The processing and properties of conductive polypropylene/polypyrrole composites

Polypropylene (PP) particles were chemically coated with polypyrrole (PPy). The content of polypyrrole varied from 0.8 to 7.6 wt.-%. Electrical conductivity of compression moulded samples depends on the concentration of polypyrrole and reached values from 4×10⁻¹⁰ to 5×10⁻³ S/cm, which is about 7 orders of magnitude higher than the conductivity in the blends prepared by mechanical mixing of PP and PPy in the same PPy concentration range. Highly conductive composites were also obtained from a mixture of coated and non-coated PP particles. The PP/PPy composites were characterized by elemental analysis, SEM and mechanical testing. The antistatic properties of PP/PPy composites were demonstrated. The electrical and mechanical properties depend on processing of composites.     

Stability of electrical properties of conducting polymer composites

The effect of slow cycle heating and cooling on the stability of electrical properties of two polymer composites‐ polypropylene/polypyrrole (PP/PPy) and polypropylene/carbon black (PP/CB) ‐ was investigated. Conductivity in composites was measured in heating/cooling cycles in the temperature range from 16°C to 105°C in PP/PPy and to 125°C in PP/CB, respectively. It was found that the thermal treatment caused the decrease of PP/PPy conductivity while in case of PP/CB the treatment increased the electrical conductivity. The positive effect was explained by increased crystallinity in the thermally treated composite.     

Shear‐induced change of exfoliation and orientation in polypropylene/montmorillonite nanocomposites

For the improved dispersion of montmorillonite (MMT) in a polypropylene (PP) matrix, PP/MMT nanocomposites prepared via direct melt intercalation were further subjected to oscillating stress achieved by dynamic packing injection molding. The shear‐induced morphological changes were investigated with an Instron machine, wide‐angle X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The original nanocomposites possessed a partly intercalated and partly exfoliated morphology. A transformation of the intercalated structure into an exfoliated structure occurred after shearing, and a more homogeneous dispersion of MMT in the PP matrix was obtained. However, the increase of the exfoliated structure was accompanied by the scarifying of the orientation of MMT layers along the shear direction. Some bended or curved MMT layers were found for the first time by TEM after shearing. However, the orientation of PP chains in the PP/MMT nanocomposites became very difficult under an external shear force; this indicated that the molecular motion of PP chains intercalated between MMT layers was highly confined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1–10, 2003     

Synthesis of a hexafluoropropylidene-bis(phthalic anhydride)-based polyimide and its conducting polymer composites with polypyrrole

A new electrically conducting composite film from polypyrrole and 4,4′-(hexafluoroisopropylidene)-bis(phthalic anhydride)-based polyimide was prepared. Pyrrole and the dopant ion can easily penetrate through the polyimide substrate and electropolymerize on the platinum (Pt) electrode due to the swelling of the polyimide on the metal electrode. The electrochemical properties of polypyrrole-polyimide (PPy/PI) composite films have been investigated by using cyclic voltammetry. The PPy/PI composite film is suitable for use as the electroactive material owing to its stable and controllable electrochemical properties. The electrical conductivity of composites falls in the range 0.0035–15 S/cm. Scanning electron micrograph, FTIR, and thermal studies indicate that PPy and PI form a homogeneous material rather than a simple mixture. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3009–3016, 1997     

Synthesis and characterization of carbon nanotube/polypyrrole core–shell nanocomposites via in situ inverse microemulsion

We demonstrate here a feasible approach to the preparation of multiwalled carbon nanotube (MWNT)/polypyrrole (PPy) core–shell nanowires by in situ inverse microemulsion. Transmission electron microscopy and scanning electron microscopy showed that the carbon nanotubes were uniformly coated with a PPy layer with a thickness of several to several tens of nanometers, depending on the MWNT content. Fourier transform infrared spectra suggested that there was strong interaction between the π‐bonded surface of the carbon nanotubes and the conjugated structure of the PPy shell layer. The thermal stability and electrical conductivity of the MWNT/PPy composites were examined with thermogravimetric analysis and a conventional four‐probe method. In comparison with pure PPy, the decomposition temperature of the MWNT/PPy (1 wt % MWNT) composites increased from 305 to 335 °C, and the electrical conductivity of the MWNT/PPy (1 wt % MWNT) composites increased by 1 order of magnitude. The current–voltage curves of the MWNT/PPy nanocomposites followed Ohm's law, reflecting the metallic character of the MWNT/PPy nanocomposites. The cyclic voltammetry measurements revealed that PPy/MWNT composites showed an enhancement in the specific charge capacity with respect to that of pure PPy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6105–6115, 2005     

