Carbon black specimen

The specimen was prepared by the following method. After mixing HAF carbon black (50 phr) with natural rubber (NR) in a laboratory mixer, carbon gel was extracted from unvulcanized mixture as an insoluble material for toluene for 48 h at room temperamre and dried in a vacuum oven for 24 h at 70°C. We made the specimen as a thin sheet of the carbon gel (including carbon black) by pressing the extracted carbon gel at 90°C. The cured specimen was given by adding sulfur (1.5 phr) to the unvulcanized mixture and vulcanized for 30 min at 145°C. The dynamic viscoelastic measurement was performed with Rheometer under the condition of 0.1% strain and 15 Hz over temperatures. 

We prepared a strip-type specimen (100 X 50 X 2 mm) from the rubber sheet of SBR filled with HAH carbon black (50 phr), vulcanized for 30 min at 155°C. On the specimen, a slit of different lengths (si = 30 mm, S2 = 20 mm, S3= 10 mm) parallel to the extension direction and a notch of different lengths (2 or 5 mm) at the center of the side surface of the specimen perpendicular to the extension direction were made by razor-cutting (see the inserted figure in Figure 18.14). The distance 8 between slits and between the slit Si and the tip of notch was 1 and 3 mm, respectively. The no-slit specimen means that it only includes a notch, without slits. 

A series of six stress-strain cycles with a crosshead rate of 600 mm/min was applied to specimens having a parallel length of 25 mm and a cross-section of 1 x 4 mm2 on a tensile testing machine. The samples were continuously stretched in six hysteresis cycles up to 60% of their elongation at break values, as shown in Fig. 47. This procedure is an established one and widely practiced for elastomeric composites reinforced with fillers such as carbon black and silica, which tend to build a strong filler-filler network [83]. 

In a typical experimental measurement a Nd YAG laser fires a 5 ns pulse on to the target electrode. It is convenient to use a polymeric material for the electrode, made conductive by the addition of conductive carbon black, to achieve intimate contact with the specimen. Adding a thin layer of a volatile liquid to the electrode surface just prior to firing the laser greatly enhances the magnitude of the signal, by helping to increase the size of the pressure pulse... 

By appropriate selection of the markers for stiffness and adhesion, it is possible to differentiate the rubbery matrix (low modulus, high adhesion) and the filler particles (high modulus, low adhesion). As shown in Fig. 3.66, elevations in the height image corresponds well with areas of higher stiffness and lower adhesion. The carbon black particles can be observed in a non-homogeneous distribution at the surface of this microtomed specimen. 

A carbon black test sample is obtained by mixing carbon black and zinc oxide with epoxidized soybean oil. The mixture is milled in a mechanical muller with frequent scraping. The specimen is prepared by film drawdown, roller spreader or by the glass slide method. Reflectometer readings are obtained. The result is a comparison of the tint strength of standard with the test sample expressed in tint... 

Temperature also has an effect on crystallite size. PVDF containing carbon black had ciystallites with mean dimensions of22.4,20.1, and 16.2 pm when specimens were respectively, slowly cooled, air cooled, and quenched. ... 

In pyrolysis, a specimen is ignited for half an hour at 900°C in the presence of nitrogen. Under these conditions the polymer matrix decomposes and only the carbon-black component remains. This method, with subsequent ignition in the presence of O2, originates from quality control and is used to check carbon-black concentrations. 

During studies of specimens with a carbon-black concentration of less than c or in the region of <1) the following photographs were taken which reveal a number of interesting facts. 

Figure 11.13 shows a specimen with a carbon-black concentration of 0.5 vol.%, i.e. less than Oc. In it there are clearly visible individual spherical carbon-black particles which are present in the polymer matrix in isolated and distributed form. This finding would agree with the percolation theory, although the shape of the carbon-black particles is more similar to a sphere than to a linear stnicture. 

BP 880 as carbon black colorant with much smaller specific surface area. Constant admixture of 2 mass % wax as external lubricant to make preparation of the specimen easier. Concentration series up to 40 mass % carbon black. 

Objects may be discrete manufactured items or test specimens generated by a particular preparation process. Materials may be tested in a direct manner, such as the modulus of a polymer, or in an indirect manner, such as the quality of a carbon black or other additive via a physical property in a standard formulation. In the case of direct testing for a bulk material, an appropriate sample taken from the lot is tested. In the case of indirect testing, the material tested is usually appropriately sampled and combined with other materials in a specified way, and the composite is tested. This composite testing may involve objects or test specimens for the measurement process. The treatment in this annex is developed in terms of random and bias deviations. The relationship between random and bias deviations and accuracy, which is a concept that includes both types of deviations, is developed in Annex C, which also describes how to evaluate bias. 

Problems of heat buildup in large specimens and scragging are beyond the scope of this chapter, but one of the reasons for the 50% carbon black in tires is to dissipate the large buildup of heat generated when any rubber sample is vibrated at frequencies above a few hertz. Some DMTS apparatus allow up to three thermometers to be placed in or on the sample to measure this, whilst other workers prefer to run down in temperature to prevent overworking the rubber samples, particularly at constant strain. 

Specimens with and without carbon black were exposed to UV light for seven days at 7O 0. Tensile strengths of specimens during the weathering tests were evaluated at 25 Q. The effects of carbon black on the mechanical properties of specimens after weathering were studied. 

FIGURE 3.9 Tapping-mode AFM height image (a) and phase image (b) of a CB/NR specimen. The structures indicated by circles are considered to be carbon black filler. 

Fig. 4.30 Tear Resistance Ts of carbon black-reinforced elastomers as a function of the CB content the tests were performed with 2 mm thick trouser specimens and a test speed of 100 mm min ...

Not only the specimen thickness is of importance, but also the ratio of the initial notch size a and the specimen width W. In Figure 5.6, crack resistance curves from quasi-static fracture mechanics tests (SSM) are shown. The materials were SBR vulcanizates without (a, c) and with carbon black N330 (b, d). The mixtures of the non-reinforced materials contained different amounts of sulphur so that a different crosslink density could be obtained. For both, the unfilled and the CB filled vulcanizates, the comparison of the crack resistance curves indicates an influence of the a/W ratio. The analysis of the data [05Rei] led to the conclusion that 0.2 is a suitable a/W ratio for such experimental investigations. 

Pre-strain was included in modulated stress testing of rubber and the dimensions of the pre-strained specimens used in calculation of the loss modulus. The loss modulus was independent of pre-strain for filled and unfilled rubbers. A test specimen geometry was chosen where pure shear could be superimposed with a small strain imparted with a shear oscillation. Again, loss modulus was mostly independent of pre-strain for filled and unfilled rubbers, including those filled with carbon black. The results enable understanding of energy dissipation mechanisms in rubber composites. ... 

NR blends with SBR were prepared, using a two-roll mill, containing carbon black and silica. The composites were tested in tensile modes using specimens with varying widths, and heat build-up measurements were performed. 

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