Polycarbonate Nanocomposites Research Articles

Effective Modulus of Single- and Multi-Walled Carbon Nanotubes in Melt-Compounded Polycarbonate Nanocomposites

This study compares the reinforcing efficiency of multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) in polycarbonate (PC) films processed using melt-compounding followed by hot-pressing. The effect of carbon nanotube (CNT) type on composite properties is studied by means of dynamic mechanical analysis (DMA). Composite theory is used to analyse the results. It is found that, despite the good dispersion and interfacial interactions reported in the literature for PC/CNT nanocomposites, SWNTs and MWNTs efficiently reinforce PC only at nanofiller contents below 0.3 wt.% and 0.5 wt.%, respectively. Nevertheless, effective moduli of CNTs (in particular SWNT) close to the theoretical values were achieved for low nanofiller content.

Retracted: Mechanical and thermal properties enhancement of polycarbonate nanocomposites prepared by melt compounding

AbstractThe following article from the Journal of Applied Polymer Science, “Mechanical and thermal properties enhancement of polycarbonate nanocomposites prepared by melt compounding” by Sanjay K. Nayak, Smita Mohanty, and Sushanta K. Samal, published online on 7 April 2010 in Wiley Online Library (J. Appl. Polym. Sci. 2010, 117, 2101; http://onlinelibrary.wiley.com/doi/10.1002/app.31222/full), has been retracted by agreement between the authors, the journal's editors, and Wiley Periodicals, Inc. The retraction has been agreed due to significant overlap with respect to another article, “Effect of hydrogen bonding on the rheology of polycarbonate/organoclay nanocomposites,” by Kyung Min Lee, and Chang Dae Han, published online on 19 June 2003 in Polymer (2003, 44, 4573).

Synthesis and characterization of transparent alumina reinforced polycarbonate nanocomposite

Transparent nanocomposite films were fabricated by blending a concentrated nanocomposite formed by in-situ polymerization of polycarbonate in the presence of alumina nanowhisker with a high molecular weight polycarbonate. Polycarbonate was grafted to the alumina nanowhisker surface to improve nanofiller dispersion and load transfer to polymer matrix. Fourier transform infrared spectroscopy confirmed the functionalization of the nanowhisker with polycarbonate. Samples produced using functionalized alumina exhibited improved dispersion compared to the raw alumina nanowhiskers in the PC. Functionalization of alumina nanowhisker enhanced tensile properties (Young’s modulus and tensile strength) relative to the pure polycarbonate and blends produced with raw alumina nanowhisker. Additionally, the nanocomposite formed using in-situ polymerization showed small decreases in transparency in the visual range compared to the base polymer with increased absorption in the UV range. The effect of reaction temperature during in-situ polymerization on the properties of the nanocomposite was investigated. Higher reaction temperature resulted in improved dispersion and sharp increases in tensile modulus and shear strength.

Polycarbonate/Clay Nanocomposites via in Situ Melt Polycondensation

Polycarbonate (PC)/clay nanocomposites were prepared via in situ melt polycondensation using novel organoclays modified using phosphonium and imidazolium based cations. The molecular weight of the separated polymer separated from the nanocomposites reveals that phosphonium ion modified organoclays catalyze the polycondensation of bisphenol A with diphenyl carbonate. Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) indicated that exfoliated polycarbonate/clay nanocomposites could be obtained using organoclays which have reactive bisphenol functionality in the modifier. The glass transition temperature (Tg) of the nanocomposites was studied using differential scanning calorimetry (DSC). The use of a more thermally stable modifier did not improve the color in polycarbonate clay nanocomposites. Although an approach to produce fully exfoliated PC nanocomposites are evident from this study, the process is far from perfect from the point of producing a color free transparent PC.

Flow induced orientation of multiwalled carbon nanotubes in polycarbonate nanocomposites: Rheology, conductivity and mechanical properties

We investigated the effect of flow field and deformation rate on the nanotube alignment and on the properties of PC/multiwalled carbon nanotube nanocomposites. Samples of various MWCNT loadings were prepared by diluting a commercial masterbatch containing 15 wt% nanotubes using optimized melt mixing conditions. Different processing conditions were then used to systematically change the degree of nanotube alignment, from random orientation to highly aligned. Morphological studies and Raman spectroscopy analysis revealed that the nanotubes are preferentially aligned in the flow direction, particularly at large injection or compression rates. Rheological measurements corresponding to high shear rate conditions showed drastic changes in the viscoelastic behavior. The complex viscosity significantly decreased and percolation threshold notably rose. High degrees of nanotube alignment also resulted in a significant increase in the electrical percolation threshold. The mechanical properties of the nanocomposites for different nanotube loadings were also shown to depend on the processing conditions, and somehow improved when the material was processed at higher rates. Finally, we used a power-law type equation to correlate the percolation behavior and the nanotube alignment. The estimated percolation threshold and the power index, q, significantly increase with the degree of nanotube alignment as determined by Raman analysis.

