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S-Glass Fibre

Topics Covered

Background

E-Glass has been used extensively in polymer matrix composites, commonly termed “fibreglass”. These materials exhibit good mechanical properties, however, these have not been sufficient in some instances. Consequently, the E-glass composition has been modified to produce more desirable properties. A higher stiffness material resulting from this is S-Glass.

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. It should be noted that S-glass is more difficult to process compared to E-glass.

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

S-Glass has a typical nominal composition of SiO₂ 65wt%, Al₂O₃ 25wt%, MgO 10wt%. 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:

• High production rates

• Improved mechanical properties compared to E-glass

• 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

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 S-glass generally outweigh the disadvantages which include:

• Significantly higher cost compared to E-glass

• 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

S-Glass is generally used for polymer matrix composites that require improved mechanical properties compared to E-glass based composites. This is often the case when the material is operated under more extreme conditions.

Primary author: AZoM.com

Date Added: Aug 30, 2001

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