Temperature Coefficient Effect Of Resistivity Research Articles

High positive temperature coefficient effect of resistivity in conductive polystyrene/polyurethane composites with ultralow percolation threshold of MWCNTs via interpenetrating structure

In this work, a novel interpenetrating system including amorphous polystyrene/polyurethane and multiwall carbon nanotubes (PS/PU-MWCNTs) was in-situ constructed by the homogeneous bulk polymerization. The ultralow percolation threshold (about 0.01 wt%) and high electrical conductivity were achieved owing to the unique conductive networks of MWCNTs in the interconnected “island chain” of PU. Surprisingly, the high positive temperature coefficient (PTC) effect of resistivity of amorphous PS/PU-MWCNTs composites, which was caused by the polymer segment motion, was achieved, such as PTC intensity of six orders of magnitude, fantastic reproducibility and favorable mechanical properties. Finally, this work provided a new promising in the development of excellent PTC materials.

Suppressing the negative temperature coefficient effect of resistance in polymer composites with positive temperature coefficients of resistance by coating with parylene

Thin parylene coating suppressed the negative temperature coefficient (NTC) effect of polymer thermistors with a positive temperature coefficient (PTC) while maintaining the PTC characteristics.

Lightweight and conductive carbon black/chlorinated poly(propylene carbonate) foams with a remarkable negative temperature coefficient effect of resistance for temperature sensor applications

Lightweight and biodegradable crosslinked CB/CPPC foams exhibit a remarkable nearly-linear negative temperature coefficient effect, which has great potential in temperature sensors.

Polyimide‐carbon nanotubes nanocomposites: electrical conduction behavior under cryogenic condition

This study is aimed to investigate the electrical conduction behavior of polyimide (PI)/multiwall carbon nanotubes (CNTs) nanocomposites in cryogenic environment (temperature from 10 to 300 K) prepared by in situ polymerization technique. The experimental results of direct current (DC) electrical conductivity have been fitted with different theoretical models to check their applicability and to understand the conduction behavior for the present nanocomposite system. The PI/CNT nanocomposites show low electrical percolation threshold. Negative temperature coefficient effect of resistivity is observed for all the composites under investigation. The analysis shows that Mott's variable range hopping (VRH) model is more applicable compared to Arrhenius and Kivelson models for the present composites over the entire range of measurement temperature. The electronic transport behavior in each composite at temperature above 70 K can be ascribed to thermally activated tunneling of charge carriers through insulating barriers between CNTs; however, the electronic transport behavior at temperature below 70 K can be attributed to three dimensional VRH of charge carriers through the networks of CNTs in the polymer composite. The current–voltage characteristics of the composite show non‐ohmic behavior for temperature below 60 K and become ohmic in nature as temperature rises to 300 K. POLYM. ENG. SCI., 57:291–298, 2017. © 2016 Society of Plastics Engineers

Mechanical, electrical, and dielectric properties of polyvinylidene fluoride/short carbon fiber composites with low‐electrical percolation threshold

AbstractIn this investigation, polyvinylidene fluoride (PVDF)/short carbon fiber (SCF) composites have been prepared by solution casting technique to enhance electrical and dielectric properties with very low‐electrical percolation threshold (0.5 phr SCF). The effect of SCF content on mechanical, thermal and morphological properties of the composites have also been investigated. The mechanical properties of the composites are found to reduce compared to neat PVDF due to poor polymer–filler interaction which can be concluded from FESEM micrographs showing poor bonding between PVDF and SCF. The PVDF/SCF composites exhibit either positive temperature coefficient effect of resistivity or negative temperature coefficient effect of resistivity depending on the loading of SCF in the polymer matrix. The change in conductivity during heating–cooling cycle for these composites shows electrical hysteresis along with electrical set. The melting point of the composites marginally increases with the increase in fiber loading in PVDF matrix as evidenced from DSC thermograms. X‐ray diffraction analysis reveals the crystallinity of PVDF decreases with the increase in SCF loading in matrix polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39866.

High performance hybrid carbon fillers/binary–polymer nanocomposites with remarkably enhanced positive temperature coefficient effect of resistance

Aiming to enhance the positive temperature coefficient (PTC) effect of resistance, immiscible polymer blends [ultra-high molecular weight polyethylene (UHMWPE)/polyvinylidene fluoride (PVDF) = 4 : 1] based composites containing hybrid fillers [carbon nanotubes (CNTs) and carbon black (CB)] were explored. The conductive fillers were premixed with UHMWPE by melt-mixing and then PVDF was introduced into the blends. The preferential distribution of conductive fillers in the UHMWPE phase was desirably observed. Besides decreasing the electrical resistivity of the single UHMWPE based PTC materials, the addition of PVDF with much higher melting point could improve the temperature range of the PTC materials, which is important for their potential applications. A remarkable synergetic effect arising from the combination of CB and CNTs with different geometric structures and aspect ratios on improving the PTC behavior was demonstrated. By introducing 0.5 vol% CNTs into the 4 vol% CB filled UHMWPE0.8–PVDF0.2 composites, the initial resistivity decreased by about two orders of magnitude and the PTC intensity (PTCI) increased by about 30%. Owing to the 3-dimensional conductive networks provided by tube-shaped CNTs and spherical CB and the high viscosity of the UHMWPE matrix, favorable PTC repeatability was also achieved.

Nonlinear conduction of irradiation‐crosslinked high‐density polyethylene/acetylene carbon black composites at the electric–thermal equilibrium state

AbstractAt the electric–thermal equilibrium state, the nonlinear conduction behaviors of high‐density polyethylene/acetylene carbon black composites crosslinked with electron‐beam irradiation have been studied in wide ranges of electric field and ambient temperature. Critical electric field E0.5 at the global electrical breakdown and the corresponding apparent resistivity are related to the intrinsic resistivity at given ambient temperatures. The relationship between the nonlinear conduction and the intrinsic positive temperature coefficient effect of resistivity is established by a discussion of E0.5 as a function of the macroscopic resistivity temperature coefficient. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1979–1984, 2006