SYNOPSISCellulose fibers were surface modified with polypropylene-maleic anhydride copolymer. The physical properties of such fibers were characterized by contact angle measurements, and the chemical structure was identified with ESCA and FTIR. ESCA showed that the modifying agent was localized at the surface of the fibers. The modified fibers were compounded with polypropylene, and composites with various amount of fibers were manufactured by injection molding. All mechanical properties were improved when treated fibers were used. SEM showed improved dispersion, wetting of fibers, and adhesion. The nature of adhesion was studied using FTIR. It was found that the surface modifying agent is covalently bonded to the fibers through esterification. The degree of esterification is enhanced by activating the modifying agent before fiber treatment. This study has shown the effects of treatment conditions on activation of reactive species and chemical reaction between fiber and modifying agent. Moreover, a better understanding has been achieved of the nature of adhesion for the system.

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The surface properties of cellulose fibers have been modified by heat treatment, by silane coupling agents, and by maleated polypropylene grafts. The effectiveness of these methods has been evaluated by electron spectroscopy (ESCA), by contact angle measurements, and by inverse gas chromatography. The latter analyses yielded information on the fibers' acid/base interaction potential. Cellulose was found to be amphoteric, with prevalent acidic properties. Heat and chloro-silane treatments accentuated acidity, while amino-silane treatment produced net basicity in the fiber surface. Modification with rnaleated polypropylene reduced specific interactions and converted the fiber to a predominantly dispersion-force solid. The modified fibers were used in composites with polypropylene (neutral), polystyrene (base), and chlorinated polyethylene (acid) as matrix. Stress/strain and dynamic mechanical parameters were found to vary with acid/base interactions between polymer and fiber, significant improvements being noted in elastic and storage moduli, in tensile strength and elongation. In polypropylene, properties were unaffected by acid/base considerations. Acid/base forces, not necessarily dominant, merit consideration in the design of surface modification strategies intended to optimize composite mechanical properties.

SYNOPSISCellulose fibers were grafted with compatibilizing agents, such as maleated polypropylenes of different molecular weights. Steric effects and surface free-energy effects were found to stimulate the stretching of grafted chains away from the cellulose fiber surface, giving rise to a brushlike configuration in a polypropylene ( P P ) melt. Inverse gas chromatography measurements on modified fibers using a model compound for PP as adsorbate showed that interactions of PP and grafted fibers, which were mainly diffusion-dependent, increased with increasing molecular weight of the compatibilizer. Dynamic mechanical measurements and tensile testing of composites showed that the presence of compatibilizing agents enhanced stress transfer and increased interphase thickness considerably, the most significant effect being obtained for the high molecular weight compatibilizers. Apparently, the longer the grafted chains, the larger the fraction of matrix molecules involved in the interactions and, thus, the thicker the interphase. The improvement of adhesion between treated fibers and PP, as detected by peel testing, was proven to be caused mainly by entanglements formed between compatibilizing agents and PP.

Electrically commanded surfaces (ECS) is a liquid crystal display concept whereby the switching of the alignment layer, which is driven by an electric field applied across the layer, is further transferred to the bulk liquid crystal material via elastic forces. This work presents the electro-optic response of a sandwich cell with alignment layer made of siloxane-based ferroelectric liquid crystal polymer, representing the ECS. The bulk liquid crystal material of choice was an in-house nematic mixture comprising fluorinated liquid crystalline compounds with negative dielectric anisotropy (Delta-epsilon < 0). We report a distinct linear electro-optic response, arising from the field-induced in-plane switching of the nematic which in turn is mediated by the ECS. © 2005 American Institute of Physics. [DOI: 10.1063/1.1849844