The present review article represents a comprehensive study on polymer micro/nanocomposites that are used in high-voltage applications. Particular focus is on the structure-property relationship of composite materials used in power engineering, by exploiting fundamental theory as well as numerical/analytical models and the influence of material design on electrical, mechanical and thermal properties. In addition to describing the scientific development of micro/nanocomposites electrical features desired in power engineering, the study is mainly focused on the electrical properties of insulating materials, particularly cross-linked polyethylene (XLPE) and epoxy resins, unfilled and filled with different types of filler. Polymer micro/nanocomposites based on XLPE and epoxy resins are usually used as insulating systems for high-voltage applications, such as: cables, generators, motors, cast resin dry-type transformers, etc. Furthermore, this paper includes ample discussions regarding the advantages and disadvantages resulting in the electrical, mechanical and thermal properties by the addition of micro- and nanofillers into the base polymer. The study goals are to determine the impact of filler size, type and distribution of the particles into the polymer matrix on the electrical, mechanical and thermal properties of the polymer micro/nanocomposites compared to the neat polymer and traditionally materials used as insulation systems in high-voltage engineering. Properties such as electrical conductivity, relative permittivity, dielectric losses, partial discharges, erosion resistance, space charge behavior, electric breakdown, tracking and electrical tree resistance, thermal conductivity, tensile strength and modulus, elongation at break of micro- and nanocomposites based on epoxy resin and XLPE are analyzed. Finally, it was concluded that the use of polymer micro/nanocomposites in electrical engineering is very promising and further research work must be accomplished in order to diversify the polymer composites matrices and to improve their properties.

Properties of Polymer Composites Used in High-Voltage Applications.

The present study is focused on the synthesis and characterization of vinyl ester/glass microballoon syntactic foams. Tensile and compressive properties of vinyl ester matrix syntactic foams are characterized. Results show that the compressive strength and moduli of several syntactic foam compositions are comparable to those of the neat matrix resin. Due to the lower density of syntactic foams, the specific compressive properties of all compositions are higher than those of the neat resin. Similar trends are observed in the tensile properties. Mechanical properties of vinyl ester matrix syntactic foams are compared to well-documented mechanical properties of epoxy matrix systems. The comparison shows that low cost vinyl ester resins, which are extensively used in marine applications, can result in syntactic foams with comparable performance to epoxy matrix systems. In addition, tensile modulus is found to be 15–30% higher than the compressive modulus for all syntactic foam compositions. This difference is related to the possibility of particle fracture in the stress range where modulus is calculated in the compressive stress–strain curves.

Comparison of tensile and compressive characteristics of vinyl ester/glass microballoon syntactic foams

In this study, the influence of micro- and nano-filler content on the mechanical properties of epoxy composites was studied. The matrix material is epoxy; the micro-fillers are Al2O3, TiO2 and fly ash added in 10 wt% to 30 wt% by weight ratio; the nano-fillers are Al2O3, TiO2 and clay added in 2.5 wt% to 10 wt% by weight ratio. Test samples were prepared using an open mould type die. Tensile, three-point bending and hardness tests were carried out. The tensile strength, elastic modulus, elongation at break, flexural strength, flexural modulus, and the hardness of the composite materials were obtained and evaluated. The results show that the tensile strength, flexural strength and elongation at the break values of composites decreased while the tensile modulus and flexural modulus increased with the increasing micro- and nano-filler content

The influence of micro- And nano-filler content on the mechanical properties of epoxy composites

This study presents the preparation of Natural fiber-reinforced biocomposites based on Recycled High Density Polyethylene (RHDPE)/Banana Fiber (BF)/Fly ash Cenospheres (FACS) and aims to increase the economic value of these waste materials. Maleic anhydride grafted HDPE (MA-g-HDPE) was used as a compatibilizer to increase the dispersion of fibers into the polymer matrix as well as to increase the compatibility between the matrix and fillers. Variation in mechanical, thermal and dynamic mechanical properties with the addition of FACS in RHDPE/BF composites was investigated. It was observed that 7.5 wt% FACS, 30 wt% BF and 3 wt% MA-g-HDPE within RHDPE matrix resulted in an increase in tensile strength to 17%, tensile modulus to 188%, flexural strength to 38%, flexural modulus to 159% and hardness to 37% as compared with the RHDPE matrix. Significant enhancement in the thermal stability of the RHDPE/BF biocomposites was also observed in presence of FACS under thermogravimetric analysis. The morphology of the prepared biocomposites has been examined by using scanning electron microscopy. Dynamic mechanical analysis tests revealed an increase in storage and loss modulus of the biocomposite system. The use of such recycled material, agricultural and industrial wastes increased the properties of the final product suggesting their use to be a good alternative in the production of polymeric composites.

Mechanical, Dynamic Mechanical and Thermal Properties of Banana Fiber/Recycled High Density Polyethylene Biocomposites Filled with Flyash Cenospheres

The fly ash (FA) particles were coated with furfuryl palmitate (FP) in different wt% like 1, 2, 3 and 5. The FP coated fly ash particles were incorporated as filler in recycled polypropylene (RPP) matrix composites by melt mixing in 1:1 wt% ratio. The composites were tested for their flexural properties, impact behaviour, dynamic mechanical behaviour and fracture surface. The highest enhancement in properties was observed in 2 wt% FP (FP2) coated fly ash filled composites, where the flexural strength, breaking energy and modulus increased by 6.4%, 64% and 1.4% respectively, with a shift of glass transition temperature to a higher temperature. The surface area and true porosity of the FP2 particles were determined to understand the interfacial phenomenon. Highest impact strength was observed in 1 wt% FP coated fly ash filled composites. So, a renewable, low cost chemical like furfuryl palmitate can be used as an effective coupling agent for fly ash in place of expensive synthetic coupling agents which are more commonly used.

Furfuryl palmitate coated fly ash used as filler in recycled polypropylene matrix composites

Vinylester resin matrix composites were prepared with a fly ash loading of 30, 40, 50 and 60 wt.-%. Flexural properties of the composites were investigated. It was found that the flexural strength was lowered in all the filled composites, but the flexural modulus showed a significant increase of 10, 57, 112% in case of 30,40 and 50 wt.-% fly-ash-loaded composites respectively, compared to the neat resin. However, there was a decrease in the mechanical properties in case of 60 wt.-% fly-ash-filled composites. The dynamic mechanical analysis was carried out to obtain information about the matrix-filler interaction at the interface. The storage modulus value at room temperature was highest for the 50 wt.-% fly-ash-filled composites, corroborating with the observed flexural modulus value. The fractured surfaces were examined under SEM and were correlated with the mechanical properties.

Debadrita Bhattacharya

Papers

Static and Dynamic Mechanical Properties of Vinylester Resin Matrix Composites Filled with Fly Ash