AbstractThe effects were studied of molecular weight, shear rate, and temperature on the viscous behavior of various linear, monodisperse polyisoprenes of about 90%cis‐1,4 structure. Viscosities of from 1010‐105poise were measured on a double cone and plate viscometer while viscosities of 104‐10−2poise were measured on rotating cylinder viscometers. For such polyisoprenes the variation of Newtonian (zero shear) viscosity η with the weight‐average molecular weight in the molecular weight range of 2 × 104‐1 × 106may be represented asdocumentclass{article}pagestyle{empty}begin{document}$eta = Abar M_w^{3.9_5}$end{document}whereAis a temperature‐dependent parameter given bydocumentclass{article}pagestyle{empty}begin{document}$log A = - 101.14 + frac{{8.999 times 10^4}}{T} - frac{{3.19222 times 10^7}}{{T^2}} + frac{{3.816 times 10^9}}{{T^3}}$end{document}The variation of the apparent viscosity ηawith shear rate is also determined and a combined equation may be formulated asdocumentclass{article}pagestyle{empty}begin{document}$eta _{rm a} = Abar M_w^{3.9_5} /[1 + 1.22(Adot gamma /T)^{0.58} bar M_w^{2.87} times 10^{- 5}]$end{document}This equation is compared with other expressions for the variation of viscosity with molecular weight, temperatur
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