An Important aspect with respect to optimal mechanical performance of fiber reinforced composites in general and durability in particular is the optimization of the interfacial bond between fiber and polymer matrix. The quality of the fiber-matrix interface is significant for the application of natural fibers as reinforcement for plastics. Since the fibers and matrices are chemically different, strong adhesion at their interfaces is needed for an effective transfer of stress and bond distribution throughout an Interface. A good compatibilization between cellulose fibers and non-polar matrices is achieved from polymeric chains that will favor entanglements and interdiffiusion with the matrix. This article gives a critical review on the physical and chemical treatment methods that improve the fiber-matrix adhesion and their characterization methods.

A review on interface modification and characterization of natural fiber reinforced plastic composites

The final performance of a composite material depends strongly on the quality of the fibre-matrix interface. The interactions developed at the interface were studied using the acid-base or acceptor-donor concept. The surface characteristics of the carbon fibres and the epoxy matrix were studied using a tensiometric method and the inverse gas chromatography technique. Acid-base surface characters could be determined allowing the interactions at the interface to be described by a specific interaction parameter. It was shown that the shear strength of the interface, as measured by a fragmentation test, is strongly correlated to this specific interaction parameter, demonstrating the importance of acid-base interactions in the fibre-matrix adhesion.

The Role of the Interface in Carbon Fibre-Epoxy Composites

The Henry's law region of the adsorption isotherms for a series of n-alkanes on cotton cellulose and on wood fibers has been studied by gas chromatography. On wood fibers, the three thermodynamic functions at zero surface coverage were determined. A linear relationship between the standard free energy, the enthalpy and the entropy, and the number of carbon atoms was found. Attempts were made to estimate the London contribution to the surface free energy of cellulose and wood fibers from the results at infinite dilution. A method based on the increment per CH2 group in the free energy of desorption, normalized per unit area of a methylene group, is in reasonable agreement with other estimates.

Adsorption of n-alkanes at zero surface coverage on cellulose paper and wood fibers

This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphology, aspect ratio, and surface chemistry. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymatic, mechanical, and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and 13C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148 ± 147 for tunicate-CNCs to 23 ± 12 for wood-CNCs. Hydrophobic interactions, measured usin...

Comparison of the properties of cellulose nanocrystals and cellulose nanofibrils isolated from bacteria, tunicate, and wood processed using acid, enzymatic, mechanical, and oxidative methods

Surface-active organic molecules are common constituents of atmospheric aerosol particles, raindrops, and snowflakes. If these compounds are present as surface films, transfer of gases into the atmospheric water systems could be impeded, evaporation could be slowed, and the aqueous chemical reactions could be influenced. To investigate these possibilities, we have reviewed the chemical literature pertaining to organic films on aqueous surfaces: their composition, structure, properties, and effects. We then review the surface-active organic compounds in atmospheric water. We report the results of new measurements of surface tension of aqueous solutions of common atmospheric organic compounds (β-pinene, n-hexanol, eugenol, and anethole) and demonstrate that the compounds produce films with properties similar to those of the more well known surfactants. We conclude that organic films are probably common on atmospheric aerosol particles and that they may occur under certain circumstances on fog droplets, cloud droplets, and snowflakes. If present, they will increase the lifetimes of aerosol particles, fog droplets, and cloud droplets, both by inhibiting water vapor evaporation and by reducing the efficiency with which these atmospheric components are scavenged. The presence of the films will not cause a significant reduction of solar radiation within the aqueous solution. It appears likely, however, that the transport of gaseous molecules into and out of the aqueous solution will be impeded by factors of several hundred or more when organic films are present. Since incorporated gas molecules provide much of the oxidizing potential of atmospheric water droplets, the organic films will play a major role in droplet chemistry by strongly inhibiting solution oxidation.

Organic films on atmospheric aerosol particles, fog droplets, cloud droplets, raindrops, and snowflakes

surface analysis of paper and wood fibres by ESCA (electron spectroscopy for chemical analysis). i. application to cellulose and lignin

Adsorption, spreading pressure, and london force interactions of hydrocarbons on cellulose and wood fiber surfaces

Adsorption of hydrocarbons on silica-supported water surfaces

Adsorption isotherms of n-decane and mesitylene on cotton cellulose paper conditioned at several relative humidities were measured using a gas-chromatographic technique. Relative humidities in the chromatographic column were achieved by controlling the partial pressure of water in the carrier gas. From the isotherms, the external area of the paper was determined while the paper was in dynamic equilibrium with the water vapour. Between 0 and 65% relative humidity the external surface area of the paper decreased irreversibly due to some stress relaxation effects, while over 85% relative humidity the area decreased reversibly due to pore-filling by water of the large external pore system of the fibres and of the paper.

Gilles M. Dorris

Papers

Adsorption of n-alkanes at zero surface coverage on cellulose paper and wood fibers

surface analysis of paper and wood fibres by ESCA (electron spectroscopy for chemical analysis). i. application to cellulose and lignin

Adsorption, spreading pressure, and london force interactions of hydrocarbons on cellulose and wood fiber surfaces

Adsorption of hydrocarbons on silica-supported water surfaces

Effect of relative humidity on the external area of paper