282 JOURNAL OF COSMETIC SCIENCE film composites should be constructed with dilute fixative solutions (e.g., 1.5% [w/w]) and 0.15 g of fiber snippets—as an example, see the SEM micrograph in Figure 16. At lower applied fixative concentrations, the contiguous polymer solution dried and spontaneously developed realistic film discontinuities consequently, the measured #AED in composite film testing better associated with #AED captured in DHSA-AED (R2 =0.77). ONGOING FILM-FIBER COMPOSITE STUDIES: NATURAL BIOPLASTICS To conclude the composite film testing discussion, it is worthwhile to mention that natural fixative polymers have been added to ongoing composite film studies in which the intrinsic durability and fracturing behavior of bioplastics—including cellulose ethers, cationic guars, and biodegradable polyesters—are being examined. In conjunction, supplemental analyses are being used to investigate the possibility that fiber alignment in the film influences the enviromechanical failure response of the composite. Put differently, recent method adaptations incorporate fiber alignment and mechanical anisotropy arguments into the discussion. Mechanical anisotropy is a material property that is likely introduced to the composite film by the ultrafine structure of the hair fiber, wherein hair fibers resist elongation but willingly bend and twist when torque is applied transversely. By way of illustration, Figure 17A models a scenario in which the longitudinal axes of the fibers were aligned with the imposed tensile forces (±F) in distinction, the long axes of hair snippets in Figure 17B were positioned parallel to the plane of the film, but normal to the applied F. Additionally, Figure 17C models a blend of the fiber patterns illustrated in Figure 17A and B, in which the hair snippets formed a crosshatch within the plane of the contiguous polymer film. Lastly, in Figure 17D a small testing sieve was attached to a ring stand and suspended above a Teflon dish containing fresh polymer solution. Several hair fibers were then inserted through the sieve mesh, and the distal ends of the fibers were immersed in polymer solution after drying, the fibers were trimmed at the film surface such that the longitudinal axes of the embedded snippets aligned perpendicularly with the plane of the dried film and applied tensile F. Figure 16. SEM micrograph of a film-fiber composite formed using 0.2 g of 10-mm fibers dispersed in a film prepared with a 1.75% (w/w) imidized p(IB/MA) solution. To create the splayed welds in the image, the composite was deformed 5 mm at 85% RH using a 0.25-inch stainless-steel ball probe and an indexable film support rig—after 15 minutes, the humidity was abruptly lowered to 35% RH to induce a relaxed rubber-to- glass transition in the splayed and cavitated welds. The subsequent micrographs demonstrate the significant tensile forces being exerted on the fibers and interspersed seam welds.

283 Enviromechanical Assessment CONCLUDING REMARKS Positive correlations between results from mechanical testing with AED and fixative composites, and outcomes from DHSA-AED testing using treated omega loop assemblies demonstrate that the requisite work to rupture neat polymer films is proportional to the assessed toughness, F1, E10/E1, and #AED of analogously treated omega loop assemblies. In addition, composite film studies using AED substantiate that acoustic emissions are frequently liberated by mechanically stressed hair fiber assemblies that had been set into fixed positions with brittle styling fixatives (16). Practical advantages with using composite films to forecast the enviromechanical performance of fixatives on hair include: 1) compared to working with treated tress assemblies, sample preparation is strikingly simple 2) flat and two-dimensional film samples are easy to handle and mount in an assortment of instruments using a variety of sample grips 3) using water vapor to plasticize films, larger composites may be safely trimmed into smaller films, whereby force data can be normalized to the sample dimensions—which is important for computing the stress response of cuboids using Instron, texture analysis, and DMA 4) similar to welds in polymer-treated hair fiber assemblies, thin and flat composite films rapidly equilibrate with fluctuations in ambient humidity 5) style durability failures and DHSA performance indices frequently correlate with the material properties of the fixative because outcomes from film-fiber composite testing include the physiochemistry of the hair fiber while accentuating the intrinsic characteristics of the polymer. Notable disadvantages associated with using fixative-fiber composite films to model interfiber bonding in tresses include: 1) by volume, treated “real world” hair tresses are 90% hair fibers in contrast, composite films are 90% fixative 2) films are easily produced by dispersing fibers into low-viscosity solutions however, dispersing fiber snippets in thick gels and mousses is quite challenging. ACKNOWLEDGMENTS Many thanks to Professor Steven Abbott. We also recognize Bill Thompson of Ashland Inc., Jeff Jones and John Rutsey of Rush, Jeff Bezos of Blue Origin, and Len Salvatore of GS Robotics LLC. +F -F +F -F +F -F +F -F (A) (B) (D) (C) l w t Figure 17. Anisotropic film-fiber composites. Rather than randomly distributing fibers in the films, the longitudinal axes of fiber snippets may be deliberately aligned with the plane of the film and (A) parallel (B) perpendicular or (C) crosshatch to the applied tensile F (D) in addition, the longitudinal axes of the fibers may be oriented perpendicular to the plane of the film and perpendicular to the applied F. To measure the stress and moduli in tensile testing or DMA, composite films should be symmetrically trimmed into cuboids.