Standardized rubber

AnnualBook ofASTM Standards, Rubber, Vol. 09.01, American Society for Testing and Materials, Philadelphia, Pa., 1994. 

Figure 20 shows the GC-MS chromatogram for the water extractables from a standard rubber compound NR2 of the formulation given in Table 8. 

Butyl rubber - This material generally had the least endurance in fatigue tests, but it may be adequate for some cardiovascular applications. Advantages include less sensitivity to stress concentrators than Pellethane, a very low permeability to fluids, a moderate creep resistance and widespread availability at low cost. Disadvantages include a relatively low fatigue resistance compared to the elastomers specifically designed for these applications. The rubber tested was not designed for medical applications and had standard rubber additives and modifiers that were cytotoxic unless the material was extracted after manufacture. 

Butyl can be processed without great difficulty on standard rubber machinery, but equipment should be well cleaned before and after processing butyl, since contamination can result in local undercure and delamination. 

Abbreviation for Nigerian Standard Rubber. A/-terf-Butyl-2-Benzothiazole Sulphenamide... 

The mastication equipment most commonly employed is standard rubber instrumentation such as roll mills, internal mixers, extruders or laboratory devices modeled on them (e.g., a single-rotor internal masticator described by Wilson and Watson (43), die model improved by Kargin and coworkers (11) and the Brabender plastograph). 

Zoom Mode Two options are available for zooming your 2D spectrum. Normal allows zooming using the standard rubber box method while Units uses predefined increments. 

There does not appear to be evidence to demonstrate the variability of either abrasion standards or abradants but within one laboratory the coefficient of variation of abrasion results using different batches of a standard rubber would probably be not much less than 8%, and the between laboratory variation could clearly be very much greater. Some abradants will certainly be more variable than this but other materials can be reproduced with better precision. Although it is a fact that standard rubbers are themselves variable, they are of very considerable value, particularly when reference is made only to standards from one batch and where they are used to monitor the change with time of one sample of abradant or to compare a number of abradants. 

Standard rubbers are given in several of the test method standards. Some are purely for normalizing the abrasive and have no particular service relevance. Others, such as those based on a tyre tread compound or a shoe sole type material, have the advantage of a practical significance as well as a normalizing role. There is no reason at all why, for a particular investigation, an in-house standard representative of the type of material being evaluated should not be used. 

Devotees of the use of standard rubbers then finally express the result as an abrasion resistance index defined by ... 

Abrasion resistance is the reciprocal of volume loss. If the volume loss or abrasion resistance only is quoted, it is desirable to have some certification of the abradant used. This is naturally supplied to some extent by specifying a particular grade and source of supply but leaves open to question the variability of that source of supply. Some workers prefer to use a standard rubber to test the abradant and to calculate a relative volume loss ... 

Whichever approach you take, the result is still dependent on the variability of the standard rubber and, arguably, it could be better to rely on the reproducible manufacture of, for example, an abrasive wheel. It would not seem beyond the bounds of ingenuity to find a standard material which is inherently more reproducible than rubber It could then be used either to certify the abradant or to use in the calculation of abrasion index. 

Results can either be expressed as a relative volume loss with the abradant normalized relative to a standard rubber or as an abrasion index relative to a standard rubber. The former is the original German approach and the latter is that approach favoured by, for example, British standards. Two standard rubbers are specified which originate from the German and British standards. This is a fine example of the chicken and egg problem of standard rubber and abradant. To understand the situation it must be appreciated that an accurately specified standard abradant has been available in Germany for many years, but the rubber used to check it has a formulation of no relevance to real products and is very difficult to reproduce in laboratories other than that of its origin. The British standard rubber is based on a tire tread and, hence, has practical relevance. 

Either way of expressing results can be used with either rotating or nonrotating test pieces but, normally, only the German standard rubber would be used with relative volume loss. In previous versions, only the abrasion index approach had the option of using a rotating test piece. 

Four standard rubbers are specified, two of which are the same as those given in ISO 4649. The other two are a high abrasion resistant SBR compound and a low abrasion resistant material which may be preferred for comparison with high and low abrasion resistant test materials respectively. For all three methods, the calculation of abrasion resistance index is specified. 

