1 Diffusion and autohesion II Introduction

They play a critical role in determining the properties, reliability and function of a broad range of materials. For example, polymer melt processing via injection molding (for plastic auto parts) and extrusion (for plastic pipe) create many interfaces in the form of internal weldlines where the fluid fronts coalesce and weld. Compression molding and sintering (of artificial hip joints) requires the coalescence of pellets or powder when their surfaces contact...

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XPS spectra obtained from low-density polyethylene (A) as received and (B) after etching in chromic acid for 30 min at 70 C. Reproduced by permission of Chapman and Hall Ltd. from Ref. 34 , Briggs et al. used XPS to investigate the effect of chromic acid etching on the surface composition of ld-PE and polypropylene 34 . Films were immersed in a solution of chromic acid (K2Cr207 .H2O. H2SO4 7 12 150 by weight) for times between 1 min and 6 h and temperatures between 20 and 70 C. After...

Adhesion Means In Civil Engg

Almost every tube of adhesive to be seen in a hardware store carries the advice roughen surfaces before applying glue. The relevance of surface roughness to adhesion has been long recognised. Galileo discussed adhesion to rough surfaces in different terms from that to smooth surfaces 1 , Over 75 years ago when a modern scientific analysis was first applied to the phenomenon of adhesion, McBain and Hopkins considered that there were two kinds of adhesion, specific and mechanical 2 . The former...

Dhd

Labeled triblocks used in the HDH + DHD experiments. The HDH chains have their centers deuterated 50 and the DHD chains have their ends deuterated 25 on each end for a total of 50 . HDH DHD interface. If the motion of the polymer was the same for each portion of the molecule, i.e., isotropic, the concentration of deuterium across the interface would remain constant. However, if the monomer motion is anisotropic, such as with reptation, where the chain ends lead the centers, a high...

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A Du Pont Volan , pre-applied to glass from water. The advent of fiberglass-reinforced organic resins in 1940 produced a need for new bonding technology 6 . Although the glass-filled composites had good strength, properties deteriorated after prolonged exposure to atmospheric moisture, indicating loss of bonding between the glass and the resin. This problem was effectively solved in the mid-1950s when the plastics industry began using small amounts of silane coupling agents to improve composite...

References

In Sharpe, L.H. (Ed.), Proceedings of the 16th Annual Meeting of The Adhesion Society, Inc., Williamsburg, VA, Feb. 21-26, 1993. Gordon and Breach, 1996. 2. Pocius, A.V., J. Adhes., 39, 101 (1992). 3. Venables, J.D., J. Mater. Sei., 19, 2431 (1984). 4. Clearfield, H.M., McNamara, D.K. and Davis, G.D. In Lee, L.H. (Ed.), Adhesive Bonding. Plenum Press, New York, 1991, p. 203. 5. Pleuddemann, E.P., Silane Coupling Agents. Plenum Press, New York, 1982. 6. Gettings, M....

Info

Substrate with an aqueous solution of the silane, addition of the silane to a latex water-based polymer system, or hydrolysis by absorbed or adsorbed moisture when applied in an organic solvent. Good interfacial bonding requires that the siloxane silanol equilibrium favors siloxane formation over silanol formation. An important side reaction, particularly when applied in aqueous solution, is self-condensation of the coupling agent to form siloxane polymers. The coupling agent remains somewhat...

Eb

Representative block copolymer structures, (a) Routes to SIS i, coupling reaction ii, sequential, (b) Three and four-arm SI stars, (c) (SIbh radial, (d) (SEB Bt radial. are physically crosslinked at room temperature due to the phase separation that takes place between the rubbery block and the aromatic block. Phase separation occurs because of the dissimilarity of the polydiene and the polystyrene segments. Individual polystyrene segments from many chains organize into a discontinuous...