Characterization of poly(vinylidene fluoride)/Na+‐MMT composites: An investigation into the β‐crystalline nucleation effect of Na+‐MMT

Poly(vinylidene fluoride)(PVDF)/Na⁺‐MMT composites have been successfully prepared utilizing sodium montmorillonite (Na⁺‐MMT) via N,N‐dimethylformamide (DMF) solution mixing. The dispersion of Na⁺‐MMT layers in composites were investigated by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The effect of adding Na⁺‐MMT on crystallization behavior of PVDF was specifically studied. The β‐crystalline nucleation effect of Na⁺‐MMT was investigated and confirmed by differential scanning calorimetry (DSC), XRD, and Fourier transform infrared (FTIR) results. The interaction between PVDF and the surface of Na⁺‐MMT layers in DMF solution was confirmed by UV‐Vis absorbency. The effect of adding Na⁺‐MMT on rheological and electrical properties of PVDF/Na⁺‐MMT composites were also determined. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 903–911, 2009     

Ethylene–acrylic acid copolymer induced electrical conductivity improvements and dynamic rheological behavior changes of polypropylene/carbon black composites

The experimental data reveal that the addition of ethylene–acrylic acid copolymer (EAA) into carbon black (CB)/polypropylene (PP) composites can improve the electrical conductivity of CB/PP composites by two to six orders of magnitude at a comparatively low CB content (φ), and when φ = 2.5 vol %, 60/40 of PP/EAA is an optimum for electrical conductivity improvement. The dynamic rheological data show that with increasing φ there are apparent rheological percolations for CB/PP composites. A modified Kerner–Nielson equation can be used to describe the correlation between electrical percolation and dynamic viscoelastic percolation. The addition of EAA into CB/PP composites leads to apparent changes in dynamic rheological behaviors. When φ = 2.5 vol %, a rheological percolation appears in CB/PP/EAA (CPE) composites with increasing EAA content. The similar rheological behaviors correspond to the similar morphological structures for CPE composites with φ = 5.0 vol %. The appearance of bumps in the van‐Gurp–Palmen plots corresponds to the formation of network structure in CB/PP and CPE composites, and the more perfect the networks, the higher the amplitude of the bumps. All data indicate that the van‐Gurp–Palmen plot is sensitive to the formation of filler particle networks or cocontinuous phase which spans the whole composite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1762–1771, 2009     

Aggregation of particulate fillers: factors,determination, properties

The aggregation tendency of 11 different CaCO₃ fillers with widely differing particle sizes was studied in polypropylene (PP) composites. The fillers were characterized by different techniques in powder form and in suspension. Homogenization and sample preparation were carried out by extrusion and injection molding, or in an internal mixer and compression molding, respectively. Thin slices were prepared from the composites and the relative area of aggregates was determined by image analysis. Tensile and fracture properties were studied as a function of filler content. The results proved that the extent of aggregation increases with decreasing particle size and increasing filler content. Surprisingly, extruded and injection molded samples contained more aggregates than those prepared by homogenization in an internal mixer followed by compression molding. Good agreement was found between the powder properties of the fillers and their performance in the composites. Deviations from the general tendency indicate that some factors, which were not accounted for in the study, also influence aggregation and composite properties.     

