Heat capacities of polyethylene from 2 to 360 K. I. Standard samples of linear and branched polyethylene whole polymer

Abstract

Heat capacities of two well characterized polyethylene samples have been measured from 2 to 360 K in a precision vacuum adiabatic calorimeter. The two sa mples are derived from the same stocks from which NBS standard reference materials (SRM) 1475 and 1476 for linear and branched polyethyl· ene whole polymers, respectively, were established. Both samples have been studied in the conditions as received. The branched polyethylene sample has also been studied following various thermal treat· ments in the calorimeter. The effect of thermal hi story on the behavior of branched polyethylene has also been studied by differential scanning calorimetry.

Ballistic thermal phonons traversing nanocrystalline domains in oriented polyethylene

“…The signal follows a single exponential decay with a decay time τ = (αq 2 ) −1 , where α is the thermal diffusivity and q = 2πd −1 is the grating wavevector. The thermal conductivity is calculated from the diffusivity using literature values for the heat capacity of semicrystalline PE (43). Because thermal transport occurs along a single direction defined by the grating, the measured thermal conductivity of highly anisotropic semicrystalline PE varies with in-plane rotation angle.…”

Heat capacities of polyethylene. IV. High molecular weight linear polyethylene

“…Although the high molecular weight sample has lower crystallinity than the SRM 1475 in the condition as received (71% crystallinity) [ 5 ], it shows a somewhat lower heat capacity over the temperature range 90 to 310 K. Only at lower and higher temperatures does this sample exhibit the expected higher heat capacity. The heat capacity of this sample is very similar to that of a sample of SRM 1475 slowly cooled from the melt (88% crystallinity) [ 6 ] in the temperature range 100 to 220 K.…”

“…Heat capacity measurements on the high molecular weight linear polyethylene sample were made with the same vacuum adiabatic calorimeter [ 4 ] that was used in the previous studies [ 5 , 6 ] on polyethylene samples derived from Standard Reference Materials 1475 and 1476.…”

Heat capacity and thermodynamic functions of crystalline poly( p ‐phenylenebenzobisoxazole), the synthetic polymer with the highest Young's modulus

“…Linear polymers have been regarded as a model system of one-dimensional crystal, with the polymer backbone identified as the one-dimensional axis. Figure 3 demonstrates the temperature dependence of the heat capacities of PBO, PE, 13 PPP, 5,9,10 and a nonpolymeric compound, 4,4Ј-difluorobiphenyl (DFBP).…”