Glass Fiber: Manufacturing &

Applications

Aravin Prince Periyasamy Asst Prof/ Textile Chemistry

D.K.T.E Society’s Textile Engineering College, Ichalkaranji

Dist- Kolhapur, M.S, 415116

aravinprince@gmail.com

History……. Ancient Egyptians made containers of coarse fibers drawn from heat softened glass.

Napoleon’s funeral coffin was decorated with glass fiber textiles.

By the 1800s, luxury brocades were manufactured by co-weaving glass with silk, and at the Columbia

Exhibition of 1893.

The scientific basis for the development of the modern reinforcing glass fiber stems from the work of

Griffiths.

The French scientist, Reaumur, considered the potential of forming fine glass fibers for woven glass

articles as early as the 18th century.

Continuous glass fibers were first manufactured in substantial quantities by Owens Corning Textile

Products in the 1930’s for high temperature electrical applications.

Raw materials such as silicates, soda, clay, limestone, boric acid, fluorspar or various metallic

oxides are blended to form a glass batch which is melted in a furnace and refined during lateral flow

to the fore hearth.

Introduction Glass in the form of fibers has found wide and varied applications in all kinds of

industry because it is the most versatile industrial materials known today.

All glass fibers derived from compositions containing Silica, which are available

in virtually unlimited supply.

They exhibit useful bulk properties such as Hardness, Transparency, Resistance To Chemical Attack, Stability, and Inertness, as well as

Desirable Fiber Properties such as Strength, Flexibility, and Stiffness.

Glass fibers are used in a number of applications which can be divided into four

basic categories: (A) Insulations, (B) Filtration Media, (C) Reinforcements, And (D) Optical Fibers.

Types of Glass Fiber

As per ASTM C 162 the glass fiber were classified according to the end use

and chemical compositions.

E, Electrical Low Electrical Conductivity

S, Strength High Strength

C, Chemical High Chemical Durability

M, Modulus High Stiffness

A, Alkali High Alkali Or Soda Lime Glass

D, Dielectric Low Dielectric Constant

A GLASS – Soda lime silicate glasses used where the Strength,

Durability, And Good Electrical Resistivity.

C GLASS-- Chemical Stability In Corrosive Acid Environments.

D GLASS – Borosilicate glasses with a Low Dielectric Constant For

Electrical Applications.

E GLASS – Alumina-calcium-borosilicate glasses with a maximum

alkali content of 2 wt.% used as general purpose fibers where strength

and High Electrical Resistivity are required.

ECRGLAS® – Calcium aluminosilicate glasses with a maximum alkali

content of 2 wt.% used where strength, electrical resistivity, and

acid corrosion resistance are desired.

AR GLASS – Alkali Resistant Glasses composed of alkali zirconium

silicates used in cement substrates and concrete.

R GLASS – Calcium aluminosilicate glasses used for reinforcement

where added strength and acid corrosion resistance are required.

S-2 GLASS® – Magnesium aluminosilicate glasses used for textile

substrates or reinforcement in composite structural applications which

require high strength, modulus, and stability under extreme

temperature and corrosive environments.

More than half the mix is Silica Sand,

Other ingredients are Aluminum, Calcium and Magnesium.

Oxides, and Borates

Manufacturing

Glass Fiber Manufacturing Process

The fiber manufacturing process has effectively two variants. One

involves the preparation of marbles, which are re-melted in the

fiberisation stage.

The other uses the direct melting route, in which a furnace is

continuously charged with raw materials which are melted and refined

as that glass reaches the forehearth above a set of platinum–rhodium

bushings from which the fibers are drawn.

The two processes are described in Figures 6.2 and 6.3.2 Glass fibers

are produced by rapid attenuation of the molten glass exuding

through nozzles under gravity.

The glass viscosity between 600 and 1000P.

The rate of fiber production at the nozzle is a function of the rate of flow

of glass, not the rate of attenuation, which only determines final

diameter of the fiber.

Furnace For Glass Melting

Fiberglass Forming Process

The molten glass flows to platinum/ rhodium alloy bushings and then through

individual bushing tips and orifices ranging from 0.76 to 2.03 mm (0.030 to

0.080 in) and is rapidly quenched and attenuated in air (to prevent

crystallization) into fine fibers ranging from 3 to 35 μm.

