Determination of adhesive strength in a thermoplastic-resin-thin-fiber system

Conclusion A method was developed for determining adhesive strength in thermoplastic-material—thin-fiber systems formed from a melt. Values of _o were determined for joints between PSF and PC On the one hand and high-modulus organic fibers on the other hand. We studied the dependence of the bond strength on the temperature at which the contact is formed, the area of the contact, and the condition of the surface. The adhesion of PC and PSF to organic polyamide fibers is good enough to make it unnecessary to develop adhesives or specially modify the fiber surfaces for the production of organic-fiber-reinforced plastics. The low shear strength of laminated plastics based on thermoplastic resins is evidently due to the small area of actual contact, which is in turn a consequence of the poor wetting and impregnation of the fiber filler by the melt.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 9–12, January–February, 1990.     

Three Specimen Geometries and Three Methods of Data Evaluation in Single-Fiber Pullout Tests

Mechanics of Composite Materials - The shapes of force–displacement curves recorded in single-fiber pullout and microbond tests are analyzed within the framework of a stress-based model of...     

Effect of electrophysical activation of components on adhesive interaction in polymer composites

The key problem in designing polymeric composites is ensuring a sufficiently strong adhesive bond between the polymer and the filler (or the reinforcement). One method for strengthening the intermolecular interaction at the phase interface is electrophysical activation of the particle surface. We have investigated the absorption activity and adhesiveness of powdered inorganic fillers and polymeric binders with triboelectric activation and activation in a corona discharge. We consider a broad class of disperse materials. We show that electrophysical activation of powdered materials causes changes in the concentration of donor and acceptor centers on the particle surface and in the adsorption activity of the materials as a whole. The presented results can be used for goal-directed selection of the most effective method of activation for disperse materials; they also are evidence for the important role of adsorption forces in the adhesion phenomenon.Report presented at the Ninth International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 734–741, November–December, 1995.     

Kinetics of adhesive contact formation between thermoplastic melts and solid surfaces: Effect on bond strength

Formation of an adhesive contact between a polymer melt (or solution) and reinforcing fibers is considered from the viewpoint of kinetics. A two-stage model of this process has been proposed, and an expression for the interfacial bond strength as a function of time and temperature is derived. Experimental data on bond strength in adhesive joints between thermoplastic polymers and reinforcing fibers formed under various conditions were obtained, and the concept of activation energy was used to analyze them. Since the process is controlled by the stage having the larger activation energy, the adhesive contact formation between fibers and polymer solutions is governed by the rate of adhesive bonding, whereas that between fibers and polymer melts is governed by the rate of the melt spreading.     

“Fundamental” and “practical” adhesion in polymer-fiber systems

The relationship between adhesion and bond strength in thin fiber-polymer matrix systems was studied. Adhesive interaction in composite materials was analyzed within the scope of thermodynamic and molecular-kinetic theories of adhesion. Methods based on wetting are shown to give poor estimation of the work of adhesion in fiber-polymer systems, which is due to their low sensibility to donor-acceptor interactions taking place at the interface. Important information about the acidity and basicity of contacting surfaces can be obtained by using inverse gas chromatography to investigate the thermodynamics of adsorption. The calculation of the work of adhesion including acid-base interactions shows the best agreement with the bond strength in the same systems. The local (ultimate) interfacial shear strength is proposed to characterize the quality of fiber-matrix bonding. Analysis of the relationship between the work of adhesion and adhesive pressure for various systems allowed us to differentiate the dispersive and acid-base components of the local bond strength as well as to estimate distances characteristic of these twoTypes of interaction. For dispersive forces, our estimation gives 7–8Å, i.e., of an order of magnitude of the center-to-center distance for van der Waals interactions. At the same time, the acid-baseInteractions have a characteristic range of 4–5Å and can be attributed to hydrogen bonding. The agreement between the calculated distances and literature data is evidence for the applicability of the proposed method to the analysis of the adhesive interaction in fibrous polymer composites.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 431–446, July–August, 1998.     

Effect of Radiation Modification of Disperse Polyethylene on Component Interaction and Properties of GFRP Based on It

The basic aspects of interfacial interaction between the polymer binder and the filler in glass-fiber-reinforced plastics (GFRP) based on a high-density polyethylene (HDPE) are considered. The plastics were produced by the film-powder technology using a disperse radiation-modified HDPE as the binder. It is shown that the use of the -treated HDPE powder extends the capabilities of controlling the strength properties of GFRP sheets.