The deficiency of GR-S in ``tackiness'' resulted in a great deal of work in the rubber industry to improve this complex property, but practically all the work had to be evaluated by qualitative ``hand tests'' because quantitative tests were not available. An analysis of the factors involved in the ``tackiness'' of various materials showed that different factors were critical in the so-called ``tackiness'' of rubber, paints, and varnishes, printing inks, adhesive tapes, etc. A quantitative test was developed to measure the effects of rate of removal on the adhesion or ``tackiness'' of pressure-sensitive adhesive tapes over a 106-fold range of rates. This showed why the results of standard ``adhesion tests'' of tapes do not predict the relative behavior of the tapes under small forces acting for long times. Another test was developed for the measurement of the ``tackiness'' of GR-S rubber which correlates well with the judgment of tackiness by hand tests and it even works reasonably well with rough samples taken from a laboratory mill. With this test, the effects of mastication conditions, aging, and of the addition of softeners and tackifiers on ``tackiness'' of GR-S (with and without carbon black) were studied. The German tackifier ``Koresin,'' which is now manufactured in this country, was found to be far more effective than rosin and similar materials formerly used, and gave a tackiness approaching that of natural rubber.

The article contains sections titled: 1. Emulsion Styrene ‐ Butadiene Rubber (E‐SBR) 1.1. Properties, Grades, and Application 1.2. Basic Chemistry and Production Processes 1.3. Producers and Production Capacities 2. Chloroprene Rubber (CR) 2.1. Properties, Grades, and Applications 2.2. Basic Chemistry and Production Processes 2.3. Producers and Production Capacities 3. Nitrile Rubber (NBR) 3.1. Properties, Grades, and Applications 3.2. Basic Chemistry and Production Processes 3.3. Producers and Production Capacities 4. Emulsion Polybutadiene (E‐BR) 4.1. Properties and Applications 4.2. Basic Chemistry and Production Processes 4.3. Producers and Production Capacities 5. Acrylate Rubber (ACM) 5.1. Properties, Grades, and Applications 5.2. Basic Chemistry and Production Processes 5.3. Producers and Production Capacities 6. Fluororubbers 6.1. Chemical Composition and Properties 6.2. Vulcanization 6.3. Production Processes 6.4. Producers, Production, Capacities, and Markets

The analysis of tackiness shows that it is a complex property which depends on a balance between a large number of different factors, including the geometry of the sample as well as the surface forces and the visco-elastic properties of the material itself. The quantitative measurements of the effect of the rate of removal on the apparent tackiness of pressure-sensitive adhesive tapes show that significant differences are found at very slow removal rates (105 seconds per cm.) which do not show up at much higher removal rates (10 seconds per cm.). These differences may affect the performance of the tapes in service. A simple quantitative test is described which can be used to study the effects of various processing treatments and various softeners, tackifiers and other compounding ingredients on the tackiness of GR-S and other rubbers. Koresin was the most effective tackifier found for GR-S. The authors wish to acknowledge the continued interest of W. E. Hanford, Director of the Laboratory, and the helpful discussions of tackiness measurements with C. E. Schildknecht. Miss Ruth Sellers and Miss J. L. Nuver helped in taking much of the data. The first Koresin samples were prepared in the laboratory by C. E. Schildknecht and A. O. Zoss before the commercial material was available.

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