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Polyurethane flexible foams have been widely used for automotive seat cushions because of the cushioning performance. It has been required so far to reduce the density of seat cushion foam. However improving the riding comfort of seat cushions is also considered important. In seating design, most foam properties specified by the design engineer are based upon static testing properties. However, the in-service mode of an automotive seat is dynamic rather than static. Therefore the dynamic properties are of greater importance for the comfort performance of a seat than such static properties as indentation force deflection (IFD), density, or ball rebound. The purpose of this paper is to show the systematic research results of polyurethane foam comfort properties. [1, 2, 3, and 4].

Polyurethane flexible foams have been widely used for automotive seat cushions because of the cushioning performance. It has been required so far to improve the polyurethane foam’s performances such as reducing the density and improving the static, dynamic vibration properties. Additionally, improving the functional properties such as antimicrobial properties are also considered important these days. In this article, new antimicrobial polyurethane foams for automotive seat with urushiol or cardanol extracted from a natural lacquer were prepared. Influences of agent’s concentration on the reactivity between polyol and isocyanate, mechanical properties of foams were investigated. It was observed that the urethane formation reaction was delayed a little when the amount of agent was increased. However, it was found that the mechanical properties of antimicrobial foams made using agent were similar to those of the neat polyurethane foam.

Polylactide (PLA), which is one of the most important biocompatible polyesters that are derived from annually renewable biomass such as corn and sugar beets, has attracted much attention for automotive parts application. The manufacturing method of PLA is the ring-opening polymerization of the dimeric cyclic ester of lactic acid, lactide. For the PLA composites including stereocomplexed with L- and D-PLA, we developed the unit processes such as fermentation, separation, lactide conversion, and polymerization. We investigated D-lactic acid fermentation with a view to obtaining the strains capable of producing D-lactic acid, and through catalyst screening test for polycondensation and depolymerization reactions, we got a new method which shortens the whole reaction time of lactide synthesis step. Poly(d-lactide) is obtained from the ring-opening polymerization of d-lactide. Also we investigated several catalysts and polymerization conditions.

Fatigue behavior of two types of automotive steel, quenched and tempered SUJ2 and carburized SCM820PRH, which are applied as powertrain parts are studied. These two types of steel are different in their hardness distribution from surface to core. The hardness of quenched and tempered SUJ2 is homogenous, in contrast to that of carburized SCM820PRH (SCM) which decreases from surface to core. These steels are investigated in terms of their monotonic tensile properties and fatigue behavior. A number of predictive methods were used to describe the fatigue behavior of these steels. A simple predictive method is based on approximation of S-N curve from ultimate tensile strength. The well-known Murakami’s defect area method was also applied for the prediction of the high cycle fatigue strength.