Effect of molecular weight on secondary Newtonian plateau at high shear rates for linear isotactic melt blown polypropylenes

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F70883521%3A28110%2F18%3A63517056" target="_blank" >RIV/70883521:28110/18:63517056 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1016/j.jnnfm.2017.11.009" target="_blank" >http://dx.doi.org/10.1016/j.jnnfm.2017.11.009</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jnnfm.2017.11.009" target="_blank" >10.1016/j.jnnfm.2017.11.009</a>

Result language

angličtina

Original language name

Effect of molecular weight on secondary Newtonian plateau at high shear rates for linear isotactic melt blown polypropylenes

Original language description

In this work, three melt blown grades of isotactic linear polypropylenes, with weight average molecular weights between 56 250–75 850 g/mol, have been characterized at 230 °C over a very wide shear rate range (10–107 1/s) by using conventional rotational and twin bore capillary rheometry equipped with novel orifice die, and by an instrumented capillary nozzle on an injection molding machine. A low shear rate primary Newtonian plateau, a pseudoplastic region and a well developed secondary Newtonian plateau (occurring between 2·106−7·106 1/s) were identified for all the polypropylene melts. Flow activation energy at low (E0) and high (E∞) shear rates was found to be 56.590 kJ/mol and 25.204 kJ/mol, respectively. Considering the typical value of pressure sensitivity coefficient for polypropylene melt, β = 20.00 GPa−1, and measured flow activation energy at the secondary Newtonian plateau, E∞ = 25.204 kJ/mol, it was found that the effect of viscous dissipation and pressure is mutually cancelled, i.e. that the measured viscosity data can be considered as the true material property within the whole applied shear rate range. For the first time, it has been revealed that the secondary Newtonian viscosity, η∞, depends linearly on the weight average molecular weight, Mw, in log-log scale as η∞=1.19·10−6Mw 1.084. The observed slope close to 1 between η∞ and Mw suggests that polymer chains in the melt are disentangled at the secondary Newtonian plateau region. This conclusion is supported by the experimental observation that the high shear rate flow activation energy E∞ for given PP melts is comparable with the flow activation energy of PP like oligomer (squalane, C30H62; 2,6,10,15,19,23-hexamethyltetracosane). The measured flow data were fitted by six different viscosity models, from which two, namely Modified Carreau and Quemada models, were suggested here for the first time. It has been found that the accuracy of utilized models to describe the measured data is the highest for the newly suggested models and decreases in the following order: Modified Quemada model, Modified Carreau model, Carreau-Yasuda model, Cross model, Generalized Quemada model and Carreau model.

Czech name

—

Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10404 - Polymer science

Project

<a href="/en/project/GA16-05886S" target="_blank" >GA16-05886S: Investigation the effect of polymer melt shear and elongational rheology on production stability of meltblown nanofibers and films</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Non-Newtonian Fluid Mechanics

ISSN

0377-0257

e-ISSN

—

Volume of the periodical

251

Issue of the periodical within the volume

Neuveden

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

12

Pages from-to

107-118

UT code for WoS article

000423003600010

EID of the result in the Scopus database

2-s2.0-85037540603