Written by Steve Brennan, Managing Director, BI Glass Fibre.
Glass fibre and glass fibre products are now used to reinforce many different materials including thermoset resins, thermoplastics, polyurethanes, cement, concrete, gypsum, bitumen and just about every material that needs improved properties to meet existing standards or meet the requirements of new world developing standards. What other material can operate in harsh environments with formidably contradictory requirements: static strength or dynamic strengths, rigidity or flexibility, high acid or high alkalinity, buried or exposed, or high or low temperature?
Industries that have found solutions with glass fibre include construction, infrastructure, mining, automotive, marine, and leisure products, each of which has a diverse range of performance requirements in a world looking to make things bigger, stronger, lighter, more durable, more adaptable, more aesthetically appealing or more corrosion resistant.
There are many types of glass fibre reinforcement constructions including rovings, mats, chopped strands, veils, scrim, mesh, cloth, fabric and veils. In composite applications glass fibre can be sprayed, pultruded, wound, sprayed, hand laid, infused, pressed, injected or dosed. It is truly a unique material as many of the articles in this edition demonstrate.
Single-end rovings (Type 30) – sometimes referred to as Direct Roving or Continuous Process Roving (CPR) which are constructed and used in pultrusion, filament winding and weaving.
Multi-end rovings (choppable) which are constructed and used for spray up roving, chop and drop roving and sheeting roving.
Continuous filament mat which is constructed for use in closed moulding or pultrusion applications.
Chopped strand mat constructed for use in emulsion or powder bound.
Dry chopped strands are used in thermoplastic reinforcement.
Veil and non-woven mat which are constructed for use as a surface finish.
Fabrics – either woven or stitched – are constructed for use in closed moulding and hand layup.
Tapes which are constructed for use in closed moulding and hand layup.
Limitless versatility and performance can be engineered into the fibres. Initially, the diameter of each filament – which can be between 6 and 32 micron – affects fibre processing in wet out and wet through, chop ability and fuzz, as well as the final strength.
The number of filaments (not to be confused with ‘tex’) is determined by the number of holes in the bushing (see breakout box) and can vary from 2,400 to 5,800 in single end (direct) roving up to 8,000 filaments in multi-end roving.
Performance can be engineered into the fibres during the final production stages by the application of proprietary chemistry by way of a chemical coating, or size (sizing) that may be lubricants, binders and/or coupling agents all developed to cause the fibre to perform a certain way and/or have an affinity for resin chemistry.
‘Sizing’ is probably one of the most important factors in glass fibre production and certainly the main IP that glass fibre manufacturers protect. Sizing is the chemistry applied to the glass fibre to make the inorganic fibre compatible with the organic resin matrix and to process acceptably. Chemical ‘sizing’ is designed for resin compatibility, static mechanical properties, dynamic mechanical properties (tensile, shear, flex, compression), fuzz, wet-out, dispersion and finally appearance.
A chemical ‘binder’ is an adhesive that is applied to glass fibre bundles to make them stick together to form a mat type product. ‘Chopped strand mats’ are referred to as emulsion or powder bound mat, which identifies the type of binder used. Both the ‘sizing’ and ‘binder’ work in unison to improve conformability, wet-out, wet through and wet and dry strength, as well as the final appearance of the laminate.
Each product type is designed with specific strengths for a given end-use application, all with an ASTM standard and specification – A Glass, D Glass, E Glass, E-CR Glass, H Glass, R Glass, S Glass, AR Glass. The majority of the products seen in Australia are E-Glass (Electrical – low electrical conductivity) or E-CR Glass (Electrical – Corrosion resistant). A brief summary of some the types and properties are in the table below.
Manufacturing Glass Fibre in Australia
In 1999 the face of the Australian Composites industry changed with the closure of A.C.I.’s fibreglass manufacturing plant in Dandenong, Victoria. For many years, A.C.I. had piloted product development and innovation in glass fibre, working closely with Australian manufacturers to drive industry growth through shared knowledge and education on the use of fibreglass reinforcements.
The plant had a capacity of 7,000 to 9,000 metric tonnes per annum across a variety of product types which, at the time, was enough volume to supply the Australia and New Zealand markets.
Textile-grade glass fibres are made from silica (SiO2) sand, which requires temperatures of up to 1720°C to melt. Molten glass is drawn through a series of small orifices or bushings which are made from precious metals such as platinum and rhodium. These extreme operating temperatures, coupled with a short operating lifespan of around 10 years as well as the required precious metals, render furnaces an expensive proposition to install, replace or even rebuild for volumes of less than 100,000 metric tonnes.
Textile-grade glass fibres are made from silica (SiO2) sand, which requires temperatures of up to 1720°C to melt. Molten glass is drawn through a series of small orifices or bushings which are made from precious metals such as platinum and rhodium. These extreme operating temperatures, coupled with a short operating lifespan of around 10 years as well as the required precious metals, render furnaces an expensive proposition to install, replace or even rebuild for volumes of less than 100,000 metric tonnes.
