THERMOPLASTIC ELASTOMERIC (TPE) MATERIALS …

1 15 THERMOPLASTIC ELASTOMERIC (TPE) MATERIALS and their use in outdoor electrical insulation ] ] A ! Rev. Adv. Mater. Sci. 29 (2011) 15-30 Corresponding author: Salman Amin, e-mail: ELASTOMERIC (TPE) MATERIALS ANDTHEIR USE IN OUTDOOR ELECTRICAL INSULATIONS alman Amin1 and Muhammad Amin21 University of Engineering & Technology, Taxila, Pakistan2 CIIT, Wah, Taxila, PakistanReceived: March 03, 2011 Abstract. The use of polymeric MATERIALS has become very popular since last thirty years in manyapplications.

2 The MATERIALS in this category can be broadly divided into two categories thermo ] ?A_ ] ] A A] ] A ] ] A]? ] protection issues thermoplastics have gained more attraction over the thermo set. Thermoplas-tic elastomers are novel constructional polymers, which are physically cross linked materialsmade up of a THERMOPLASTIC and an elastomer. TPE have been the interest of numerous re-searchers world wide since last three decades.

3 THERMOPLASTIC elastomers have a very wide-spread application domain. This paper reviews the history, physical, chemical, mechanical,electrical characteristics, advantages and uses of these MATERIALS along with a particular focuson their use as outdoor electrical insulation. Results of using different kinds of thermoplasticmaterials as outdoor insulation in different environments of world are also reviewed. This reviewexpected to be useful for researchers working on THERMOPLASTIC elastomers in general andparticularly for those working in filed of electrical INTRODUCTIONP olymeric MATERIALS can be classified as Thermo-sets and Thermoplastics.

4 Before looking onto ther-moplastic ELASTOMERIC MATERIALS it is necessary tounderstand the thermosets and thermoplastics ThermosetThermoset is a polymer that is cured by heat orchemical reaction and becomes infusible and in-soluble material . Thermoset polymers have a per-manent irreversible polymerization. Thermoset poly-mers posses a cross linked molecular structure andare formed in two stage polymerization. The firststage is formation of a polymer with linear second stage of polymerization results in finalcross linked structure.

5 The end product can be maderigid or flexible. The Polymerization is controlled toresult in heavily cross linked short chains for hardproduct and lightly cross linked long chains for softand flexible products [1]. ThermoplasticThermoplastic is a plastic that softens upon heat-ing and hardens when cooled. Thermoplastics aremade up of linear molecular chains and can beshaped by flow into articles by molding or extrusionwithout need of any chemical processing beforemolding. The most useful physical property of a ther-moplastic is its glass transition temperature at whichit begins to soften.

6 Glass transition temperatures ofdifferent thermoplastics can be seen in [1]. Thereare three types of thermoplastics crystalline, amor-phous and semi- crystalline [2,3]. Crystalline thermoplasticsThey are usually translucent and their molecularchains have a regular arrangement. They have highand sharp melting temperatures. Compared to amor-phous thermoplastics they have more mechanicalimpact resistance. Their load bearing capacity canbe enhanced considerable with addition of Amin and M. AminUpon curing they shrink more as compared to amor-phous thermoplastics.

7 Examples are polypropylene(PP), polyethylene (PE) [1]. Amorphous thermoplasticsThey are usually transparent and have diffused melt-ing point. The molecules are arranged randomly and A ]A A ] A ?A A?_ to crystalline polymers. Upon curing they shrink lessas compared to crystalline thermoplastics [3,4].Examples are polycarbonate (PC),polymethylmethacrylate (PMMA), polystyrene (PS),polyphenylene oxide (PPO), acrylonitrile butadienestyrene (ABS) [1]. Semi-crystalline thermoplasticsSemi-crystalline polymers plastics have combinedproperties of crystalline polymers and amorphouspolymers.

8 Examples are polyester Polybutyleneterephtalate (PBT) and Polyamide (Nylon 6, Nylon66). THERMOPLASTIC elastomersThermoplastic elastomers are one of the most ver- _ ] A ? THERMOPLASTIC elas-tomeric MATERIALS are a physical mixture of poly-mers (a plastic and a rubber). They exhibit the prop-erties of both plastics and rubbers. The unique prop-erties of both MATERIALS exist because TPE materi-als are created only by physical mixing of a ther-moplastic and elastomer and no chemical or cova-lent bonding exists between the two.

9 This behaviorhas opened a new field of polymer elastomers have become a signifi-cant part of the polymer industry. They are used inmany applications like adhesives, footwear, medi-cal devices, automobile parts house hold goods, were introduced commercially in 1960. ] ] A ] _ ] A annual consumption of TPE MATERIALS is growing ata rate of 11% per first generation TPE were made using Eth-ylene Propylene Diene Monomer (EPDM) andppolypropylene(PP) [5-7].

10 Later onEthylene Pro-pylene Rubber (EPR) replaced EPDM due to its lowcost. Since these MATERIALS were mixed only physi-cally and no cross linking existed there so hard ther-moplastic cannot be produced using them. Anotherdraw back is that both EPR and EPDM have lowtensile strength and less resistance to organic sol-vents especially oil or order to resolve the problem of low thermaland chemical stability of THERMOPLASTIC elastomers ,dynamic vulcanization techniques were used in late A ? A A?