Nanomechanical measurements for the design of solid fabric enhancer (SFE)

Solid Fabric Enhancers (SFE) are delivered onto garment surface during tumble drying process to prevent the built-up of statics on fabrics and to lubricate the fibres, hence improving sensorial benefits of handling and wearing clothes. Nanomechanical properties of SFE coatings were investigated by atomic force microscopy (AFM) based force spectroscopy, which underpins the delivery effectiveness and efficiency of the SFE coating.

Model SFE coatings (thickness 15 µm) consisting of quaternary ammonium ester (EQ) and fatty acid (FA) were prepared on a solid substrate, and their nanomechanical properties were quantified. Two types (A, B) of EQ and FA were used to prepare the mixtures, each exhibiting different nanomechanical properties. While the adhesion of both FAs was similar (5.0 ± 0.02 nN vs 5.1 ± 0.01 nN), their Young’s modulus varied distinctively (3.3 ± 0.1 MPa vs 6.1 ± 0.1 MPa). For EQs, the Young’s modulus was similar (1.8 ± 0.04 MPa vs 1.6 ± 0.10 MPa), while adhesion showed greater variation (6.5 ± 0.10 nN vs 12.6 ± 0.01 nN). Subsequently, resulting mixtures of A and B materials behaved differently. Unlike pure EQs, pure FAs, and mixtures of type B, mixtures of type A exhibited characteristics that are likely due to different molecular orientation at the surface. Nanoindentation data evidences that the AFM tip penetrates different layers with varying Young’s modulus, implying that the molecules form an organised structure at the proximity to the surface of the SFE formulation.

Nanomechanical measurements show that the individual components can adapt different molecular configuration and structural characteristics which dictates product performance of soft solid formulations used further in sectors such as healthcare (drug delivery), food (chocolate) or in consumer goods.