Determination of the surface free energy of modified carbon fibers and its relation to the work of adhesion

Abstract

Surface free energy of various carbon fibers was determined by tensiometric method in three different procedures. The dispersive ys a and the nondispersive y~ components were separately determined by contact angle measurements in two-phase system, formamide-n-alkanes. The yw increased by oxidation and decreased by hydrogen reduction, while the ys a remained almost constant. The y~ value determined from contact angle of water/ethyleneglycol solution tended to become higher. The critical surface flee energy was in harmony with the total free energy determined from formamide-n-alkanes system as long as liquids were properly selected. The formation of oxygen-containing functional groups was evidenced by ESCA, and the surface [O]/[C] ratio was related linearly to the surface polarity defined by yw a + y~]. Oxidation in liquid phase resulted in the formation of both hydroxyls and carboxyls, while only hydroxyls were formed in gas phase. The interracial shear strength of the fiber-epoxy resin could be closely correlated with thermodynamical work of adhesion calculated on the basis of surface free energy and its component.

Influence of Oxygen Plasma Treatment of PAN-Based Carbon Fibers on Their Electrokinetic and Wetting Properties

“…However, ␥ d was drastically diminished (approximately 30%) to a constant value for the treated fibers compared to the unmodified fibers; the polar part ␥ p of the surface tension increased much more strongly. ␥ d should reflect the essential surface characteristics of carbon fibers or the graphitic framework of the fiber surface (28). These results are consistent with those obtained by Bourgeois and Davidson (5) and Bascom and Chen (6), who also treated carbon fibers in oxygen plasma, and Xie and Sherwood (7), who modified carbon fibers in air plasma.…”

Application of the surface free energy concept in polymer processing

“…Table 5. Acid-base term of the work of adhesion and the surface free energy y,, calculated from the contact angles of water and methylene iodide, for the surface-treated carbon fibres, and the tensile strength amax and the notched impact strength ak of PA6 composites reinforced with the surface-treated fibres toughness than values reported in the literature [4,6]. More systematic work has to be done to confirm this correlation.…”

“…Equation (4) is based on Good's geometric mean approach [15]. For liquids such as alkanes, in which intermolecular interactions are due only to dispersion forces (y, = yd), the dispersion force component of the solid surface free energy can be determined from equation (4) by contact angle measurements with these liquids. In this study, methylene iodide (CH2I2) was used to determine Ys.…”

“…The mechanical properties of fibre-reinforced polymers (strength, stiffness, toughness) are governed by the adhesion of the polymer matrix to the reinforcing fibre. Several authors have used contact angle, electrokinetic, and inverse gas chromatographic measurements to characterize the interaction forces at glass or carbon fibre surfaces [1][2][3][4][5][6][7][8][9][10][11][12][13]. The objective of this study was to compare the results obtained by the methods mentioned above and to see if a correlation existed between the surface characteristics of carbon and glass fibres and the mechanical properties of fibre-reinforced polymers.…”

Surface Energy Compatibilites of Cellulose and Polypropylene

“…The Wilhelmy method of contact angle measurement has been widely used to measure fiber surface characteristics [15,[19][20][21][22][23]. This technique [12], involves using a very sensitive microbalance to measure the downward force that a liquid's surface tension exerts on a fiber or rod submerged vertically in the liquid.…”