene with the soft envelope made now using the Santoprene rubber material. A two shot process is used, which is greatly aided by the Santoprene rubber material’s ability to adhere to the polypropylene.”
When he embarked on re-designing the part, Mr. Arreghini brought in Santoprene rubber experts for material analysis, prototype development, mold design assistance, and to evaluate the rate of return. “They quickly pinpointed how the life of the part could be extended by analyzing the component and the materials. And then made suggestions for improvements, including materials and the process,” he notes.
According to Mr. Arreghini, Electrolux decided on injection molding for the dryer project. “Injection has allowed us to greatly improve the cycle time and also use a multi-cavity mold, which reduced part assembly time and cost,” he explains.
Santoprene rubber was chosen because it adheres well to the polypropylene section, Mr. Arreghini continues. The rubber material is also said to provide the dryer roller with compression resistance, excellent mechanical properties, and the required resilience and flexibility that promote quiet operation.
Most importantly, Mr. Arreghini knew that the polyurethane was prone to compression set, and he wanted to make sure the roller would operate for more than the average life of a dryer. “[Santoprene] provides a good cushioning agent that can stand up to long-term use, even when enveloped in hot dry heat from this home appliance,” Mr. Arreghini explains. According to ExxonMobil Chemical, accelerated life testing at the Santoprene rubber laboratory rated the use life of the dryer part at more than the 5,000 hr specified by Electrolux.
In the end, Mr. Arreghini not only improved the life of Electrolux’s dryer, but ended up with several other benefits as well. “Working with the Santoprene rubber technical experts saved us money, gave us a quieter machine, and we ended up with parts that are less expensive, can be made faster, and have a longer life,” he says.
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