Bakhtiarian, Elaheh (2014) Synthesis and properties of conducting polymer blends. (PhD thesis), Kingston University, .

Abstract

Polymers and polymer-based composite materials with electrically-conductive properties are materials with various potential uses. Novel materials are becoming available in each field and new products are continuously being produced. Amid these new materials, conductive elastomers are presently being employed as antistatic materials in the carpets, antistatic coatings, sensors and electromagnetic screening. One promising method for making this type of material is to introduce carbon black or metal fillers, or more currently conducting polymer powders into natural or synthetic rubbers. Several polyaniline-rubber blends, mostly with poor electrical conductivity, have been reported in the literature. An important aim of this work was to improve the compatibility, thermal stability, electrical and mechanical properties of this kind of blend, produced by different mixing techniques for instance solution and thermo-mechanical with further methodical mixing processes and greater improved mixing circumstances. Polyepichlorohydrin, polychloroprene rubber, chlorosulfonated polyethylene rubber and polyaniline dodecylbenzenesulfonate (PAni-DBSA) were selected for study as blends in this project, since the solubility parameters of polyepichlorohydrin rubber, polychloroprene, chlorosulfonated polethylene and polyaniline dodecylbenzenesulfonate were calculated to be well-matched, and also because the polyepichlorohydrin rubber (PECH), polychloroprene rubber (PCR) and chlorosulfonated polyethylene (CSPE) were thermally stable and easily obtainable. No previous literature was discovered in relation to the electrical properties of the polyepichlorohydrin, polychloroprene or chlorosulfonated polyethylene blends with polyaniline dodecylbenzenesulfonate (PAni-DBSA). Hence, the PECH, PCR and CSPE rubbers were also chosen in this work with the purpose of studying them. Non-vulcanised PECH/P Ani-DBSA, non- vulcanised PCRlPAni-DBSA and non-vulcanised CSPEIPAni-DBSA blends with appropriate electrical conductivities were produced by solution mixing for the first time in this project. Blends of the PECH, PCR and CSPE rubbers and polyaniline doped with dodecylbenzenesulfonic acid, consisting of various proportions of P Ani- DBSA, were cast from solution onto polytetrafluoroethylene (PTFE) substrates with the aim of making electrically conductive films. Electrical conductivities of the cast films of non-vulcanised blends were calculated. Decomposition steps of electrical conductive polymer blends were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stabilities of the PECHlPAni-DBSA, PCRJPAni-DBSA and CSPEIP Ani-DBSA blends were affected by the proportion of polyaniline dodecylbenzenesulfonate to the rubbers. The influence of composition on the glass transitions in the blends was defined by the use of thermomechanical analysis (TMA). Electrically conductive polymer blends of vulcanised PECHIPAni-DBSA were prepared by the use of an internal mixer for the first time. A remarkable agreement was seen in that both the vulcanised and the nonvulcanised blends had the electrical conductivities of the order of 10-8 S.cm-1 with approximately 20 wt% polyaniline dodecylbenzenesulfonate. The electrical conductivities of all the vulcanised PECHIP Ani-OBSA blends (with a conductivity percolation threshold 1 wt% or 1.07 vol % of P Ani-OBSA) were riot influenced by the addition of Zisnet-F as the vulcanizing agent. The ATIR spectra of vulcanised PECHIPAni-OBSA blends were similar to a superposition of the spectra of the pure vulcanised polyepichlorohydrin and pure polyaniline dodecylbenzenesulfonate, but with some distinctive peak shifts due to the changing intermolecular interactions among the PECH and PAni-OBSA polymers. The X-ray diffraction patterns of polyaniline dodecylbenzenesulfonate, the vulcanised pure polyepichlorhydrin and vulcanised polyepichlorhydrinl polyaniline dodecylbenzenesulfonate blend with 10% of PAni-OBSA were studied. The effects of addition of the polyaniline dodecylbenzenesulfonate on the morphology of the vulcanised PECHIP Ani-OBSA blends were evaluated by optical microscopy. The influence of orientation and alignment of the PAni-OBSA particles on the mechanical and electrical properties of vulcanised blends was investigated. The electrical conductivities of all vulcanised polyepichlorhydrin/polyaniline dodecylbenzenesulfonate blends were identified by stretching them. All vulcanised PECHIPAni-OBSA blends strained parallel to the flow direction when passed through the two roll-mills had their electrical conductivities improved with increasing strain in tension. A traveling microscope was used to investigate any possible dimensional change of samples versus applied voltage in order to define the effect of voltage to size change of the vulcanised blends. The electrical percolation threshold stage for the vulcanised PECHIP Ani-DBSA blends was studied. A tensile testing machine was employed to determine energy storage of each vulcanised PECH/P Ani-DBSA blend. Tensile property testing for the vulcanised polyepichlorhydrin /polyaniline dodecylbenzenesulfonate blends was accomplished according to the British Standards Institution (BS!) requirements in order to measure tensile strength, elongation at break and tensile modulus, and the samples all presented good mechanical properties. The stress-strain data of the vulcanised polyepichlorhydrin /polyaniline dodecylbenzenesulfonate blends have been analyzed and the crosslink density of them has been calculated. With good mechanical properties and reversible electrical behaviour, this kind of vulcanised blend may potentially be developed as a novel class of flexible smart material.

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