Static and dynamic compressive properties of polypropylene/zinc oxide nanocomposites

The effect of strain rate is widely recognized as an essential factor that influences the mechanical properties of polymer matrix composites. Despite its importance, no previous work has been reported on the high‐strain rate behavior of polypropylene/zinc oxide nanocomposites. Based on this, static and dynamic compression properties of polypropylene/zinc oxide nanocomposites, with particle contents of 1%, 3%, and 5% by weight, were successfully studied at different strain rates (i.e., 0.01 s^?1, 0.1 s^?1, 650 s^?1, 900 s^?1, and 1100 s^?1) using a universal testing machine and a split Hopkinson pressure bar apparatus. For standardization, approximately 24 nm of zinc oxide nanoparticles were embedded into polypropylene matrix for each of the tested polypropylene/zinc oxide nanocomposites. Results show that the yield strength, the ultimate strength, and the stiffness properties, of polypropylene/zinc oxide nanocomposites, were greatly affected by both particle loading and applied strain rate. Furthermore, the rate sensitivity and the absorbed energy of all tested specimens showed a positive increment with increasing strain rate, whereas the thermal activation volume showed a contrary trend. In addition, the fractographic analysis and particle dispersion of all composite specimens were successfully obtained using a field emisission scanning electron microscopy. POLYM. ENG. SCI., 54:949–960, 2014. © 2013 Society of Plastics Engineers     

Scratch behavior of glass fiber reinforced polyester matrix composite after solid particle erosion

In current study, the tested material is a glass fiber reinforced polyester matrix composite with one stacking sequence namely [0/90]_s. First of all, the solid particle erosion behavior of composite samples was investigated under various impingement angles (15°, 30°, 45°, 60°, 75°, and 90°, respectively). Eroded composite samples were examined by non‐contact optical profilometer and 3D surface roughness maps were obtained. From optical profilometer results, it was clearly shown that values of erosion crater hole volumes were well suited with erosion rate values versus impingement angles. Maximum and minimum erosion crater hole volumes observed at 60° and 15° impingement angles due to semi‐ductile characteristic of the target material, respectively. After erosion tests, the scratch behavior of composite samples was examined. The results showed that the coefficient of friction was decreased by the increase in impingement angles of 45° and 60°. The maximum scratch hardness value was determined at 60° impingement angle. Scratch damage morphologies were determined by using optical microscope and scanning electron microscope. It was observed that low (15° and 30°) and high (75° and 90°) impingement angles result in remarkably severe surface deformation on the samples. POLYM. COMPOS., 36:1958–1966, 2015. © 2014 Society of Plastics Engineer     

A preliminary account of char structures produced from Liddell vitrinite pyrolysed at various heating rates

Liddell-seam vitrinite particles were heated to 1000 °C in nitrogen at uniform rates ranging from 10^?1 °C s^?1 to 10⁴ °C s^?1. Little melting or swelling was observed when the particles were heated at 10^?1 °C s^?1 even though the vitrinite is from a coking coal of high-volatile bituminous rank. Particle size (100 μm) and loose packing were probably major influences on the plasticity. Vitrinite particles heated at rates faster than 10^?1 °C s^?1 showed an increase in plasticity with heating rate but the effects related to plasticity and volatile evolution appeared to be approaching a limit. Simple cenospheres (primary vesicles) were formed and preserved at a heating rate of 1 °C s^?1. At a heating rate of 10 °C s^?1 secondary vesicles were produced and preserved in the walls of the primary vesicles. At faster heating rates only secondary and tertiary vesicles were preserved. At a heating rate of 10⁴ °C s^?1 the vesicles preserved were very small.     

