Polyolefin degradation
Abdelhay Smaida; Yacine Mecheri; Larbi Boukezzi; Slimane Bouazabia
Abstract
This study focuses on the study of long-term electrical aging effects on dielectric behavior of cross-linked polyethylene (XLPE) used as insulation in high voltage cables. For this reason, we have performed long-term electrical aging tests on full size of HV 36/60 kV XLPE cable samples at three voltage ...
Read More
This study focuses on the study of long-term electrical aging effects on dielectric behavior of cross-linked polyethylene (XLPE) used as insulation in high voltage cables. For this reason, we have performed long-term electrical aging tests on full size of HV 36/60 kV XLPE cable samples at three voltage levels (U0 = 36 kV, 2U0 = 72 kV and 3U0 = 108 kV) during 680 hours. The studied properties are partial discharge threshold, dielectric loss factor, relative permittivity and transverse resistivity. Besides, physico-chemical changes were assessed using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD). In the end of paper, the evolution of mechanical properties and hot set test with aging time and voltage levels have been presented and analyzed as additional diagnostic precursors. The obtained results illustrate that examined properties are widely affected by long-term electrical aging. The increase in partial discharges and dissipation factor depending to the voltage level and the aging time and the decrease in partial discharge threshold voltage and transverse resistivity are the mostly marked degradation precursors. These degradation precursors are supported by the increase of carbonyl groups and reduction in the crystallinity degree of the polymer under long-term electrical aging. These parameters are useful parameters for evaluating the quality of underground XLPE cable insulator.
Structure and property relationship
Derradji Dadache; Farid Rouabah; Zahir Rahem
Abstract
This study demonstrates that quenching and annealing significantly influence the mechanical and thermophysical behavior of low density polyethylene (LDPE). Rapid quenching at temperature of –25 °C enhances ductility by increasing elongation at break, despite reducing thermophysical properties, ...
Read More
This study demonstrates that quenching and annealing significantly influence the mechanical and thermophysical behavior of low density polyethylene (LDPE). Rapid quenching at temperature of –25 °C enhances ductility by increasing elongation at break, despite reducing thermophysical properties, likely due to microstructural refinement. In contrast, post-quenching annealing especially at 100 °C improves thermal conductivity and crystallinity but reduces ductility. The results underscore a tunable balance between thermal and mechanical performance, governed by the interplay of beta (β-) and alpha (α-) relaxation modes during heat treatment. Post-quenching annealing of low density polyethylene LDPE, particularly at 100 °C, significantly enhanced thermal conductivity, diffusivity, and crystallinity, albeit with a trade-off in ductility and increased brittleness. Quenching within the beta (β-) relaxation range promoted maximum ductility, while annealing in the alpha (α-) relaxation range improved thermophysical properties. These findings reveal that precise control of heat treatment conditions enables a tunable balance between mechanical flexibility and thermophysical performance in LDPE
Olefin polymerization and copolymerization
Fakhrossadat Mirtaleb; Mohammadreza Jozaghkar; Farshid Ziaee
Abstract
In this study, well-defined α-methyl styrene – olefin triblock copolymers were synthesized via living anionic polymerization using alkyl lithium as an initiator and 1,12-dibromododecane as a coupling agent. The polymerization was conducted in cyclohexane under an inert atmosphere at moderate ...
Read More
In this study, well-defined α-methyl styrene – olefin triblock copolymers were synthesized via living anionic polymerization using alkyl lithium as an initiator and 1,12-dibromododecane as a coupling agent. The polymerization was conducted in cyclohexane under an inert atmosphere at moderate temperature, allowing for precise control over the molecular architecture and narrow molecular weight distribution. Gel permeation chromatography (GPC) revealed monomodal elution curves with dispersity values close to unity, confirming the living nature of the polymerization process and the high structural homogeneity of the resulting copolymers. Structural characterization was performed using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The 1H NMR spectra confirmed the successful formation of block copolymers through the identification of characteristic chemical shifts corresponding to the initiator, αMS blocks, and central dodecane units. Notably, the absence of brominated end-groups in the spectrum supports complete coupling and high end-group fidelity. Furthermore, 13C NMR analysis revealed well-defined chemical shifts associated with aromatic, methine, and methylene carbons. The disappearance of signals corresponding to bromine-bound methylene carbons confirmed the full consumption of the coupling agent and the effective formation of the triblock structure. These findings validate the successful synthesis of αMS-based triblock copolymers with a high degree of control over molecular parameters, establishing a robust foundation for tailoring thermomechanical and morphological properties for advanced material applications.
Food Packaging
Rizel Marie S. M. Ting; Elyson Keith P. Encarnacion; Anne C. Alcantara; David J. Alcarde Jr.; Harold E. Armario; Winnie P. Alejandro; Agaseve F. Del Rosario; April Star L. Canonizado
Abstract
The widespread consumption of disposable plastics as food contact articles (FCAs) in the Philippines has raised concerns on food safety due to the potential chemical migration of contaminants. In this study, validation of modified 21 Code of Federal Regulations (CFR) Part 177 method was performed through ...