Mechanical, Morphological and Thermal Properties of Polycarbonate/SEBS-G-MA/Montmorillonite Nanocomposites

Nanocomposites based on polycarbonate (PC) containing sodium montmorillonite (NaMMT) and maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MA) were prepared by melt compounding method followed by injection molding. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed the formation of intercalated nanocomposites. Incorporation of SEBS-g-MA into the PC/MMT nanocomposites enhanced ductility and impact strength but slightly reduced tensile strength and stiffness. The glass transition temperature (T g – detected from DMTA) and onset temperature (T onset – detected from TGA) of the PC nanocomposites was increased in the presence of SEBS-g-MA. For this PC/NaMMT system, SEBS-g-MA could act as an effective toughening agent.

Preparation, characterization, and thermal studies of γ-Fe2O3 and CuO dispersed polycarbonate nanocomposites

Abstract Polycarbonate with γ-Fe2O3 and CuO dispersions were carried out by solvent casting method to make polycarbonate-γ-Fe2O3 and polycarbonate-CuO composite films. These films were characterized for the molecular structure through FTIR spectroscopy and crystallinity by X-ray diffraction (XRD) measurements. The morphology of polycarbonate-γ-Fe2O3 was found to be different from that of polycarbonate-CuO composite films based on the scanning electron micrograph (SEM) images. The thermal traces of composites are different from that of pure polycarbonate which indicating the catalytic decomposition when compared with virgin polymer which is oxidative decomposition. An understanding of the structure, morphology, and thermal behaviour of the composite films are envisaged in the present study.

Dynamic mechanical, thermal, and morphological properties of silane‐treated montmorillonite reinforced polycarbonate nanocomposites

AbstractThree different loading of 3‐aminopropyltriethoxysilane (APS) was used to modify the Na‐montmorillonite via cation exchange technique. The Na‐MMT and silane‐treated montmorillonite (STMMT) were melt‐compounded with polycarbonate (PC) by using Haake Minilab machine. The PC nanocomposite samples were prepared by using Haake Minijet injection molding technique. The intercalation and exfoliation of the PC/MMT nanocomposites were characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal properties of the PC nanocomposites were investigated by using dynamic mechanical analyzer and thermogravimetry analyzer. XRD and TEM results revealed partial intercalation and exfoliation of STMMT in PC matrix. Increase of APS concentration significantly enhanced the storage modulus (E′) and improved the thermal stability of PC nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Poly(ethylene terephalate) prepolymer graft modification of nano-TiO2 and its effect on mechanical property of polycarbonate nanocomposites

Nano-TiO2 particles were modified by the poly(ethylene terephalate) prepolymer (pre-PET) via polycondensation. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results showed that pre-PET was successfully grafted on the surface of the nano-TiO2 particles. Thermogravimetric analysis results indicated that the grafting efficiency depended on the vacuum degree. Compared to the original nano-TiO2, the grafted nano-TiO2 had better compatibility with the polycarbonate (PC) matrix and could be dispersed more homogeneously in PC. Hence, interfacial adhesion between TiO2 and PC was enhanced. The mechanical properties of the resultant PC/nano-TiO2 composites like tensile strength and notched impact strength were greatly improved. Calculated respectively from tensile yield stress PC/nano-TiO2 composites, the interfacial interaction parameter B was employed to quantitatively characterise the effective interfacial interaction between the nano-TiO2 and PC matrix. It demonstrated that the nano-TiO2 grafted with pre-PET had stronger effective interfacial interaction with PC matrix than original nano-TiO2.

Metal Oxide Mineral Filler Containing Polymer Nanocomposites

Metal oxide mineral filled polycarbonate (PC) nanocomposites have been investigated. Plasma-chemical synthesis has been used to obtain metal oxide nanoparticles (MON). Melt mixing has been utilized to obtain PC/MON composites with regularly organized nanostructure. Consequently, an increasing in MON content caused a small decrease of surface and volume resistivities and an increase of nanocomposites magnetic activity.

Polyamide- and polycarbonate-based nanocomposites prepared from thermally stable imidazolium organoclay

This paper explores the possible advantages of the more thermally stable imidazolium-based organoclay over a more conventional ammonium-based organoclay for facilitating exfoliation and minimizing polymer matrix degradation in melt blended polyamide 6 (PA-6) and polycarbonate (PC) nanocomposites. The thermal stability of the two organoclays was evaluated by TGA analyses. The extent of clay exfoliation was judged by analysis of the morphology and tensile modulus of these nanocomposites formed using a DSM Microcompounder, while the extent of color formation and molecular weight change were used to evaluate polymer matrix degradation. For PA-6 and PC nanocomposites, the use of the imidazolium organoclay only produced slight differences in both exfoliation and molecular weight change, although the imidazolium organoclay is remarkably more thermally stable than the ammonium organoclay.