Morphological and physical properties of a thermoplastic polyurethane reinforced with functionalized graphene sheet

BACKGROUND: Functionalized graphene sheet (FGS) was recently introduced as a new nano‐sized conductive filler, but little work has yet examined the possibility of using FGS as a nanofiller in the preparation of polymer nanocomposites. In particular, there are currently no published papers that evaluate polyurethane/FGS nanocomposites. The purpose of this study was to prepare a polyurethane/FGS nanocomposite and examine the morphological and physical properties of the material. RESULTS: A cast nanocomposite film was prepared from a mixture of thermoplastic polyurethane (TPU) solution and FGS suspended in methyl ethyl ketone. The FGS dispersed on the nanoscale throughout the TPU matrix and effectively enhanced the conductivity. A nanocomposite containing 2 parts of FGS per 100 parts of TPU had an electrical conductivity of 10^?4 S cm^?1, a 10⁷ times increase over that of pristine TPU. The dynamic mechanical properties showed that the FGS efficiently reinforced the TPU matrix, particularly in the temperature region above the soft segment melt. CONCLUSION: Our results show that FGS has a high affinity for TPU, and it could therefore be used effectively in the preparation of TPU/FGS nanocomposites without any further chemical surface treatment. This indicates that FGS is an effective and convenient new material that could be used for the modification of polyurethane. It could also be used in place of other nano‐sized conductive fillers, such as carbon nanotubes. Copyright © 2009 Society of Chemical Industry     

Kinetics of leaching of tunisian phosphate ore particles in dilute phosphoric acid solutions

Van der Sluis et al.'s model was used to determine the rate of the partial dissolution of a Tunisian phosphate rock with dilute phosphoric acid (1.5 mass% P₂O₅). When the temperature rises from 25 to 90°C, for a given particle size, the mass-transfer coefficients, k_L°, vary from 3 × 10^?3 to 8 × 10^?3 m ·s^?1. The corresponding diffusion coefficients, D, lies between 6 × 10^?7 and 27 × 10^?7 m²·s^?1. Activation energy is equal to 14 kJ·mol^?1 and values of k_L°, at 25°C, are in the range of 0.28 × 10^?3 and 4 × 10^?3 m·s^?1 when the agitation speed goes from 220 to 1030 rpm, showing that the leaching process is controlled by diffusion rather than by chemical reaction.     

Composite polymer electrolytes based on electrospun thermoplastic polyurethane membrane and polyethylene oxide for all‐solid‐state lithium batteries

To improve the electrochemical properties and enhance the mechanical strength of solid polymer electrolytes, series of composite polymer electrolytes (CPEs) were fabricated with hybrids of thermoplastic polyurethane (TPU) electrospun membrane, polyethylene oxide (PEO), SiO₂ nanoparticles and lithium bis(trifluoromethane)sulfonamide (LiTFSI). The structure and properties of the CPEs were confirmed by SEM, XRD, DSC, TGA, electrochemical impedance spectroscopy and linear sweep voltammetry. The TPU electrospun membrane as the skeleton can improve the mechanical properties of the CPEs. In addition, SiO₂ particles can suppress the crystallization of PEO. The results show that the TPU‐electrospun‐membrane‐supported PEO electrolyte with 5 wt% SiO₂ and 20 wt% LiTFSI (TPU/PEO‐5%SiO₂‐20%Li) presents an ionic conductivity of 6.1 × 10^?4 S cm^?1 at 60 °C with a high tensile strength of 25.6 MPa. The battery using TPU/PEO‐5%SiO₂‐20%Li as solid electrolyte and LiFePO₄ as cathode shows an attractive discharge capacity of 152, 150, 121, 75, 55 and 26 mA h g^?1 at C‐rates of 0.2C, 0.5C, 1C, 2C, 3C and 5C, respectively. The discharge capacity of the cell remains 110 mA h g^?1 after 100 cycles at 1C at 60 °C (with a capacity retention of 91%). All the results indicate that this CPE can be applied to all‐solid‐state rechargeable lithium batteries. © 2018 Society of Chemical Industry     

Thermoplastic Polyurethane Nanocomposites Produced via Impregnation of Long Carbon Nanotube Forests

TPU was infiltrated into vertically aligned, 3.5 mm‐long MWNT forests to produce continuously reinforced anisotropic nanocomposites, and thermomechanical and electrical testing has revealed multifunctionality which shows promise for numerous applications. A 1000% increase in the storage modulus at 70 °C was observed as compared to the neat TPU, and these continuously aligned composites showed electrical conductivity two orders‐of‐magnitude greater (≈1.5 S · cm^?1) than randomly aligned composites prepared using CNTs from these forests. The heightened improvement for the continuously reinforced composite appears to be owed to the extremely high aspect ratio of these CNTs and the interconnected network which remains after infiltration.

