Papers by Keyword: PE

Abstract: This study discusses the development of enhanced insulating materials for High Voltage Direct Current (HVDC) cable insulations by reinforcing Low-Density Polyethylene (LDPE) with nanomagnesia (MgO) particles. The main emphasis of this work is to investigate the DC breakdown voltage performance of LDPE/MgO nanocomposites as a function of filler content. Increase in DC breakdown strength is very important for long-term reliability and safety of HVDC cable insulation. Besides electrical performance, tensile strength and morphological study were made as complementary studies to check the mechanical stability and quality of particle dispersion. The nanocomposites were fabricated using the melt-blending method, where 40 grams of LDPE was mixed with 1.25 wt.%, 2.5 wt.% and 5wt.% of nanomagnesia at 170 [°C] and 50 rpm (rotation per minute) using a Haake internal mixer. The resulting materials were hot-pressed into 1 mm thin films at 160 [°C] and 50 bar pressure. DC breakdown voltage tests were conducted on the samples to determine their breakdown voltage. Tensile testing was conducted for the mechanical property evaluation where the LDPE and 2.5 wt% MgO composite show slightly lower strain, indicating decreased ductility. Overall, the incorporation of MgO enhances stiffness but reduces flexibility and strain-hardening capacity, resulting in a stronger yet less ductile material. Scanning Electron Microscopy (SEM) was undertaken to complement the results, which included the dispersion quality of MgO particles and the filler interfacial bonding. Results indicated that nanomagnesia incorporation improved the DC breakdown voltage of LDPE, with the optimum value at 2.5 wt.% of MgO. At this loading, the material showed the strongest dielectric strength while retaining reasonable tensile properties. Thus, this study has proven that LDPE reinforced with 2.5 wt.% of nanomagnesia is a viable and efficient insulation material for HVDC cable applications at average of 40.1 [kV] compared to pure LDPE at 32.41 [kV].

Abstract: In this paper, trap levels around the glass transition temperature (T_g) of polymers have been characterized using Thermally Stimulated Current (TSC) technique. Deconvolution on α-peaks of the T_g for PE (-104 °C), plasticized PVC (-35 °C), PMMA (90 °C) and PET (96 °C) were carried out based on the first-order kinetic theory for non-Debye relaxation. Using temperature, T from TSC experimental data, we have successfully separated the α-peaks of the thermoplastic polymers. It is found that the complex curve of α-peaks can composed of four (4) to eight (8) sub peaks. Dominant sub peaks were identified at T_max = -105 °C, -34 °C, 89 °C and 92 °C for PE, pPVC, PMMA and PET, respectively. These peaks show activation energy, E_a of shallow and deep trap centers ranged from 0.3 eV to 4.6 Ev where they represent the depolarization of localized dipoles and space charges relaxations in the polymers.

Abstract: The effects of orientation on flame spread over the upper surface of PMMA and PE slabs were studied through a series of experiments. For fuel inclined angles smaller than 75° in this study, flame spread would arrive a steady-state stage finally. The flame spread rate and the angle of the fire plume near pyrolysis front in the steady-state stage were measured to investigate the differences between flame spread over melting and non-melting solids. Compared to the flame spread over polymethyl methacrylate (PMMA), the melting behaviors of high density polyethylene (PE) significantly decrease the flame spread rate, which is mainly attributed to the decreased size of fire plume and reduced interactions between fire plume and solid surface. The angles of the fire plume in the steady-state stage under different fuel inclined angles were measured to better understand the melting effects on flame spread over the inclined solid surface.

Abstract: Innovative lightweight structures realized by employing assembly injection molding bears high potential. Using assembly injection molding, complex shaped hybrid structures can be manufactured in a precise and fast processing step. Though, especially the interface quality of a hybrid joint is a crucial factor, which determines the overall quality of such lightweight structures. High bonding strength values were achieved between aluminum and multiple polymeric materials with double-lap joints manufactured by employing assembly injection molding. Thereby, the influence of aluminum surface pre-treatments as well as intrinsic adhesion modifications of the polymeric materials were investigated.

