A special lead core for fine-core mechanical pencils, featuring high flexural strength and good writing performance. It mainly uses synthetic resin as the lead core binder, commonly used are polyvinyl alcohol, asphalt, furan resin, polyvinyl chloride, ABC resin, vinyl chloride-vinyl acetate copolymer, etc.; graphite as the lead core colorant;
Commonly used solvents are water, ethanol, etc.; dioctyl phthalate, tricresyl phosphate, etc. are often used as plasticizers to reduce the flow viscosity of resin at high temperature and improve molding performance; lead stearate is often used. It is a stabilizer to prevent resin aging and inhibit the oxidation process; liquid paraffin, low molecular polyethylene, etc. are used as lubricants to improve the flow properties of resin melt.
The manufacture of resin fine lead core is under the protection of inert gas (such as argon) or under sealing conditions, and it is calcined and carbonized at high temperature to form a graphitized structure, so that it has higher mechanical strength and better writing performance.