Particulate fillers characteristics

The principal characteristics of polymers which control their ability to dissipate energy are their stiffness, surface mass, and their inherent damping characteristics. In this chapter we are only concerned with the last of these three. Briefly, however, if lack of stiffness is a problem with a particular polymer in a damping system, this can be enhanced, if not completely obviated, by using the material in a constrained layer (29) mode. Surface mass refers to the mass of material behind a unit surface area. Clearly, for polymers which are all inherently low density materials, this can be increased by the incorporation of dense, particulate fillers such as lead, barytes etc. 

Polymers, as well as elastomers, are reinforced by the addition of small filler particles. The performance of rubber compounds (e.g. strength, wear resistance, energy loss, and resilience) can be improved by loading the rubber with particulate fillers. Among the important characteristics of the fillers, several aspects can be successfully interrogated by AFM approaches. For instance, the particle and aggregate size, the morphology, and in some cases the surface characteristics of the filler can be assessed. 

Of course, the ability to dissipate energy is only one of the characteristics concerned in toughness, or the ability to resist fracture (see Section 3.2). Thus the modulus itself contributes to the total energy and the stress required for fracture a particulate filler may, by raising the modulus of a very low-modulus polymer, increase the toughness. 

There are three basic procedures for mixing rubber compounds in an internal mixer namely, the conventional method, the rapid oil addition method, and the upside-down mix method. Many variations of these three methods are also used to suit the special characteristics of individual formulations and equipment. It is, in general, necessary to add particulate fillers early in the mixing cycle, so that good dispersion is achieved as a result of the high shear stress and high viscosity at the lower temperatures then prevailing. Similarly, the oils and plasticizers which reduce viscosity should be added later. Upside-down procedures and variants of it are attempts to implement these ideas in practice. 

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. 

The growth rate in the use of particulate filled polymers, including those prepared from polyolefins, is very rapid in all fields of application [1], Household articles, automotive parts and various other items are equally prepared from them. In the early days mostly particulate fillers were introduced into polymers and the sole reason for their application was to decrease cost. However, as a result of filling, all properties of the polymer change in fact a new polymer is created. Some characteristics improve, while others deteriorate, so properties must be optimized to utilize all the potentials of modification. Optimization must include all the factors infiuencing properties from component characteristics through structure to interactions. 

Numerous filler characteristics influence the properties of particulate filled polymers [13, 14]. Chemical... 

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