Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session Q42: Polymer Composites |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Tirtha Chatterjee, The Dow Chemical Company Room: A302/303 |
Wednesday, March 23, 2011 11:15AM - 11:27AM |
Q42.00001: Dispersion and composite processing of polymer coated graphene Sriya Das, Ahmed Wajid, John Shelburne, Abel Cortinas, Micah Green Liquid phase exfoliation and dispersion of graphene, i.e. single layer graphite, is a critical challenge for bulk processing of graphene into advanced materials and devices. We demonstrate a suite of techniques for dispersing pristine graphene using polymer coatings for the purpose of liquid-phase nanocomposite processing. First, we illustrate a unique in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets in solution. These polymer coatings do not disrupt the pristine structure or superior properties of the graphene sheets; instead, these coatings allow for stable, aggregation resistant graphene dispersions, as characterized through rheology, SEM, and AFM. We also demonstrate that certain polymers naturally wrap and stabilize pristine graphene in various organic solvents. We use this technique to prepare epoxy and PVA nanocomposites loaded with polymer-wrapped graphene as filler. [Preview Abstract] |
Wednesday, March 23, 2011 11:27AM - 11:39AM |
Q42.00002: Fabrication of Graphene Oxide/Polypropylene Nanocomposites and Their Electrical Conductivity Study Jinyong Dong Graphene oxide (GO) /polypropylene nanocomposites were fabricated via in situ polymerizing propylene monomer over a GO that had been treated with a Grignard reagent and TiCl$_{4}$ successively when GO was not only catalytically activated but also largely reduced to an almost O- free state. The polymerization led to the in situ formation of the PP matrix, which was synchronized by the nanoscale exfoliation of the reduced GO as well as its gradual dispersion. Morphological examination of the ultimate GO/PP nanocomposites by TEM and SEM techniques revealed effective dispersion in nanoscale of GO in PP matrix. High electrical conductivity was discovered with thus prepared GO/PP nanocomposites, e.g. at a GO loading of 4.9 wt{\%}, $\sigma _{c}$ was measured at 0.3 S$\cdot$m$^{-1}$ [Preview Abstract] |
Wednesday, March 23, 2011 11:39AM - 11:51AM |
Q42.00003: Controlling nanorod self-assembly in polymer thin film composites Miguel Modestino, Jeffrey Urban, Rachel Segalman Semiconducting nanorods are of particular interest for use in polymer composites due to their anisotropic physical properties; however such properties can only be harnessed in systems with orientational order. Here, we demonstrate control over nanorod self-assembly in solution which leads to arrays of vertically aligned nanorods in polymer thin films over large areas ($>$1 cm$^{2})$. Transmission electron microscopy and X-ray scattering techniques were used to determine the structure of composites and probe the nanorod self-assembly mechanism. This work demonstrates that strong interactions between alkane-covered colloidal nanorods can enable the formation of hexagonally packed arrays of nanorods in a wide range of polymer matrices. Kinetic effects during the casting process are shown to affect the final morphology of the composites, leading to reduced array sizes for systems with increasing polymer molecular weight and nanorod concentration. The results presented show that thin film confinement as well as surface segregation of the nanorod arrays enhance the orientational order of nanorods in composites. [Preview Abstract] |
Wednesday, March 23, 2011 11:51AM - 12:03PM |
Q42.00004: Multi-Walled Carbon Nanotube Network Formation in Extruded High Density Polyethylene/MWNT Composites Frank Yepez Castillo, Brian P. Grady, Daniel E. Resasco Multi-walled carbon nanotube (MWNT) / high density polyethylene (HDPE) composites with varying amounts of carbon nanotubes were investigated and the effect of MWNT weight fraction on their electrical conductivity, crystallinity and mechanical properties is presented here. Samples were prepared by melt dilution of a HDPE masterbatch containing 20 wt{\%} MWNT with varying amounts of neat HDPE. Conductivity measurements on compression molded samples showed that electrical percolation occurs at 4.5 wt{\%} MWNTs. The effect of processing conditions on the formation of a MWNT network in extruded samples was assessed by the addition of a low-shear annealing zone (shear rate 1-10 s$^{-1})$ before final extrusion through a die. The time in the low shear zone was varied from almost zero to 90 sec. Extruded samples above the compression-molded percolation threshold were tested, and electrical conductivity did not develop. However, a significant increase in electrical conductivity was observed in these samples when annealed for 5 minutes at the same temperature. [Preview Abstract] |
