Does SIZE really matter?
We are, of course, talking about fibre ‘Size’; a thin homogenous surface coating of mainly organic materials applied during the manufacturing process of glass and other fibres / yarns. The manufacturing process is known as ‘Sizing’.
Glass yarns are easily characterised by filament count, fibre diameter, TEX, Twist Direction (S or Z), Twists per cm etc and so choosing the appropriate yarn on these attributes tends to be relatively straightforward and understood even by those new to textiles.
However, the SIZE on a fibre / yarn shouldn’t be overlooked and consideration should be given to the textile process and final application when choosing a yarn with a particular Size. Glass fibre sizing at its most basic is water and a coupling agent but fibre producers tend to create their own closely guarded formulations for two predominant reasons:
- To physically protect the filaments during handling and further textile processing like weaving, braiding and texturizing.
- To play an important role in determining the properties of the final application. For example in composite applications, a specific sizing might improve:
- Adhesion between the inorganic fibre / finished textile and the organic resin matrix.
- Reduce the amount of deposits and fuzz.
- Improved process-ability.
- Lower friction coefficient.
- Allow for easier impregnation of the resin in to the glass fibre.
Sizing can also improve mechanical properties, chemical or water resistance, and thermal stability.
Size formulations therefore tend to be complex and composed of much more than just water and coupling agents; including additives or modifiers such as surfactants, plasticizers, anti-static agents, antifoams, and rheology modifiers.
It should also be noted that the complexity of the Size could also have the reverse effect and impede on the desired performance of the inorganic substrate. For example in end use thermal applications where temperatures are likely to exceed the tolerances of the components within the size; it is often necessary to remove the size by a gentle heat treatment leaving behind a clean non contaminated textile substrate designed for purpose. This is often the case with ceramic oxide and alumina fibre textiles utilised in critical aerospace applications.
For more insight, understanding or guidance on Size contact Textile Technologies Europe Ltd.
- Eddy Ashworth
