Non-Combustibility Of Glass Fibre

Glass fibre is inherently non-combustible. This is because glass comprises mainly of oxides, such as silica. These elements are in their highest oxidation state and will therefore not react with oxygen. This simply means that in a fire, glass fibre will simply heat up until it turns from a solid into a liquid.  Hence, glass is deemed incombustible. 

Although glass fibre has a high temperature resistance, its continuous service temperature is much lower than its melting point. This is because as glass fibre heats up it will become brittle before it melts, this defines its useful working temperature, for E-glass this is around 550°C. 

There are different forms of glass fibre, all with different continuous usage limits and defined applications:

A-Glass – (Alkali Glass) The first type of glass used for fibre glass. Alkali-lime glass, containing little to no boron oxide. A for Alkali-lime glass.

C-Glass – (Chemical Glass) Alkali-lime glass, containing high boron oxide. C for Chemical resistance. Continuous at 450°C

E-Glass – (Electrical glass) Alumino-borosilicate glass, with low alkali oxides. E for Electrical (low electrical conductivity). Continuous at 550°C

S-Glass – Alumino silicate glass, without CaO, but high MgO giving high tensile strength, S for Strength. Continuous 650-750°C 

It is possible to increase the continuous operating temperature of glass through the acid leeching method – transforming glass fibre into silica fibre. This method consists of glass fibre yarns being processed in a bath of acid to remove impurities, mainly the other oxides present that make up the original composition. The result is an increase of silica content from around 50-60% up to around 96%.