Crosslinkable Polyethylene Based Blends and Nanocomposites

Polymeric matrix can be reinforced with fillers and be capable of accomplishing a promising material with improved physicochemical properties than the pristine polymeric materials. This concept is well equipped in nanocomposites or blends of cross-linked polyethylene (XLPE). This chapter is a comprehensive study of XLPE/nanocomposites and XLPE blends with exclusive highlighting on the properties and potential applications. The implementation of XLPE/nanocomposites is more significant in insulation cable. These insulation materials can reduce some defects like electrical treeing, water treeing, partial discharges, etc., that are challenging toward XLPE. The important nanofillers and polymers used in XLPE/nanocomposites or XLPE/polymer blends and its outcome and some important patents in this category are figured out here. This chapter concludes with the challenges and outlook of XLPE/nanocomposites and XLPE/polymer blends in various applications.

Nanocomposites have been attaining great attention from the researchers to deal with electrical insulation applications. They improve dielectric breakdown strength, suppress the partial discharge and space charge, and prolong the treeing, etc. The cross-linked polyethylene (XLPE) serves as an important base polymer matrix for nanocomposites in cable insulation. This chapter discusses the various nanomaterials used in XLPE nanocomposites along with their characterization. The major XLPE nanocomposites emerging with great applications in the present stage includes SiO₂/XLPE nanocomposites, TiO₂/XLPE nanocomposites, MgO/XLPE nanocomposites, OMMT/XLPE nanocomposites, Al₂O₃/XLPE nanocomposites, SiC/XLPE nanocomposites, XLPE/clay nanocomposites, XLPE/GO nanocomposites, XLPE/BNNs nanocomposites, etc.

The inorganic nanocomposite of XLPE yields hybrid properties and is widely used in pipe systems for buildings, radiating heating and cooling systems of hydronic boilers, household water pipe fittings, and as an insulating electric cable for high-voltage applications. Nanoparticle-embedded XLPE possesses high mechanical performance exhibiting high tensile strength (30–25 MPa) and Young’s modulus (500–900 MPa), thermal stability, and dielectric characteristics. The fabrication of inorganic nanocomposites of XLPE is achieved by two-main approaches: a top-down and bottom-up comprising several methods extending from a very simple to highly complex processes. The present chapter discusses various methods used for the functionalization of the inorganic nanomaterials and the methods used in the preparation of inorganic XLPE nanocomposites.

Thanks to its excellent properties, cross-linked polyethylene (XLPE) is widely used in the insulation of medium and high voltage cables. However, under service conditions, the insulation of XLPE encounters several problems such as space charge accumulation, water trees, electrical trees, and partial discharges. Recently, research for cable insulating material has shown that nano-size filler added to XLPE may help reducing these problems. Currently, XLPE-based nanocomposites can be used as reliable insulation materials due to its excellent mechanical, thermal, and electrical properties. However, although it offers a number of advantages including its usage as insulator in power cables, some other issues remain to be addressed. In this chapter, the critical issues in XLPE-based nanocomposites are discussed. It includes significant tutorial elements as well as some analyses.

A plethora of applications are celebrated by the crosslinked polyethylene blends and their nanocomposites. This chapter documents the wide applications of XLPE-based blends and nanocomposites. These materials are tremendously used in various applications like piping and foam industries, orthopaedic, smart shape polymers and cable and wire insulations due to their inherent mechanical, electrical and thermal properties. Due to the ease of processability and control, blending and crosslinking attained great attention in various research areas. Abundant number of polymers are being crosslinked and blended to get innovative products and could be tuned properly even for new-fangled applications. Among the various crosslinked polymer blends and composites, crosslinked polyethylene (XLPE) stands apart from others. Crosslinking and blending improved the thermal, mechanical and electrical properties of polyethylene. Addition of nanofillers to XLPE yields XLPE nanocomposites. These new substitutes promise more sustainable economic systems and give greater modifying freedom.

