Showing papers on "Polymer blend published in 2014"

Highly efficient charge-carrier generation and collection in polymer/polymer blend solar cells with a power conversion efficiency of 5.7%

Abstract: A polymer/polymer blend solar cell with an external quantum efficiency approaching 60% and the best power conversion efficiency of 5.73% is fabricated. The efficient charge-carrier generation and collection, comparable to those of polymer/fullerene solar cells, are found to be the main reasons for the superior device performance.

Designing Multiple-Shape Memory Polymers with Miscible Polymer Blends: Evidence and Origins of a Triple-Shape Memory Effect for Miscible PLLA/PMMA Blends

Abstract: Shape memory properties of polymers represent one of the most expanding fields in polymer science related to numerous smart applications. Recently, multiple-shape memory polymers (multiple-SMPs) have attracted significant attention and can be achieved with complex polymer architectures. Here, miscible PLLA/PMMA blends with broad glass transitions are investigated as an alternative platform to design multiple-SMPs. Dual-shape memory experiments were first conducted at different stretching temperatures to identify the so-called “temperature memory effect”. The switch temperature of the symmetric 50% PLLA/50% PMMA blend smoothly shifted from 70 to 90 °C for stretching temperatures increasing from 65 to 94 °C, attesting for a significant “temperature memory effect”. Asymmetric formulations with 30% and 80% PMMA also present a “temperature memory effect”, but the symmetric blend clearly appeared as the most efficient formulation for multiple-shape memory applications. A programming step designed with two succe...

Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites

Abstract: The present review focuses on summarizing key advances made on controlling polymer blend morphology to improve electrical conductivity in carbon-based polymer composite materials, including those based on carbon black, carbon nanotubes, and graphene. Fundamentals for controlling polymer morphology and the distribution of conductive fillers in various polymer composite systems and the impact on the electrical, rheological, mechanical, and thermal properties are reviewed. The concept of triple percolation and its beneficial effect on electrical conductivity is then reviewed. A high level overview of key theories and mechanisms related to phase morphology, percolation, and conductive properties in polymer composites is provided. POLYM. ENG. SCI., 54:1–16, 2014. © 2013 Society of Plastics Engineers

The impact of Janus nanoparticles on the compatibilization of immiscible polymer blends under technologically relevant conditions

Abstract: Several hundred grams of Janus nanoparticles (d ≈ 40 nm) were synthesized from triblock terpolymers as compatibilizers for blending of technologically relevant polymers, PPE and SAN, on industry-scale extruders. The Janus nanoparticles (JPs) demonstrate superior compatibilization capabilities compared to the corresponding triblock terpolymer, attributed to the combined intrinsic properties, amphiphilicity and the Pickering effect. Straightforward mixing and extrusion protocols yield multiscale blend morphologies with “raspberry-like” structures of JPs-covered PPE phases in a SAN matrix. The JPs densely pack at the blend interface providing the necessary steric repulsion to suppress droplet coagulation during processing. We determine the efficiency of JP-compatibilization by droplet size evaluation and find the smallest average droplet size of d ≈ 300 nm at 10 wt % of added compatibilizer, whereas at 2 wt %, use of JPs is most economic with reasonable small droplets and narrow dispersity. In case of excess...

Novel ABS-based binary and ternary polymer blends for material extrusion 3D printing

Abstract: Material extrusion 3D printing (ME3DP) based on fused deposition modeling (FDM) technology is currently the most commonly used additive manufacturing method. However, ME3DP suffers from a limitation of compatible materials and typically relies upon amorphous thermoplastics, such as acrylonitrile butadiene styrene (ABS). The work presented here demonstrates the development and implementation of binary and ternary polymeric blends for ME3DP. Multiple blends of acrylonitrile butadiene styrene (ABS), styrene ethylene butadiene styrene (SEBS), and ultrahigh molecular weight polyethylene (UHMWPE) were created through a twin screw compounding process to produce novel polymer blends compatible with ME3DP platforms. Mechanical testing and fractography were used to characterize the different physical properties of these new blends. Though the new blends possessed different physical properties, compatibility with ME3DP platforms was maintained. Also, a decrease in surface roughness of a standard test piece was observed for some blends as compared with ABS.

