Abstract: There is provided a process for producing a multi-layer molded product having a plurality of thermoplastic resin layers. This process provides for (i) a step of supplying first and second molten thermoplastic resins each through first and second resin supplying gates which are temperature-controllable independently of each other, to between female and male molds kept in an open state with a time difference being provided between supply starts of the first and second resins, and (ii) a step of closing the female and male molds after completion of supply of the first and second resins. The process enables production of high-quality multi-layer molded products having a plurality of resin layers with good repeatability under relatively low resin supply pressure and by single mold closing. Further, high-quality multi-layer molded products can readily be produced without restrictions on materials used.

Abstract: A drive shaft made of fiber-reinforced plastics comprising a pipe made of fiber-reinforced plastics to which a fitting is connected, in which a connecting portion of the pipe and a connecting portion of the fitting engage each other through bite of serrations formed on the inner or outer surface of the connecting portion of the fitting into the connecting portion of the pipe, with the space between the pipe and the fitting at the biting sites being filled with an adhesive.

Abstract: Inorganic fiber such as carbon fiber is modified by a surface treatment with a dinitrodiamine compound represented by the formula of ##STR1## wherein X is a divalent aliphatic, alicyclic or aromatic group which may contain halogen or oxygen in the group, R.sup.1 is hydrogen, an aliphatic group, an alicyclic group or an aromatic group, with the proviso that two nitrogen atoms linking through X may further link through R.sup.1 when both X and R.sup.1 are the aliphatic groups, and R.sup.2 and R.sup.3 independently of one another are each hydrogen or an alkyl of 1 to 12 carbon atoms, with the proviso that R.sup.2 and R.sup.3 may conjointly form a ring. The inorganic fiber thus modified is useful for reinforcement of resins.

Abstract: A drive shaft made of fiber reinforced plastic includes pipe made of fiber reinforced plastic to which a fitting is connected. A connecting portion of the fiber-reinforced resin-made pipe and a connecting portion of the fitting engage each other through the bite of serrations formed on the outer side or inner side of the fitting, with a film, e.g., a metallic foil, being interposed therebetween.