Mechanical Interlocking Effect Research Articles

Modification of Copper Surfaces: Effect on Adhesion at the Copper Polyimide Interface

AbstractCopper surfaces were derivatized resulting in the formation of Mx[Cu(II)(CN)Fe(II/III)(CN)5] at the interface. Polyimides were spin coated onto the modified metal surfaces and the degree of adhesion measured by the tape pull test. Effects of mechanical interlocking were evident in the case of modified copper samples, due to derivatization by ferricyanide. The chemical bonding and elemental analyses of the interfaces were studied by XPS and SEM.

The effect of surface preparation on metal/bone cement interfacial strength.

This study is concerned with finding practical ways for strengthening metal/bone cement (M/BC) interfaces via surface alterations and identifying fundamental mechanisms underlying M/BC adherence. Shear strengths have been inferred from torsion tests using shear-lag analysis. The variables examined with regard to their effects on interfacial strength are substrate material, surface roughness, interface porosity, passivation and sterilization, surface cleaning procedures, and use of bone cement precoated metals. M/BC interfaces can be substantially strengthened by applying the bone cement to the metal with high pressure. This would be a practical way to strengthen interfaces for precoated implants. The acrylic polymerized in vivo would employ the usual low pressure method. Otherwise, the main method for improving M/BC interfaces is through changing surface topography. Cleaning or chemical treatments have relatively minor effects. Roughened surfaces, as expected, produce stronger interfaces. Dramatic strength improvements occurred with a porous arc plasma sprayed layer on the substrate. Surprisingly, highly polished surfaces also improve interface strength (compared to less polished surfaces). The hypothesis is advanced that M/BC adherence depends upon superposition of mechanical interlocking and atomic interaction effects, with the latter predominating for finer finishes and vice versa. Differences exist between materials which are independent of roughness.

New Copper Surface Treatment for Polyimide Multilayer Printed Wiring Boards

A new treatment method for the copper innerlayers of polyimide multilayer printed wiring boards has been developed. Conventional oxide coatings experience acid penetration through the bonding interface during through‐hole plating pretreatment. This problem was eliminated by substitution of metallic copper for the surface oxide. Promotion of the copper innerlayer adhesion to the prepreg by the oxide coating was based upon a mechanical interlocking effect caused by the minute roughness of the oxide crystals. Reduction treatment of the surface oxide layer was found to give a metallic copper surface with no changes in its morphology. Adhesion strength of polyimide prepregs to copper foils after the reduction treatment was equivalent to that of the original brown oxide coating. Acid resistance was enhanced by elimination of the oxide layer from the bonding interface. The reduction treatment, combined with the conventional oxide coating technique, can realise high density multilayer printed wiring boards with greater reliability and performance.

Modification of the Interfacial Zone Between Aggregate and Cement Paste

ABSTRACTIn order to improve the properties of concrete, the composition and structure of the interfacial zone must be modified. This may be done by pretreating the inert aggregate with special reagents to form a reactive surface, which will then react with the cement paste, resulting in an enhancement of the bond strength between cement paste and aggregate through the combination of the physical, chemical and mechanical interlocking effects. A cylindrical hole was drilled in a limestone cake and the surface of the hole coated with special solutions; cement slurry was then poured into the hole and the specimens were cured in a fog room. The shearing strength was determined to evaluate the effect of the aggregate pretreatment on the bond strength. The mechanical strength, porosity, electric conductivity of the concrete, orientation degree of the Ca(OH)2 and morphology in the interfacial zone were also examined. It was found that the compressive and flexural strengths increased, and the bond strength between aggregate and cement paste also increased; the porosity, average pore size, number of large harmful pores, electric conductivity and the orientation index of the Ca(OH)2 decreased.

Modification of poly(vinyl chloride). XIX. Electroplating of poly(vinyl chloride)

AbstractAs a preliminary treatment in the PVC‐electroplating procedure, treatment with dimethylformamide followed by sensitization leads to a finely roughened and a highly hydrophilic surface with reducing power. This is caused by the formation of an ionic complex compound between dimethylformamide and tin(II) chloride absorbed in the PVC surface. A much more finely and deeply etched surface which exhibits higher adhesion through the mechanical interlocking effect is obtained with the PVC blends containing the plasticizer with a low value of interaction parameter and with a solubility parameter approximate to that of PVC. Adhesion of the metal layer to the PVC surface thus obtained is improved about 1.5 times by thermal aging at 120°C for 20 min.

Metal Transfer and Wear

A new theory of metal transfer and wear is suggested in this paper. The essence of the theory is as follows: Metal transfer and wear take place at points of actual contact. The interfaces of the high spots that actually make contact are roughened as the result of plastic deformation when they carry normal load. The mechanical interlocking effect of these roughened interfaces is the primary cause of metal transfer and wear. Due to the mechanical interlocking effect of the roughened interface, and the strain-hardening that accompanies plastic deformation, the application of a tangential force will break one of the pair of the contacting high spots a certain distance away from the interface rather than at the original interface. A secondary cause of metal transfer is the adhesion or the diffusion process which takes place during the temperature flash that occurs during breakage. If the adhesive force is very weak and the diffusion process is not rapid enough to cause the sheared-off peak of the high spot to become a blob of transferred metal, the small piece of metal sheared from the high spot can leave as a loose wear particle. This proposed theory explains the welding of the sheared-off peak to its opponent high spot as the consequence of friction, whereas, in the ``welding'' theory of friction, welding is considered as the cause of friction. Most metallic surfaces in ordinary atmosphere are always covered by a surface film. The effect of surface contamination on metal transfer, wear, and the shear component of friction is discussed. Difficulties encountered in applying the ``welding'' theory to explain the friction of and metal transfer between contaminated surfaces where metallic adhesion is absent, are obvious. Experimental support of this new theory is given here. It includes as direct evidence (1) the roughening of the interface as the result of the plastic deformation, (2) the perfect matching at the roughened interface, which gives a strong mechanical interlocking effect, and (3) a definite region of severely strain-hardened metal near the interface.