Kuan Yong Ching’s research while affiliated with University of Reading and other places

Polymer blends have attracted significant research interest due to their potential use as power cable insulating materials. Specifically, polypropylene (PP) blends offer improved dielectric properties over conventional crosslinked polyethylene insulating materials attributable to PP’s high melting temperatures, hence high rated voltages. Despite numerous promising findings have been reported regarding the potential application of PP blends as power cable insulating materials, there have been relatively less investigations into the dielectric effects of incorporating nanofillers into PP blends. The current work therefore explores the influence of calcined magnesia (MgO) nanofiller on the structure and dielectric properties of PP blended with ethylene-octene copolymer (EOC). Nanofiller-wise, calcination of MgO does not significantly affect the structure of MgO, albeit that water-related molecules are removed from MgO. Upon adding the calcined MgO to the PP/EOC blend, the breakdown performance of the PP/EOC/MgO blend nanocomposites becomes jeopardized, especially under the direct current field. This is primarily attributed to the presence of residue water molecules within the PP/EOC/MgO blend nanocomposites, even after MgO calcination. Although the addition of the calcined MgO to the PP blend does not result in favorable dielectric properties, the findings suggest that nanostructuration of PP blends could be further explored to pave the way for the development of nanostructured PP blends for use in advanced power cable insulation applications.

With a global shift toward energy sustainability, power cable insulation materials vital for modern energy transmission have seen needs for improvements. In this regard, thermoplastic polypropylene (PP) blends offer exceptional thermal and electrical properties over conventional insulation materials. Notably, nanostructuration of PP blends can further enhance the electrical properties of PP blends, but the underlying physics governing nanostructured PP blends has yet to be systematically explored. The current work therefore evaluates the effects of surface‐treated nanomagnesia (MgO) on the electro‐mechanical properties of PP blended with 10 wt%, 20 wt%, and 30 wt% of ethylene‐propylene‐diene monomer (EPDM). The results show that blending PP with EPDM exhibits significantly improved mechanical properties, with the elongation‐at‐break increasing beyond 400%, albeit that the breakdown strength deteriorates by 34%. Significantly, adding surface‐treated MgO to the PP/EPDM blends improves the breakdown strength of the materials by up to 14% without compromising the elongation‐at‐break of the materials. The mechanisms governing the improved breakdown strength of the PP/EPDM/MgO nanocomposites over the PP/EPDM blend counterparts are explained through changes in the materials' structures. These findings provide fundamental insights into the structure–property relationship of nanostructured PP blends crucial for the development of PP‐based power cable insulation.

The current work discusses the effects of vacuum and oxidative aging at $110~^{\circ }$ C on the direct current breakdown performance of pure polypropylene (PP) and PP nanodielectrics having 1 wt%, 2 wt%, and 5 wt% of magnesium aluminate, calcium carbonate, and surface-treated calcium carbonate nanoparticles. The results show that aging pure PP under vacuum changes the structure of the material, with the breakdown performance of pure PP consequently being reduced by 13%. Meanwhile, aging pure PP in circulating air causes the breakdown performance to reduce by as much as 29%, due to both structural and chemical changes within the material. In contrast, all the nanodielectrics experience much less detrimental effects on the breakdown performance even after thermo-oxidative aging, with the most substantial reduction being almost half that of the pure PP. Possible mechanisms governing changes in the breakdown performance, especially under thermo-oxidative aging, are discussed. The role of the nanoparticles in preserving the breakdown performance of the nanodielectrics against thermo-oxidative aging is particularly highlighted.

Hydrogels present attractive opportunities as flexible sensors due to their soft nature and tunable physicochemical properties. Despite significant advances, practical application of hydrogel‐based sensor is limited by the lack of general routes to fabricate materials with combination of mechanical, conductive, and biological properties. Here, a multi‐functional hydrogel sensor is reported by in situ polymerizing of acrylamide (AM) with N,N′‐bis(acryloyl)cystamine (BA) dynamic crosslinked silver‐modified polydopamine (PDA) nanoparticles, namely PAM/BA‐Ag@PDA. Compared with traditional polyacrylamide (PAM) hydrogel, the BA‐Ag@PDA nanoparticles provide both high‐functionality crosslinks and multiple interactions within PAM networks, thereby endowing the optimized PAM/BA‐Ag@PDA hydrogel with significantly enhanced tensile/compressive strength (349.80 kPa at 383.57% tensile strain, 263.08 kPa at 90% compressive strain), lower hysteresis (5.2%), improved conductivity (2.51 S m⁻¹) and excellent near‐infrared (NIR) light‐triggered self‐healing ability. As a strain sensor, the PAM/BA‐Ag@PDA hydrogel shows a good sensitivity (gauge factor of 1.86), rapid response time (138 ms), and high stability. Owing to abundant reactive groups in PDA, the PAM/BA‐Ag@PDA hydrogel exhibits inherent tissue adhesiveness and antioxidant, along with a synergistic antibacterial effect by PDA and Ag. Toward practical applications, the PAM/BA‐Ag@PDA hydrogel can conformally adhere to skin and monitor subtle activities and large‐scale movements with excellent reliability, demonstrating its promising applications as wearable sensors for healthcare.

