2.1.3. Elastomers

Elastomers are polymers that can be stretched usually too many times their original length but quickly return to the original shape without suffering permanent deformation when the stress is removed. Elastomer comes from the word "elastic" (describing the ability of a material to return to its original shape when the load is removed) and "mer" (from polymer, in which "poly" means many and "mer" means part). Upon elongation, the polymer chains assume a more ordered arrangemen<sup>t</sup> that corresponds to lower entropy and results in warming of the elastomer [9]. When the stress is removed, the elastomer contracts and cools at the same time. Figure 1 illustrates the concept of elastomers.

Thermoplastic elastomer (TPE) has gained recognition as the third generation of polymeric materials for high voltage (HV) insulators. The TPE electrifying aspects were observed to achieve few particular HV insulations, at least for the distribution class applications, especially in light contamination environments. Nowadays, TPEs, mainly silicone rubber (PDMS), ethylene-vinyl acetate copolymer (EVA), ethylene propylene diene rubber

(EPDM), styrene-butadiene rubber (SBR), chloroprene rubber, have become the material of choice as an insulator due to their performance and less expense [46–48].

**Relaxed**:-disordered (high entropy)

**Figure 1.** Model of elastomer with a low degree of cross-linking under stress.

#### *2.2. Preparation and Characterization of Polymeric Materials*

Several techniques are used in producing the nanocomposites to have optimal dispersion of fiber in the matrix [49]. A well-known and established method of processing polymer nanocomposites is the sol-gel process, in-situ polymerization, solution mixing process, melt mixing process, and in-situ intercalative polymerization [3,6,13,50–52]. In addition, Thomas et al. [50], Müller et al. [3], Ilona et al. [6], and Shaoyun et al. [52] have extensively discussed the process of preparing the nanocomposite polymer.

#### 2.2.1. Poly(9,10-phenanthrenequinone) for HV Electrode

Polyanthraquinone (P.A.Q.) can be produced directly with halogenated quinone used for low voltage system (Figure 2). Still, high voltage quinone- based polymers such as poly(9,10-phenanthrenequinone) (P.F.Q.) required indirect polymerization consisting of five steps of synthesis (Figure 3). Initially, a precursor 2,7-dibromo-9,10-phenanthrenequinone, as a monomer, was prepared by using phenanthraquinone and N-bromosuccinimide (N.B.S.) in the presence of concentrated sulfuric acid (H2SO4) followed by bromination [53]. Then reduced by tin (Sn) in acidic medium (Hydrochloric acid, HCl, and glacial acetic acid, CH3COOH) and a monomer, 2,7-dibromo-9,10-dihydroxyphenanthrene was obtained [54]. Later, acetylation of this hydroxy compound monomer using acetic anhydride, pyridine, ethyl acetate produces the monomer (9,10-diacetoxy-2,7-dibromophenanthrene) [55]. Finally, a polymer poly(9,10-diacetoxyphenanthrene) was obtained using 1,5-cyclooctadiene, nickel complex Ni(C.O.D.)2 and 2,2-bipyridyl dissolved with D.M.F. after polymerized with bromophenanthrene, [56]. This polymer was treated with lithium aluminum hydride (LiAlH4), anhydrous tetrahydrofuran (T.H.F.) in an acidic medium (HCl) resulted in less active poly(9,10-phenanthrenequinone), called PFQ\_L. The final step, oxidization of less active PFQ\_L to P.F.Q. (poly(9,10-phenanthrenequinone) utilizing 2,3-dichloro-5,6-dicyanobenzoquinone (D.D.Q.), as an oxidizing agent. The reduced graphene oxide (rGO) was prepared by incorporating graphene oxide with potassium permanganate and H2SO4, H3PO4, HCl, H2O2, and hydrazine hydrate [57]. The composite (rGO-PFQ) was produced by adding rGO during the polymerization reaction with 9,10-diacetoxy-2,7- dibromophenanthrene in the presence of Ni(C.O.D.)2 and 2,2-bipyridyl [58].

GLEURPR DQWKUDTXLQRQH

SRO\DQWKUDTXLQRQH 3\$4

**Figure 2.** Direct polymerization of low voltage polymer.

**Figure 3.** Indirect polymerization of HV polymer.

Low voltage quinone-based polymers like P.A.Q. can be directly polymerized with Ni(C.O.D.)2. Whereas indirect multistep polymerization prevents the oxidation of Ni(C.O.D.)2 while protecting quinone groups with acetyl groups helped to synthesize increased operating voltage polymers such as P.F.Q. Additionally, P.F.Q./rGO composite has a better porosity, enhancing electrical performance and rate capabilities compare with P.A.Q. polymers. Indirect polymerization of high redox potential ortho quinones also helps to synthesize higher operating voltage polymers such as P.F.Q. preferred over direct polymerization of para-quinones producing low voltage polymers.

#### 2.2.2. Thermoplastic High Performance for Cable Insulation System

The polyethylene is cross-linked with different fillers' sizes to change the polymer's physical properties and make it capable of working with HV systems (cable system).
