The moisture sorption analysis was carried out for two kinds of Kevlar fiber, Kevlar 49 and Kevlar 149, which are well-known as high strength/high-modulus aramide fiber. The moisture regain (g-water/g-dry fiber) for Kevlar 149 was about 1% at 65% relative humidity at 30°C, and was fairly lower than that of Kevlar 49. The properties of the water sorbed in the two fibers were also characterized in terms of the calorimetric quantities.
　Although the heat of wetting for Kevlar 149 was less than half of that for Kevlar 49, the differential heat of moisture sorption (enthalpy difference compared with the liquid water) was not so different. These findings are considered as the important problem for the fiber-reinforced plastics (FRP) used in the sporting goods in light of the security, because the interfacial failure between the fiber and the matrix can be caused by the water invading into cracks of FRP, of any.

DESCENTE SPORTS SCIENCE Vol.11/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE