Mechanical properties of filled polymers

It is concluded that surface modification of mica, produced by exposing the material to microwave plasmas, can create large positive or negative effects in the mechanical properties of filled polymers and polymer blends. Property enhancement is associated with the production of surface layers on the filler which... 

Nitroxyl radicals can also be used to improve the mechanical properties of filled polymers, resins in particular, by increasing the adhesive quality of the fillers by treating their surfaces with solutions of nitroxyl radicals. The efficiency of nitroxyl radicals as modifiers is higher than that of well-known modifiers e.g., 4-toluene isocyanate. 

T.S. Chow, The effect of particle shape on the mechanical properties of filled polymers, J. Mater. Sci. 15 (1980) 1873-1888. 

In the same work, it was shown that the mechanical properties of filled polymer mixtures may be described by various equations connecting the moduli with the filler amount (see Chapter 5). It is of interest also to attempt calculation of a thickness of the boundary layer, using data on heat capacities (see Chapter 3). It was established that the boundary layer associated with PVC component has a smaller thickness. Since most of the matrix consisted of PVC, it was suggested that silica, because of its acid character, immobilizes to a greater extent the proton-accepting PU component hence, the thickness of the boundary layer for PU is higher. 

The fact that the appearance of a wall slip at sufficiently high shear rates is a property inwardly inherent in filled polymers or an external manifestation of these properties may be discussed, but obviously, the role of this effect during the flow of compositions with a disperse filler is great. The wall slip, beginning in the region of high shear rates, was marked many times as the effect that must be taken into account in the analysis of rheological properties of filled polymer melts [24, 25], and the appearance of a slip is initiated in the entry (transitional) zone of the channel [26]. It is quite possible that in reality not a true wall slip takes place, but the formation of a low-viscosity wall layer depleted of a filler. This is most characteristic for the systems with low-viscosity binders. From the point of view of hydrodynamics, an exact mechanism of motion of a material near the wall is immaterial, since in any case it appears as a wall slip. 

The mechanical properties of filled PP have to be analysed as a function of the filler itself (content, particle size and particle-matrix bonding) but also through microstructural modifications of the polymer matrix induced by the filler. 

We briefly discuss the following mechanical properties of a polymer matrix composite material filled with whiskers. 

Table 11.4 Mechanical properties of thermoset polymer matrices-filled NFC.

Han, C.D., Sandfbrd, C. and Yoo, H.J. (1978) Effects of titanate coupling agents on flie rheological and mechanical properties of filled polyolefins, Polym. Engg Sci., 18,849-54. 

Yanovslgr, Yu.G. and Zaikov, G.E. (1990) Rheological properties of filled polymers, in Encyclopedia of Fluid Mechanics, (ed. N.P. Qteremisinofi), Gulf Publishing, Houston, TX, 9,243-76. 

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