Apparent activation energy for the viscous flow of polymer solutions

Valls

et al. 1987

Colloid & Polymer Sci

Abstract:The ORD spectra of three types of glycogen in salt solutions at different concentrations, pH and ionic strength values were determined to investigate the influence of these variables on the rotatory power.The ORD curves obtained with the samples recently prepared correspond to positive monotone dispersion curves, similar to available data for the other polysaccharides.Once the mutarotation equilibrium is attained a maximum is observed at 210 + 10 nm. The rotatory power decreases with the elapsed time and in some cases, it is possible to find a change in the sign of these curves. Such a phenomenon may be attributed to conformational changes in the monomer units constituting the macromolecule.A considerable increase in the rotatory power is found at pH extreme values. The dispersion constant, go, was calculated by means of a modified Drude equation and results indicate that the,to value is higher for muscle glycogen in the mussel species, suggesting a higher degree of asymmetry in this macromolecule.

Section: Discussionsupporting

confidence: 82%

Optical rotatory dispersion (ORD) of glycogen

Valls

et al. 1987

Colloid & Polymer Sci

J of Applied Polymer Sci

“…The formulation and importance of c [η] is described in detail in the Formulation of c[η] Master Curve section. The activation energy for viscous flow can be adequately described by the quadratic relation:

E_{η} = Q_{0} + Q_{1} ((), c ([], η)) + Q_{2} {(c [normalη])}^{2}

where Q 1 and Q 2 are the adjustable parameters and Q 0 = 8.37 is the flow activation for pure MMA . These parameters are presented in Table for each PMMA sample.…”

Section: Resultsmentioning

confidence: 99%

“…where Q 1 and Q 2 are the adjustable parameters and Q 0 = 8.37 is the flow activation for pure MMA. 48 These parameters are presented in Here, η is the shear viscosity, _ γ is the shear rate, η 0 is the zeroshear viscosity, τ η is the characteristic relaxation time, n is an adjustable parameter that characterizes the final slope of the curve in the power-law region, and δ is a parameter that describes the breadth of the transition from Newtonian to powerlaw behavior, which decreases with increasing polydispersity. 41 Table III shows the values of the parameters for the Carreau-Yasuda model for the solutions that displayed shear thinning.…”

Section: Resultsmentioning

confidence: 99%

Infusible acrylic thermoplastic resins: Tailoring of chemorheological properties

Cousins

Howell

Suzuki

et al. 2019

Infusible liquid resins that polymerize into a thermoplastic are desirable for many applications. Similar to unsaturated and vinylester thermosetting systems, they consist of polymers dissolved in reactive monomer. This work presents a method to decrease cycle time by tuning the molecular weight and concentration of the predissolved polymer in the resin. Variation of these properties allows precise control of the viscosity which in turn controls the time at which peak exotherm is reached, the maximum temperature for a given part thickness, and cure time. Predictive models for the viscosity dependence on molecular weight, polymer concentration, shear rate, and temperature are developed. Two fiberglass panels are fabricated and tested; one with a lower molecular weight (Mw~30 kg mol−1) poly(methyl methacrylate) dissolved in methyl methacrylate and the second with higher molecular weight (Mw~500 kg mol−1) predissolved polymer in the resin. Mechanical properties are indistinguishable but the lower molecular weight panel cures up to three times faster. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48006.

“…In most cases, activation energy for the viscous flow of polymer solution increases continuously with increasing polymer concentration, except in particular cases of critical mixtures [13]. The reason being the activation energy for the viscous flow of polymer solutions in poor solvent decreases with polymer concentration at high dilution and this is ascribed to the temperature dependence of the limiting viscosity number [14]. For Polystyrene in toluene, it is observed that the activation energy increases with increase in concentration.…”

Section: Activation Energy Studiesmentioning

confidence: 93%

A Study on the Acoustic and Rheological Properties of Polystyrene in Different Solvents

Padmanaban¹,

Venkatramanan²,

Arumugam³

2018

IJCRR

Polystyrene (PS) is a synthetic aromatic hydrocarbon polymer prepared from the monomer styrene. Polystyrene can be foamed or solid. General-purpose polystyrene is hard, clear and rather brittle. It is a low cast resin per unit weight. It is a rather poor barrier to oxygen and water vapour and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year. Polystyrene can be naturally transparent, but can be coloured with colourants. Uses include protective packaging (such as packing peanuts and DVD and CD cases), bottles, trays, containers, lids, tumblers, disposable cutlery and in the making of models. In the present study an attempt has been made to compute the viscosity of Polystyrene (M.W: 35000) in toluene and 1,4-Dioxane at different concentrations (0.2%, 0.4%, 0.6%, 0.8% & 1.0%) at different temperatures (303 K, 308 K, 313 K & 318 K). From these experimental data, activation energy is calculated and the effect of solvent is analyzed. Density and ultrasonic velocity have been estimated for the above systems at 303K. From these experimental values, various molecular interaction parameters like free volume, internal pressure, viscous relaxation time, interatomic free length, etc. are calculated and discussed in terms of solute-solvent interactions.