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Maleic anhydride plasma polymer was deposited at the surface of carbon fibers and functionalized with vinyl and thiol groups to improve its adhesion strength with an acrylate matrix cured by an electron beam. A characterization of the fiber surface properties was done before and after coating (topography, surface chemistry, and surface energy). Sharp improvements of the interfacial shear strength (+ 120%), measured by a micromechanical test derived from the pull-out test, were obtained and, to the best of our knowledge, never reported before. The values were close to the ones obtained with a thermal cure. The comparison of this approach with other types of surface treatments (oxidation, grafting of coupling agents) enabled the establishment of a general strategy for the improvement of the interfacial adhesion in carbon fiber composites cured by an electron beam and potentially the improvement of their mechanical properties. This strategy is based on a high surface density of functionalities that are generating covalent bonding during the polymerization of the matrix and on the insertion of a polymer layer strongly attached to the fiber surface and acting as a buffer between the fiber surface and the matrix to counteract the generation of stress in the interphase.

The development of technologies to tune lignin properties for high-performance lignin-based materials is crucial for the utilization of lignin in various applications. Here, the effect of methanol (MeOH) fractionation on the molecular weight, molecular weight distribution, glass transition temperature (Tg ), thermal decomposition, and chemical structure of lignin were investigated. Repeated MeOH fractionation of softwood Kraft lignin successfully removed the low-molecular-weight fraction. The separated high-molecular-weight lignin showed a Tg of 211 °C and a char yield of 47 %, much higher than those of as-received lignin (Tg 153 °C, char yield 41 %). The MeOH-soluble fraction of lignin showed an increased low-molecular-weight fraction and a lower Tg (117 °C) and char yield (32%). The amount of low-molecular-weight fraction showed a quantitative correlation with both 1/Tg and char yield in a linear regression. This study demonstrated the efficient purification or fractionation technology for lignin; it also established a theoretical and empirical correlation between the physical characteristics of fractionated lignins., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)