Weight, molecular viscous flow influence

Molecular Weight and Distribution Dependences. The influences of molecular weight and its distribution on the viscous flow (82) viscoelastic behavior... 

Under different deformation conditions, natural rubber (NR) may exhibit predominant viscous flow, elastic or viscoelastic behaviour. Thus, the time for the movement of the NR molecular chains, i.e. relaxation time, is vastly affected by those deformation rate and NR types. The variation of NR types such as smoked rubber sheet, rubber blocks such as skim block, STR 5L and STR 20, is another factor that influences rheological properties and processing of NR due to their different Mooney viscosity, molecular weight distribution and gel content. Types of NRs are based on the different production processes of NR in which rubber smoked sheets are produced from NR in the latex form whereas block types are produced from various types of NR sources such as from latex in the case of STR 5L, from rubber scrap in the case of STR 20 and from skim latex in the case of skim block. 

For highly viscous, non-Newtonian flows, even without considering reaction, the temperature dependence of the properties such as density and viscosity has an important influence in determining the flow patterns. A consequence of this is that heat transfer dominates the design because of heat generation due to chemical reaction. In the case of a polymer reaction, temperature has an important effect on the molecular weight distribution so it is essential to try to ensure a uniform temperature in the reactor. 

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