Relevance and performance of LDH platelets in coatings

The present article presents a review devoted to Layered Double Hydroxide (LDH) as filler in coatings from the patent domain and the applicative literature. Other than bulk properties generally encountered in polymer nanocomposite aspect, LDHs filler relevance for coatings concerns surface properties as well as requiring diffusion barrier into limited width by isolating or healing substrate from aggressive medium. Enhancement of the substrate is performed with rather low pigment/filler concentration underlining the importance of nanometric dispersion to create large interfacial exposure between filler and polymer as well as being crucial for substrate adhesion. Largely exemplified with corrosion coating protection, LDHs is reported here as a corrosion inhibitor nano-container (C.I.NC.), and the self-healing protective effect is occurring from the delivery of inhibitor on demand, the guest interleaved species possess corrosion inhibition ability triggered when it is spontaneously released from the host matrix into aqueous environments in contact with corroding metal substrates. From the academic and patent literature, the review enlists the strategy to employ LDHs as efficient filler for bare metal substrate, mostly aluminum, magnesium and steel, as well as for polymer coatings and conversion films to prevent corrosion, as well as other properties: anti-UV, anti-abrasion and impact resistance, bactericide and antifouling. LDHs platelets dispersion either exfoliated or intercalated is found to be a key to provide great properties such as barrier properties and energy dissipation through nano-spring effect, respectively. The accent is also underlined on the concerns relative to ecological and economic considerations for coatings in an industrial setting and the chemicals regulation. Finally perspectives point out the topical relevance of LDHs nanofiller to supply adaptive and multifunctional properties to coatings.