Sheet molding compound (SMC) and bulk molding compound (BMC) compositions are complex mixtures of resins and various ingredients (fillers, catalysts, thickeners, etc.), all of which influence important property and processing characteristics. SMC and BMC have been prepared from various resins, e.g. phenolics, epoxies, thermosetting polybutadienes and even thermoplastics, However SMC & BMC from unsaturated polyesters and vinyl esters are the major systems used.
A typical low-profile SMC composition is useful for molding automotive body panels with quality surfaces. Although BMC compositions are similar to SMC compositions, there are some differences. For example in some cases, BMC is made without chemical thickening.
For making parts in larger production series material solutions based on SMC (Sheet Molding Compound) and BMC (Bulk Molding Compound) are frequently used, as they can be easily molded into unique shapes and have a capability to be made with high dimensional accuracy. Also, they bring light weight compared to steel, aluminum, and stone, can resist heat (thermal insulation, dimensional stability), and provide great strength, stiffness, mechanical integrity, better than what is possible with thermoplastics.
SMC and BMC are mixtures of resin, fillers and reinforcement, processed in heated mold to form a cured component. SMC is a sheet consisting of uncured resin reinforced with glass fibers, which is laid into the mold and compression molded. Whereas BMC is a bulk mixture of uncured resin reinforced with glass fibers, which is injected into the mold.
Comparing the length of fibers SMC has longer fiber length than BMC and a higher fiber content, resulting in greater flexural strength and tensile strength. SMC is used for larger flat parts, components with higher structural requirements, and parts that need good cosmetics. Parts where SMC is used include automotive body panels, building façade panels, deck lids, and electrical cabinetry.
Because of the shorter fiber length and lower fiber content, BMC can be injection molded and fill finer cavities and thinner parts. The higher filler content results in a smoother surface. Application examples include car headlamp reflectors, appliance components (iron heat shields, coffee machine parts, fuse switches, oven handles), and car engine throttle bodies.
Orson Resins and Coatings is the leading supplier of high quality resin systems, which provide the right solutions for achieving required superior mechanical properties superior surface smoothness, low shrinkage, and full part pigment-ability.
To know more about Resins for SMC & BMC applications, Please feel free to connect with Orson Resins on email@example.com