Examining impact of vapor-induced crosslinking duration on dynamic mechanical and static mechanical characteristics of silane-water crosslinked polyethylene compound

Silane-crosslinked polyethylene (Si-XLPE) compounds are widely used cable insulation materials, cured by water as the crosslinking inducer. Herein, an attempt was made to evaluate the alterations of dynamic mechanical and static mechanical properties of Si-XLPE by increasing the water vapor-triggered crosslinking duration. The criterion for determining the progress of crosslinking was based on an industrially-used method (hot set test), and results indicated 16 h of vapor exposure as an appropriate duration for approaching maximum attainable crosslinking extent. Progress in crosslinking during this period was confirmed by FTIR spectroscopy. DMA was employed to assess the variations of dynamic mechanical behavior. Extending the crosslinking duration affected the storage modulus noticeably, and decreased it due to adverse effect of crosslinking on crystallinity. DSC confirmed the diminishment of crystallinity owing to the extended crosslinking time. Furthermore, prolonged vapor exposure period impacted β and γ transitions due to the influence of formed crosslinks on the mobility of chains. Tensile testing was carried out to ascertain the static mechanical characteristics of crosslinked samples. Findings demonstrated that tensile strength at yield increased below 5%, and tensile stress at break grew around 17%. Besides, elongation and Young's modulus experienced nonmonotonic changes due to the lengthened crosslinking period

Tethering vapor-phase deposited GLYMO coupling molecules to silane-crosslinked polyethylene surface via plasma grafting approaches

Herein, an attempt was made to deposit and graft GLYMO (3-glycidyloxypropyltrimethoxysilane) self-assembled layers on silane-crosslinked polyethylene (Si-XLPE). The principal objective was to create an anchoring layer on the pristine surface of Si-XLPE to modify its poor surface bonding properties. Since attachment of the GLYMO self-assembled layers to the partially non-polar surface of Si-XLPE seemed challenging, plasma post-irradiation and syn-irradiation grafting methods were utilized separately for activating the substrate and the deposited GLYMO molecules to provide the necessary condition for grafting and fabrication of uniform self-assembled layers. According to surface chemistry analyses, plasma grafting methods appeared to be beneficial tools for enhancing grafting of GLYMO molecules and reducing the self-condensed GLYMO aggregates and its self-assembled multilayer structures. Morphology investigations confirmed the positive role of plasma grafting in decreasing the self-condensed aggregated GLYMO structures on the surface. Moreover, GLYMO plasma grafting flattened the surface owing to the special orientation of the deposited molecules during the grafting and plasma etching. Surface wettability studies, along with chemistry outcomes, demonstrated the tendency of GLYMO molecules to tether to the surface with their trimethoxysilane groups, while their closed epoxide rings aligned to the out of surface. Overall, the plasma post-irradiation grafting approach exhibited higher grafting density

Assessing effects of (3-aminopropyl) trimethoxysilane self-assembled layers on surface characteristics of organosilane-grafted moisture-crosslinked polyethylene substrate: A comparative study between chemical vapor deposition and plasma-facilitated in situ grafting methods

Silane coupling agents can act as bonding intermediates at the interface of two dissimilar materials by altering surface properties. In this study, (3-aminopropyl) trimethoxysilane (APTMS) was used as a silane precursor for vapor-phase deposition on organosilane-grafted moisture-crosslinked polyethylene (Si-XLPE) substrate. Chemical vapor deposition (CVD) and plasma-facilitated in situ grafting methods (grafting-from and grafting-onto) were employed to graft APTMS, and the consequent effects on surface of Si-XLPE were evaluated. In-depth analysis was done to determine the assembly behavior of the fabricated APTMS layers and their influences on the surface properties. Characterizations were based on the assessment of surface chemistry (by XPS, EDX, and ATR-FTIR), morphology (by AFM and FESEM), and wettability (by contact angle measurement). The results showed that APTMS molecules inclined to form multilayer structures instead of monolayers. Height of the formed layers ranged approximately 5-30 nm. Also, it was deduced that crosslinking of deposited layers happened through different siloxane configurations in siloxane polyhedral networks on the surface. The arrangement of APTMS molecules led to the creation of hydrophobic surfaces (water contact angle >= 100 degrees) implying prevailing attachment of APTMS molecules from amino groups to the substrates. Findings confirmed that the plasma grafting-from approach possessed the highest APTMS attachment efficiency

Internal and interfacial microstructure characterization of ice droplets on surfaces by X-ray computed tomography

Hypothesis: Characterizing the microstructure of an ice/surface interface and its effect on the icephobic behavior of surfaces remains a significant challenge. Introducing X-ray Computed Tomography (XCT) can provide unprecedented insights into the internal (porosity) and interfacial structures, i.e. wetting regime, between (super)hydrophobic surfaces and ice by visualizing these optically inaccessible regions. Experiments: Frozen droplets with controlled volume were deposited on top of metallic and polymeric substrates with different levels of wettability. Different modes of XCT (3D and 4D) were utilized to obtain information on the internal and interfacial structure of the ice/surface system. The results were supplemented by conventional surface analysis techniques, including optical profilometry and contact angle measurements. Findings: Using XCT on ice/surface systems, the 3D and 4D (imaging with temporal resolution) structural information can be visualized. From these datasets, qualitative and quantitative results were obtained, not only for characterizing the interface but also for analyzing the entire droplet/surface system, e.g., measurement of porosity size, shape, and location. These results highlight the potential of XCT in the characterization of both droplets and substrates and proves that the technique can aid to develop hydrophobic surfaces for use as icephobic materials