Wednesday, March 23, 2011 12:03PM - 12:15PM |
Q42.00005: Effect of Nanowire Size Dispersity on the Electrical Conductivity in Polymer Nanocomposites Rose Mutiso, Michelle Sherrott, Ju Li, Karen Winey In this simulation study, we model the percolation threshold and electrical conductivity of three-dimensional networks containing finite, conductive cylinders with experimentally typical (Gaussian) and engineered (Bidisperse) distributions in their length and/or diameter. We have previously used this approach to explore the effects of cylinder orientation and aspect ratio. Preliminary results suggest that narrow Gaussian distributions do not affect the threshold concentration or electrical conductivity significantly in both isotropic and oriented networks, while the addition of a small fraction of longer rods in a bidisperse system can improve the electrical properties considerably. Additionally, polydispersity in the filler length has a more pronounced effect on the electrical percolation behavior than that in filler diameter. This implies that the separate effects of length and diameter should be decoupled from the overall filler aspect ratio when probing the effects of size dispersity in conducting polymer nanocomposites with elongated fillers. [Preview Abstract] |
Wednesday, March 23, 2011 12:15PM - 12:27PM |
Q42.00006: Simulating the Effect of Flame Retardant Materials on Heat Diffusion in Polymers Joseph Ortiz, Arpon Raksit, Dilip Gersappe Many commonly used polymers have low ignition temperatures, presenting the dangers of combustion and thermal degradation. Simulating the effect of flame retardants on the spread of heat throughout a polymer may provide a better understanding on how to effectively manipulate and make use of flame retardant materials. Using the lattice Boltzmann method, a simulation of heat diffusion from a heat source to sink was implemented in three dimensions. The polymer and flame retardant material were incorporated into the system by implementing ignition within the particles of the polymer and by adding heat absorbing microscale filler particles within the polymer matrix, while allowing for reduced-rate heat transfer between interspecies particles. Flame retardant particles were given various volume fractions and morphologies in order to simulate the addition of a variety of particles such as carbon nanotubes. By manipulating the flame retardant particles' ability to absorb heat, and their efficiency in removing heat from the system, different degrees of polymer heat transport were simulated while polymer systems ranged from single polymer systems to multi-component blends. [Preview Abstract] |
Wednesday, March 23, 2011 12:27PM - 12:39PM |
Q42.00007: Diffusion of small molecules in polymer nanocomposites: relationship between local free volume dynamics and penetrant diffusivity Victor Pryamitsyn, Venkat Ganesan Polymer membranes are widely used as barrier or gas/vapors separation materials. Recent experiments have demonstrated that the barrier properties of the polymer nanocomposites (PNC) dramatically different from pure polymer. Usually such properties are quantified by the permeability $P$ of the material to a penetrant which consists of two contributions: the penetrant solubility $S$ and diffusivity $D$: $P=S~D$ In present work we only discuss term $D$. We use the Bond Fluctuation Model, which allows us to model the diffusivity of the penetrant, the dynamics of the polymer and the dynamics of the polymer free volume in a single framework. We modeled PNC's at different particle load and the penetrant size and found that addition of nanoparticles increseses the penetrant diffusivity and selectivity to the penetrant size. This increase is attributed to the free volume increase and the acceleration of the free volume relaxation in PNC relatively to the pure polymer. We have compared the penetrant diffusivity in a rubbery and glassy PNC's and found than the effect of the PNC load on diffusivity and selectivity is much stronger for the glassy system which is due to rubbery system $D$ is controlled by the rate of matrix free volume relaxation and in glassy regime it is controlled by the static free volume percolation, which is more sensitive to the PNC load. [Preview Abstract] |
Wednesday, March 23, 2011 12:39PM - 12:51PM |
