Filler content range

The rheological properties of gum and carbon black compounds of an ethylene-propylene terpolymer elastomer have been investigated at very low shear stresses and shear rates, using a sandwich rheometer [50]. Emphasis was given to measurements of creep and strain recovery at low stresses, at carbon black filler contents ranging between 20 and 50% by volume. The EPDM-carbon black compounds did not exhibit a zero shear rate viscosity, which tended towards infinity at zero shear stress or at a finite shear stress (Fig. 13). This was explained... 

Similarly, a substantial decrease in the specific wear rate, w, can be observed in Si02-g-PAAM filled composites with the rise in filler content and all vv values are lower than those of untreated nano-SiOj-filled systems, although the untreated nanoparticles can also result in decreased w, with respect to the unfilled epoxy. Within the filler content range firom 2 to 6 vol.%, the wear resistance of epoxy is increased by a factor of about 20 by the addition of SiOj-g-PAAM. Bearing in mind the fact that 40 wt.% micron-sized SiOj (180 /tm) particles were needed to acquire a significant decrease in the wear rate of epoxy, the present systems are clearly characterized by a broader applicability. 

For the production of preceramic slurries, fillers in the submicron range have to be used to achieve homogeneous infiltration of a fiber bundle with several thousands of filaments. This requires detailed knowledge of the rheological behavior of the powder-filled dissolved polymers. Additives are necessary to achieve high filler contents and good rheological behavior. 

EVA-copolymers are used as sealants. With vinyl acetate contents ranging from 15-40 % these copolymers are particularly applicable for the production of hot melts because of their good compatibility with fillers and other plastics. Ethylene vinyl alcohol copolymer (EVOH) is a plastic with exceptional barrier properties. It is manufactured by saponification of EVA. 

Over small temperature ranges, a linear dependence of the transverse relaxation time T2 on temperature is observed for technical SBR samples in the vicinity of room temperature (Fig. 7.1.13(a)). The temperature coefficients depend only weakly on the filler contents... 

Fillers improve the hardness of PTFE by 10%-15%, which is preserved over a wide range of temperatures. Increasing the filler content, in general, elevates the hardness of the compound. 

In filled polymer systems, it has been observed that the effect of filler content on viscosity decreases as shear rate increases [14, 49]. In the case of nanocomposite flllers, this effect has been explained in terms of a detachment/reattachment mechanism [49]. With respect to the dimensions of the flllers, it has been observed that as the surface area of the filler increases so does the viscosity of the filled polymer melt [18, 48]. For particles with similar shapes, an increase in the surface area means a reduction in particle size. In this sense, nanoflllers are expected to significantly increase the viscosity of polymer melts in relation to flllers with sizes in the range of micrometers. An analysis of filler shape and other relevant aspects of polymer flllers can be found in the work by Shenoy [50]. 

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