Abstract: In order to investigate the electrical conductivity of carbon nanotubes (CNTs)/polyethylene (PE) composites, the relationship curves between the external electrical filed strength and the electrical conductivity of CNTs/PE composites with different microstructures were generated based on numerical simulation. The simulation models of CNTs/PE composites were designed through changing the content, aspect ratio and orientation degree of CNTs. After DC electrical field is applied between top and bottom surfaces of the composites, the distribution of electrical current density was calculated based on the finite element method by using the COMSOL simulating software, and then the electrical conductivity is obtained. Research results indicated the electrical conductivity of the composites increases significantly with the increase of aspect ratio of CNTs at the same CNT content and electrical field strength. As the orientation degree of CNTs along the applied electrical field increases, the electrical conductivity of the composites obviously increases. It can therefore be concluded that the changing of microstructures of CNTs/PE composites is effective to control the electrical conductivity of the composites.

Abstract: This paper, by using multi-layer B/S framework model, combines with VB programming to carry out innovative design of physical education (PE) platform, which has got the B/S framework platform of PE management. PE information management platform mainly comprises the teacher end, the central processor unit (CPU) and the student end, where the communication interface mainly comprises the editor and the computer, and the input of teacher end includes the computer buttons, sensors, and so on. While for the core parts of the system, they are the CPU and the memory demonstrated by PE. Student end through the I/O expansion function analyzes and displays the teaching sound and video signal displayed by using LED or LCD. Finally, the paper designs the data analysis and transfer function of PE information platform, and obtains the curve of information throughput with time changing, which provides a new computer method for the research of PE.

Abstract: In this study, the physical properties of thermoplastic composites manufactured from linear medium density polyethylene (LMDPE), rice husk (RH) and maleic anhydride polyethylene (MAPE) were evaluated. Composites were manufactured with RH loadings of 15 wt%, 30 wt% and 50 wt% with 1 wt% of MAPE to investigate the effect of RH loading on the physical properties (water absorption and thickness swelling) of the composites. The results show that the water absorption and the corresponding thickness swelling increased with an increase in RH loading. Further manufacturing was carried out with 50 wt% of RH and 1wt%, 3.5 wt% and 6 wt% of MAPE to evaluate the effects of interfacial modification on the physical properties of the composites. The results show that the composites with 3.5 wt% of MAPE had least water absorption and the corresponding thickness swelling, whereas the composites having 1 wt% of MAPE had maximum water absorption and the thickness swelling. It can be concluded from these experiments that fibre loading as well as interfacial modification play a significant role in determining the physical properties of the composites.

Abstract: Chitosan-PE bi-layer films exhibit antimicrobial activity but poor antioxidant activity. Oregano essential oil (100μL/100mL) was incorporated into chitosan solution to improve films antioxidant and antimicrobial behaviors. The present work investigated the scavenging of O₂·, ·OH, DPPH radical and reducing power of film, antimicrobial activity was also evaluated. The results showed that the scavenging effect of film solution on O₂·, ·OH, and DPPH was 80.87%, 85.56%, and 87.24%, respectively. Reducing power of film increased with the improvement of oregano essential oil. The antibacterial activity against E. Coli and B. Subtilis increased from 80.77% to 96.15% and from 93.02% to 98.10%, respectively. The preservation experiments showed that chitosan-PE film incorporated with oregano essential oil could extend the shelf life of pork to 810 days at 4°C.

Abstract: In the present work, effect of field irrigation on tensile behaviors of disposable drip tape made from virgin PE is studied. Results show that after 5 months (from Novomber, 2012 to next April, 2013) field irrigation tests, there are no intrinsically changes in tensile stress-strain behaviors for the disposable drip tape made from virgin PE along the longitudinal direction. Tensile stress-strain behaviors for the disposable drip tape made from virgin PE along transverse direction is different. After field irrigation tests, the tapes are prone to sudden rupture at the seams accompanied with a relative smaller elongation and acute stress drops while those as-received show large elongation with gradual stress decrease under transverse tensile. However, rebound of the stretched tapes after field irrigation tests is distinctly smaller than those of as-received samples.

Abstract: The MWNTs/PE nanocomposites are prepared by in situ polymerization with mulltiwalled carbon nanotubes (MWNTs) supported Cp2ZrCl2 catalyst and MAO as cocatalyst. The SEM and AFM results show that MWNTs are exfoliated and homogenously dispersed in PE matrix by the in situ polymerization. The up-shifting of the G band in Raman spectra show the strong compressive forces associated with PE chains on the MWNTs. The storage modulus of the MWNTs/PE nanocomposite can be increased by 160% even at low amount of MWNTs (0.2 wt %) due to MWNTs well-dispersed and exfoliated in the matrix. The TGA and DMA tests point to significant improvements on thermal and mechanical properties of the PE/MWNTs nanocomposites compared to pure PE.