An empirical concept of flow for polyisobutene systems

Abstract

Viscosities were measured on 11 polyisobutenes with molecular weight of 224 to 71,000. Measurements were made on cetane and tetralin solutions containing 11.2–100 wt.‐% polymer. Tests were made at 80–135°C. and a t shear rates to 8 × lo6 sec.‐l. Low shear capillary and two types of rotational viscometers were used. The data confirm that polyisobutene systems show an abrupt transition in log viscosity—log molecular weight correlations. This transition occurs near 15,000 for MV where M is Viscosity‐average molecular weight and V is polymer volume fraction. Below a product of 15,000, polyisobutene systems exhibit essentially Newtonian flow and an absence of laminar flow shear degradation to stresses above 2 × 105 dynes/cm.2. In this region the viscosity dependence on molecular weight approaches fist order at higher temperatures and lower polymer concentrations. For polyisobutene systems above the transition near 15,000, low shear viscosities uniformly increased aa the 3.4 power of molecular weight. Systems in this range exhibited large and predictable non‐Newtonian effects and frequently showed laminar flow shear degradation at low rates of shear.

Determination of the intermolecular entanglement coupling spacings in polyisoprene by viscosity measurements

“…Th e p olym er concen trations r epor ted correspond to volum e p ercen t values of 2, 4, and 16 at 25 D C. Sin ce each sample served for measuremen ts at the two temper atures, it was n ecessary to correct for the density ch ange at t he higher te mp er ature in ord er to accurately calculate M e at 75 D C. These results clearly indicate th e existence of the t ransition p oint to at least t wo volume percen t concentration and the inverse first power dependence of th e mol ecular weight for t r ansition (M b) on concen tration. This latter point is at variance with t h e interpretation given to data ob tained from st udies [32][33][34] The constancy of the molecular weight-concentration product found for th e polyisoprene solutions is in complete accord wit h t h e results obtained from investigations [36][37][38][39][40][41][42] of the rheological behavior of p olystyr ene and polyisobutylen e in bulk and concentrated solutions. A similar conclusion is r each ed from the combin ed r esults of Buech e [10,12] and Bletso [43] for solutions of poly(meth yl m eth acrylate) .…”

Non-Newtonian viscosity of concentrated polymer solutions

“…This dependence manifests itself by two crossing lines. This is in agreement with the theoretical prediction of Bueche for the solutions (21) and the data of Porter and Jonson (22). At the range of higher molecular weights the lines are parallel and are described by the Fox-Loshack equation.…”

Packing Length Influence in Linear Polymer Melts on the Entanglement, Critical, and Reptation Molecular Weights

“…Fox and Allen 2 proposed a relationship between M c and 〈 R 〉 0 /M which, in the terminology used here, can be expressed as follows: where 〈 R 〉 0 is the mean-square unperturbed radius of gyration and the quantity 6 X c N a is proposed to be universal with X c = 45.7 ± 9.2. Accordingly, the data for the various species − in Table should give a straight line through the origin when plotted as N c = M c / m b vs p . This relationship, shown in Figure , exhibits a rather poor fit to the data and yields a correlation coefficient R of only 0.853.…”