Fiberglass

Summary

Fiberglass, or glass-reinforced plastic, is glass fiber (usually E-glass) in a thermoset matrix of polyester, vinyl ester, or epoxy. It gives corrosion-resistant, non-conductive, moldable shapes, but resin shrinkage and loss of resin function above about 356°F limit detailing and fire performance.

Cols

Image

FRP / GRP: fiber-reinforced / glass-reinforced plastic
E-glass / S-glass: alumino-borosilicate glass with less than 1 percent alkali oxides / higher-strength glass
Chopped strand mat / woven cloth / roving: forms of glass reinforcement
Matrix: thermoset resin (polyester, vinyl ester, epoxy)
Fiberglas: Owens Corning trade name from 1936

History and demand

Invention

1880: Hermann Hammesfahr received the earliest glass fiber patent in the United States
1932: Games Slayter of Owens-Illinois accidentally made fibers with compressed air on molten glass; 1936 Owens Corning's patented "Fiberglas"
1937: Ray Greene built the first composite boat; fiberglass composite boats appeared in the early 1940s; aircraft radomes in WWII

Sourcing

Global glass fiber capacity was about 12 million tons in 2025, with China about 70 percent; Japanese producers are about 6 percent (industry reports)
Jushi (China) has about 2 million tons a year of capacity and Owens Corning about 1.4 million tons (about 2021 figures)

Demand trend

E-glass makes up most of the world's fiberglass

Composition and production

Raw materials

E-glass reinforcement (alumino-borosilicate, less than 1 percent alkali oxides) in epoxy, polyester, or vinyl ester resin; thermoplastic matrices also occur

Product forms

Chopped strand mat, woven cloth, and rovings molded into panels, profiles, tanks, and tubs

Properties

Physical

Density: 1.5 to 2.5 g/cm³ (about 94 to 156 lb/ft³)

Mechanical

Tensile strength: 2,000 to 3,500 MPa for the fiber (290 to 508 ksi); E-glass epoxy 1,770 MPa (257 ksi); S-glass epoxy 2,358 MPa (342 ksi)
Described as stronger than many metals by weight

Thermal and moisture

Thermal conductivity: 0.035 to 0.045 W/(m·K), about 0.24 to 0.31 Btu·in./(h·ft²·°F)
Resin shrinkage on cure: about 5 to 6 percent for polyester, about 2 percent for epoxy

Fire behavior

Resin can lose function above about 180°C (356°F); GRP may retain significant strength after exposure to 200°C (392°F)

Standards

Material specifications

AAMA 305: fiber-reinforced thermoset profiles

Uses in buildings

Building elements

Fiberglass Entry Doors, Fiberglass Windows: molded door skins and pultruded window frames
Horizontal Sliding Windows, Wood and Clad Wood Windows: stable fiberglass frames and exterior cladding
Showers and Tubs, Grease Interceptors: molded tubs and receptors, and tanks
Asphalt Shingle Roofing: glass-fiber mat base for shingles

Pros and cons

Pros

Non-magnetic, non-conductive, and transparent to electromagnetic radiation
Strong for its weight
Moldable into tubs, tanks, and profiles

Cons

Resin shrinkage of 2 to 6 percent can distort parts and cause internal stress
Resin loses function above about 356°F
Fibers and styrene vapors irritate eyes, skin, and airways

Sustainability

Health

Fiberglass irritates the eyes, skin, and respiratory system; styrene vapors during curing irritate mucous membranes
OSHA limits: 15 mg/m³ total and 5 mg/m³ respirable (8 hours); NIOSH recommends 3 fibers/cm³ and 5 mg/m³ total
Insulation-grade glass wools are IARC Group 3 (not classifiable as to carcinogenicity)

Manufacturing and cost

Main manufacturers and suppliers

Trade association: American Composites Manufacturers Association.

Sources

Wikipedia: Fiberglass, https://en.wikipedia.org/wiki/Fiberglass
Wikimedia Commons: Glass reinforced plastic SEM Stereo 50x.JPG, photo by SecretDisc (CC BY-SA 3.0), https://commons.wikimedia.org/wiki/File:Glass_reinforced_plastic_SEM_Stereo_50x.JPG
Faxiang Gongchang: China glass fiber 2026, https://faxiangongchang.com/en/reports/china-glass-fiber-2026