Rigid fiberglass products are manufactured through a process of molding glass fibers, and/or thermoset plastics to produce what are known as fiberglass, fiberglass reinforced plastics (FRP) and composites. Different molding options include open, closed, and centrifugal. Other fiberglass processes produce fibers and filaments for insulation, yarn, and mat or roving production.

Rigid fiberglass products are very durable and corrosion resistant. Common rigid fiberglass products are boat or canoe hulls, but other products include furniture, corrosion resistant equipment, bathtubs and bath fixtures, other building materials, heat exchanger components, floating pier modules, large storage tanks, truck body and airplane body and components, sporting equipment, printed circuit board substrate, ductwork, piping, fans, and machinery housings. Non-rigid fiberglass products include strands and yarn used in insulation, woven mats, and other products.

While the composition, shape, and size of rigid fiberglass products vary significantly from one facility to the next, and from one production line to the next, the essential steps and material inputs are somewhat similar.

Many manufacturers use open molding, which utilizes a one-piece mold or structure. First, a layer of gel coat is applied and cured. Then, fiberglass and sprayed resin are layered into the mold or structure and allowed to cure. Open molding tends to release the highest amount of emissions during processing. Other options include closed-mold and centrifugal molding systems.

Closed molding uses a two-part mold wherein the initial gel coat application is first applied. Fibers are then sprayed or placed in the female mold (in the form of chopped fibers or laminated sheets or mats respectively) on top of the gel coat. The mold is then sealed by vacuum, the catalyzed resin is injected into the vacuum-pressurized mold, and then the part is allowed to cure.

Centrifugal molding uses a spinning mold to from cylindrical pieces such as pipes and tanks. Gel coat is first applied to the sides of the mold. Then, catalyzed resins saturated with short fibers are sprayed into the spinning mold, layer by layer, until wall thickness is achieved.

Fiberglass molding incorporates the following unit processes, with some variations depending on the type of molding process.

• Mold preparation
• Gel coat application and cure
• Fiberglass placement (via laminate sheets or mats, or spraying of chopped fibers)
• Catalyzed resin application with other additives as applicable
            Some fabricators saturate the resin formulation
            with chopped fibers and apply all at once,
            or use separate nozzles and spray the resin, catalyst,
            and chopped fiber at the same time.
• Additional fiber and resin applications until all layers are added
• Cure at varying time and temperature, depending on the workpiece size and shape, throughput rates, and resin cure requirements
            Most poly-based resins cure at ambient temperature,
            while epoxy-based resins cure at elevated temperatures
            that usually require an autoclave or oven.
• Demold
• Trim
• Clean up of mold, tooling, rollers, transfer hoses, drums, spray guns, and other tools

Additional supporting operations and important facets of fiberglass manufacturing which require environmental management are air filtration and ventilation, chemical management and storage, finish operations (e.g., adding foam for insulation, lightweighting, or structural support, upholstering, coating, painting, padding, carpeting and accessorizing), solid waste management, recycling and reuse, and energy and water use.

Additional discussion of these and fiberglass facility operations, including respective inputs and outputs, are discussed in the Operations section. Also, a number of pollution prevention opportunities for rigid fiberglass manufacturing are found in the P2 Opportunities section.