Abstract: Thermoplastic synthetic resin pen nib is disclosed, which may suitably be employed in writing instruments for fine lettering or for drawing fine lines. The pen nib is formed of thermoplastic crystalline synthetic resin, e.g. polyethylene terephthalate resin, whose molecules are in a specific mixed cystallization structure obtained by controlling the crystallization. This structure consists essentially of molecularly oriented crystals, non-oriented fine crystals dispersed and grown between the oriented crystals, and remaining amorphous regions, and provides the pen nib with highly improved physical and chemical properties.

Abstract: Method of manufacturing synthetic resin pen nibs is disclosed, which pen nibs may suitably be employed in writing instruments for fine lettering or drawing fine lines. The pen nibs are formed of thermoplastic crystalline synthetic resin, e.g. polyethylene terephthalate resin, which is extruded from a molding die and subjected to rapid cooling to form a continuous rod in amorphous state. The rod is axially stretched under predetermined temperature condition to achieve oriented crystallization of the resin molecules, and is further heat-treated such that non-oriented fine crystals are dispersed and grown between oriented crystals and remaining amorphous regions. Pen nib thus obtained has highly improved physical and chemical properties.