聚吡咯/Ba_(0.9)Nd_(0.1)Fe_(11.5)Cr_(0.5)O_(19)复合物的可控合成及电磁性能

用溶胶凝胶法制备了一系列Nd掺杂Ba-铁氧体粉末(Ba1-xNdxFe11.5Cr0.5O19,x=0.00,0.05,0.10,0.15,0.20),选取磁性能相对较好的Ba0.9Nd0.1Fe11.5Cr0.5O19作为磁核,通过原位聚合法制备了不同铁氧体含量的聚吡咯/Ba0.9Nd0.1Fe11.5Cr0.5O19(PPy/BNFCO)复合物.用X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、红外光谱(FTIR)、振动样品磁强计(VSM)、四探针测试仪和矢量网络分析仪等表征了铁氧体粉末和复合物微粒的结构、形貌以及电磁性能.结果表明,Nd的掺杂明显改变了Ba-铁氧体的饱和磁化强度和矫顽力;PPy/BNFCO复合物具有比较明显的核壳结构;复合物的饱和磁化强度随BNFCO含量的增加而增大;电导率则与PPy含量成正比,mpy/mBNFCO=5/1为复合体系渗流阈值;复合物对电磁波的反射损耗和有效带宽是PPy和ZCGFO协同作用的结果,当mpy/mBNFCO为5/1时,PPy/ZCGFO复合物中组分间的协同作用达到最大,其反射峰值和有效带宽分别达到-27.68dB和9.04GHz.PPy/ZCGFO复合物由于良好的微波吸收性能,有望成为电磁波吸收与屏蔽领域的候选材料.     

Synthesis,characterization, and electrical properties of polypyrrole/multiwalled carbon nanotube composites

Size‐controllable polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites have been synthesized by in situ chemical oxidation polymerization directed by various concentrations of cationic surfactant cetyltrimethylammonium bromide (CTAB). Raman spectra, FTIR, SEM, and TEM were used to characterize their structure and morphology. These results showed that the composites are core (MWCNT)–shell (PPy) tubular structures with the thickness of the PPy layer in the range of 20–40 nm, depending on the concentration of CTAB. Raman and FTIR spectra of the composites are almost identical to those of PPy alone. The electrical conductivities of these composites are 1–2 orders of magnitude higher than those of PPy without MWCNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6449–6457, 2006     

A holistic evaluation of the influence of shear rates and matrix viscosity on the properties of polypropylene/multi-walled carbon nanotubes composites

In this work, a comparative study on the electrical, morphological, and thermal properties of polypropylene/multiwalled carbon nanotubes (PP/CNT) composites which were prepared by three different processing methods, such as compression molding (CM, shear rate: ~0 s⁻¹), conventional injection molding (CIM, shear rate: ~10² s⁻¹), and microinjection molding (μIM, shear rate: ~10⁵ s⁻¹), was reported. The difference in shear rates among these processing methods and matrix viscosity would significantly affect the state of filler distribution, thereby determining the properties of subsequent moldings. Electrical conductivity results showed that the percolation threshold of PP/CNT moldings followed a trend of μIM > CIM > CM. A higher degree of CNT orientation and a better filler distribution were achieved under the influence of higher shearing conditions, as corroborated by scanning electron microscope observations and Raman spectral analysis. Moreover, increasing filler concentrations played a positive role in improving the thermal stability of PP/CNT composites and the formation of CNT network was believed to be a contributing factor.     

Characterization of 3D angle-interlock thermoplastic composites under high strain rate compression loadings

In the present work, dynamic compression response of polypropylene (PP) based composites reinforced with Kevlar/Basalt fabrics was investigated. Two homogeneous fabrics with Kevlar (K3D) and Basalt (B3D) yarns and one hybrid (H3D) fabric with a combination of Kevlar/Basalt yarns were produced. The architecture of the fabrics was three-dimensional angle-interlock (3D-A). Three different composite laminates were manufactured using vacuum-assisted compression molding technique. The high strain rate compression loading was applied using a Split-Hopkinson Pressure Bar (SHPB) set-up at a strain rate regime of 3633–5235/s. The results indicated that the dynamic compression properties of thermoplastic 3D-A composites are strain rate sensitive. In all the composites, the peak stress, toughness and modulus were increased with strain rate. However, the strain at peak stress of Basalt reinforced composites (B3D, H3D) decreased approximately by 25%, while for K3D specimens it increased approximately by 15%. The K3D composites had a higher strain rate as compared to the B3D and H3D composites. In the case of K3D composite, except strain at peak stress, remaining dynamic properties were lower than the B3D composite, however, hybridization increased these properties. The failure mechanisms of 3D-A composites were characterized through macroscopic and scanning electron microscopy (SEM).     