Rheology of polycarbonate reinforcedwith functionalized and unfunctionalized single-walled carbon nanotubes

Nanocomposites of polycarbonate (PC) containing low concentrations of pristine and COOH and OH functionalized single-walled carbon nanotubes (SWNTs, COOH-SWNTs and OH-SWNTs) were prepared by melt-mixing and analyzed using rheology and scanning electron microscopy (SEM). The steady state and linear viscoelastic behavior of each nanocomposite material is presented and compared to that of the neat PC. SEM analysis revealed that samples containing functionalized SWNTs were more dispersible than samples containing the pristine SWNTs.

The effect of synthesis procedure on the structure and properties of palladium/polycarbonate nanocomposites

In this paper, we compare two procedures for the synthesis of palladium (Pd)/polycarbonate (PC) nanocomposites as well as their morphological, optical, thermal and electrical properties. Pd nanoclusters were produced by the reduction of palladium chloride using a variation of Brust's method. Discrete Pd nanoclusters of ∼15nm size were formed in the absence of PC in the reaction mixture (ex situ method) while agglomeration of Pd nanoclusters was noticed in the presence of PC in the reaction mixture (in situ method). Fourier transform infrared spectroscopy (FTIR) suggests nanoparticle–polymer interactions and polymer conformational changes in the in situ nanocomposite films. Even after having the same Pd content, the ex situ nanocomposites films were found to transmit more light than the in situ nanocomposites. The glass transition temperature (Tg), decreased by ∼16°C for both the ex situ and in situ samples. Thermogravimetric analysis (TGA) indicated that the presence of Pd nanoclusters significantly improved the thermal stability of the nanocomposites, as evidenced by the enhanced onset of degradation by ∼20°C and ∼40°C for the in situ and ex situ nanocomposites, respectively. The electrical conductivity measurement shows a dramatic difference between these nanocomposites with a significantly higher value for the in situ nanocomposite (resistivity=2.1×105Ωm) compared to the ex situ nanocomposite (resistivity=7.2×1013Ωm).

Physical and tribological properties of a new polycarbonate-organoclay nanocomposite

A new polycarbonate (LS2) nanocomposite containing a 3 wt% proportion of the organically modified montmorillonite bentone 2010 (B 2010) has been prepared by extrusion and injection moulding, and its tribological properties determined under a pin-on-disc configuration against stainless steel. The nanocomposite (LS2 + 3% B 2010) presents a 88% reduction in friction and up to two orders of magnitude reduction in wear rate with respect to the base polymer. The new nanocomposite has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD), and its thermal and dynamic mechanical properties have been determined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) techniques. The nanocomposite shows a uniform dispersion of the nanoclay as pointed out by two different statistical methods. The good tribological performance of the new nanocomposite is attributed to this uniform microstructure and to the increase in the nanoclay stacking distance.

Thermal, Morphological and Dynamic Mechanical Characterization of Melt Blended PC Nanocomposites

Polycarbonate (PC) nanocomposites were prepared by melt intercalation technique in an intermeshing co-rotating twin-screw extruder. Both unmodified (Na+MMT) and organo-modified (Cloisite 10A & OMMT) clays were used for the preparation of nanocomposites. The effect of addition of clays on the morphological and dynamic mechanical properties of PC matrix has been studied. The wide angle X-ray (WAXD) studies reveal a dominated exfoliated morphology of the nanocomposites at a clay content of 5%. The intercalated morphology is predominated upto clay content of 3%. Transmission electron microscopy (TEM) demonstrated the co-existance of intercalated/exfoliated morphology in all the composites. Dynamic mechanical analysis (DMA) shows an increase in storage modulus indicating higher stiffness in case of organomodified clay filled composites as compared to unmodified & virgin matrix.

Electrical and rheological properties of polycarbonate/multiwalled carbon nanotube nanocomposites

Nanocomposites of polycarbonate (PC) and multiwalled carbon nanotube (MWCNT) were prepared using a precipitation method, and the surface resistivities and rheological properties of the nanocomposites were investigated. The nanocomposites showed a threshold decrease in their surface resistivities with increasing MWCNT content at a relatively low concentration of 0.91vol.%. The low concentration required for the threshold decrease in the surface resistivities was attributed to the pristine MWCNT, without modifications unfavorable for the electrically conductive fillers. Yield behavior was observed with the change in the steady shear viscosities with shear stresses. The viscosities of the nanocomposites were lower than that of the neat PC. It is postulated that the decreased viscosity had resulted from the increase in the mobilities of the PC molecules and free volumes in the PC/MWCNT nanocomposites, which were supported by the decreased glass transition temperatures of the nanocomposites compared to the neat PC.