     

Synthesis,characterization and electrorheological properties of poly(o‐toluidine)/Zn conducting composites

In this study, the synthesis, characterization, and electrorheological (ER) properties of poly(o‐toluidine)/Zn, (POT/Zn), composites were investigated. Syntheses of the composites were carried out by a chemical method using ammonium persulfate, (NH₄)₂S₂O₈, (APS), as a free radical initiator. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, electrical conductivity, magnetic susceptibility, particle size measurements, and scanning electron microscopy (SEM). A series of Zn‐containing composites were prepared (0.8–7.6% by mass), and their conductivities were measured to be within the range of 1.7 × 10^?3–5.0 × 10^?2 Scm^?1. Magnetic properties of POT/Zn composites were analyzed by Gouy scale measurements; it was found that their conducting mechanisms are bipolaron. A series of particle size (13, 17, 18, 26, 83 μm) were prepared by ground milling the crude POT/Zn composites. Colloidal suspensions of POT/Zn composites were prepared in silicone oil (SO), at a series of concentrations (10–30%, m/m), and sedimentation stabilities were measured at 25°C. ER measurements showed that the POT/Zn/SO suspension system was ER active. Thus, the effects of solid particle concentration, shear rate, electric field strength, addition of polar promoters, and temperature (25–125°C) onto ER activities of suspensions were investigated. The ER activity of suspensions was increased with increasing particle concentration and electric field strength and decreasing shear rate and showing a non‐Newtonian flow behavior. τ = 1.1 kPa shear stress was reached for POT/Zn (4.1 wt %, Zn) composite under E = 2.0 kV, c = 15 (%, m/m), , and T = 25°C conditions. It was found that the ER activity was slightly decreased with increasing temperature. Further, the addition of polar promoters had no promoting effect on the ER activity of the suspensions and POT/Zn/SO system was classified as dry ER materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1058–1065, 2007     

Reversible photochromic nanofibrous membranes with excellent water/windproof and breathable performance

Electrospun nanofibrous membranes (NFMs) with outstanding photochromic property, waterproof, and breathability have attracted considerable interest owing to their multifunctional applications in intelligent clothing, self‐cleaning, and protection. However, great challenges still remain in creating such functional materials. A novel waterproof–breathable membrane with robust photochromic property is fabricated by introducing photochromic microcapsule (PM) into electrospun thermoplastic polyurethanes (TPU) membranes. Compared with the pristine TPU NFMs, the composite TPU/PM membranes are endowed with reversible photochromic properties. In addition, the composite membranes not only exhibited a water contact angle of 137° and a milk contact angle of 130°, but also had integrated properties of modest water vapor transmittance rate of 19,278 g m^?2 day^?1, high air permeability of 962 mm s^?1, low waterproofness of 2.813 kPa, and comparable tensile strength of 12.08 MPa. Furthermore, the convenience and efficiency of this fabrication process will allow for large‐scale production of the multifunctional NFMs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46342.     

Effect of strain rate on tensile properties of polyurethane/(multiwalled carbon nanotube) nanocomposite

In this research, polyurethane (PU)/(carbon nanotube) (CNT) samples, with two different contents of multiwalled carbon nanotubes (MWCNTs; i.e., 0.5 and 1.0 wt%) were fabricated through a solution casting method. To investigate the effect of strain rate on tensile properties, tensile tests were done on standard samples at constant temperature and different strain rates (2 × 10^?5 to 2 × 10^?2 s^?1). Eyring's model was performed to clarify the role of both strain rate and CNTs content on activation volume and activation enthalpy of PU. To elucidate the role of strain rate and CNTs content on fracture behavior of PU, fracture surfaces of some samples were also investigated by scanning electron microscopy. The results of tensile tests show the intense effect of strain rate on tensile properties of PU/MWCNTs nanocomposites. Also, it was proved that the dependency of tensile properties of PU nanocomposites on strain rate decreases as CNTs content increases. The microscopic observations of the samples also demonstrate that increasing the strain rate changes the behavior of the fracture surface to less a ductile fracture, and increasing CNTs content causes much surface roughness. Finally, by investigation of the activation enthalpies, it is confirmed that much higher enthalpy is needed to fracture the samples with increased MWCNTs content, as the activation enthalpy changes from 45 for neat PU to 131 kJ/mol for PU/(1% MWCNTs) samples. J. VINYL ADDIT. TECHNOL., 22:356–361, 2016. © 2014 Society of Plastics Engineers     