High-Performance All-Polymer Solar Cells Based on Face-On Stacked Polymer Blends with Low Interfacial Tension

Abstract: We report highly efficient all-polymer solar cells with power conversion efficiencies of over 4.5% by highly intermixed blends of PTB7-Th donor and P(NDI2OD-T2) acceptor polymers. The low interfacial tension and the face-on π–π stackings of the all-polymer blends afforded desired nanophase morphology, which facilitates efficient charge transport from the active layer to each electrode. In addition, the incorporation of 1,8-diiodooctane additives was able to tune the degree of crystallinity and orientation of P(NDI2OD-T2) acceptors, resulting in remarkable enhancement of electron mobility, external quantum efficiency, and JSC values.

Conductivity and electrical properties of corn starch-chitosan blend biopolymer electrolyte incorporated with ammonium iodide

Abstract: This work focuses on the characteristics of polymer blend electrolytes based on corn starch and chitosan doped with ammonium iodide (NH4I). The electrolytes were prepared using the solution cast method. A polymer blend comprising 80wt% starch and 20wt% chitosan was found to be the most amorphous blend and suitable to serve as the polymer host. Fourier transform infrared spectroscopy analysis proved the interaction between starch, chitosan and NH4I. The highest room temperature conductivity of (3.04±0.32)◊10 4 Scm 1 was obtained when the polymer host was doped with 40wt% NH4I. This result was further proven by field emission scanning electron microscopy study. All electrolytes were found to obey the Arrhenius rule. Dielectric studies confirm that the electrolytes obeyed non-Debye behavior. The temperature dependence of the power law exponent s for the highest conducting sample follows the quantum mechanical tunneling model.

A study on polymer blend electrolyte based on PVA/PVP with proton salt

Abstract: Proton-conducting polymer blend electrolytes based on PVA–PVP–NH4NO3 were prepared for different compositions by solution cast technique. The prepared films are investigated by different techniques. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR and laser Raman studies confirm the complex formation between the polymer and salt. DSC measurements show decrease in T g with increasing salt concentration. The ionic conductivity of the prepared polymer electrolyte was found by ac impedance spectroscopy analysis. The maximum ionic conductivity was found to be 1.41 × 10−3 S cm−1 at ambient temperature for the composition of 50PVA:50PVP:30 wt% NH4NO3 with low-activation energy 0.29 eV. The conductivity temperature plots are found to follow an Arrhenius nature. The dielectric behavior was analyzed using dielectric permittivity (e*) and the relaxation frequency (τ) was calculated from the loss tangent spectra (tan δ). Using this maximum ionic conducting polymer blend electrolyte, the primary proton battery with configuration Zn + ZnSO4·7H2O/50PVA:50PVP:30 wt% NH4NO3/PbO2 + V2O5 was fabricated and their discharge characteristics studied.