Q42.00008: Nanoparticle Size Dependence of a Polymer's Mechanical Properties Joseph Moll, Shushan Gong, Sanat Kumar, Ralph Colby Nanoparticle size critically affects the properties of polymer nanocomposites. We use a silica/poly(2-vinyl) pyridine (P2VP) polymer nanoparticle composite to investigate these effects by varying the nanoparticle sizes from 2nm to a micron. Since silica and P2VP are miscible, we obtain uniform nanoparticle spatial distribution in all cases. Rheology is employed to measure the macroscopic mechanical properties. X-ray photon correlation spectroscopy is used to probe nanoparticle dynamics. We rationalize our search for an optimal nanoparticle size (with regards to composite mechanical properties) by using thermogravimetric analysis to determine particle bound layer thickness as a function of particle size. [Preview Abstract] |
Wednesday, March 23, 2011 12:51PM - 1:03PM |
Q42.00009: Preparation and Characterization of Electrospun Poly(Methyl Methacrylate)-QDs NanoComposite Fibers Suying Wei, Jayanthi Sampathi, Dan Rutman, Ashwini Kucknoor, Zhanhu Guo In this talk, we describe the simple electrospinning method to fabricate PMMA-CdSe/ZnS Quantum Dots (QDs) nanocomposite fibers followed by property analysis using a variety of techniques. The parameters that affect the electrospinning process including concentration, feed rate, applied voltage and working distance between the needle tip and the fiber collector are investigated and optimized to acquire uniform and defect-free polymer nanocomposite fibers. The surface morphology of the fiber was characterized by scanning electron microscopy, while the fluorescence emission characteristics were analyzed with fluorescence microscopy. In addition, the PMMA-QDs nanocomposite is thermally more stable than the pristine PMMA fibers as determined by the thermal-gravimetric analysis technique. The glass transition temperature and the melting temperature of the polymer are also altered due to the incorporation of QDs. This can be attributed to the interaction between the included QDs and the polymer structure, as disclosed by the surface analysis techniques attenuated total reflectance-infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS).It showed new vibration bands in the composite fiber in the ATR-IR spectra while the binding energy of both C1s and O1s shifted in their corresponding high-resolution XPS spectra. [Preview Abstract] |
Wednesday, March 23, 2011 1:03PM - 1:15PM |
Q42.00010: Improvement of the dispersion of silica nanoparticles in PMMA Kerem Goren, Osman B. Okan, Limeng Chen, Linda S. Schadler, Rahmi Ozisik Creating well-dispersed polymer nanocomposites is an important part of controlling composite properties. Nanoparticles have been shown to demonstrate quite beneficial electrical and thermo-mechanical properties when they are added to polymers. In the current study, the effects of foaming on de-aggregation of nanoparticles in silica/PMMA nanocomposites are investigated. It was found that the saturation of polymer nanocomposite with supercritical carbon dioxide and subsequent rapid de- pressurization is successful in improving the dispersion of nanoparticles in polymer matrix. In addition, by varying saturation pressure, the degree of dispersion improvement can be controlled. Controlled saturation pressure experiments demonstrated that a decrease in saturation pressure led to decreased improvement of nanoparticle dispersion in polymer matrix. By monitoring the inter-nanoparticle distance using transmission micrographs, a quantitative comparison via radial distribution function (RDF) was constructed for before and after each saturation pressure. [Preview Abstract] |
Wednesday, March 23, 2011 1:15PM - 1:27PM |
Q42.00011: Dispersion of Magnetic Brushes in Polymer Melts Yang Jiao, Pinar Akcora It is now known that polymer grafted amphiphilic spherical silica nanoparticles can self-assemble into anisotropic nanostructures. In this study, we will show how dipolar interactions can affect the self-assembly mechanism of magnetic nanoparticles in polymer composite melts. Hydrophobic iron oxide nanoparticles of 6nm in size are synthesized and then decorated with poly(styrene) by reversible addition fragmentation chain transfer (RAFT) polymerization at various grafting densities and brush lengths. Dispersion of these magnetic brushes are examined in poly(styrene) matrices in TEM. Structures obtained from the balance of attractive dipolar interactions and repulsive forces between polymer chains are investigated. The influence of grafting densities and grafted chain lengths on the dispersion of magnetic nanoparticles and formation of the ``equilibrium'' structures will be discussed. [Preview Abstract] |
Wednesday, March 23, 2011 1:27PM - 1:39PM |