Azo-Polymer Based Hybrids Reinforced with Carbon Nanotubes and Silver Nanoparticles: Solution and Melt Processing

The research initially involved the decoration of silver nanoparticles on carbon nanotubes using N,N-dimethylformamide. A new heteroaromatic azo-polymer was prepared and employed as a matrix while Ag–CNTs as filler. Two techniques were exploited to prepare nanocomposites (i.e., melt compounding and solution mixing). The solution mixing method resulted in better dispersion leading to higher mechanical strength 55.09–58.22 MPa relative to melt system 40.11–46.28 MPa. Filler content from 1 to 5 wt% increased electrical conductivity from 3.8 to 5.2 Scm^?1. 10% gravimetric loss was found to increase from 532 to 578°C (solution) and 503 to 544°C (melt).     

Effect of polymer–clay interaction on solvent transport behavior of fluoroelastomer–clay nanocomposites and prediction of aspect ratio of nanoclay

Diffusion and sorption of methyl ethyl ketone and tetrahydrofuran through fluoroelastomer‐clay nanocomposites were investigated in the temperature range of 30–60°C by swelling experiments. Slightly non‐Fickian transport behavior was found for these nanocomposites, having variation of type of nanoclay and loading. Different transport parameters depend on the size and shape of the penetrant molecules. The results were used to study the effect of nanoclay on the solvent transport‐properties of nanocomposites and their interactions with solvents. The diffusion coefficient of methyl ethyl ketone at 30°C for neat rubber was 1.43 × 10^?8 cm² s^?1, while those of the unmodified and the modified clay filled samples at 4 phr loading were 0.24 × 10^?8 and 0.50 × 10^?8 cm² s^?1, respectively. At 8 and 16 phr loading of the unmodified clay, it was found to be 0.44 × 10^?8 and 0.64 × 10^?8 cm² s^?1, respectively. The samples were also reswelled after deswelling. Surprisingly, transport behavior became Fickian on reswelling. Interestingly, ratio of diffusion coefficients of the filled system to the neat system was found to be almost same for the first time swelling and reswelling experiments. The results showed that better polymer‐clay interaction in the case of the unmodified‐clay filled nanocomposites is responsible for enhanced solvent‐resistance property. From the permeation data, for the first time, aspect ratio of nanoclays in different composites was calculated and found to have good correlation with the morphology data obtained from transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Influence of erodent particle types on solid particle erosion of polyphenylene sulphide composite under low particle speed

The influence of erodent particle types on solid particle erosion of randomly oriented short glass fiber and mineral particle reinforced polyphenylene sulphide (PPS) was investigated. The solid particle erosion studies were carried out using low speed solid particle erosion test rig with 150 to 212‐μm brown fused aluminum oxide (Al₂O₃), 150 to 200‐μm silica sand and 150 to 250‐μm glass bead. Glass bead eroding particles appear spherical in shape whereas aluminum oxide and silica sand eroding particles have sharp and angular edges. The erosion tests were conducted at six different contact angles of 15, 30, 45, 60, 75, and 90°, respectively. The results showed a strong dependence of the eroding particle types on the erosive wear behavior of PPS composite. The peak erosion rate occurred at 45° contact angle for silica sand eroding particles while the peak erosion rate occurred at 30° contact angle for aluminum oxide and glass bead particles. The morphologies of eroded surfaces were characterized by the scanning electron microscopy. In case of aluminum oxide and silica sand, the erosive wear mechanism occurs firstly by the erosion of matrix, followed by the fracture of un‐supported fibers and their detachment; however, the erosive wear mechanism occurs different for glass bead particles. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Preparation and physicochemical performances of poly[(vinylidene fluoride)‐co‐hexafluoropropylene]‐based composite polymer electrolytes doped with modified carbon nanotubes

