BMC Bulk Molding Compound

BMC Bulk Molding Compound

Premix manufactures Bulk Molding Compounds (BMC) that are used in compression, transfer and injection molding processes. BMC is available in bulk bags as well as slug form. The mixing operation can be done in a number of ways. Premix employs three methods for combining glass with paste: a continuous screw mixer, a sigma blade mixer and a plough blade mixer. The process chosen is dependent upon specific product properties, product form and volume.

BMC is a thermoset plastic made up of a polymer resin, various inert fillers, fiber reinforcement, catalysts, stabilizers, and pigments that form a viscous, 'playdough like' compound for molding. BMC is highly filled and reinforced with short fibers. Glass reinforcement represents between 5% to 30%, with glass length typically between 1/8" and 1/2".

Depending on the end-use application, compounds are formulated to achieve tight dimensional control, flame resistance, high dielectric strength, corrosion and stain resistance and color stability. Its excellent flow characteristics make BMC well suited to a wide variety of applications requiring precision in detail and dimensions. The material is available in a wide variety of colors.

SMC Sheet Molding Compound

Premix manufactures Sheet Molding Compounds (SMC) that are primarily used in compression molding. Premix offers SMC's that are suitable for molding a wide range of parts from very small to very large, from flat panel to very complex shapes. Through our Engineered Solutions, SMC's are tailored to specific customer needs providing part performance as well as manufacturing efficiency. The pliable sheet allows enough body for handling and cutting but enough rigidity for manual charge building or automation.

The SMC manufacturing process allows glass percentages from 15% to 65% to be incorporated into the matrix. The glass length can also be increased up to 2" vs. a BMC that may range between 1/8" and 1/2". SMC also offers the possibility of continuous strand or matte. SMC's come in a wide range of colors and can often be color matched. SMC's have excellent physical, thermal, flame and chemical resistance properties.

As with other thermosets, SMC is a mixture of polymer resin, inert fillers, fiber reinforcement, catalysts, pigments, stabilizers, release agents, and thickeners. Manufacturing of SMC is a continuous in-line process. The base components of liquids and solids (paste) are bulk mixed and continuously metered onto to the surface of a carrier/barrier film, coating the film surface. Two mirror imaged metering stations operate simultaneously. One of the paste-coated carrier films are then layered with chopped fibers. The 2 carrier webs, paste & fiber are then brought together in the compaction section, where the sandwich-like layered components are kneaded into one homogenous compound sheet. The sheet is then fan folded into a container and stored in a controlled environment where maturation takes place, on its way to a specified viscosity.

TMC Thick Molding Compound

Premix manufactures Thick Molding Compounds (TMC) that are used in compression, transfer and injection molding. These thermoset materials are manufactured using a unique process that produces a material with the best combined properties of a BMC (excellent flow properties) and SMC (excellent mechanical properties). The glass/paste combining process creates a glass orientation like BMC, while allowing longer fiber lengths (up to 2"), like SMC, to be incorporated. TMC can be delivered to you in festooned sheet, slab or post-extruded slug form.

The actual thickness of TMC is up to 6x a typical SMC. The additional thickness (matte weight) enables molding charges to be built for compression molding with a fewer number of layers. The end result is a stronger part for complex shapes.

For injection molding the longer glass lengths, in combination with proper injection tool and nozzle design, produces parts that are stronger. This allows the manufacturing economics of an injection process typically reserved for smaller parts to be expanded to larger parts that might typically be done in compression molding.