UV radiation resistant polyimide based composites reinforced with nanostructured titanate particles: preparation and properties

Abstract

Ultraviolet (UV) exposure is one of the most deleterious threats to polymers. UV light may alter chemical bonds, leading to discoloration of the polymer and even degradation of its properties. Polyimide (PI) is a well-known polymer in electronic devices, filtration and as components for spacecraft and satellites. PI has desirable properties as a lightweight material, which is flexible and resistant to heat and chemicals. This work is focused on protection of polyimide from UV damage by incorporating titanate nanostructures. The effects of titanate particle incorporation within a PI based polymer on mechanical and thermal properties are discussed.
Addition of titanate nanosheets (TiNS) (2 wt%) to a polyimide precursor enhanced the hardness (by 90%) and modulus (by 103%) due to the high aspect ratio (l/h = 133.33) and aligned orientation of the TiNS, observed by TEM and SAXS. In contrast, 2 wt% titanate nanotubes (TiNT) increased the hardness and modulus by 91% and 165%, respectively; these values are higher than theoretical predictions using TiO2 properties, indicating TiNT may have higher mechanical properties than TiO2. Small additions of TiNT (0.1 wt%) to polyimide, either by an in-situ or ex-situ method, increased its Tg by ca. 69 oC, probably due to strong bonding between TiNT and PI.
The incorporation of TiNT protected functional groups of polyimide (e.g., C=O and CF) from UV light. Long cracks and degradation of mechanical properties were not observed in TiNT-PI samples. The protection of PI from UV exposure was similar to the existing polyhedral oligomeric silesquioxane (POSS). A novel characterisation method of polymer UV degradation by methylene blue adsorption was developed. Methylene blue reacted with moieties created from UV damage. Changes in its concentration indicated degradation.

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