Filler elastomers

Wang, M.-J., Effect of Filler-Elastomer Interaction on Hysteresis, Wet Eriction and Abrasion of EiUed Vulcanizates, Paper presented at a meeting of the Rubber Division, ACS, Akron, May 8-10, 2006. 

The structure of crystalline polymers may be significantly modified by the introduction of fillers. All aspects of the structure change on filling, crystallite and spherulite size, as well as crystallinity, are altered as an effect of nucleation [9]. A typical example is the extremely strong nucleation effect of talc in polypropylene [10,11], which is demonstrated also in Fig. 2. Nucleating effect is characterized by the peak temperature of crystallization, which increases significantly on the addition of the filler. Elastomer modified PP blends are shown as a comparison crystallization temperature decreases in this case. Talc also nucleates polyamides. Increasing crystallization temperature leads to an increase in lamella thickness and crystallinity, while the size of the spherulites decreases on... 

After a screening of the different parameters available for the characterization of reinforcing fillers, the nature of filler-elastomer interactions is examined (occluded and bound rubber). 

In the last part of the paper, filler-elastomer chemical interactions which are able to take place through surface functional groups or surface reactive hydrogens are studied. The effect exerted by the created filler-elastomer bonds in the reinforcement process is then discussed. 

Effect of Filler-Elastomer Interactions on Vulcanizate Properties.117... 

In this connection, Fig. 2 provides a qualitative illustration for interpreting modulus change of an elastomer upon filler blending 9). A hydrodynamic or strain amplification effect, the existence of filler-elastomer bonds, and the structure of carbon black 10) all play a part in this modulus increase. 

From the technological standpoint, numerous empirical parameters have been used to characterize the effect of reinforcement. Two of them based on rheometry and filler-elastomer interactions will be discussed the aF parameter17) and the reinforcement factor RF ]8 20). 

By plotting the percentage of carbon particles separated from the vulcanizate versus the stress applied to the sample during extension, Hess et al. determined the stress at which the arbitrary quantity of 20% of the black had been separated from the matrix. This stress was indicated as the adhesion index. It appears (Fig. 12) that blacks of higher structures are associated with an increase of the adhesion index, i.e., with an enhancement of filler-elastomer interactions. 

It appears, beyond all doubt, that filler-elastomer interactions result in the formation of chemical bonds between the polymer and the solid surface, which are due to a reaction of the macromolecule either with the surface chemical groups or with the surface hydrogen atoms. Is, however, the formation of covalent filler elastomer bonds a prerequisite for reinforcement to occur ... 

Graphitized carbon blacks, thus undoubtly display reinforcing abilities which become obvious when considering the tensile strength of the unfilled vulcanizate. It follows that the formation of a filler-elastomer chemical bond is not a requirement for reinforcement to occur. It strongly participates, however, in its effectiveness, and determines the good mechanical properties connected with rubber reinforce-... 

Another way for increasing filler-elastomer interactions could be the grafting of a polymer on the solid surface. A number of methods exist to secure the attachment of macromolecules to the surface of carbon black particles e.g., a polymeric chain may be grown on an initiation site on the surface, small molecules previously attached to the surface may be copolymerized with a monomer, a polymeric chain, either radical, cationic, or anionic in nature, may be terminated on an active site of the solid surface, etc. 55 63). 

The filler-elastomer chemical interactions take place through its surface functional groups and hydrogen atoms. Coupling agents improve polymer-filler adhesion. From the point of view of dynamic-mechanical properties for low strains, the filler-elastomer bonds have a positive effect in the reinforcement process. 

Dannenberg, E. M. Influence of filler-elastomer interactions on reinforcement behavior . In Le renforcement des elastomeres. Paris CNRS 1975, pp. 129-135... 

Nonreinforcing Filler-Elastomer System, I. Experiments Based on Model Systems , JA-PolymSci 1974, 18(1), 1-20 CA80, 109562 (1974) 5) A.J. Hammond H.R. Lobowitz,... 

Nonreinforcing Filler-Elastomer Systems—2. Silane-Treated Ammonium Perchlorate in Polybutadiene , JApplPolymSci 18 (1), 21—43... 

The high mechanical strength of natural and organic rubbers as used in tires is due to the incorporation of pyrogenic carbon blacks as active fillers. Elastomers of a more polar polymer backbone, such as polyacrylates, polyurethanes or polysulphides, require fillers of higher polarity. In particular the performance of polydimethylsiloxane elastomers (silicone rubber) is basically related to the addition of fumed silica. 

A random siloxane copolymer containing 90 mol% dimethyl-, 10 mol% methylphenyl-, and 0.3 mol% methylvinyl-chain units is used for the sample preparation. The copolymer is filled with hydrophilic Aerosil (300 m g ) (A300) and hydrophobic Aerosil (60 m g ) (AM60). The weight ratio filler/elastomer is 30 100. 

Cameron CG, Underhill RS, Rawji M, Szabo IP (2004) Conductive filler elastomer composites for Maxwell stress actuator applications. Proc SPIE 5385 51... 

Diatomaceous earth, amorphous filler, dynamite Wood flour filler, elastomers Calcium silicate filler, electrical insulation Ozokerite... 

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