Effect of Filler Geometry on Interfacial Friction Damping in Polymer Nanocomposites

Single-walled carbon nanotube polycarbonate and C60 polycarbonate nanocomposites were fabricated using a solution mixing method. The composite loss modulus was characterized by application of dynamic (sinusoidal) load to the nanocomposite and the pure polymer samples. For a loading of 1 weight %, the single-walled nanotube fillers generated more than a 250% increase in loss modulus compared to the baseline (pure) polycarbonate. Even though the surface area to volume ratio and surface chemistry of C60 is similar to that for nanotubes, we report no significant increase in the energy dissipation for the 1% weight C60 nanoparticle composite compared to the pure polymer. We explain these observations by comparing qualitatively, the active sliding area (considering both normal and shear stresses) for a representative volume element of the nanotube and the nanoparticle composites. These results highlight the important role played by the filler geometry in controlling energy dissipation in nanocomposite materials.

Experimental Investigation of the Machinability of Polycarbonate Reinforced With Multiwalled Carbon Nanotubes

The machinability of a polycarbonate nanocomposite containing multiwalled carbon nanotubes is investigated and contrasted with its base polymer and with a conventional carbon fiber composite. The material microstructures are characterized using transmission electron and scanning electron microscopy methods. Micro-endmilling experiments are conducted on the three materials. Chip morphology, machined surface characteristics, and the nature of the cutting forces are employed as machinability measures for comparative purposes. Polycarbonate chips are seen to transition from being discontinuous to continuous as the feed-per-tooth (FPT) increases, while, at all FPT values the nanocomposite is seen to form comparatively thicker continuous chips. The nanocomposite and the carbon fiber composite are seen to have the lowest and the highest magnitudes, respectively, for both the surface roughness and cutting forces. Shearing along the nanotube-polymer interface and better thermal conductivity are speculated to be the mechanisms responsible for the observations seen in the nanocomposite.

Polycarbonate/Montmorillonite Nanocomposites Prepared by Microwave‐Aided Solid State Polymerization

AbstractSummary: Polycarbonate/montmorillonite (MMT) nanocomposites were prepared by microwave solid‐state polymerization. The MMTs were modified with alkyl ammonium salt. Pre‐intercalated polycarbonate nanocomposite was prepared using two conventional methods; a melt process and a solution process. Melt processing was accomplished in a Haake internal mixer for 30 mins at 180 °C. Solution processing was accomplished in a homogenizer using chloroform. The wide‐angle X‐ray diffraction (WAXD) peak indicating the gallery size of MMTs was shifted to lower levels after the pre‐intercalation process. Subsequently, microwave solid‐state polymerization converted the pre‐intercalated nanocomposite into the exfoliated nanocomposite. WAXD revealed that exfoliation and/or further intercalated structures were obtained when comparing the results from the microwave solid‐state polymerization with results from conventional solid‐state polymerization using oil heating. This means that microwave solid‐state polymerization is more effective than conventional solid‐state polymerization using oil heating. It was shown that conventional melt and solution processing of MMT and polycarbonate prepolymer yielded intercalated nanocomposites with interlayer spacing of 2.5 and 2.7 nm respectively. Microwave solid‐state polymerized nanocomposite showed the exfoliated and/or intercalated structure, whereas conventional solid‐state polymerization using oil heating only increased the gallery size of MMT. The thermal decomposition behavior and morphologies were investigated by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM).Schematic diagram of microwave solid‐state polymerization.magnified imageSchematic diagram of microwave solid‐state polymerization.

Mechanical response and rheological properties of polycarbonate layered‐silicate nanocomposites

AbstractThe effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties of intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, the linear dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. The 3.5 and 5 wt% clay nanocomposites exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared to the pure PC and the 1.5 wt% clay nanocomposite. Thermal degradation of PC resulted from the melt compounding of organo‐modified nanoclays was evident from the reduction in the glass transition temperature and molecular weight of the PC nanocomposites. These nanocomposites also exhibited a significant decrease in the extent of tensile elongation and ductility with respect to the nanoclay incorporation. A concomitant decrease in the rheological properties at high frequencies was also observed, and was consistent with the lowering of the molecular weight of PC, particularly near or above the percolation threshold of nanoclay. These nanocomposites, nevertheless, exhibited elastic‐plastic deformation in compression, regardless of nanoclay content. Polym. Eng. Sci. 44:825–837, 2004. © 2004 Society of Plastics Engineers.