ASTM has the DIN abrader specified as D596356. It has the rotating and non-rotating methods and both standard rubbers but does not cater for the lower force for soft rubbers. The details are said to be equivalent to the 1985 version of ISO 4649 and there is no indication of why it has not been updated. 

The Pico abrader is specified in D222857. This device uses a pair of tungsten carbide knives which rub the test piece whilst it rotates on a turntable. The direction of rotation is reversed at intervals throughout a test and a dusting powder is fed to the test piece surface, which doubtless helps to avoid stickiness. The apparatus is calibrated by the use of no less than five standard rubbers and the result also expressed as an abrasion index. Force on the test piece and speed of rotation can be varied and, presumably, different abradant geometries could be used, although the distinctive feature of the Pico is the use of blunt metal knives in the presence of a powder. 

The capital and process control costs to prepare rubbers must be considered against the cost to process the polyurethanes. The straight raw material cost of the standard rubbers (natural, SBR, and chloroprene) will be less than the polyurethanes cost, but the overall processing cost of the polyurethanes will be lower. 

A check spring is supplied with the Durometer and can be used for day-to-day checks. A series of standard rubber blocks also can be purchased for checking over the full range. The blocks need to be rechecked every 2 years. Durometer suppliers also offer a recalibration service. 

Millable urethanes are processed on standard rubber-processing machinery. They may be either peroxide or sulfur cured. The sulfur-cured varieties have some chemicals added to enable sulfur curing to take place. These polyurethanes also have the properties of castable polyurethanes but need to be processed on standard rubber machinery. 

Because no vacuum system can be truly leak-free, it is important to determine whether or not you have a leak of consequence. In other words, does any system leak actively affect your work For example, a common rubber balloon holds water better than it holds air, and it holds air better than it holds helium. If your needs are to contain water, a standard rubber balloon is sufficient. Similarly, if you want to contain helium for a limited time, again a rubber balloon is sufficient. However, if you want a helium balloon to stay up for several days, then a rubber balloon is insufficient and you must spend the money for a Mylar balloon, which can contain helium much better than a rubber balloon. 

A reactor (Fig. 3) as described in U.S. Patent 3,060,003 was supplied with a feedstock of BCMI-120 using air and natural gas and a water quench to produce standard HAF and standard ISAF, All carbon black samples were tested substantially by physical tests and standard rubber tests. 

Natural-mbber-based pressure-sensitive adhesives can be cured by standard rubber curatives, eg, sulfur plus an accelerator (see Rubber, natural) ... 

RMs for engineering and technical properties (standard rubbers, standard sieves, etc. 

It is found that the abrasion value is minimal at a side of the gradient sample contained from PU only or its content is greater in relation to the PIC component, and obtains the values typical of standard rubbers [3], As PIC concentration in the rigid part increases, the abrasion value also increases to significant values (6-7-10 3 cm3/m). It is found that the abrasion value also is affected the technical carbon trademark. As the trademark P803 is used, the abrasion index is insignificantly lower compared with K354 trademark use. 

For a gradient reinforced material, the following regularity is observed abrasion is maximal for the rigid side consisting of PIC only. As the PU component in the material increases, the abrasion index becomes minimal exceeding insignificantly abrasion indices typical of standard rubbers. This indicates that PU component addition to polyisocyanurate materials increases wearability of the materials obtained. 

Anecdotal evidence suggests that rubber outsoles change over time leading to consumer perceptions of decreased performance. The purpose of this ageing study was two fold. First, the physical properties of a standard rubber compound were evaluated over time to quantify changes. Second, simple formula and process adjustments were made to see if it was possible to produce a rubber product that 1) exhibited... 

Introduction. The National Bureau of Standards (NBS) currently issues over 900 Standard Reference Materials (SRMs), with various groups being represented, such as clinical laboratory standards, trace element standards, nuclear materials, glass viscosity standards, rubber materials, color standards, and coating thickness standards. We are now endeavoring to add an additional group to this list, namely, trace organic chemical SRM. 

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