Does Fiberglass Have an Expiration Date?

Commonly, when customers ask sales representatives about the expiration date of fiberglass, they are often told that it has no expiration date and can be stored indefinitely. However, this overlooks a critical factor: moisture can negatively affect fiberglass, compromising the strength of the resulting fiberglass products.

Impact of Water on Fiberglass

Water affects fiberglass in two main ways:

Adsorption: Fiberglass has a large specific surface area, which means it can absorb more water than traditional glass. This surface adsorption of water can reduce the electrical insulation properties of the fibers. Additionally, the water film on the surface weakens the bond between the fibers and the resin, ultimately affecting the curing strength of the fiberglass and potentially leading to incomplete curing.
Dissolution: Water can dissolve alkali metal oxides present in fiberglass, which decreases the fibers’ strength. Therefore, for fiberglass and its products used in applications where moisture levels are high, it is advisable to dry them before use.

Hygroscopic Nature of Fiberglass

Hygroscopicity refers to the ability of fibers to absorb moisture. Compared to other fibers, fiberglass has relatively low hygroscopicity, primarily affected by the uneven adsorption of moisture in surface cracks. Fiberglass has much lower moisture absorption compared to organic fibers. The higher the humidity in the air, the more water it absorbs. Alkali-free fiberglass has the lowest moisture absorption, while alkali-containing fiberglass absorbs more. Fiberglass fabrics tend to absorb moisture more than the fiber itself, and the moisture absorption of fiberglass fabric is influenced by its weaving pattern.