Modified carbon nanotubes (m‐CNTs) were successfully prepared by the interactions between nitric and sulfuric acids and CNTs, which was confirmed using Fourier transform infrared spectroscopy. Poly[(vinylidene fluoride)‐co‐hexafluoropropylene]‐based composite polymer electrolyte (CPE) membranes doped with various amounts of m‐CNTs were prepared by phase inversion method. The desired CPEs were obtained by soaking the liquid electrolytes for 30 min. The physicochemical and electrochemical properties of the CPE membranes were investigated using scanning electron microscopy, X‐ray diffraction, thermogravimetry, electrochemical impedance spectroscopy and linear sweep voltammetry. The results show that the CPE membranes doped with 2.2 wt% m‐CNTs possess the smoothest surface and the highest decomposition temperature about 450 °C. Obviously, adding an appropriate amount of m‐CNTs into the polymer matrix can decrease the crystallinity and enhance the ionic conductivity; the temperature dependence of ionic conductivity follows the Arrhenius relation and the ionic conductivity at room temperature is up to 4.9 mS cm^?1. The interfacial resistance can reach a stable value of about 415 Ω cm^?2 after 10 days storage. The excellent rate and cycle performances with an electrochemical working window up to 5.4 V ensure that the CPEs doped with 2.2 wt% m‐CNTs can be considered as potential candidates as polymer electrolyte for lithium ion batteries. © 2013 Society of Chemical Industry     

Study on the properties of multi-walled carbon nanotubes reinforced poly (vinyl alcohol) composites

Nanocomposite films based on polyvinyl alcohol(PVA) and multi-walled carbon nanotubes (MWCNTs) at different weight ratios (i.e.0.0,0.5, 1.0,1.5, 2.0 wt%), were prepared by dispersion techniques. Cationic geminisurfactant and its monomeric form (0.01 wt%) were used as dispersants to achieve homogeneous and stable dispersionof CNTs in water and subsequent PVA/CNTs nanocomposites. Surface charge of CNTs in aqueous suspension with addition of the used dispersants were investigated by measuring its zeta potential. The structural and interaction studies have been analyzed from X-ray diffraction (XRD) and Raman spectroscopy. The effect of the used surfactantson the separation and distribution of CNTs in PVA matrix was studied by visual characterization based on scanning electron microscopy (SEM). Thermal, mechanical and electrical properties of the prepared nanocomposites were evaluated and the results were discussed in relation with the CNTs content and surfactant type as dispersant. Surfactant effect improved the dispersion homogeneity of CNTs (at 1.0 wt%) within the polymer matrix. The physical interaction between. CNTs and PVA macromolecular chains resulting in nanocomposites with largely enhanced properties compared to those prepared with higher filler loading by avoiding the agglomeration phenomenon of nanotubes. On the other hand, the addition of CNTs by content up to 2 wt%, increases the electrical conductivity to be 10^?6 Scm^?1 at room temperature which highly recommends such composites to be used in electrostatic dissipation applications upon using gemini surfactant. Furthermore, useful nanosized capacitor structure based onnanocomposites containing its monomeric form, characterized by high permittivity and low dielectric loss, can be formed.     

Selective Laser Sintering 3D Printing: A Way to Construct 3D Electrically Conductive Segregated Network in Polymer Matrix

Selective laser sintering (SLS), which can directly turn 3D models into real objects, is employed to prepare the flexible thermoplastic polyurethane (TPU) conductor using self‐made carbon nanotubes (CNTs) wrapped TPU powders. The SLS printing, as a shear‐free and free‐flowing processing without compacting, provides a unique approach to construct conductive segregated networks of CNTs in the polymer matrix. The electrical conductivity for the SLS processed TPU/CNTs composite has a lower percolation threshold of 0.2 wt% and reaches ≈10⁻¹ S m⁻¹ at 1 wt% CNTs content, which is seven orders of magnitude higher than that of conventional injection‐molded TPU/CNTs composites at the same CNTs content. The 3D printed TPU/CNTs specimen can maintain good flexibility and durability, even after repeated bending for 1000 cycles, the electrical resistance can keep at a nearly constant value. The flexible conductive TPU/CNTs composite with complicated structures and shapes like porous piezoresistors can be easily obtained by this approach.     

