Entanglement relaxation of poly(1-butene) and its copolymer with ethylene detected in conventional shear rheometer and quartz resonator

Abstract

This study examined linear viscoelasticity (LVE) of stereo-regular poly(1-butene) (PB) and its random copolymer with polyethylene (PBE), with number fraction of ethylene comonomer ≤ 10%, using a conventional shear rheometer combined with a quartz resonator.This combination resulted in the detection of LVE in a broad frequency range from Rouse region to terminal relaxation. LVE thus determined was fit to the double reptation model through utilizing inputting molecular weights determined by gel permeation chromatography equipped with refractive index and two-angle laser light scattering monitors, and the segmental time and entanglement molecular weight as the two fitting parameters.Quantitative prediction was finally achieved when the two fitting parameters changed systematically by the increase of ethylene content; a decrease of segmental time quantified a plasticizing effect and a decrease of entanglement molecular weight reflected enhanced chain flexibility. The entanglement molecular weight of the PB samples was found to be lower than those reported for stereo-irregular PB, suggesting the important effect of stereo-regularity on chain flexibility.

Bulk rheometry at high frequencies: a review of experimental approaches

“…For homogeneous polymers with structural length scales that are sufficiently small (4), faster processes at or above the intermediate regime can be probed by performing measurements at even higher frequencies. Szántó et al (2017) measured the entanglement relaxation time of polyethylene melts by means of quartz resonators operating in the MHz range, which was recently extended for copolymers of poly-1-butene and polyethylene (Liu et al 2019).…”

Shear-Induced Oriented Crystallization for Isotactic Poly(1-butene) and Its Copolymer with Ethylene

“…Figure shows the master curves of storage and loss moduli, G ′ and G ″, as functions of angular frequency ω for the (a) PB and (b) PBE samples. The master curves were shown in our previous study and reduced to different reference temperatures T r here, i.e., T r = 125 °C for PB and 115 °C for PBE, which are above their respective melting temperatures of the form II crystals ( T m = 115.9 °C for PB and 99 °C for PBE) and chosen for studying the shear-induced crystallization (for PB, shear-induced crystallization was also studied at 130 °C). The low-frequency moduli (ω < 10 3 rad/s) were measured using the rotational rheometer, while the high-frequency moduli (ω > 10 6 rad/s) were measured using a quartz resonator (QR), as shown in our previous study .…”

“…The PB0110 and PB8640 samples are Ziegler–Natta-catalyst-based linear PB-1 products provided by LyondellBasell. The tacticity of PB0110 had been determined from 13 C nuclear magnetic resonance to be 0.970 in our previous study . The molecular weights (MWs) and distribution of PB0110 and PB8640 were characterized by high-temperature gel permeation chromatography (HT-GPC) analysis with PL-GPC 220 (Agilent) equipped with a two-angle (15 and 90°) laser light-scattering (TALLS) detector, a viscometer, and a differential refractive index (DRI) detector, as explained in detail in our previous study and briefly summarized below …”

“…Molecular weight M , radius of gyration R g , intrinsic viscosity [η], and concentration C were calculated for each elution fraction of the solution. The weight- and number-average molecular weights, M w and M n , of the samples were calculated with established absolute calibration curves, as explained in detail in ref and summarized in Table . Plots of [η] against M are shown in Figure S1 of the Supporting Information, giving [η] ∼ M 0.72 for PB and [η] ∼ M 0.73 for PBE.…”

“… a Reported in refs − . b Determined from analysis of linear viscoelasticity (LVE) in ref . c T m of form II crystal. d PB0110 at 125 °C and PB8640 at 115 °C, from LVE; see Figure . …”