Read More
The widespread consumption of disposable plastics as food contact articles (FCAs) in the Philippines has raised concerns on food safety due to the potential chemical migration of contaminants. In this study, validation of modified 21 Code of Federal Regulations (CFR) Part 177 method was performed through preliminary screening, determination of validation parameters, and profiling. 18 randomly screened low-density polyethylene (LDPE) bags from 16 brands across Philippine markets were analyzed to identify low and high absorbance levels of total UV-absorbing contaminants (TACs) to be considered for method validation. Validation parameters demonstrated limit of detection (LOD) and quantification (LOQ) of 0.013 AU and 0.033 AU per 50 cm2, ensuring reliable detection at low levels. Results from profiling 47 samples presented variability in migration of TACs across brands and locations, however, all samples were within the maximum allowable limit (MAL) of 0.300 AU set by the Food and Drug Administration (FDA) Philippines for aqueous foods. These findings account for the potential migration of contaminants throughout production, transportation, environmental conditions, and storage processes. Comparison between food simulants, n-Heptane to mimic fatty and oily foods and water for aqueous foods, was conducted through statistical analysis using previously reported same-laboratory data for n-Heptane. An independent nonparametric Mann–Whitney U test indicated a statistically significant difference between TACs levels of the two simulants. Comprehensive research on yet to be specified contaminants is proposed to further explore probable adverse health effects associated with their toxicokinetics and toxicodynamics.
Food Packaging
Ali Alkhair
Abstract
The aim of this study is to encourage a shift in industry towards using natural, biodegradable materials with antimicrobial properties to produce polymeric materials that can be used effectively in areas such as food and pharmaceutical packaging. In this study, polymeric films based on low-density polyethylene ...
Read More
The aim of this study is to encourage a shift in industry towards using natural, biodegradable materials with antimicrobial properties to produce polymeric materials that can be used effectively in areas such as food and pharmaceutical packaging. In this study, polymeric films based on low-density polyethylene (LDPE) were produced using extrusion technology with the addition of marjoram powder at concentrations of 1%, 3% and 5%. The second phase of the study involved determining the technological properties of the obtained films, including their antimicrobial, barrier, physical, and mechanical properties. The results of the research showed that polyethylene samples supplemented with marjoram powder exhibited antimicrobial properties against Bacillus subtilis and Candida albicans at concentrations of 3% and 5%. However, the same samples did not exhibit any antimicrobial properties against Escherichia coli and Aspergillus niger at any concentration. Polyethylene samples with a 3% concentration demonstrated the greatest tensile strength in both the longitudinal and transverse directions. However, as the marjoram concentration increased, the elongation-at-break of the samples declined. Polyethylene films recorded the lowest elongation-at-break values at a 5% concentration in both directions. Water vapor permeability of the films also increased with marjoram powder concentration; it increased by 2.8 times at 3% compared to the control sample.
Composites and nanocomposites
Maziyar Sabet
Abstract
Polypropylene (PP), a widely used polyolefin, suffers from poor electrical conductivity, which limits its use in electronic packaging and electromagnetic interference (EMI) shielding. In this study, conductive and EMI-shielding PP nanocomposites were fabricated using dual-functionalized carbon nanotubes ...
Read More
Polypropylene (PP), a widely used polyolefin, suffers from poor electrical conductivity, which limits its use in electronic packaging and electromagnetic interference (EMI) shielding. In this study, conductive and EMI-shielding PP nanocomposites were fabricated using dual-functionalized carbon nanotubes (CNTs) via a solvent-free melt-blending route. Sequential acid and silane treatments improved CNT dispersion and interfacial compatibility, yielding a low percolation threshold of ~0.3 wt.% and an electrical conductivity of 1.2 × 10⁻² S/m at 3 wt.% CNT. At 5 wt.%, the EMI shielding effectiveness exceeded 41.5 dB, with more than 80% of the attenuation arising from absorption, as confirmed by S-parameter analysis. AI-assisted image segmentation (U-Net architecture) quantified an ~80% reduction in CNT agglomeration and increased interparticle spacing, correlating with the enhanced electrical, dielectric, and thermal properties. The dielectric constant increased from ~2.3 in neat PP to ~6.0 at 5 wt.% CNT with low dielectric loss (tan δ < 0.02), while thermal conductivity improved by ~75%. Tensile strength and modulus increased up to 3 wt.% CNT with a moderate loss in ductility. The combination of dual CNT functionalization, scalable melt processing, and AI-based dispersion quantification provides a reproducible approach for designing lightweight, conductive, and EMI-shielding polyolefin nanocomposites for electronic, automotive, and aerospace applications.
)
