Effect of Gypsum and Etepon on Crop Yield Siamese Orange (Citrus Nobilis Var. Microcarpa L.)

This study aims to determine the effect of Gypsum and Etepon on the yield of Siamese orange (Citrus nobilis Var Microcarpa. L) conducted in Belancan Village, Kintamani District, Bangli Regency from December 2020 to July 2021. This study used a randomized block design (RAK) with 2 factors arranged in a factorial manner. The first factor that was tried was the dose of gypsum fertilizer (G) which consisted of 4 levels, namely: G0 (0 g/tree), G1 (250 g/tree), G2 (500 g/tree) and G3 (750 g/tree. While the second factor is the concentration of etepon (E) which consists of 3 levels, namely: E0 (0 ml/l water/tree), E1 (0.75 ml//l water/tree) and E2 (1.5 ml/l water)/tree). Thus, there were 12 combination treatments, each of which was repeated 3 times so that 36 citrus trees were needed. The results showed that the interaction between the dose of gypsum and the concentration of etepon had no significant effect on all observed variables. The highest harvested fruit weight per tree was obtained at a dose of gypsum 750 g/tree which was 6.32 kg or an increase of 70.35% when compared to treatment without gypsum which was only 3.71 kg. The highest harvested fruit weight per tree was obtained in the etepon treatment with a concentration of 1.5 ml/l/tree, which was 6.54 kg, an increase of 51.38% compared to the treatment without etepon, which was only 4.32 kg. Keywords: dose, etepon, gypsum, Siamese orange, yield

Evaluation of graphene/crosslinked polyethylene for potential high voltage direct current cable insulation applications

This paper evaluates the potential usage of graphene/crosslinked polyethylene (graphene/XLPE) as the insulating material for high voltage direct current (HVDC) cables. Thermal, mechanical and electrical properties of blends with/without graphene were evaluated by differential scanning calorimetry (DSC), tensile strength, DC conductivity, space charge measurements and water tree aging test. The results indicate that 0.007–0.008% weight amount of graphene can improve the mechanical and electrical insulation properties of XLPE blends, namely higher tensile/yield strength, improved space charge distribution, and shorter/fewer water tree branches. The improvements mainly attribute to the high stiffness of graphene, deep traps introduced by the interaction zones of graphene and XLPE, and the blockage effect of graphene within XLPE. For thermal performance of XLPE blends, graphene nano-fillers have but limited improvement. The crystallinity of the blends barely changes with the addition of graphene. However, the crosslinking degree increases as the additive-like amounts of graphene doped. The above findings provide a guide for tailoring lightweight XLPE materials with excellent mechanical and electrical performances by doping them with a small amount of graphene.

Water-Tree Resistant Characteristics of Crosslinker-Modified-SiO2/XLPE Nanocomposites

Trimethylolpropane triacrylate (TMPTA) as a photoactive crosslinker is grafted onto hydrophobic nanosilica surface through click chemical reactions of mercapto double bonds to prepare the functionalized nanoparticles (TMPTA-s-SiO2), which are used to develop TMPTA-s-SiO2/XLPE nanocomposites with improvements in mechanical strength and electrical resistance. The expedited aging experiments of water-tree growth are performed with a water-knife electrode and analyzed in consistence with the mechanical performances evaluated by means of dynamic thermo-mechanical analysis (DMA) and tensile stress–strain characteristics. Due to the dense cross-linking network of polyethylene molecular chains formed on the TMPTA-modified surfaces of SiO2 nanofillers, TMPTA-s-SiO2 nanofillers are chemically introduced into XLPE matrix to acquire higher crosslinking degree and connection strength in the amorphous regions between polyethylene lamellae, accounting for the higher water-tree resistance and ameliorated mechanical performances, compared with pure XLPE and neat-SiO2/XLPE nanocomposite. Hydrophilic TMPTA molecules grafted on the nano-SiO2 surface can inhibit the condensation of water molecules into water micro-beads at insulation defects, thus attenuating the damage of water micro-beads to polyethylene configurations under alternating electric fields and thus restricting water-tree growth in amorphous regions. The intensified interfaces between TMPTA-s-SiO2 nanofillers and XLPE matrix limit the segment motions of polyethylene molecular chains and resist the diffusion of water molecules in XLPE amorphous regions, which further contributes to the excellent water-tree resistance of TMPTA-s-SiO2/XLPE nanocomposites.