KP-Sheet is a stampable sheet made of glass fiber and polypropylene and has distinct characteristics of expansion in thickness. For the development of lightweight and high stiffness KP-Sheet, glass fiber content and glass fiber arrangement in thickness direction were studied in order to increase the expansivity. Although the expansivity increased with an increase of glass fiber content and the elastic slope was enhanced due to an increase in the thickness, the value of the maximum elastic slope was saturated at over 50 mass% of the glass fiber content. By controlling the glass fiber arrangement in the thickness direction, the spring back of glass fibers was enhanced and the expansivity increased more than 30% at the same unit weight. A newly developed UL-grade improved the elastic slope, which was enhanced to 7.2 N/mm at a unit weight of web 800 g/m2 and is able to reduce further the weight of the parts while holding superior moldability and dimensional stability equal to those of the normal grade.
