Relationships between molecular weight, solution viscosity, and melt index for narrow distribution, high pressure polyethylene whole polymers. Fast M̄_n determinations

Abstract

SynopsisMelt and solution viscosity properties of laboratory-prepared batch polymerized high pressure polyethylene have been found to correlate well with molecular weight. These polymers have narrow and nearly constant molecular weight distributions and contain essentially no long-chain branches. Short-chain branching was found to have little or no effect on the relationships. Polyethylene made in the same reactor having longchain branches had melt and solution viscosity properties which deviated seriously from these relationships. The deviations serve as a semiquantitative measure of long-chain branching. When long-chain branching is absent, the correlations serve as rapid methods of determining a,, for narrow-distribution polymers.

Optimized Synthesis of Poly(deoxyribose) Isobutyrate, a Viscous Biomaterial for Bone Morphogenetic Protein-2 Delivery

“…The molecular weight and molecular weight distribution of polymers can strongly affect the mechanical properties of the polymer. It has previously been shown that polycondensation reactions can be utilized to attain high-molecular-weight polymers. , As such, the molecular weights of PDIB compositions were studied using GPC. Governed by the processing parameters, PDIB samples had a broad peak with polydispersity in the range of 1.5–3.5 and molecular weight ranging between 1212 and 4216 Da.…”

Physicochemical characterization of pectinase activity from Bacillus spp. and their accessory role in synergism with crude xylanase and commercial cellulase in enzyme cocktail mediated saccharification of agrowaste biomass

“…Viscosity is a characteristic of the fluid that opposes relative motion between two surfaces of the fluid which are moving at different velocities. Positive correlations between the molecular weight or length of the polymers or branching pattern of the polymer with viscosity has been shown by Mortimer et al (1964). Breakdown of the polymer eases the branching and reduces the length and molecular weight of the polymer, which consequently reduces the force required for movement of two fluid layers.…”

General and more precise relationships between molecular weight, blend ratio, and melt index of binary polyethylene blends

“…In linear polymers, such as high-density (linear) polyethylenes and polypropylenes, a linear relationship between molecular weight or logarithm of molecular weight and logarithm of MFI has been observed. 2,4,5 Also some authors have attempted to predict MI using MWD for polyethylenes and polypropylenes. 9,11,12 Bremner and coworkers have found a simple relationship between MI and molecular weight of linear polymers.…”

“…Therefore, some authors have reversed the process and attempted to deduce MWDs by measurements of rheological behavior. Several articles have been published in this field such as: to obtain molecular weight averages polymer by using melt flow index (MFI) of the polymer [1][2][3][4][5] and by melt viscosity, 5,6 to obtain MWD of polymer by dynamic melt viscoelasticity. 7 In addition, study of rheological properties of polymeric materials through online method in industrial production lines has been provided during recent years.…”