Characterization and electrical properties of polypyrrole/multiwalled carbon nanotube composites synthesized by in situ chemical oxidative polymerization

This study describes the preparation of polypyrrole (PPy)/multiwalled carbon nanotube (MWNT) composites by in situ chemical oxidative polymerization. Various ratios of MWNTs, which served as hard templates, were first dispersed in aqueous solutions with the surfactant cetyltrimethylammonium bromide to form micelle/MWNT templates and overcome the difficulty of MWNTs dispersing into insoluble solutions of pyrrole monomer, and PPy was then synthesized via in situ chemical oxidative polymerization on the surface of the templates. Raman spectroscopy, Fourier transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the fabricated composites. Structural analysis using FESEM and HRTEM showed that the PPy/MWNT composites were core (MWNT)–shell (PPy) tubular structures. Raman and FTIR spectra of the composites were almost identical to those of PPy, supporting the idea that MWNTs served as the core in the formation of a coaxial nanostructure for the composites. The conductivities of these PPy/MWNT composites were about 150% higher than those of PPy without MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1413–1418, 2006     

Effect of silane‐grafted polypropylene on the morphology of polypropylene and nylon 6/clay composites

Polypropylene (PP)/nylon 6/clay composites were prepared by compounding of PP, which had previously been treated with two kinds of silane compounds, with a master batch composed of 90 wt % of nylon 6 and 10 wt % of octadecyl amine‐modified sodium montmorillonite (NM10). The morphology of the composites was investigated by means of SEM, TEM, XRD, and energy‐dispersive X‐ray analysis. All of the composites exhibited a phase‐separated morphology, irrespective of whether the PP was modified with the silane compounds or not. However, adhesive strength between the modified PP and NM10 was stronger than that between neat PP and NM10. Moreover, the PP grafted with 3‐(trimethoxysilyl)propyl methacrylate (PP2) reacted with the silanol groups of the clay to form PP‐clay hybrid during the compounding, which acted as a compatibilizer for the PP/nylon 6/clay composite. PP2NM composite (PP2/NM10 80/20 on weight basis) exhibited a peculiar morphology, in that the PP‐rich phase formed island domains within the nylon 6‐rich domains, which were in turn dispersed in the PP‐rich continuous matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 607–615, 2007.     

Morphology,crystalline structure,and properties of poly(vinylidene fluoride)/silica hybrid composites

Poly(vinylidene fluoride)/silica (PVDF/SiO₂) hybrid composite films were prepared via sol–gel reactions from mixtures of PVDF and tetraethoxysilane in dimethylacetamide. Their morphology, crystalline structure, and thermal, mechanical, and electrical properties were examined. For morphology measurements, scanning electron microscopy and optical microscopy were applied. X‐ray diffraction and infrared analyses showed that the crystalline structure of PVDF was not changed much by the addition of SiO₂, indicating that there was no interaction between PVDF and SiO₂. With increasing SiO₂ content, the melting temperature rarely changed, the degree of crystallinity and the dielectric constant decreased, and the decomposition temperature slightly increased. A PVDF/SiO₂ hybrid composite film with 5 wt % SiO₂ exhibited balanced mechanical properties without a severe change in the crystalline structure of PVDF, whereas for the hybrid composites with higher SiO₂ contents (>10 wt %), the mechanical properties were reduced, and the spherulite texture of PVDF was significantly disrupted by the presence of SiO₂ particles. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 19–30, 2002     

Simultaneously Improving the Tensile and Impact Properties of Isotactic Polypropylene with the Cooperation of co-PP and β-nucleating Agent through Pressure Vibration Injection Molding

