Optical Properties Of Polyethylene Research Articles

Effect of calcium bromide hydrate on the structural and optical properties of polyethylene glycol/niobium pentoxide polymer layers

The blend polymer layers of polyethylene glycol with various Nb2O5 and CaBr2⋅xH2O concentrations were synthesized using the solution-dropping process. X-ray diffraction spectra revealed polyethylene glycol peaks, which could be attributed to the polymers' inherent semi-crystalline phase. The Raman spectra revealed stretching Nb–O bonds and confirmed the Nb2O5 phase. The stretching modes of the CH, CH2, and CH3 groups are presented for polyethylene glycol. Adding more CaBr2⋅xH2O (0–3 wt%) increases the transmittance values to about 0.64 %, 1.18 %, 2.79 %, and 6.29 %. At the same time, the band gap values of the polymer layers go down from 3.0 eV to 2.06 eV. The refractive index values increased from 6.16 (0 wt% CaBr2⋅xH2O) to 7.46 (3 wt% CaBr2⋅xH2O). The low Urbach energy of 837.26 meV for the 2 g polyethylene glycol/4 wt% Nb2O5/1 wt% CaBr2⋅xH2O sample confirms the appropriate concentration of less disorder in the polymer layer.

The Effect of Slip Polymer Additives on the Characteristics of Polyethylene Films

Polymer additive’s function is to improve film quality, including slip additives which function as film surface lubricants. Slip additives affect the physical characteristics of the film as indicated by the coefficient of friction and optical properties. In this research, the influence of slip additives and the aging time of the coefficient of friction (COF) and the optical properties of polyethylene (PE) films have been studied. The optical properties of the film are measured based on the haze value and the gloss value. The additives used in this study were erucamide, stearyl erucamide, and a mixture of the two. Observations were made for 14 days at 23 °C and 50 °C. Measurements of the COF, haze value, and gloss value were carried out on days 0, 1, 3, 7, 10, and 14. The results showed that the lowest COF was produced on films with erucamide additives. Films with erucamide additives had the best friction coefficient value of 0.129 on the 3rd day of aging at 50 °C, a haze value of 4.63% and a gloss value of 56.5 GU.

A combined experimental and numerical approach for radiation heat transfer in semi-crystalline thermoplastics

This paper proposes a novel experimental-numerical approach for radiation heat transfer in semi-crystalline thermoplastics. The proposed experimental and numerical approaches were analyzed here for the case of IR heating of linear polyethylene (PE). The challenges for radiation transport in semi-crystalline polymers may be categorized into the two main aspects: optical heterogeneity in polymer medium due to semi-crystalline nature and, semi-transparency in certain type of such polymers, like PE. In this study, we address the temperature dependence in the thermo-optical properties of semi-crystalline thermoplastics concerning its effect as a thermal radiation parameter for radiation heat transfer modeling of such type of polymers. The temperature dependence in the optical properties of PE, namely transmittance and reflectance characteristics, were experimentally analyzed under heating condition and, the temperature-dependent thermo-optical properties of PE was determined. The experimental analyses showed that the change in the thermo-optical properties under heating is related to change in the optical scattering behavior in PE medium since it is strongly affected by its crystalline structure. The radiation heat transfer model was built based on optically homogeneous medium assumption at which the change in the amount of radiative energy absorbed by the PE medium under heating was introduced without modeling how the light scatters inside of the medium. Thus, the effect of optical scattering on the absorption characteristics of PE under varying temperature was taken into account without modeling the spatial distribution of the scattered light intensity at microscopic level, which offers computationally cost-effective numerical solutions. The accuracy of the numerical model was analyzed performing IR heating experiments where IR thermography and thermocouples were employed for the surface temperature measurements. Due to the semi-transparent nature of PE, an experimental method was developed for IR thermography of PE and its accuracy was analyzed. The experimental-numerical comparisons showed that the temperature field on PE can be closely predicted using its temperature-dependent thermo-optical properties. Thanks to the adopted comparative case study, it was demonstrated how the temperature field predictions may deviate from the experimental thermal measurements due to the ignorance of this temperature dependence. Considering any type of monochromatic or polychromatic radiation source, the combined experimental-numerical approach proposed here may be adopted for temperature field predictions and non-invasive surface temperature measurements on the radiatively heated semi-crystalline thermoplastics.-

Optical Properties of Polyethylene Filled with Bi2Te3 Nanocrystallites

Composite mixtures with various component concentrations are fabricated by the thermal pressing of low-density polyethylene and Bi2Te3 in the powder-like state with a nanocrystal size of ~50 nm. These samples preliminarily characterized by X-ray diffractometry and Raman spectroscopy are investigated by spectroscopic ellipsometry in a photon energy range of 1–6 eV. The dielectric functions for composites with a nominal Bi2Te3 weight concentration of 5, 10, 30, 40, 50, 60, and 70% are calculated based on the measured optical constants of polyethylene and the Bi2Te3 crystal in the approximation of the Bruggeman effective medium. The analysis of depolarization features of reflected light makes it possible to establish the actual inhomogeneity of the composite samples under study caused by the clusterization of nanocrystallites with an increase in the Bi2Te3 weight concentration in polyethylene and propose the most reliable optical model of the formed composites.

Effects of metal impurities on the optical properties of polyethylene in the warm dense-matter regime

For the warm dense-matter regime, we have examined the effects on the equation of state, conductivity, and optical properties of the introduction of a metal impurity (Al) into a poorly conducting mixture $({\text{CH}}_{2})$ by means of quantum molecular-dynamics simulations employing temperature-dependent density-functional theory for temperatures between 1 and 4 eV and densities from ambient solid to a few times compressed. The properties such as dc conductivity and Rosseland mean opacity exhibit significant departures from the pure ${\text{CH}}_{2}$ results only for metal concentrations above about 50%. The system is representative of a wide range of environments that include planetary interiors, inertial confinement fusion capsules, and laser-produced plasmas.

Optical Properties of Polyethylene: Measurement and Applications

The optical properties of polyethylene, obtained from transmission measurements on thin films, are presented for photon energies from 0.5 to 76 eV. The results for the extinction coefficient are combined with calculated values in the soft and hard X-ray regions, and both their internal consistency and their consistency with data obtained previously for polystyrene are verified through a sum rule calculation. Based on these optical data, the mean excitation energy for polyethylene is calculated to be 62 eV. A model insulator theory, with parameters fixed by the optical data, is employed to calculate inverse mean free paths and energy losses per unit pathlength for low-energy electrons (10 eV through 10 keV) in polyethylene.

On the Existence of Local Segmental Order in Undiluted Bulk Polymers

The mean-square end-to-end distance and its temperature coefficient, the change in the intramolecular conformational entropy on melting, and the optical anisotropy, as manifested by the strain birefringence, and its temperature coefficient are calculated in the rotational isomeric-state approximation for unperturbed linear polyethylene chains containing short stretches of skeletal bonds exclusively in the all trans or planar zigzag conformation. The results are compared with the corresponding quantities calculated for a polyethylene chain free of such conformational constraints and with experimental data taken from the literature which were obtained on undiluted bulk polyethylene. This comparison shows that the optical properties of polyethylene are more sensitive to the local segmental order, as defined in this study, than are its dimensions and their temperature coefficient or the change in intramolecular conformational entropy on melting. An estimate of the upper limit of local segmental order in bulk polyethylene, which is consistent with experimental and calculated results, is presented, and the conclusion that little, if any, segmental order exists in bulk polymers is drawn. The effect of diluents on the strain birefringence of polymer networks is commented upon in this connection.