Linear and nonlinear relations between DSC parameters and elastic moduli for chemically and thermally treated human hair

Against the practical context of thermal straightening, hair samples were obtained with a chemical (bleaching) as well as a cumulative thermal history (0–800 s, 200 °C). On these samples, tensile testing and DSC analysis, both in the wet state, were conducted to obtain the elastic moduli Ew as well as denaturation temperatures TD and enthalpies ΔHD. 3D plots show overall linearity for the relationships between the parameters for natural hair. For bleached hair, pronounced nonlinearities develop beyond 300 s of thermal treatment. At this stage, TD as well as Ew approaches limiting values, consistent with the state of a highly cross-linked, thermoset polymer. 2D projections are used to investigate the correlations between pairs of parameters. The results show that bleaching imparts a specific sensitivity for thermal damage, namely, to the matrix proteins, which more readily than the intermediate filaments (IF) turn into a thermoset. Overall, correlations between parameters hold well prior to the thermoset range. It is thus suggested that tensile testing to determine the elastic modulus and DSC come to consistent and equivalent results, at least, for the current experimental context. However, while Ew combines contributions of IFs and matrix, DSC differentiates the specific property changes of these components. © 2019, The Author(s)

High-strain stress relaxation: probing the main structural components in the cortex of human hair

The relation between the main cortical structures in hair (IFs & matrix) and its mechanical properties has been studied for many years. Beyond fundamentals aspects, this was also done with the objective to gain insight into structure specific effects of environmental damage and cosmetic treatments. In practice, mechanical analyses to determine internal structural changes have largely been limited to studying fibre modulus, breakage, and a limited number of other parameters in the dry and the wet state. High-strain stress relaxation experiments of hair in water provide the opportunity to study the strain-dependent, elastic properties of IFs and matrix via the creation of isochronal stress-strain curves. This approach is combined with the analysis of the non-linear viscoelastic relaxation performance of the matrix. This paper discusses the experimental and theoretical methods used and the implications of its findings with respect to widely held theories about the relationship between the stress-strain properties of hair and its morphological and molecular structures

Second-order polarizability of donor-acceptor substituted oligothiophenes : substituent variation and conjugation length dependence

Second-order polarizabilities and excited state dipole moments of a number of donor-acceptor substituted α-oligothiophenes have been investigated by use of electric field induced second harmonic generation (EFISH), solvatochromism and electrooptical absorption measurements (EOAM). The experimental results reveal that oligothiophenes are very effective conjugation units offering substantial enhancement of the second-order polarizability with increasing chain length

Анализ и выбор оптимальной технологии проведения работ по реконструкции компрессорного цеха линейно-производственного управления магистральных газопроводов

На основе нормативно-технической документации выбрана оптимальная технология проведения ремонтных работ на компрессорном цехе. Разработаны рекомендации по проведению ремонтных работ по реконструкции компрессорного цеха. Рассчитаны показатели энергоэффективности и коэффициенты технического состояния газоперекачивающих агрегатов до и после реконструкции компрессорного цеха.On the basic of technical documentation the optimal technology of repair at the compressor department was chosen. Recommendations for the repair work on the reconstruction of the compressor department. The energy efficiency indicators and the technical state coefficients of gas compressor units before and after the reconstruction of the compressor department are calculated