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Typically, nanocomposites have better and significant properties due to the addition of nanoparticles, which modify the electrical, thermal and mechanical properties of the polymer matrix. The improvement in electrical conductivity is mainly due to the formation of electrical pathways by electron tunneling of the embedded nanofillers. The improvement in the electrical conductivity of nanocomposites depends on the type, size, morphology, and state of dispersion of the fillers, the concentration of fillers in the polymer, and the polymer matrix itself. Due to the formation of electrical pathways within the nanocomposites, carbon nanofillers have been used to develop smart self-sensing nanocomposites.
In the last few years, there has been a growing interest in the study of thermoresistive effects (resistance changes due to temperature changes) and Joule heating (resistive heating due to current flow) in polymer nanocomposites. These thermoresistive properties are of great interest to the scientific community due to their potential applications in electronics, energy harvesting and sensor applications.
The main point of this paper
1. Properties of PVDF: PVDF has a complex semi-crystalline structure consisting of five different crystalline polycrystals, and its piezoelectricity originates from the presence of the beta phase.
2. Research Focus: Incorporation of carbon nanoparticles and nanoscale filler blends into PVDF matrix to improve thermal and electrical properties.
3. Role of carbon nanostructures: as polymer fillers to improve thermal and electrical properties.
4. Literature review: MWCNTs have been studied more intensively than GNPs in terms of Joule heating behavior, and a study reported the self-healing ability of TPUs filled with MWCNTs under the Joule effect.
5. Thermal resistance behavior studies: The thermal resistance behavior of MWCNTs as fillers has been investigated using various combinations of polymer matrices and copolymers.
6. XRD and DSC analysis: Used to obtain information on MWCNT-doped PEG and PU blends, it was found that physical mixing reduced the crystallinity of PEG and improved the thermal resistance behavior.
7. Self-regulating effect of graphene: embedding it in PVDF-HFP to prepare self-regulating heating devices.
8. Carbon black (CB) blend composition: improving positive temperature coefficient (PTC) characteristics and piezoresistive properties.
9. Thermal resistance behavior of CNT: dispersion of CNT and key parameters affecting the bulk thermal resistance response are discussed.
10. Multilayered graphene sheets (GSs) and multi-walled carbon nanotubes (CNTs): the thermal resistance properties of polysulfone nanocomposites reinforced with GSs and CNTs are investigated.
Thermal resistance and Joule heating characterization of semi-crystalline polyvinylidene fluoride (PVDF) nanocomposites
Conducting polymer nanocomposites are of interest for their thermal resistance and Joule heating properties in areas such as heating elements, smart materials and thermistors.
RESEARCH OBJECTIVES:
Semi-crystalline poly(vinylidene fluoride) (PVDF) nanocomposites containing 6 wt.% carbon-based nanofillers including graphene nanoparticles (GNPs), multi-walled carbon nanotubes (MWCNTs), and hybrid combinations of them.
ANALYTICAL METHODS:
The effects of single and mixed fillers on the crystal structure of PVDF were analyzed using X-ray diffraction (XRD) and differential scanning calorimetry (DSC).
Crystal structure changes:
The amorphous fraction of the nanocomposites increased and the nanocomposites increased the β-phase of PVDF by 12%, mainly attributed to the presence of MWCNTs.
Resistive properties:
The resistive properties of the nanocomposites were less affected by temperature in the temperature range of 25-100°C, and the mixed filler composites were more sensitive than the single filler composites.
PVDF-based nanocomposites reinforced with GNPs and MWCNTs and their hybridized combinations (6 wt.% filler content) prepared by melt extrusion were studied. The crystal structures of the nanocomposites were investigated by DSC and XRD. The nanoparticle inclusions increased the content of β phase as compared to pure PVDF. It was observed that MWCNTs were a better nucleating agent to promote the formation of β-phase as compared to GNPs.SEM analysis showed good adhesion between the polymer and the nanofillers, which had a great impact on the properties. Thermal resistance analysis showed that the behavior of the single filler nanocomposites was temperature independent in the analysis region of 25-100 °C. The thermal resistance of the nanocomposites was also found to be high. The two-filler hybrids showed a higher temperature coefficient of resistance and therefore a higher sensitivity to temperature, which was mainly characterized by a GNP/CNT ratio of 4.5:1.5. However, based on these results, the composition of 4.5% GNP, 1.5% CNT, and PVDF could not be recommended for Positive Temperature Coefficient of Resistance (PTCR) applications, and further studies are needed. The nanocomposites embedded with GNP were more conductive compared to the MWCNT-filled nanocomposites. Measurement of the generated heat by the Joule thermal effect concludes that the GNP and MWCNT inclusions are self-regulating at both applied voltages. In general, by selecting a combination of carbon nanofillers and suitable hybrid fillers, the heating temperature and self-regulation function can be successfully adjusted by applying voltage to meet the application requirements.
