279 Enviromechanical Assessment arising from fracture events in composite films as a function of applied deformation and increased environmental humidity. Figure 14 demonstrates that moisture influenced the audible release of mechanical stresses from all examined film-fiber composites. Relative to the 35% RH #AED results, the 75% RH environment plasticized the composite films Figure 12. Work of tensile extension for fixative-polymer composite films (50% and 90% RH). The asterisk (*)highlights the resistance of the imidized p(IB/MA) composite film to extension at 90% RH. Figure 13. Optical microscopy (A,B) and SEM (C,D) images of film-fiber composites: A) PVP K-60 at 30% RH B) PVP K-60 at 30% RH C) PVP K-60 at 30% RH and D) PVP K-60 at 85% RH.

280 JOURNAL OF COSMETIC SCIENCE hence—by deforming plastically—the flexible film mitigated the brittle response to applied stress, and the #AED dramatically decreased. Concerning interfacial charge specificity, the lower-viscosity treatments (i.e., imidized p(IB/MA), PVP K-15, PVP K-30, PVP K-30/PEG 400, and PVP K-60) produced directionally higher #AED with bleached snippets at higher humidity, demonstrating that annealing plasticized hygroscopic polymers against a higher- energy surface promotes relaxation, healing, and efficient self-assembly of the polymer-fiber interface. In the final analysis, apart from the apparent PVP K-15 and imidized p(IB/MA) composite synergism, at ≤50% RH the composite film work-to-break results reveal that the requisite energy to introduce dissipative plasticity was greater than the crack initiation energy and critical failure stress—hence, the majority of #AED were attributed to brittle-film cracking, propagation, and near-interfacial debonding events (16,18,23). However, at humidity levels that plasticized the fixative T g to ambient temperature, viscous dissipation of stress modified the polymer matrix and limited crack initiation (16,23–25) instead, weld debonding occurred elastoplastically or viscoplastically, with negligible acoustic emissions. COMPARISON OF RESULTS FROM COMPOSITE FILMS AND DHSA-AED ANALYSES Since rupture testing of composite films is a less conventional measurement technique, it is worthwhile to compare outcomes obtained with DHSA-AED using treated omega loop assemblies (16) against results collected by fracturing film-fiber composites using mechanical testing with synchronous AED: 1) #AED released at 50% RH from virgin fiber composites containing higher MW fixatives was significantly lower than the #AED liberated from virgin fiber composites formed with lower MW fixatives 2) #AED released from composites with bleached fibers was greater than #AED released by composites constructed with virgin fibers 3) when breaking bleached and virgin composite films, the average upper limits of dB-SPL were much lower than audible intensities observed when fracturing respective neat fixative films however, the average dB-SPL liberated while fracturing composite films was similar to the average dB-SPL recorded in DHSA-AED and 4) absorbed moisture plasticized fixatives in both DHSA and composite films, and accordingly lowered #AED. Figure 14. Total #AED as a function of applied deformation and testing humidity for polymer-fiber composite films comprised of virgin and bleached snippets. EDB =virgin European dark brown hair snippets.