SynopsisThe fracture behavior of a piperidinemisphenol A diglycidyl ether (A) resin has been determined in bulk a q l as an adhesive using the linear elastic fracture methods developed by Mostovoy. The effect of adding carboxy-terminated butadiene-acrylonitrile (CTBN) elastomer to resin A was investigated. The opening-mode fracture energy (91~) of resin A was 120 to 150 J/m2, and largely attributable to plastic deformation. Fractographic evidence was obtained for plastic flow a t the crack tip during crack initiation. Propagation was unstable due to the rate dependence of the plasticity. There were no significant differences in the bulk and adhesive fracture behavior. Addition of 5-15% CTBN to resin A produced minute elastomer particles which increased Sic to -4000 J/m2 (at 15%). Further CTBN addition resulted in an elastomerepoxy blend and a decrease in fracture energy. Fractography again indicated that crack initiation involved plastic deformation but that the elastomer had greatly increased the volume in which the deformation occurred. The adhesive fracture of the elaatomer-epoxy was found to be strongly dependent on the crack-tip deformation zone size (ryJ in that 9 1~ was a maximum when bond thickness was equal to 2 rye. At bond thicknesses less than 2 r,, there was a restraint on the development of the plastic zone resulting in lower 91. values.

A study by interference microscopy and ellipsometry shows that the spontaneous spreading of nonpolar liquids on smooth, clean metal surfaces is characterized by the advance from the bulk liquid of a primary film less than 1000 A. thick, usually followed by a thicker secondary film. The movement of the secondary film results from a surface tension gradient across the transition zone between the primary and secondary films. This gradient is produced by the unequal evaporative depletion from these two regions of a volatile contaminant having a lower surface tension. If the volatile contaminant has a higher surface tension than the main component, the gradient is reversed, and the liquid recedes. Removal of the volatile constituents eliminates the secondary but not the primary spreading. Liquid may also spread by capillary flow in microscratches. The tendency of certain liquids to spread spontaneously or "creep" over solid surfaces is sometimes desirable and sometimes a distinct annoyance. Lubrication engineers must often rely upon the creep of oils to carry the lubricant to surfaces which otherwise would be inaccessible.On the other hand, the ease with which some liquids will creep out of a container and contaminate the surrounding area can be most disconcerting. The spontaneous spreading of liquids over solids is not simple, and it presents an intriguing problem in surface chemistry which has not received the detailed attention it deserves.Three previous studies of spontaneous spreading are pertinent to this present investigation: Sir William Hardy's studies [9], the somewhat later work of Bangham and Saweris [2], and the recent studies by Zisman and coworkers [8] of liquids spreading on polar surfaces.

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The adhesional shear strength has been determined for ice formed against polished steel, monolayers adsorbed on steel and thin plastic coatings painted on metal surfaces, The adsorbed monolayers reduced the shear strength to about one-third of that for ice on clean steel. The monolayers also had the effect of changing the character of the breaks from clearly cohesional to apparently adhesional failure. The shear strength from the plastic coatings ranged from values equal to that of ice against clean steel to values 70 to 80% lower. The reduction in shear strength did not correlate with the water contact angle on the coatings but was usually found to be due either to air entrapment at the ice/coating interface or to cohesive failure of the coating itself.The ice separated from the various substrates was examined microscopically by forming lastic replicas of the ice surface. These studies helped determine 8 e mechanism of failure and, since one of the replicating solutions was also an ice etchant, much was learned about the crystal structure and the crystal defects of ice near surfaces. The ice lattice was found to be highl defective near the substrates and this is discussed in connection w i x the "liquid-like," behavior of interfacial ice.

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