Rule of Thumb Polymer Material Selection – Glass Fiber Sizing

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Glass fiber reinforced compounds which are used in a glycol environment (for instance thermal management systems) need to use a special glass fiber sizing. 

But why? 

In general, glass fibers come with a sizing attached. The sizing increases the interfacial adhesion of the base polymer to the glass fiber. The strength of the material is influenced by this adhesion of the polymer to the glass fiber surface. Standard glass fiber sizing is cleaved when exposed to glycol. The cleavage results in a decrease of the adhesion between glass fiber and polymer and as a consequence mechanical properties will drop. 

Therefore, glass fibers with special sizing need to be used when parts are exposed to water glycol since they resist this type of cleavage. As a rule of thumb, glycol resistant glass fiber sizing in compounds must be used in any application that is exposed to coolants in order to keep the desired mechanical property level over time. 

Rule of Thumb - Selection of optimal glass fiber sizing for glycol application environments

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Herwig Juster

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Literature: 

[1] https://www.michelman.com/markets/reinforced-plastic-composites/fiber-sizing/

[2] https://www.sciencedirect.com/science/article/pii/S1359835X19303689

[3] https://www.researchgate.net/publication/256849998_Sizing_stability_is_a_key_element_for_glass_fibre_manufacturing