Interaction chain filler

It has been well established that wear resistance of filled rubber is essentially determined by filler loading, filler morphology, and polymer-filler interaction. For fillers having similar morphologies, an increase in polymer-filler interaction, either through enhancement of physical adsorption of polymer chains on the filler surface, or via creation of chemical linkages between filler and polymer, is crucial to the enhancement of wear resistance. In addition, filler dispersion is also essential as it is directly related to the contact area of polymer with filler, hence polymer-filler interaction. 

Another interaction is responsible for the recovery of the material after it is subjected to stress. " Rubber bridging the neighboring particles of filler is an example. Some particles are connected through several rubber chains which makes their association more permanent and assures filler-filler contact. These filler-filler contacts are responsible for the recovery since, unlike chain-filler contacts, they store the strain energy which is then used in the recovery process. Chain-filler contacts can easily debond or rearrange in different location and this process does not result in recovery of the initial shape. 

The variation of polymer chains solubility owing to specific interactions with inorganic substrates was clearly evidenced, particularly in the field of filled elastomers The interaction between filler and elastomer materials is revealed by formation of a polymer fraction not extractable (insoluble) called "bound rubber" that seems to play a significant role in... 

Filler morphologies such as particle size, structure, and essentially surface characteristics have a drastic effect on the physical performance of the elastomeric material. The most important of these parameters however, are the surface characteristics and the chemical active sites which determine the interaction between filler and polymer chains. ... 

A small amount of clay dispersed in a polymer matrix gives better final properties. The dispersion is controlled by various interactions between filler particles and polymer chains however, it is difficult to achieve a homogeneous dispersion on a nanoscale without the pretreatment of clay surfaces, since, in many cases, the hydrophilic clay surface and hydrophobic polymer chains are incompatible. 

Figure 7.16 shows interface formation with painted substrate. The mechanism of organization was discussed in the previous section. The alignment in the polymer layer plays a large part in polymer-filler interaction in the adjacent layers. The way in which polymer is configured on the substrate surface determines if polymer chains are readily available for interaction with filler. This example shows that it is not only the filler and the matrix which play a role in the interphase organization. 

TTie influence of fillers on crystallization behavior of polymer matrix depends on the interaction between filler surface and polymer chains. In numerous cases, fillers act as nucleation sites for polymer crystallization. Intense nucleation on the surfaces of reinforcing fibers leads to the development of transcrystaUinity. However,... 

Both tear resistance and hysteresis increase on incorporation of silica, but the effect is less pronounced as compared to the stress-strain properties. Tension set of the ZnO-neutralized m-EPDM system is low (around 20%) and incorporation of filler causes only a marginal increase in set due to chain slippage over the filler surface, as previously discussed. Measurement of physical properties reveal that there occurs an interaction between the filler surface and the polymer. Results of dynamic mechanical studies, subsequently discussed, support the conclusions derived from other physical properties. 

Zinc salt of maleated EPDM rubber in the presence of stearic acid and zinc stearate behaves as a thermoplastic elastomer, which can be reinforced by the incorporation of precipitated silica filler. It is believed that besides the dispersive type of forces operative in the interaction between the backbone chains and the filler particles, the ionic domains in the polymer interact strongly with the polar sites on the filler surface through formation of hydrogen bonded structures. 

In pressing, the threshold concentration of the filler amounts to about 0.5% of volume. The resulting distribution of the filler corresponds, apparently, to the model of mixing of spherical particles of the polymer (with radius Rp) and filler (with radius Rm) for Rp > Rm as the size of carbon black particles is usually about 1000 A [19]. During this mixing, the filler, because of electrostatical interaction, is distributed mainly on the surface of polymer particles which facilitates the forming of conducting chains and entails low values of the percolation threshold. 

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