Q42.00012: Modeling nanoparticle aggregation in nanocomposites Tanya Chantawansri, Lee Trask, Eric Cochran, Jan Andzelm A hybrid self-consistent field theory model (H-SCFT) was utilized to model the morphology of nanocomposities composed of cylinder forming ABA triblock copolymer and large nanoparticles (radius on the order of 10 nm). In this system, the size of the nanoparticles is comparable to the cylindrical domains such that nanoparticle segregation into this otherwise compatible phase would cause a significant loss in conformational entropy. To reduce this loss, the nanoparticles could instead macrophase separate out to form aggregates. To capture this particle aggregation in the H-SCFT model, we incorporated a Lennard-Jones potential into the framework. The incorporation of this interaction into the model can significantly alter the observed phase morphology since aggregation can prevent the nanoparticles from swelling and distorting the compatible block copolymer domain. We will demonstrate how the morphology of this nanocomposite varies as a function nanoparticle volume fraction and functionalization. Results will be compared to experimental findings when available. [Preview Abstract] |
Wednesday, March 23, 2011 1:39PM - 1:51PM |
Q42.00013: Effect of Silicon Dioxide Nanoparticles on the Morphology and Interphase Structure of Electrospun PET Nanofibers Qian Ma, Bin Mao, Peggy Cebe Poly(ethylene terephthalate), PET, nanofibers containing silicon dioxide nanoparticles were electrospun from solutions in hexafluoro-2-propanol. Various fill fractions of silicon dioxide nanoparticles in PET were used, ranging from 0-2.0{\%} by weight. The morphologies of both the electrospun (ES) nanofibers and the SiO2 powders were investigated by scanning and transmission electron microscopies. The phase structure of the non-woven, nanofibrous composite mats was investigated with differential scanning calorimetry and real-time wide-angle X-ray scattering. The amount of immobilized layer, the rigid amorphous fraction (RAF), was obtained based on measurement of the specific reversing heat capacity for both as-spun amorphous and isothermally crystallized PET/silica nanocomposite fibers. For the first time, existence of rigid amorphous phase in the absence of crystallinity was verified for electrospun nanocomposite fibers, and two locations of the rigid amorphous fraction are proposed. The effect of interaction between the filler and polymer matrix on the mechanical properties of single fiber is also investigated using atomic force microscopy. [Preview Abstract] |
Wednesday, March 23, 2011 1:51PM - 2:03PM |
Q42.00014: Flexible Polymer Nanocomposite Hydrogen Sensors by Solution Processes Howard Wang, Yayong Liu, Liwei Huang, Kaikun Yang, Lianfeng Zou, Cheol Park Using solution processes such as flow coating and inkjet printing, flexible hydrogen sensors arrays have been fabricated on thin polymer nanocomposite films containing dispersed palladium nanoparticles (Pd-NPs). Composite films were annealed at temperatures from 150 $^{\circ}$C to 200 $^{\circ}$C to allow Pd-NPs to sinter and form a conductive network. An optimal processing temperature is found to yield the most sensitive sensors due to a good balance between the electrical resistance and connectivity of the Pd-NP network. As-fabricated hydrogen sensors can detect a hydrogen level of ca. 200 ppm or lower with a response time of less than 1 second upon the exposure to hydrogen gas, and a recovery time of \textit{ca.} 5 min upon the removal of hydrogen. The sensitivity, repeatability and linearity of sensor arrays are shown to depend on the processing history, the morphology of sensing films, and the geometry of sensor layout. [Preview Abstract] |
Wednesday, March 23, 2011 2:03PM - 2:15PM |
Q42.00015: Thermal Properties of PEO-anatase nanocomposites Mircea Chipara, He Huang, Karen Lozano, David Hui, Xu Hailan, Rafael Villegas, Thomas Mion Polyethylene-oxide (PEO) - anatase composites containing various amounts of anatase ranging between 0 and 20 {\%} wt. have been prepared. The as obtained samples have been investigated by Thermogravimetric Analysis at different heating rates ranging from 5 to 40 K/min. This study was focused on the effect of nanofillers on the activation energy and overall reaction order as well as on the temperature at which the mass loss rate is maxim. The first derivative of the as obtained thermogram has been fitted by using an extended Wigner-Breit-Fano function. The effect of the concentration of anatase nanoparticles on the parameters of the Wigner-Breit-Fano are discussed in detail. Non-isothermal differential scanning calorimetry measurements have been performed in order to determine the effect of anatase nanoparticles on the melting and crystallization of PEO. Isothermal crystallization at various temperatures ranging from 303 to 320 K have been also performed. The study aimed to correlate isothermal crystallization data with non-isothermal results and to determine the effect of anatase nanoparticles on the melting and crystallization of PEO. The crystallization process has been investigated within Avrami and Ozawa approaches. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700