What is BMC (Bulk Molding Compound)?

BMC is a material formed by adding a paste-like mixture of chopped glass fibers, resin, and fillers, similar to SMC. Although other reinforcing materials such as sisal, asbestos, carbon, and aramid can also be used, the most commonly used reinforcement in BMC is E-glass fiberglass.

Since BMC is generally mixed into a dough-like form rather than a sheet, it is also referred to as Dough Molding Compound (DMC) and is typically supplied in block or rope form.

ADVANTAGES OF BMC

Composite materials are an excellent design option for many applications. With their ability to accommodate and adopt complex geometries, dimensional stability, and high strength-to-weight ratio, composites are a cost-effective alternative to many high-cost materials. The main structure of BMC does not undergo phase transitions (gas/liquid/solid) after processing, allowing it to retain its properties and providing several advantages such as the following.

Heat Resistance (continuous operating temperature up to 200°C)
High Strength-to-Weight Ratio
Chemical Resistance
UV Resistance
Corrosion Resistance
Low Moisture Absorption
Electrical and Thermal Insulation
Non-Magnetic Property

Production

The resin formulation of BMC materials is similar to that of SMC materials. Chopped glass fibers are mixed with a paste in a mixer and packaged in a continuous bale/log form.

The glass fiber content of BMC is generally 5–10% lower than that of SMC, and the fibers are shorter (typically less than 25 mm). Therefore, the mechanical properties of BMC are lower than those of SMC. Impact resistance largely depends on fiber length. For this reason, BMC fiber lengths rarely exceed 12.7 mm, with the most common fiber length being 6.35 mm (0.25 inch).

In general, it is packaged in 15–20 kg nylon bags and sold in boxes of approximately 900 kg.

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