Cross-linked polyethylene finds application in the insulation of high-voltage cables, constituting a high demanding domain in terms of electrical performances. High-quality XLPE grades are now produced for insulation under high-voltage direct current (HVDC) stress. Luminescence techniques have constituted original techniques along the development of such materials, particularly as regards the role of defects and residues in the behaviour of materials in terms of electrical charges stabilization. Luminescence provides a family of extremely sensitive techniques, though limited to substances with unsaturated groups: in materials like XLPE only additives, residues and defects are optically active. After recalling the grounds of luminescence principles in organic materials, we explain the implemented techniques, mainly based on photoluminescence and on an analysis of optical emissions related to charge traps into materials. The main results obtained with the identification of the role of these ‘defects’ are presented before addressing the knowledge brought by luminescence methods, including electroluminescence, on thermal and electrical ageing aspects of polyethylene materials.

Polyethylene is being considered as a unique polymer in the whole plastic industry and it has numerous applications. Several modifications have been done to improve the properties and the better replacement of LDPE is by cross-linked polyethylene (XLPE). XLPE has superior heat deformation characteristics. This chapter deals with morphological and mechanical characteristics of XLPE nanocomposites and blends composites. Main fabrication method of XLPE-based nanocomposites is melt mixing. Morphological analysis is done by several microscopic techniques. Evaluation of mechanical performance is very crucial to determine the end use of polymer nanocomposites. So here we analyzed both static and dynamic mechanical characteristics of XLPE-based nanocomposites.

This chapter deals with thermal and flame retardant properties of XLPE nanocomposites and blends. Properties of composites and blends are highly temperature dependent. Thermal properties include thermal stability, melting point, glass transition temperature, thermal conductivity, flame retardant properties, etc. Herein, a detailed investigation is made on the thermal and flame retardant properties of cross-linked polyethylene (XLPE) nanocomposites and blends with special emphasis on thermal stability, glass transition temperature, thermal conductivity and flame retardancy.

Cross-linked polyethylene (XLPE) and its nanocomposites have found various application in recent years. As many key factors for HVDC cable insulation design, low conductivity and good mechanical, thermal and electrical stability too are required. Various methods have been used to improve the current challenges of cross-linked polyethylene (XLPE). Addition of nanoparticles (NPs) is been improving the above properties and cleared the pathway for long lifetime application. This chapter includes various strategies for cross-linking PE coupled with different nanofillers to enhance the electrical insulation properties to attain high power transmission. Some of the challenges in dielectric insulation for cables, like partial discharge (PD), space charge accumulation, water trees, volume resistivity, and DC breakdown strength, are addressed.

The first part of this chapter presents information about the evolution of power cables and their insulation materials as papers, oils, natural and synthetic rubbers, polyethylene, polyvinyl chloride, polypropylene, polytetrafluoroethylene, etc. The second part analyzes comparatively the values of typical properties of these materials, which are important for the operation of insulation, and their changes under the electrical, thermal, mechanical, and environmental stresses. The variations of conductivity and electrical permittivity, loss factors, and dielectric strength under the action of electric field and temperature are described, as well as the accumulation of space charge and tracking, partial discharges, electrical, and water treeing resistance of DC and AC cable insulation. Among the thermal properties, thermal expansion, thermal conductivity, thermal stability, melting effect, and working temperature are analyzed, and among the mechanical ones are the elasticity, elongation at traction, tensile strength, strength, compressibility, and hardness. The chapter continues with the presentation of chemical, microorganisms, termites, rodents, and resistance to radiation and the estimated lifetime of cable insulation. Finally, the conclusions are shown that XLPE has higher values for most of the properties and are recommended in the manufacture of DC and AC power cables.

