When selecting graphite materials, two popular types are extruded graphite y molded graphite. While both are synthetic graphites, they differ significantly in terms of manufacturing process, grain size, propiedades mecánicas, and common applications.
Both are types of synthetic graphite made from petroleum coke and coal tar pitch binder, but their manufacturing processes lead to significant differences in structure, properties, y aplicaciones.
Difference between extruded graphite and molded graphite
1. Manufacturing Process:
Extruded Graphite:
Proceso de: A mixture of calcined petroleum coke (filler) and coal tar pitch (aglutinante) is heated to make it plastic. This hot, semi-solid mix is then forced (extruded) through a die with a specific cross-sectional shape (p.ej., round, square, rectangular). Think of it like squeezing toothpaste from a tube or extruding aluminum profiles.
Result: Produces long, continuous shapes like rods, blocks, or tubes.
Molded Graphite:
Proceso de: The coke and pitch mixture (often using finer coke particles than extrusion) is placed into a mold cavity. High pressure is then applied to compact the material into the desired shape. This pressure can be:
Uniaxial/Biaxial: Applied from one or two directions (like pressing powder in a die).
Isostatic (Isotropic): Applied uniformly from all directions, typically using hydrostatic pressure (fluid pressure in a chamber). This is often referred to as “iso-molded” o “isostatically pressed” graphite.
Result: Produces discrete parts or blocks within the confines of the mold. Isostatic molding creates billets that are then machined.
2. Grain Structure and Isotropy:
Extruded Graphite:
Estructura: The extrusion process tends to align the graphite particles (coke grains) parallel to the direction of extrusion.
Isotropy: This alignment makes the graphite anisotropic. Its properties (like strength, thermal conductivity, electrical resistivity) are different when measured parallel versus perpendicular to the extrusion direction (Introducción de las ventajas de rendimiento de la máquina para fabricar bolsas con válvula).
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