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The effect of micro-roughness on the preferred contact angle. The observed contact angle is shown as a function of rugosity r- A tnominal for various intrinsic contact angles, 6 . Larger scale roughness leads to hysteresis as indicated by the dashed lines diverging from the 60 60 curve, with the top line corresponding to the advancing angle, and the lower line corresponding to the receding angle. does not contact the solid. The effective contact angle over such gaps is 180 , and if the...

3 Xray photoelectron spectroscopy XPS

In X-ray photoelectron spectroscopy (XPS), a beam of soft X-rays with energy hv is focused onto the surface of a solid that is held under an ultra-high vacuum, resulting in the ejection of photoelectrons from core levels of the atoms in the solid 20 . Fig. 15 shows an energy level diagram for an atom and illustrates the processes involved in X-ray-induced photoelectron emission from a solid. Fig. 15. Energy level diagram for an atom near the surface of a solid, showing the processes involved in...

2 uux

It should be noted that, if the medium between the particle and substrate is something other than vacuum and possesses a dielectric constant e, the interaction energy in Eq. 68 is reduced by a factor of e2. Eq. 68, which relates the interaction energy between permanent electric dipoles and their separation distances is known as the Keesom effect. 6.2. Permanent-induced dipole interactions In the second type of interaction contributing to van der Waals forces, a molecule with a permanent dipole...

Contents

Semi-empirical strategies for predicting adhesion Chapter 2. Direct estimation of the adhesion of solid polymers Chapter 4. Surface mechanical measurements at the nanoscale Chapter 5. Micro-mechanical processes in adhesion and fracture Chapter 6. Surface analysis in adhesion science 243 Chapter 7. Surface roughness and adhesion 317 Chapter 9. Coupling agents chemical bonding at interfaces Chapter 10. Priming to improve adhesion Chapter 11. Pressure sensitive adhesives A.I. Everaerts...

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XPS survey spectra of plasma polymerized acetylene films as a function of reaction time with a model rubber compound. The reaction times were (A) 0, (B) 15, (C) 35, and (D) 65 min. Reprinted by permission of Gordon and Breach Science Publishers from Ref. 23 . the C(ls) binding energy of the ester carbon was about 0.1 eV greater for PMMA adsorbed onto silicon than for bulk PMMA. This small increase in the binding energy of the ester carbon atom was attributed to hydrogen bonding between...

6000

All failures were cohesive within the adhesive. Adhesive E610 nylon epoxy (Asulab SA). a Asuclean is a proprietary formulation of Asulab SA. All failures were cohesive within the adhesive. Adhesive E610 nylon epoxy (Asulab SA). a Asuclean is a proprietary formulation of Asulab SA. This interaction energy is reversible because removal of the wetting liquid from the surface only requires the disruption of these interaction sites. Solidification of the liquid into an adhesive changes the...

Ch3

An occasional silanol functional end group makes the MQ resin a very rigid molecule with methyl groups and, if present, a few silanol groups exposed at its surface. Typical MQ resins would have molecular weights of several thousands with variations possible in the M to Q ratio, the absolute molecular weight, and the amount of silanol functionality. The very rigid MQ molecules do not melt without degrading first. This characteristic and the hybrid inorganic organic nature of the material make it...

Em

Relationship between the measured interfacial strength and the negative Gibbs free energy of mixing, AGKM, for glass beads treated with various silane coupling agents embedded in a PMMA matrix. Error bars correspond to 95 mean confidence intervals. regardless of the mechanism by which adhesion is effected. The intimacy of contact, in turn, depends on the completeness of the wetting of the adherend by the liquid adhesive, i.e. spontaneous spreading, and the latter requires that the...

Semiempirical strategies for predicting adhesion

Department of Chemical Engineering, University of Washington, Seattle, WA 98105-1750, USA 1. Predicting adhesion is it a reasonable objective . . The scope of the question 1.1.1. The meaning of adhesion, adhesive failure and interfacial strength Adhesion refers to a complicated set of inter-connected phenomena that is far from completely understood, and it therefore makes sense at the outset to inquire into the reasonableness of any attempts to 'predict' it using semi-empirical methods. To...