Thermoelectric properties of carbon nanotube reinforced cement-based composites fabricated by compression shear

Carbon nanotubes (CNTs) with weight percent of 5.0%, 10.0% and 15.0% were added into the cement matrix to fabricate CNT reinforced cement-based composites (CNTs/CC) by mixing and dry compression shear methods. Seebeck coefficient, electrical conductivity and thermal conductivity of the as-received CNTs/CC were measured and analyzed in detail. The CNTs/CC exhibits the thermoelectric behavior of p-type semiconductor. CNTs were dispersed uniformly in cement matrix by compression shear stress, which promoted a relatively high electrical conductivity (0.818 S/cm) and Seebeck coefficient (57.98 μV/°C) of CNTs/CC. Combining with their lower thermal conductivity ranged from 0.734 to 0.947 W m^?1 K^?1, the CNTs/CC shows the highest thermoelectric figure of merit (ZT) has reached 9.33 × 10^?5, Which is benefit to the applications in large-scale energy harvesting in the buildings and pavements with low cost in the future cities.     

Pressure-sensitive polymer nanocomposites: Carbon nanofiber-reinforced MWCNT-coated PMMA microbeads

ABSTRACT

A unique, thermoplastic polyurethane (TPU)-based, pressure-sensitive nanocomposites were prepared by the solution mixing method. Poly (methyl methacrylate) (PMMA) microbeads (10µm) were coated with multiwall carbon nanotubes (MWCNT) and dispersed in TPU matrix dissolved in tetrahydrofuran. 1, 2, and 5 wt. % of carbon nanofiber (CNF) were also added to the TPU matrix. The influence of MWCNT coated PMMA-microbeads along with different CNF contents on the pressure sensing properties were studied. Electrical and thermal conductivities were measured at different external loads. The prepared nanocomposites showed repeatable and reliable electric response with increasing external load and are suitable as pressure sensors.     

Morphology control of polyoxy‐methylene/thermoplastic polyurethane blends by adjusting their viscosity ratio

Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = η_TPU/η_POM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (T_p) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at T_p < 190 °C, filamental morphology when P ≈ 1 at T_p ≈ 190 °C and spheroidal morphology when P < 1 at T_p > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (～14 kJ m^?2). Copyright © 2006 Society of Chemical Industry     

Aramid–multiwalled carbon nanotube nanocomposites: effect of compatibilization through oligomer wrapping of the nanotubes

Aramid–multiwalled carbon nanotube (MWCNT) nanocomposites with different CNT loadings were prepared by the solution‐blending technique. Aramid oligomeric chains having reactive amine end‐groups were covalently grafted and wrapped over the surface of acid‐functionalized MWCNTs. The presence of functional groups and surface modification of MWCNTs were studied using Raman, Fourier transform infrared and X‐ray photoelectron spectroscopic and transmission/scanning electron microscopic techniques. Addition of these MWCNTs resulted in a homogeneous dispersion throughout the aramid matrix. Dynamic mechanical thermal analysis showed an increase in the storage modulus and the glass transition temperature involved with α‐relaxations on CNT loading. The coefficient of thermal expansion (CTE) of aramid was reduced on loading with such CNTs. Strong interfacial interactions of the matrix with the surface‐modified CNTs reduced the stress‐transfer problem in the composite material and resulted in higher modulus of 4.26 GPa and a glass transition temperature of 338.5 °C, whereas the CTE was reduced to 101.8 ppm °C^?1 on addition of only 2.5 wt% CNTs in the aramid matrix. © 2016 Society of Chemical Industry