IntroductionIn the United States the principal market for molded, flexible urethane foam is the transportation industry, with a major share being consumed by automotive seating applications. The development of molded, high resiliency foam technology coincided with a major investment by automotive manufacturers in new seating designs. This marked change in the design and construction of automotive seats resulted in a significant increase in the amount of flexible foam required per cushion.[1 ] High resiliency flexible foam has become synonymous with a quality seating material. These foams possess outstanding cushioning and resiliency properties normally associated with good latex rubber foam.[2] The use of polyether polyols with increased reactivity provides several processing advantages for high resiliency foams. Because molded foams cure much faster than that attained with earlier systems based on less reactive polyols, a substantial savings in time and energy is realized.The processing characteristics, as well as physical properties, of molded, high resiliency foams are substantially improved by the use of polymer-polyols. [3] This specialty class of polyols allows for precise control of foam load-bearing properties over a wide range, which is necessary for the requirements of various automotive seating applications. This increase in foam load-bearing occurs without substantial alteration of other physical properties related to comfort, durability and low temperature flexibility. In addition, the demold and handling characteristics of these foams are improved dramatically by the unique ability of polymer-polyols to provide a more open and breathable product.Earlier work has shown that the load-bearing properties of high resiliency foam can be altered by various formulating techniques. [3, 41 In these studies it is demonstrated how the combination of both formulating and mechanical processing tech-niques can be utilized to broaden the range of foam hardness. Formulating and mechanical changes, which affected the load-bearing properties of high resiliency foams were also evaluated with regard to the crushing and breathability characteristics of cushions at demold.
ExperimentalMolded, high resiliency, flexible foams were prepared with standard laboratory formulation techniques. Test samples were produced in a 15&dquo; X 15&dquo; X 4-3/4&dquo; aluminum mold with either 1 /4&dquo; or 1/16&dquo; vent holes depending upon the degree of &dquo;packing&dquo; needed. The mold was preheated to 120°F, tightly clamped after introduction of the foam ingredients, allowed to remain at ambient conditions for two minutes and finally, to minimize heat losses, was placed in an air-convection oven at 250°F for six minutes. Molded foam samples made specifically for physical property evaluations were crushed twice immediately upon demold and allowed to cure for seven days at controlled ambient conditions. Physical properties were determined in accordance with ASTM D-2406-73, &dquo;Standard Methods of Testing Molded Flexible Urethane ...
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