Nanocomposite coating materials reinforced by nanocellulose

A recent study presents polyester–melamine coil coating formulation reinforced with surface-modified cellulose nanofibrils.

Cellulose is the structural component providing plant tissues with impressive mechanical properties, which are combined with excellent flexibility. These are very attractive properties in the perspective of designing coating materials. Image source: silencefoto - AdobeStock (symbol image).

In light of the need to redesign industrially produced materials by utilizing renewable resources, nanoscopic forms of cellulose are regarded as a valuable asset. In a new work, the potential of cellulose nanofibrils (CNFs) as an unconventional nanoadditive for a polyester–melamine coil coating formulation is explored. CNFs, hydrophilic nanomaterials with high aspect ratios, were successfully incorporated in the solvent-borne formulation. Coatings were prepared with extremely low loadings of the nanoadditive (0.5 and 0.7 wt%). At these concentrations, the volume fraction of the nanofibrils in the coatings was calculated to be close to their percolation threshold. Two different pathways of CNF surface modification were applied to allow for a good compatibilization in the resin matrix, and the formulations were cured in two different settings. The effective compatibilisation of the nanoadditive led to a significant variation of the viscoelastic properties in the coatings containing CNFs.

Significant matt effect

The results from dynamic mechanical analysis (DMA) highlighted the effect of CNFs on the crosslinked network at the nanoscale, resulting in an increase in Tg. Additionally, an increase in the stress at break and Young’s modulus was determined by tensile testing, while satisfactory elongation at break was preserved. Other relevant effects induced by the presence of CNFs on the properties of the coatings were highlighted, such as a significant matt effect, increased surface roughness and lower scratch resistance. A preliminary evaluation of the water barrier properties by electrochemical impedance spectroscopy (EIS) is also presented, suggesting that the incorporation of a hydrophilic nanoadditive did not lead to a deterioration of the coatings’ performance.

The study has been published in Progress in Organic Coatings, Volume 182, September 2023.

Event tip

Bio-based systems are also the focus of the EC Conference Bio-based and Water-based Coatings on November 14 and 15 in Berlin, Germany. At the conference, you will learn about the latest developments in bio-based and water-based coatings.

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