Adhesion Improvement between PE and PA in Multilayer Rotational Molding

The aim of this study is to investigate a multilayer structure made of polyethylene and polyamide by rotational molding. Due to the different polarity of these polymers, it is difficult to ensure enough adhesion between created layers. Two methods leading to improve adhesion are introduced. Plasma modification of polyethylene powder, after which new functional groups are bound to the treated surface, may enhance specific adhesion by forming hydrogen bonds with-CONH groups of polyamide. Different strategies of adding material to the mold give rise to complicated interlayer which increases joint strength by mechanism of the mechanical adhesion. Mechanical tests show a significant improvement of joint strength, where treated samples reached two-fold values of peel strength (7.657 ± 1.024 N∙mm−1) against the untreated sample (3.662 ± 0.430 N∙mm−1). During bending test, delamination occurred only in samples that were made of the untreated polyethylene. Adding polyamide during the melting stage of polyethylene powder in rotomolding resulted in the formation of entanglements which improve the peel strength almost eight times in comparison with the sample where the polyethylene was left to completely melt and create smooth interlayer surface.

Plasma Activation of Polyethylene Powder

Polyethylene powder of average particle diameter of 160 µm was activated in a plasma reactor made from aluminum of volume 64 dm3 at the pressure 100 Pa. Dense oxygen plasma was sustained with a microwave discharge powered by a pulsed magnetron source of power 1 kW mounted onto the top flange of the plasma reactor. Polymer powder was treated in a batch mode with 0.25 kg/batch. The powder was placed into a stainless-steel dish mounted in the center of the reactor where diffusing plasma of low ion density, and the O-atom density of 2 × 1021 m−3 was sustained. The powder was stirred in the dish at the rate of 40 rpm. The evolution of powder wettability versus treatment time was measured using the Washburne method, and the surface composition was determined by X-ray Photoelectron Spectroscopy (XPS). The wettability versus the oxygen concentration assumed a parabolic behavior. The maximal oxygen concentration, as revealed by XPS, was 17.5 at.%, and the maximal increase of wettability was 220%. The efficiency of O-atoms utilization in these experimental conditions was about 10% taking into account the spherical geometry of dust particles and perfectly smooth surface. The method is scalable to large industrial systems.

Heat-Treated Micronized Polyethylene Powder for Efficient Oil/Water Separating Filters

The targeted separation of oil/water mixtures is a rapidly growing field of research, mainly due to contaminated water becoming an increasingly important environmental issue. Superhydrophobic materials are highly suited to this application; however, growing efforts are being devoted to developing applicable technologies within a range of research communities. The optimal technical solution is one that combines a high separation efficiency with a straightforward fabrication procedure at a low cost. In this report, micronized polyethylene powder has been utilized as a low-cost hydrophobic material to manufacture easy-to-fabricate filters. The effect of heating and solvent addition on the water repellence behaviour has been investigated, according to which the optimum fabrication conditions were determined. The filters show high water repellence (WCA = 154°) and efficient oil/water separation (~99%). The filters are designed to provide a readily achievable approach for the separation of oils (hydrophobic solvents) from water in a range of potential applications.

Temperature dependent dielectric spectroscopy of muscle tissue phantom

The temperature dependence of the dielectric parameters of tissues and tissue-mimicking phantoms is very important for non-invasive temperature measurement in medical applications using microwaves. We performed measurements of this dependence in the temperature range of 25–50°C using distilled water as a reference liquid commonly used in dielectric property studies. The results were compared with the literature model in the frequency range of 150–3000 MHz. Using this method, the temperature dependence of dielectric parameters of a new muscle tissue-mimicking phantom based on agar, polyethylene powder, and polysaccharide material TX-151 was measured in the temperature range of 25–50°C. The temperature dependence of the dielectric properties of this new muscle phantom was fitted to that of the two-pole Cole–Cole model and the deviation of the results between measured and modeled data was quantified.

The effect of radiation exposure on the electrical conductivity of LDPE + x vol.%TlInSe2

The paper presents results of studying temperature dependences of the specific volume resistance of nonirradiated and irradiated [Formula: see text]-rays with a different dose of [Formula: see text] vol.%TlInSe2 composites in the temperature range 300–380 K. The technique for modifying the structure of composites with semiconductor filler was carried out on a [Formula: see text]Co-type MPX [Formula: see text]-25 M isotope [Formula: see text]-emitter at a temperature of 300 K in vacuum ampoules at doses of [Formula: see text]–[Formula: see text] Gy. The electrical properties of the composites were studied before and after irradiation with [Formula: see text]-rays. Samples were prepared by mechanically mixing the filler [Formula: see text] powder with a low density polyethylene powder until obtaining a uniform mixture. The mixture is kept for 5 min at the melting temperature of the polymer under a pressure of 5 MPa. At the same temperature, by pressing a homogeneous mixture, the pressure rises to 15 MPa, at this pressure the sample is held for another 5 min, and then quickly cooled in water. The specific volume resistivity of the composites was measured using a DC bridge of the P-4053 type with additional measuring electrodes. Samples before testing are aged for 24 h at a temperature of [Formula: see text]C and a relative humidity of [Formula: see text]%. It was revealed that with an increase in the volume content [Formula: see text], the specific volume of resistivity of composites decreases. Under the action of [Formula: see text]-radiation and a change in the filler content, the magnitude and nature of [Formula: see text] dependence changes, and this allows to manage the physical parameters of studied composites by varying the filler content and [Formula: see text]-radiation dose.

Multilayer Nanofiber Composite Separator for Lithium-Ion Batteries with High Safety

An original Von Koch curve-shaped tipped electrospinneret was used to prepare a polyimide (PI)-based nanofiber membrane. A multilayer Al2O3@polyimide/polyethylene/Al2O3@polyimide (APEAP) composite membrane was tactfully designed with an Al2O3@ polyimide (AP) membrane as outer shell, imparting high temperature to the thermal run-away separator performance and a core polyethylene (PE) layer imparts the separator with a thermal shut-down property at low temperature (123 °C). An AP electrospun nanofiber was obtained by doping Al2O3 nanoparticles in PI solution. The core polyethylene layer was prepared using polyethylene powder and polyterafluoroethylene (PTFE) miniemulsion through a coating process. The addition of PTFE not only bonds PE power, but also increases the adhesion force between the PE and AP membranes. As a result, the multilayer composite separator has high safety, outstanding electrochemical properties, and better cycling performance as a lithium-ion battery separator.