Get to Know Bulk Molding Compounds

Bulk molding compounds (BMCs) are ready-to-mold, glass-reinforced polyester materials. They’re pre-mixed to achieve special characteristics. When molded, the finished product offers these characteristics inherently. Depending on the product and final application, the right BMC can achieve certain properties. For example, Mar-Bal produces electrical standoff insulators using a BMC featuring flame retardant polymer and track-resistant glass.

The versatility of BMCs

BMCs encompass a broad range of practical applications. Thanks to their composition — which includes proportions of plastic resin, inert fillers, reinforced fibers, catalysts, stabilizers, and dyes — BMCs are incredibly versatile. Depending on the blend, a BMC could imbue any or all of the following properties in a molded product:

• Resistance to heat and corrosion
• UV stability
• Minimal shrink or expansion
• Low density
• Electrical insulation and stability
• Smoke and flame retardance

Add to this the fact that BMCs can be compression or injection molded and it’s easy to see why so many applications benefit from molded products.

A diverse scope of applications

BMCs are molded into thermoset composites, which find practical application across industries. Some of the most common places BMCs contribute their benefits include:

• Appliance parts — Thanks to the inert materials within BMC formulations, they’re great for molding appliance parts exposed to heat or cold. Think about products like handles and knobs, trim, kick plates, and more.
• HVAC components — Their general nonreactive properties make BMCs a superior material choice for HVAC components. They’re able to resist rust, corrosion, vibration, UV exposure, and much more.
• Lighting components — The arc- and track-resistant properties of BMCs lend themselves to diverse lighting applications. Look for them in motor controls, insulators, circuit breakers, metering devices, and a variety of other components.
• Special automotive parts — Most vehicle-specific plastic components are thermoset materials, which require specific BMC formulations for UV resistance, heat resistance, and minimal shrink.
• Marine applications — Low density, low shrink, and corrosion resistance are all BMC properties for marine applications. Thermoset plastics made from marine-specific BMCs are often featured as part of the boat hull or as outboard accessories.

Thermoset plastics are found in just about every industry today thanks to BMC formulations that are as diverse as the applications themselves.

Perfect for mass production

The common theme among all the above applications is mass production. The speed and convenience of thermoset molding — combined with the versatility of BMC formulation — lends itself to the demand for rapidly produced, replicable, cost-effective components. For most mass-produced goods, this is a winning combination that keeps costs low and ensures quality control.

The right BMC is an invaluable asset. Considering the vast number of molded products in use across industries today, the ability to customize a formulation for a specific application unlocks a wealth of possibilities for companies.