E-Glass Fibre

Topics Covered

Background

E-Glass or electrical grade glass was originally developed for stand off insulators for electrical wiring. It was later found to have excellent fibre forming capabilities and is now used almost exclusively as the reinforcing phase in the material commonly known as fibreglass.

Fibre Manufacture

Glass fibres are generally produced using melt spinning techniques. These involve melting the glass composition into a platinum crown which has small holes for the molten glass to flow. Continuous fibres can be drawn out through the holes and wound onto spindles, while short fibres may be produced by spinning the crown, which forces molten glass out through the holes centrifugally. Fibres are cut to length using mechanical means or air jets.

Fibre dimension and to some extent properties can be controlled by the process variables such as melt temperature (hence viscosity) and drawing/spinning rate. The temperature window that can be used to produce a melt of suitable viscosity is quite large, making this composition suitable for fibre forming.

As fibres are being produced, they are normally treated with sizing and coupling agents. These reduce the effects of fibre-fibre abrasion which can significantly degrade the mechanical strength of the individual fibres. Other treatments may also be used to promote wetting and adherence of the matrix material to the fibre.

Composition

E-Glass is a low alkali glass with a typical nominal composition of SiO₂ 54wt%, Al₂O₃ 14wt%, CaO+MgO 22wt%, B₂O₃ 10wt% and Na₂O+K₂O less then 2wt%. Some other materials may also be present at impurity levels.

Key Properties

Properties that have made E-glass so popular in fibreglass and other glass fibre reinforced composite include:

· Low cost

· High production rates

· High strength, (see table 1)

· High stiffness

· Relatively low density

· Non-flammable

· Resistant to heat

· Good chemical resistance

· Relatively insensitive to moisture

· Able to maintain strength properties over a wide range of conditions

· Good electrical insulation

Table 1. Comparison of typical properties for some common fibres.

Materials	Density (g/cm³)	Tensile Strength (MPa)	Young modulus (GPa)
E-Glass	2.55	2000	80
S-Glass	2.49	4750	89
Alumina (Saffil)	3.28	1950	297
Carbon	2.00	2900	525
Kevlar 29	1.44	2860	64
Kevlar 49	1.44	3750	136

The advantageous properties of E-glass generally outweigh the disadvantages which include:

· Low modulus

· Self abrasiveness if not treated appropriately leading to reduced strength

· Relatively low fatigue resistance

· Higher density compared to carbon fibres and organic fibres.

Applications

Composite Materials

The use of E-Glass as the reinforcement material in polymer matrix composites is extremely common. Optimal strength properties are gained when straight, continuous fibres are aligned parallel in a single direction. To promote strength in other directions, laminate structures can be constructed, with continuous fibres aligned in other directions. Such structures are used in storage tanks and the like.

Random direction matts and woven fabrics are also commonly used for the production of composite panels, surfboards and other similar devices.