Composite compounds are thermoplastic or thermosetting resin, reinforced with fillers or fibers. The combination of these two components produces lighter materials with greater mechanical resistance. These materials are used in a wide range of applications: road, air, sea and rail transport, construction, sports, leisure products, etc.

Glass and carbon fibers are the most commonly used materials in composite compounds because they significantly improve the mechanical properties of thermoplastics. Natural fibers are increasingly used because they are efficient reinforcements, and also because they are recyclable or more environmentally friendly.

Short Fibers

Sunstrand short fibers can be compounded with thermoplastics such as polypropylene and polyethylene that are suitable for injection or compression molding. Thermoplastic polymers typically soften to a liquid-like form when heated, to allow for molding, and then solidify when they cool. Typical fiber lengths for these applications are ¼” (~7mm) but the fibers can be cut to any length required by the manufacturer. Injection and compression molding with thermoplastics are relatively less expensive than other manufacturing techniques, and thus, injection molding with thermoplastics is used in everything from small handheld consumer products, to large automotive components.

Short fibers can also be used in Bulk Molding Compound (BMC). BMC is a thermoset polymer system that contains short fibers added for reinforcement. Thermoset polymers are differentiated from thermoplastics in that they are usually liquid at room temperature and require a chemical reaction to “catalyze” the polymer into a solid form. BMC is used over thermoplastic injection molding when properties such as good surface finish, dimensional stability, geometry complexity, and higher mechanical properties are desired. Sunstrand short natural fibers can be used as a replacement for fiberglass in the reinforcement of thermoplastic compounds as well as bulk molding compounds.

Fillers

Sunstrand milled compounding fibers can be used as fillers when combined with thermosets to form a bulk molding compound (BMC). These compounds are then suitable for compression molding.  BMC is a thermoset polymer system that contains short fibers and fillers. Thermoset polymers are differentiated from thermoplastics in that they are usually liquid at room temperature and require a chemical reaction to “catalyze” the polymer into a solid form.

BMC is used instead of thermoplastic injection molding when properties such as good surface finish, dimensional stability, geometry complexity, and higher mechanical properties are desired in a part. Typical fiber length for this application is less than ¼” (~7mm) but the fibers can be cut to any length required by the manufacturer. Fillers in plastics are typically added to reduce part cost, reduce part weight, increase mechanical properties and increase aesthetics. Sunstrand natural fiber fillers can be used as a replacement for fiberglass and other fillers in thermoset bulk molding compounds.

Long Fibers

Sunstrand long fibers can be used in non-woven applications. Typical lengths are 1 ½”- 4” long depending on application. These fibers are typically used in Chopped Strand Mat (CSM), Sheet Molding Compound (SMC), and wet-lay applications.

CSM is typically supplied in a fabric like roll form where the fibers are randomly oriented, and held together with a resin specific binder. CSM is used as a reinforcement layer by itself, or added to multiple layers of woven or unidirectional fabrics. During component manufacturing, CSM is saturated with a thermoset polymer using a variety of infusion techniques. CSM is commonly used in marine and aerospace applications.

Sheet Molding Compound (SMC), can have directional or randomly oriented fibers that are imbedded in a thermoset polymer system. SMC differs from CSM in that the SMC is supplied as a flexible sheet good whose fibers are already imbedded in the thermoset polymer. The SMC sheet is then compression molded to form the desired parts. Wet-lay applications of long discontinuous fibers, produces continuous fiber mats that can be mixed with thermoset or thermoplastic polymers for subsequent compression molding. Wet-lay mats can also be needle-punched to increase the mat density and integrity.  Sunstrand’s long natural fibers have a unique cosmetic appeal that is preferred over synthetic fibers. Sunstrand’s long natural fibers are compatible with both thermoset and thermoplastic resin systems, depending on your specific application.