Acoustic insulation is usually made of polyethylene or polyester foams that allow sound waves to bounce off. These lightweight, sound-dampening materials may also include a sound-absorbing barrier. Most acoustic insulation has an open cellular structure that permits the passage of air, a good insulator. Closed cell acoustic foams are used mainly in underwater applications rather than land vehicles.
Thermal insulation is designed to absorb heat from a vehicle's engine compartment and deflect heat away from the cab. Silicone, a durable synthetic resin, is often used because it resists high temperatures and provides acoustic insulation from high-decibel diesel engines. Self-extinguishing firestocks and custom composite insulation are also available.
Thermal and acoustic insulation can be made of composite materials and formed into application-specific shapes and thicknesses. For example, thermal-proof panels made of ceramic fiber, polyurethane foam, and microcellular or silicone foam can provide heat shielding as high 1200° C in locomotives. By laminating multiple layers of insulating materials together, suppliers can build sandwich-like panels that are suitable for all applications.
Truckers also appreciate the benefits of high-quality insulation. Whether for long-haul trucking, construction site work, or local runs in a garbage truck, sound insulation is important. As with thermal insulation, sound insulating products can be color-matched to the vehicle. In commercial trucks, for example, a vinyl exterior may be applied to enhance the cab's appearance.