Crystal orientation relaxation studies of polyethylene

Abstract

SynopsisWide-angle x-ray relaxation studies were performed on films of low-and high-density polyethylene (PE). The samples were rapidly stretched by a pneumatic stretcher and held a t a fixed length. The rate of crystal reorientation was monitored by measuring diffracted intensity changes using a count-rate meter with output displayed on a storage oscilloscope as well as a digital counter-timer. Experiments were completed a t several temperatures and activation energies comparable to those reported for the relaxation in P E were obtained.

Review of Long-Term Durable Creep Performance of Geosynthetics by Constitutive Equations of Reduction Factors

“…However, the activation energies resulted from this study as well as those calculated from data published is much higher than other published values [10]. It was found an activation energy value of 118 kJ/mol for PE fibers and an energy value of 85 ± 30 kJ/mol was obtained by studying the stress relaxation of an oriented HDPE [11,12]. Creep performance tests using TTS with test durations of 1,000 hours were done at each temperature [13,14].…”

Solid-State13C NMR Analyses of the Orthorhombic-to-Hexagonal Phase Transition for Constrained Ultradrawn Polyethylene Fibers

“…The mechanical α relaxation consists of at least three subrelaxations, namely α 1 , α 2 , and α 3 in the order of increasing temperature . The α 1 relaxation arises from the interlamellar slip or the deformation of intermosaic regions within the crystalline lamellae . The α 2 relaxation is believed to originate from the thermal oscillation of intracrystalline polymer chains, − including twisting motion about the c -axis as well as translational motion along the c -axis. , The reality of the α 3 relaxation is suggested to be associated with the transition from the orthorhombic phase to the hexagonal phase. , The α relaxation temperature for polyethylenes is somewhat diffuse, ranging from 30 to 120 °C. ,, When a polyethylene sample is measured by solid-state 13 C NMR spectroscopy near the α relaxation temperature, the spectra mainly reflect the α 2 and α 3 relaxations.…”

“…46 The mechanical R relaxation consists of at least three subrelaxations, namely R 1 , R 2 , and R 3 in the order of increasing temperature. 47 The R 1 relaxation arises from the interlamellar slip 48 or the deformation of intermosaic regions within the crystalline lamellae. 49 The R 2 relaxation is believed to originate from the thermal oscillation of intracrystalline polymer chains, [47][48][49] including twisting motion about the c-axis as well as translational motion along the c-axis.…”

“…47 The R 1 relaxation arises from the interlamellar slip 48 or the deformation of intermosaic regions within the crystalline lamellae. 49 The R 2 relaxation is believed to originate from the thermal oscillation of intracrystalline polymer chains, [47][48][49] including twisting motion about the c-axis as well as translational motion along the c-axis. 50,51 The reality of the R 3 relaxation is suggested to be associated with the transition from the orthorhombic phase to the hexagonal phase.…”

Dynamic birefringence studies of high‐density polyethylene

“…The sample examined in the study was a Monsanto experimental HDPE (MPE 200) and is identical with that described in a previous paper. 8 The polymer has M , = 155,000, M , = 163,000, and a degree of branching of 2.9 CHd1000 C. Films were melt pressed at 150°C and 200 kg/cm2 for ten minutes and then plunged into an ice-water bath. The films were annealed at 104OC in a vacuum oven for two hours and then allowed to cool slowly in the oven.…”