Urethane sheets, technically referred to as polyurethane (or PU) sheets, are durable, long-lasting sheets that are constructed from an elastic polymer, or elastomer, containing urethane carbamate links. Valued primarily as rigid and flexible memory foam sheets, polyurethane sheets are extremely useful in solid plastic form as well.
Urethane manufacturers construct sheets in different sizes, colors harnesses and thicknesses, with standard thicknesses ranging from .031″ to 1″. Different types of urethane sheets include urethane films, thermoset urethane sheets and urethane sheet adhesive compounds.
Urethane sheets combine many of the desirable qualities of plastic, rubber and metal with longer service life than plastics, higher impact resistance than rubber, elastic memory, noise reduction, heat and chemical resistance, and many other properties.
This combination of “the best of the best” outperforms metal, rubber and plastic sheets in many applications. Additional benefits of urethane sheeting includes higher abrasion, cut, tear, oil, ozone and radiation resistance, greater load bearing ability, broader hardness range and excellent colorability.
As a result, urethane sheets are commonly used as liners or pads in industries such as dunnage, transportation, airline, salt mining, steel service, residential and industrial manufacturing. Other urethane sheet applications include conveyor belting, prototyping, gasket materials, metal forming and bulk material handling.
The raw materials of polyurethane exist in a liquid state, which allows for easy mixing and measuring in preparation for sheet extrusion or thermosetting. Urethane sheet extrusion is the most common method, where granulated solid urethane is poured into a hopper, a funnel-shaped receptacle, and transferred to a heater, consisting of a screw and barrel which plasticize the urethane granules while pushing the amorphous material out through a die.
Once fed through the die, the urethane is pulled through cooling rolls and shaped by calendar rolls, machines that smooth and stretch the urethane into sheets through rollers.
Thermosetting is a less common method in which energy or catalysts are added to molecular chains and cause them to react at chemically active sites, cross-linking the urethane molecules into a rigid, 3-D structure.
The cross-linking process forms a molecule with a larger molecular weight, resulting in a urethane with a higher melting point. During the reaction, the molecular weight has increased to a point so that the melting point is higher than the surrounding ambient temperature, then the urethane sheet is formed.
Some characteristics of the newly formed urethane sheets include resistance to extreme environments and noise reduction capabilities that the residential industry uses for soundproof household insulation.
In addition, the cost of urethane extrusion and thermosetting is on par with the cost of rubber and typical polymer molding, giving urethane sheets an economic advantage as well.