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Glass Fiber

Glass fiber is a kind of inorganic non-metallic material with excellent properties. Alfa Chemistry offers a wide variety of fiberglass products to meet the needs of composite reinforcements, electrical insulation and thermal insulation.


According to the monofilament diameter, glass fibers can be divided into coarse fibers (30 μm), primary fibers (greater than 20 μm), intermediate fibers (10-20 μm), high-grade fibers (3-10 μm) and ultrafine fibers (less than 4 μm). Generally speaking, fibers of 5-10 μm are used as textile products; fibers of 10-14 μm are generally used for roving, non-woven fabrics, chopped fiber mats, etc.

Depending on the glass raw material, types of glass fibers include E-glass, C-glass, S-glass, A-glass, D-glass, R-glass, and EGR-glass, etc. The corresponding physical properties of different types of glass fibers are shown in the figure below. [1] In general, glass fiber has the features of high temperature resistance, non-flammability, corrosion resistance, good heat and sound insulation, high tensile strength, good electrical insulation, low coefficient of linear expansion and dielectric permeability, etc.


Chemical Composition

  • E-glass fibers, also known as alkali-free glass fibers, have an alkali metal oxide content < 0.05%.
  • C-glass fiber is also known as medium alkali glass fiber, and its alkali metal oxide content is 11.5-12.5%.
  • glass fiber is also known as high-alkali glass fiber with an alkali metal oxide content > 15%.
  • D- glass fiber contains a large amount of boron trioxide, which provides low dielectric constant properties. This makes glass fibers ideal for fiber optic cable applications.
  • S-glass fiber, also known as special glass fiber, is a high-strength glass fiber composed of pure magnesium-aluminum-silicon ternary. S-glass fibers mainly include magnesium-aluminum-silicon-based high-strength and high-elastic glass fibers, silicon-aluminum-calcium-magnesium-based chemical corrosion-resistant glass fibers, lead fibers, high silica fibers, and quartz fibers.
  • The chemical composition of different glass fibers in wt% is summarized in the table below for reference.
Type (SiO2) (Al2O3) TiO2 B2O3 (CaO) (MgO) Na2O K2O Fe2O3

Chemical Structure

The glass structure at the atomic level has been the subject of much theoretical speculation and experimental work. Zachariasen's model shows that quartz glass is composed of a random network of SiO4 tetrahedra. Schematic diagrams of glass crystals and multicomponent glasses have been proposed. The short-range order but lack of long-range order in the figure (b) is due to the fact that SiO4 tetrahedra are the basic building blocks of amorphous silica, but the orientation of the tetrahedra with each other has some random characteristics. The O atoms at the corners of the tetrahedra are shared between the two tetrahedra. Therefore, the overall chemical composition of glass is SiO2. Although pure silica glasses appear to mostly have random arrangements of atoms beyond the nearest neighbors, when network modifiers (e.g., Na, Ca) and alternative network formers (e.g., B and Al) are introduced, some of the randomness of the structure is compromised. [2]

2D schematic diagram of (a) crystal structure; (b) simple glass; (c) multicomponent glass.2D schematic diagram of (a) crystal structure; (b) simple glass; (c) multicomponent glass.


  1. TP Sathishkumar, et al. Journal of Reinforced Plastics and Composites, 2014, 33, 13, 1258-1275.
  2. Frank R. Jones, et al. Handbook of Properties of Textile and Technical Fibres (Second Edition), 2018, 757-803.

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