Mechanical energy losses in commercial crosslinked low‐density polyethylene in the temperature range between 200 and 400 K

Abstract

Aging treatments in water and in air and controlled neutron irradiation were performed on commercial crosslinked lowdensity polyethylene (XLPE) for promoting different mesostructural arrangements of crystallites and crosslinking degree. Infrared spectroscopy, differential scanning calorimetry, differential thermal analysis, thermogravimetry, and dynamic mechanical analysis were used as characterization techniques. The relaxation peak related to the mobility of the grain boundaries from crystalline zones in XLPE was identified at around 260 K (at 7 Hz), involving an activation energy of 90 AE 4 kJ mol −1 . The usual equation for describing the grain boundary mobility in metals involving the movement of grain boundary dislocations was adapted for studying the mobility of the boundaries among the crystalline zones, successfully. In addition, a new mechanical relaxation peak that appears at around 300 K (at 7 Hz), which involves an activation energy of 94 AE 5 kJ mol −1 , was found. The driving force controlling this peak was determined as the dragging of the polymer chains at the amorphous zones adjacent to the crystals controlled by the mobility of the crystallites boundaries. The chains movement was done with break away from the physical pinning points.

High functional 3D printed PCL/FSMA magnetic composites

“…It gives rise to a departure from the linear relationship between stress and strain, which exists previously to the break-away of the dislocation line [45,46,52,53,74,78]. Consequently, the ADD effects in polymers can be related to the unpinning of polymer chains from pinning points both thermally-and mechanically-assisted during the DMA studies [52,64,79,80]. It is convenient of being mentioned here, that we are considering that the ADD effects are occurring in the polymeric matrix, due to the unpinning of polymeric chains.…”

Fluorescence monitoring of the degradation evolution of aliphatic polyesters

“…15 In particular, due to the susceptibility to degradation, a highly sensitive methodology is required for testing the degradable plastics so that any sign of degradation is found as early as possible. Disappointingly, the current gravimetric analysis and mechanical property evaluation are mainly focused on the macro-variations for plastics, 16,17 which fails to raise a timely alarm. Although Fourier transform infrared (FT-IR) spectroscopy could be used to detect the micro variations of functional groups in polymer degradation, the unsatisfactory sensitivity of FT-IR still failed to determine the slight changes in plastics in early-stage degradation.…”