264 J. Cosmet. Sci., 73, 264–284 (September/October 2022) Address all correspondence to: Timothy W. Gillece, tgillece@gmail.com Enviromechanical Assessment of Fixative Hair Fiber Composite Films TIMOTHY W. GILLECE AND ROGER L. MCMULLEN Ashland Inc., Bridgewater, New Jersey, USA (T.W.G, R.L.M.) Accepted for publication December 04, 2022. Synopsis Mechanical analysis with acoustic emission detection was used to characterize bonding failure in polymer-fiber composite films composed of styling resins and virgin or bleached hair fiber snippets. Composites prepared with bleached snippets required more energy to induce film rupture while producing greater numbers of detectable acoustic emissions than films containing virgin fibers. Texture analysis and scanning electron microscopy revealed that film-fiber composites failed adhesively at lower humidity levels, while augmented film ductility inhibited brittle fracturing in higher-humidity environments. The work to rupture film-fiber composites correlates with the maximum force response (R2 =0.94) and toughness (R2 =0.86) that were evaluated using treated omega loop assemblies and dynamic hairspray analysis. In addition, outcomes from dynamic vapor sorption, humidity-controlled differential scanning calorimetry, humidity-controlled dynamic mechanical analysis, tensile testing, and impact testing were considered. INTRODUCTION Apart from trained-panel, half-head, and costly in-home usage testing protocols, numerous objective laboratory methods have been established to routinely characterize the durability of hold after applying styling fixatives to shaped hair tresses (1–17). Early fixative-testing evaluations were adopted from the lacquer and adhesives industries, wherein film-formation, dry times, tack, resistance to bending and extension, and film-flaking protocols were used to differentiate products and establish performance claims (4). In the years that followed, digital analysis and instrumental methods were introduced to quantify fixative strength and weld durability, including curl retention (1–3), twist-retention analysis (5), single-fiber junction analysis (6), three-point bending (8,13), two-point stiffness (7), dynamic hairspray analysis (DHSA) (10–17), DHSA in conjunction with acoustic emission detection (AED) (DHSA-AED) (16), and dynamic mechanical analysis (DMA) (9). Each stiffness-testing assay employs specialized instrumentation to controllably introduce a load to the sample— wherein Instrons, texture analyzers, torsional braid analyzers, rheometers, and DMAs are commonly used. In addition, researchers routinely integrate environmental control with mechanical measurements to account for atmospheric film plasticity.