In this article, crystalline morphology and molecular orientation of isotactic polypropylene(i PP), random copolymerized polypropylene(co-PP) and ?-nucleating agent(?-NA) composites prepared by pressure vibration injection molding(PVIM) have been investigated via polarized light microscopy, scanning electron microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Results demonstrated that the interaction between co-PP and i PP molecular chains was beneficial for the mechanical improvement and the introduction of ?-NA further improved the toughness of i PP. In addition, after applying the pressure vibration injection molding(PVIM) technology, the shear layer thickness increased remarkably and the tensile strength improved consequently. Thus, the strength and toughness of i PP/co-PP/?-NA composites prepared by PVIM were simultaneously improved compared to those of the pure i PP prepared by conventional injection molding(CIM): the impact toughness was increased by five times and tensile strength was increased by 9 MPa. This work provided a new method to further enhance the properties of i PP/co-PP composites through dynamic processing strategy.     

Swift heavy ion induced modification in dielectric and microhardness properties of polymer composites

Polymer composites with different concentrations of organometallics (ferric oxalate) dispersed PMMA were prepared. PMMA was synthesized by solution polymerization technique. These films were irradiated with 120 MeV Ni¹⁰⁺ ions in the fluence range 10¹¹-5 × 10¹² ions/cm². The radiation induced modifications in dielectric properties, microhardness, structural changes and surface morphology of polymer composite films have been investigated at different concentrations of filler and ion-fluences. It was observed that electrical conductivity and hardness of the films increase with the concentration of the filler and also with the fluence. The dielectric constant (?) obeys the Universal law given by ?αfⁿ⁻¹. The dielectric constant/loss is observed to change significantly due to irradiation. This suggests that ion beam irradiation promotes the metal to polymer bonding and convert polymeric structure into hydrogen depleted carbon network. This makes the composites more conductive and harder. Surface morphology of the films has been studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average surface roughness is observed to increase after irradiation as revealed by AFM studies. The SEM images show the blisters type of phenomenon on the surface due to ion beam irradiation.     

十六烷基膦酸表面修饰纳米镍粉及其复合材料的制备和性能

以十六烷基膦酸作为修饰剂, 对纳米镍粉进行表面改性处理, 通过溶液共混的方法制备改性镍粉与聚丙烯的聚合物基复合材料. 利用X射线光电子能谱(XPS)、 X射线衍射(XRD)及透射电子显微镜(TEM)等测试手段研究改性镍粉的表面形态; 利用扫描电子显微镜(SEM)研究复合材料断面形貌; 利用介电频谱分析系统对复合材料的介电常数和介电损耗等进行了测试. 结果表明, 纳米镍粉表面形成厚度为2~4 nm的十六烷基膦酸包覆层, 使纳米镍粉由亲水性变为亲油性; 聚丙烯基复合材料中, 改性镍粉均匀分散; 复合材料的介电常数在镍填充量为40%时, 可以达到纯聚丙烯的近10倍.     

Fabrication and Properties of Conducting Polypyrrole/SWNT‐PABS Composite Films and Nanotubes

We report the electropolymerization and characterization of polypyrrole films doped with poly(m‐aminobenzene sulfonic acid (PABS) functionalized single‐walled nanotubes (SWNT) (PPy/SWNT‐PABS). The negatively charged water‐soluble SWNT‐PABS served as anionic dopant during the electropolymerization to synthesize PPy/SWNT‐PABS composite films. The synthetic, morphological and electrical properties of PPy/SWNT‐PABS films and chloride doped polypyrrole (PPy/Cl) films were compared. Characterization was performed by cyclic voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. SEM and AFM images revealed that the incorporation of SWNT‐PABS significantly altered the morphology of the PPy. Cyclic voltammetry showed improved electrochemical properties of PPy/SWNT‐PABS films as compared to PPy/Cl films. Raman Spectroscopy confirmed the presence of SWNT‐PABS within composite films. Field effect transistor (FET) and electrical characterization studies show that the incorporation of the SWNT‐PABS increased the electronic performance of PPy/SWNT‐PABS films when compared to PPy/Cl films. Finally, we fabricated PPy/SWNT‐PABS nanotubes which may lead to potential applications to sensors and other electronic devices.     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008