Mechanical winders pull the fibers at lineal velocities up to 61m/s over an

applicator which coats the fibers with an appropriate chemical sizing to aid

further processing and performance of the end products.

Furnace

The temperature is so high > 1600 °C that the sand and other

ingredients dissolve into molten glass.

The inner walls of the furnace are lined with special

"refractory" bricks that must periodically be replaced.

Bushings

The molten glass flows to

numerous high heat-resistant

platinum trays which have

thousands of small, precisely

drilled tubular openings, called

"bushings."

Design and Manufacture of Bushings for Glass Fiber Production

Filaments

This thin stream of molten glass is pulled and attenuated (drawn down)

to a precise diameter, then quenched or cooled by air and water to fix

this diameter and create a filament.

Bunker,

Bushing,

Cooler

Sizing

The hair-like filaments are coated with an aqueous

chemical mixture called a "sizing," which serves two

main purposes:

1) Protecting the filaments from each other during

processing and handling,

2) Ensuring good adhesion of the glass fiber to the resin.

Sizing thickness ~ 50 nanometers

Immediately after cooling with water the fibers are coated with an aqueous size (usually an emulsion) in contact with a rubber roller.

The size (or finish) is crucial to the handle ability of the fibers and their compatibility with the matrix.

The ‘finish’ therefore may consist of:

1. lubricant(s),

2. surfactant(s),

3. antistatic agent(s), and

4. an optional polymeric binder (emulsion or powder) used for fiber mats

Strands

After the sizing is applied,

filaments are gathered

together into twine-like

strands that go through

one of three steps,

depending on the type of

reinforcement being

made.

Properties of Glass Fiber

Physical Properties

High strength S-2 Glass fibers’ annealed properties

measured at 20°C are as follows:

Young’s Modulus 93.8 GPa

Shear Modulus 38.1 GPa

Poisson’s Ratio 0.23

Bulk Density 2.488 g/cc

Other Properties….

Chemical Resistance

The chemical resistance of glass fibers to the corrosive and leaching

actions of acids, bases, and water is expressed as a percent weight loss.

The lower this value, the more resistant the glass is to the corrosive

solution.

Thermal Properties

The viscosity of a glass decreases as the temperature increases.

Note that the S-2 Glass fibers’ temperature at viscosity is 150-260°C

higher than that of E Glass, which is why S-2 Glass fibers have higher

use temperatures than E Glass.

Radiation Properties

E Glass and S-2 Glass fibers have excellent resistance to all types

of nuclear radiation.

Alpha and beta radiation have almost no effect. But some times it

produce 5 to 10% decrease in tensile strength.

E Glass and C Glass are not recommended for use inside atomic

reactors because of their high boron content.

Composite Properties

Application of glass fiber composite materials depends on proper

utilization of glass composition, size chemistry, fiber orientation,

and fiber volume in the appropriate matrix for desired mechanical,

electrical, thermal, and other properties.

Strength and stiffness

For glass this will be about 7GPa, but the practical strength would

be significantly less at about 0.07GPa.

A typical E-glass fiber can have a strength of 3GPa.

Static Fatigue

Glass fibers are subject to static fatigue,

Which is the time-dependent fracture of a material under a constant load,

as opposed to a conventional fatigue test where a cyclic load is employed

Environmental Stress Corrosion Cracking (ESCC)

E-glass fibers have a reduced lifetime under load and this is more severe

in an acidic environment.

This is generally referred to as environmental stress corrosion cracking

or ESCC.

Here, a synergism between stress and chemistry occurs as described in

the previous section under II.

At low loads and in alkaline environments, chemical corrosion dominates

but is stress assisted.

Typical Tensile Strength of Glass Fiber

Glass Fiber Forms

• Fibers

• Roving's

• Chopped Strands

• Yarns

• Fabrics

• Mats

Chopped-strand Production

These are fibers which have been chopped to lengths of 1.5 to 50mm,

depending on the application.

These are combined with thermoplastic or thermosetting resins for molding

compounds.

Chopped strands are either soft- or hard-sized, depending on the molding

application.

Multiend Roving Process Production

Twisting

Texturising

Texturizing is a process in which the glass yarn is subjected to an air jet

that impinges on its surface to make the yarn “fluffy’’.

Glass Fiber Product Applications

- Composite Applications

- Transportation

– Electrical/Electronics

– Building Construction

– Infrastructure

– Aerospace/Defense

– Medical Products

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