Rheology rubber processing

With respect to stream rheological effects in rubber processing, and despite all the restrictions discussed above, it seems nevertheless that the key information is how the nonlinear viscoelasticity is related to the processing behavior of mbber compounds. Such information can be deduced from the appropriate test procedure with the RPA, providing one considers the capabilities of the instmment to provide nonlinear viscoelastic data. 

The molecular weight distribution is an important parameter for controlling the rheological and processing properties of rubber ... 

J. L. White, Elastomer Rheology and Processing, Rubber Chem. Technol., 42, 256-338 (1969). 

The discussion in rheological terms of the problems associated with rubber processing is relatively recent and results from theoretical and experimental progress in understanding flow properties of pure polymers, and particularly thermoplastics. However the rheology of elastomers is further complicated by the necessary presence of fillers, plasticizers and other ingredients. These lead to peculiar flow properties associated with heterogeneous matter and therefore not yet well understood. 

The rheological approach to rubber processing allows a better understanding of the flow behaviour of elastomers to be achieved. Obviously the picture is far from being complete and due to their complexity, rubber compounds are exhibiting phenomena not yet completely understood. 

At the opposite extreme, it may be required to disperse very fine particles into a highly viscous liquid. For example, the incorporation of carbon black into rubber is such an operation. Here, as with emulsification in liquid-liquid mixing, the product is stable, highly viscous and may well exhibit complex rheology. Such processes often involve surface phenomena and physical contacting only, in contrast to the mass transfer and chemical reactions described in the previous paragraph. The dispersion of fine particles in liquids is considered in detail in Chapter 6. 

Uses Catalyst in polyethylene crosslinking, styrene polymerization, polyester resins crosslinking agent for plastics, rubber rheology and processing aid for PP initiator in prod, of propylene homopolymer for use in food pkg. 

Rheological studies must be carried out to obtain information about the optimal time to vulcanization process, adjusting the vulcanization system to get the best mechanical properties or thermal properties and to estimate the cure rate index of the vulcanization process. Equipments like the rubber process analyser (RPA), a dynamic mechanical rheological tester, is a common equipment in the rubber industry. 

Lippe, R.J. (1980) Rheological parameters a versatile tool for the sealant formulator. Plastics and rubber Processing, 51-54 Qune). 

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