IntraductionThe adequate dispersion of carbon black in rubber has long been recognized as an important factor in obtaining good physical properties in black rubber masterbatches. At the present time the most widely used methods for the microscopic evaluation of carbon black dispersions in rubber are those described by Sweitaer, Hess, and Callan' and Leigh-Dugmore.2 These methods are based on the fact that in dry mixed masterbatches the major difference between two dissimilar dispersions is likely to be in the size and the number of the agglomerate black particles.' With the development of wet masterbatching methods,3.* which greatly reduces the size and quantity of carbon black agglomerates, such evaluations prove inadequate.Preliminary results indicated that simply evaluating the manner in which the carbon black was scattered or dispersed in the polymer matrix could not account for observed changes in physical properties of wet masterbatches. This electron microscopic study was made to establish and define terms relating to the reinforcement of rubber stocks by carbon black at levels below the limits of resolution of the light microscope. Experimental ProceduresSamples of the masterbatches to be studied were frozen in a Dry Iceisopropyl alcohol bath and subsequently fractured. Replicas were then made of this freshly fractured surface. Either raw or compounded stocks yielded equivalent results.The replication procedure employed was a refinement of that used by Andrews and Walsh6 to produce preshadowed positive carbon replicas. Faxfilm,6 a cellulose-based tape, was substituted for the gelatin as the intermediate negative replica in this two-stage system. This substitution greatly reduced the time necessary for replication, as gelatin requires enzymatic digestion for complete removal from the positive. Light uranium shadowing was then applied before the deposition of the carbon film. This method permits routinely resolutions of better than 100 A.Since acetone was used as the softener for the Faxfilm during repli- 27

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With the advent of wet masterbatching methods, which provide a preliminary dispersion of carbon black in latex, techniques for the microscopic evaluation of the quality of this incorporation proved inadequate. Three reinforcement criteria were developed for such evaluations: dispersion, grinding, and bonding. Using these criteria the performance characteristics of a tread stock made with such masterbatches can be predicted with good reliability. The correlation of reinforcement criteria and the raw Mooney of the masterbatch reveals the striking effect of improved carbon black incorporation on this property. Using this correlation it should be possible to evaluate masterbatch production on a continuous basis.

The modern workstation, with its inherent high speed and massive memory, allows the use of complicated image analysis and processing algorithms and artificial intelligence programs not available to current PCs and mini-computers.There is no single feature that differentiates the UNIX based workstation from a PC. Rather, it is its fundamental design that gives the workstation superior performance. This superiority in no small part is the result of the UNIX operating system. UNIX is a word that sometimes strikes fear into the hearts of mortal men! There is no reason to fear, however. Users of UNIX-based systems have no more interaction with the operating system than say users of WordPerfect running on a MS-DOS or MAC OS machine.UNIX is the only operating system that runs on a wide range of systems from laptops to mainframes. It is unique in at least five areas: 1) massive data sets handling, 2) multitasking, 3) multi-user, 4) security, and 5) networking. Let me give you what I think are usable descriptions for these five areas.

Most of the electron microscope studies of the fracture surfaces of impact plastics have been made using direct carbon replication. This method of replication is very difficult to employ on the rough, non-glassy fractures obtained from rubber reinforced plastics such as acrylonitrile-butadiene styrene (ABS) types. The surfaces are too rough to allow the easy removal of the thin carbon film and many replicas are lost before a usable one is obtained. Most recently a Japanese worker reported a two-stage polyvinylalcohol (PVA) carbon replica which worked well on etched surfaces of plastics. Here, too, when the PVA film is thick enough to strip from rough surfaces, the film swells so badly when removed by water washing that the carbon replica is destroyed. The method described here is a two-stage PVA-carbon replication system that from even very rough surfaces obtains large unbroken final replicas.