The pencil lead we usually use is made of graphite. What are the characteristics of graphite? Urgent! ! ! ! ! ! ! ! ! ! ! !

1. lubricity: the lubricity of graphite depends on the size of graphite flake. The larger the flake, the smaller the friction coefficient and the better the lubricity.

2. Chemical stability: Graphite has good chemical stability at room temperature, and can resist the corrosion of acid, alkali and organic solvents.

3. Plasticity: graphite has good toughness and can be ground into thin slices.

Pencil lead produced by different clay proportions in graphite has different hardness and color. This is the origin of H (rigid pencil), B (soft pencil) and HB (pencil with moderate hardness) marked on pencils today. The higher the hardness, the less graphite content.

use

The pen core made of graphite or colored clay is used as a writing medium and as a writing or painting tool for study, office work, engineering drawing, art, painting, various marks, etc.

The raw materials and auxiliary materials of graphite lead core are graphite and clay. Graphite is used as a colorant. Using the lubricity and plasticity of lead core, you can draw black marks, stick them firmly on paper and erase them with rubber. Graphite with high carbon content and fine particles should be selected. Clay is a binder, and graphite particles are bonded together by its plasticity and cohesiveness. Clay with good plasticity, low iron content and wide sintering range is needed. Auxiliary materials include molding materials and materials that change the properties of lead cores. Molding materials are used to improve plasticity and adhesion, and improve the formability of lead cores. Commonly used are maltose, tragacanth and so on. The material that change that properties of the lead core are use for oil immersion treatment of the sintered lead core to improve the physical properties of the lead core (such as wear, concentration, stress at the core tip, smoothness, hardness, etc.). ). Commonly used are paraffin, cattle and sheep oil, vaseline, etc. , usually two or more are used together. The raw materials of colored lead core are pigment, physical raw materials, adhesive, grease and wax. Pigments (including pigments and dyes) play a coloring role, which requires good coloring power, high hiding power, soft texture, high fineness, good heat resistance and non-toxicity. Commonly used are titanium dioxide, carbon black, phthalocyanine blue and so on. Physical raw materials play the role of bonding, skeleton and hardness adjustment.