Rubber types particulates

Elastomers, of which vulcanized natural rubber is the most important example, also undergo dramatic changes in mechanical properties when filled with particulate solids. In part, knowledge of this particular type of system has been developed empirically as the technology of car-tyre manufacture has advanced. 

Table 2.7 lists techniques used to characterise carbon-blacks. Analysis of CB in rubber vulcanisates requires recovery of CB by digestion of the matrix followed by filtration, or by nonoxidative pyrolysis. Dispersion of CB within rubber products is usually assessed by the Cabot dispersion test, or by means of TEM. Kruse [46] has reviewed rubber microscopy, including the determination of the microstructure of CB in rubber compounds and vulcanisates and their qualitative and quantitative determination. Analysis of free CB features measurements of (i) particulate and aggregate size (SEM, TEM, XRD, AFM, STM) (ii) total surface area according to the BET method (ISO 4652), iodine adsorption (ISO 1304) or cetyltrimethylammonium bromide (CTAB) adsorption (ASTM D 3765) and (iii) external surface area, according to the dibutylphthalate (DBP) test (ASTM D 2414). TGA is an excellent technique for the quantification of CB in rubbers. However, it is very limited in being able to distinguish the different types of... 

The soil found on hair can be classified into two types solid particulate and liquid or oily soil. Solid soils can come from hair care products or from the environment. Examples of the former might be polymeric resins or antidandruff agents, while the latter includes airborne particles carried by air currents, dust, carbon particles in the form of soot or clays, or rubber abraded from automobile tires [113-116],... 

Py-GC/MS of samples (prepared as were the ICM samples) of the four materials thought to be the major sources of the tunnel air particulates — tire rubber, road salt, diesel exhaust, and gasoline exhaust — showed that road salt gave no pyrolysis products and the other three materials gave pyrograms of complexity similar to those of the ICM samples. The overlap of compound types and the absence of unique marker compounds made an assessment of the relative contribution of each of the three sources to the total impractical using the Py-GC/MS profiles. 

Even this definition needs to be classified [7, 8]. To some researchers it is still too broad because it includes many materials that are not usually thought of as composites such as concrete, copolymers and blends, reinforced plastics, and carbon-black-filled rubber. On the other hand, some of the more recent composites are excluded from the category of composites if this definition is strictly applied. For example, many particulate-type composites such as dispersion-hardened alloys and cermets have composite structures that are microscopic rather than macroscopic [2,8]. In some cases, the composite structures are nano-scopic, with the physical constraint of several nanometers as the minimum size of the components [9-16]. The terms... 

Porosity is a characteristic property of carbon black and can be seen with other particulate type of fillers. Filler porosity can affect the properties of the vul-canizate. However, its effect on reinforcement is secondary. In most cases, the pores are too small for the polymers to enter although some smaller molecules in the compound may do so. Particulate fillers used in rubber industry in general can be classified as black and non-black , depending on their origin. 

As reported by Zelikin et al. (571), hydrophobic pyrogenic silicas were used as reinforcing Tillers in silicone rubber giving a tensile strenjgth of 71 kg cm and 460% elongation at break. However, the reinforcement of this type of elastomer is now probably considerably advanced by new techniques of introducing particulate silica with optimum characteristics. 

High-intensity internal mixers are used for incorporating particulate additives into most polymer types, including thermoplastics, thermosets and rubbers. Limitations, such as the manual intervention generally encountered with two-roll mills, can be overcome, whilst maintaining a significant dispersive and distributive mixing capability. 

Fillers of many types are used in rubber formulations. A filler may be considered to be any particulate material, which is added for one or more of the following reasons ... 

The effects of ozone, UV irradiation and sunlight on the peel adhesion of NR-based compounds were investigated and methods of preventing and/or overcoming poor interfacial adhesion evaluated. These methods included simple protection of the rubber surface, compounding variations, use of particulate-type adhesives and solvent scmbbing of the rabber surfaces. 7 refs. 

---