The structure–property relation is the key to all applications in macromolecular systems. Computational simulations are used for better understanding of such structure–property relations. This molecular modeling has now become an indispensable complementary tool for experimental scientific research. The XLPE/nanocomposites studies are mostly done by quantum theories due to the better understanding of electronic structure levels; however, some calculations are done using classical mechanics. But classical mechanics and quantum mechanics are insufficient for certain analysis, and these defects point out the possibility to explore the studies in multi-scale theories for this field. The theoretical section of this chapter provides all the detailed description of most common theoretical techniques for the better understanding of such studies in XLPE/nanocomposites and blends. Another section of this chapter provides a short survey of the general principles and selected applications of molecular modeling in XLPE/nanocomposites and blends. The selection of efficient nanofillers and polymers for blends are suggested, and discussion on the mechanisms for electrical treeing by means of molecular modeling is also included.

Today, power cables use primarily solid extruded insulation compounds of polyethylene in its cross-linked form. Thermoplastic polyethylene was first used, but quickly evolved into longer lasting cross-linked materials. In North America, high molecular weight polyethylene (HMWPE) was also used with poor results. For medium voltage cables, either cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), or polypropylene (PP) are used as insulation for medium voltage cables. For high and extra high voltage cables, mainly XLPE is used. This chapter will describe the differences that exist in commercially produced polyethylene, specifically high-pressure, low-density polyethylene (LDPE), since this is most commonly used in power cable applications as the base resin. Understanding the differences between the two production methods that are used to produce LDPE, that is the autoclave and the tubular reactor, may clarify the influence of material properties on cable performance, especially cleanliness. This polymer, LDPE, is then further processed to produce XLPE. On the other hand, EPR is produced in a different way and afterwards compounded as cable insulation. At the beginning of this century, PP was introduced as an insulation compound for medium voltage cables and has recently seen equal market share with XLPE in several countries. With PP, the final formulation is produced during the cable production process. Further investigations are currently underway using other polymers such as POE or PB-1 for medium voltage applications. PP is currently used up to 150 kV for AC cables and has passed Type and PQ testing for 600 kV DC cables. This chapter presents the differences between cable compounds and examines the specific features of individual XLPE compounds that are currently available on the market. In addition, details will be presented on the application of different polymers that are currently used for the semi-conductive layers as part of the cable insulation system.

This chapter reviews the latest advances in research and development of cross-linked polyethylene (XLPE) nanocomposites and blends, in terms of published articles, patents, and related products. The first part briefly introduces the development history of XLPE, research background and progress of XLPE nanocomposites and blends. The second part analyzes the research papers on XLPE nanocomposites and blends published by academic journals mainly from 2005 to 2020 in detail. A large number of current research on XLPE nanocomposites and blends aim to improve their properties in relation to the electrical, mechanical, and thermal ones as well as the microstructure, through chemical or physical methods. In the case of comprehensive electrical properties, the studies are distributed on dielectric properties, space charge behavior, and their applications in electrical engineering. The third part outlines the licensed patents about of XLPE nanocomposites and blends. The vast majority of patents related to XLPE nanocomposites and blends focuses on the compounding process and manufacturing technique, among which 35 representative patents are selected for discussion. The final part introduces several typical XLPE products. The potential advantages, product maturity, and market growth of XLPE nanocomposites or blends are analyzed in the application of cables, tubes, and foams.

Crosslinked polyethylene (XLPE) nanocomposites and blends are extensively utilized in different industries owing to their superior properties and characteristics compared to uncrosslinked and pristine polyethylene (PE). These excellent properties enable XLPE nanocomposites and blends to be employed in specialized applications and conditions. Despite their numerous favorable features, they face several risks, challenges, and problems that bring limitations and restrictions for their usage in some cases. Cable industry is one of the leading industries employing XLPE nanocomposites and blends. While these materials can grant outstanding characteristics to the cable insulation (such as dielectric properties), they can also encounter operative challenges in the meantime. This chapter attempts to define these risks and limitations via a comprehensive survey in recent case studies and publications. The described topics are categorized into several parts. They include risks, challenges, and constraints associated with electrical issues, embedded nanoparticles, crosslinking agents, recyclability, surface characteristics, and aging behaviors of XLPE nanocomposites and blends. The definitions of the mentioned problems are accompanied by the most recent and updated proposed solutions to resolve them. For providing inclusive insights in each of the categories, they are additionally subcategorized based on the suggested addressing approaches.