Polypropylene (PP) has recently been actively investigated as a potential power cable insulation substitute for crosslinked polyethylene (XLPE). This is mainly due to PP's higher thermal withstand capability over XLPE. Notably, PP has much higher stiffness than XLPE and therefore needs to be modified with tougher materials to reduce its overall stiffness while maintaining its desirable dielectric properties. To date, many investigations have been conducted on the mechanical and dielectric effects of PP blended with various copolymers. Nevertheless, systematic investigations on the dielectric effects of PP blended with ethylene‐based copolymers having different ethylene contents are less explored. The current work therefore reports on the impact of different ethylene contents of ethylene‐based copolymers on the breakdown performances of PP. The findings reveal that PP blended with a copolymer having a low ethylene content (68.7 wt%) results in at least 11% higher breakdown performance than PP containing a copolymer having a high ethylene content (77.0 wt%). Specifically, PP containing 10 wt% of copolymers having 68.7 wt% of ethylene content results in comparable breakdown performance to XLPE (325 kV mm⁻¹). These results suggest that ethylene‐based copolymers with an appropriately low ethylene content can be blended with PP to achieve desirable breakdown properties. Highlights PP is blended with copolymers of varying amounts and ethylene contents. PP blended with low amounts of copolymers has good breakdown strength. PP blended with low ethylene level copolymers has favorable breakdown strength. PP blended with copolymers of low ethylene contents is desirable. The breakdown mechanisms are related with the structure and permittivity.

Thermoplastic polypropylene (PP) has garnered a significant attention in power cable insulation research because of its exceptional thermal tolerance and dielectric properties. Due to its poor impact strength at room temperature, PP has been blended with various elastomers, including ethylene-propylene-diene monomer (EPDM), to improve the mechanical stiffness of the final material. This, however, comes with compromised dielectric properties of the material. Recently, the addition of nanofillers to polymers has demonstrated promising properties that can be tailored for various dielectric applications, provided that nanofiller and polymer interactions are appropriately formulated. Nevertheless, the effect of nanostructuration in PP/elastomer blends, especially from the perspective of dielectrics, have yet to be systematically explored. In the current work, magnesia (MgO) nanofiller is added to a model PP/EPDM blend system to determine the effect of MgO on the breakdown properties of PP/EPDM. The results show that adding 0.5 wt% of MgO to PP/EPDM reduces the AC and DC breakdown strengths by 7% and 16%, respectively. As the amount of MgO increases to 3 wt%, the AC and DC breakdown strength reduces further by 25% and 29%, respectively. Significantly, appropriate modification of the nanocomposites with polypropylene-graft-maleic anhydride (PP-g-MAH) can result in 5% higher breakdown strength of the nanocomposites with respect to comparable nanocomposites without modification. The mechanisms surrounding these breakdown effects are discussed with the aid of materials structure interpretations. Overall, the results demonstrate that appropriate modification of nanocomposites with PP-g-MAH is crucial in tailoring breakdown properties of PP blend nanocomposites.

This paper aimed at maximizing the application of oil palm empty fruit bunch (EFB) fibers to reinforce the starch-based bioplastics with superior mechanical and water resistance properties. EFB fibers were thermally modified with dry method by incorporating different concentrations of sodium hydroxide (NaOH). Thermal treatments with NaOH exceeding 10 wt% caused significant fiber loss. Fourier transform infrared spectroscopy (FTIR) exhibited the part removal of fatty acid, hemicellulose, and lignin and SEM observed clean surfaces for the treated fibers. The crystallinity index of the fibers increased from 13.82% to 97.60%, but their thermal stability decreased due to the treatments. The influence of treated fibers on the structure and properties of starch-based bioplastics was characterized. EFB fibers treated with 10 wt% NaOH attained the high yield of 52.44% and demonstrated the best reinforcing effects on the bioplastics. This was confirmed by higher thermal stability, tensile strength, and water resistance compared to the other starch-based bioplastics.