Polymer Nanotubes Nanocomposites: Synthesis, Properties and Applications

Abstract: Preface. 1. Carbon Nanotubes: An Introduction ( V. Mittal ). 1.1 Introduction. 1.2 Properties. 1.3 Synthesis. References. 2. Overview of Polymer Nanotube Nanocomposites ( V. Mittal ). 2.1 Introduction. 2.2 Methods of Nanotube Nanocomposites Synthesis. 2.3 Properties of Polymer Nanotube Nanocomposites. 3. New Microscopy Techniques for a Better Understanding of the Polymer/Nanotube Composite Properties ( K. Masenelli-Varlot, A. Bogner, C. Gauthier, L. Chazeau and J.Y. Cavaille ). 3.1 Introduction. 3.2 Near Field Microscopy. 3.3 Transmission Electron Microscopy. 3.4 Scanning Electron Microscopy. 3.5 Conclusions. 4. Polymer Nanocomposites with Clay and Carbon Nanotubes ( Qiang Fu, Changyu Tang, Hua Oeng and Qin Zhang ). 4.1 Introduction. 4.2 Electrical Properties of Polymer Composites with Clay and CNTs. 4.3 Mechanical Properties of Polymer Composites with Clay and CNTs. 4.4 Thermal and Flame Properties of Polymer Composites with Clay and CNTs. 4.5 Conclusion and Future Outlook. 5. Polyethylene Nanotube Nanocomposites ( S. Kanagaraj ). 5.1 Introduction. 5.2 Surface Modification of Carbon Nanotubes. 5.3 Dispersion of Nanotubes in Polyethylene Matrix. 5.4 Method of Preparation of CNT-PE Composites. 5.5 Interfacial Bonding and Load Transfer. 5.6 Material Characterization. 5.7 Conclusions. 6. Properties of Polyurethane/Carbon Nanotube Nanocomposites ( Tianxi Liu and Shuzhong Guo ). 6.1 Introduction. 6.2 Preparation of CNT-Based Polyurethane Nanocomposites. 6.3 Functionalization, Dispersion Morphology and Micro-/Nano-structures. 6.4 Physical Properties. 6.5 Applications. 6.6 Conclusions. 7. Properties of PMMA/Carbon Nanotubes Nanocomposites ( R.B. Mathur, Shailaja Pande and B.P. Singh ). 7.1 Introduction. 7.2 Fabrication/Processing of CNT-PMM A Composites. 7.3 Mechanical Properties of CNT-PMMA Composites. 7.4 Electrical Properties of CNT-PMMA Composites. 7.5 Thermal Properties. 7.6 Conclusion. 8. Synthesis of Vinyl Polymer/Carbon Nanotube Nanocomposites Prepared by Suspension Polymerization and Their Properties ( P. Slobodian ). 8.1 Introduction. 8.2 Free Radical Polymerization. 8.3 Suspension and Bulk Polymerization Techniques. 8.4 In-situ Radical Polymerization in Presence of CNT. 8.5 Polymer/CNT Composite Microspheres. 8.6 Electrorheology of Polymer/CNT Nanocomposites Prepared by in-situ Suspension Polymerization. 9. Polylactide-Based Carbon Nanotube Nanocomposites ( Srikanth Pilla, Shaoqin Gong and Lih-Sheng Turng ). 9.1 Introduction. 9.2 Synthesis of PLA. 9.3 Carbon Nanotubes. 9.4 Preparation of PLA-CNT Nanocomposites. 9.5 Viscoelastic Properties. 9.6 Thermal Properties. 9.7 Mechanical Properties. 9.8 Thermal Degradation Properties. 9.9 Electrical Conductivity Properties. 9.10 Biodegradability. 9.11 Applications. 9.12 Conclusions. 10. Synthesis and Properties of PEEK/Carbon Nanotube Nanocomposites ( A.M. Diez-Pascual, J.M. Gonzalez-Dominguez, Y. Marttnez-Rubi, M. Naffakh, A. Anson, M.T. Martinez, B. Simara ana M.A. Gomez ). 10.1 Introduction. 10.2 Poly(ether ether ketone)s: Structure, Synthesis and Properties. 10.3 Synthesis, Purification and Characterization of the SWCNTs. 10.4 Integration of the Carbon Nanotubes in the PEEK Matrix. 10.5 Characterization of PEEK/Carbon Nanotube Nanocomposites. 10.6 Concluding Remarks. 11. Synthesis and Properties of PVA/Carbon Nanotube Nanocomposites (C. Mercader, P. Poulin and C. Zakri ). 11.1 Introduction. 11.2 Synthesis Methods and Structural Properties of Nanotubes / PVA Composites. 11.3 Mechanical Properties of the Composites. 11.4 Electrical Properties. 11.5 Other Original Properties of PVA/Nanotube Composites. 11.6 Conclusion. 12. Elastomers Filled with Carbon Nanotubes ( Liliane Bokobza ). 12.1 Introduction. 12.2 Composite Processing. 12.3 Electrical Properties. 12.4 Mechanical Properties. 12.5 Spectroscopic Characterization. 12.6 Thermal Stability. 12.7 Conclusions. 13. Specific Interactions Induced Controlled Dispersion of Multiwall Carbon Nanotubes in Co-Continuous Polymer Blends ( Suryasarathi Bose, Arup R. Bhattacharyya, Rupesh A. Khare and Ajit R. Kulkarni ). 13.1 Introduction. 13.2 Experimental. 13.3 Results and Discussion. 13.4 Summary. 14. Effect of Structure and Morphology on the Tensile Properties of Polymer/Carbon Nanotube Nanocomposites ( Jtngjing Qiu and Shiren Wang ). 14.1 Background. 14.2 Structure and Morphology Characterization. 14.3 Concluding Remarks. 15. Polymer Nanotube Composites: Promises and Current Challenges ( Atnal M.K. Esawi and Mahmoud M. Farag ). 15.1 Carbon Nanotubes. 15.2 Case Studies. 15.3 Conclusions. References. Index.

Crystallization features of normal alkanes in confined geometry.

Abstract: How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials. The confined geometry is closely related to both the phase metastability and lifetime of polymer. This affects the phase miscibility, microphase separation, and crystallization behaviors and determines both the performance of polymer materials and how easily these materials can be processed. Furthermore, the size effect of metastable states needs to be clarified in polymers. However, scientists find it difficult to propose a quantitative formula to describe the transition dynamics of metastable states in these complex systems. Normal alkanes [CnH2n+2, n-alkanes], especially linear saturated hydrocarbons, can provide a well-defined model system for studying the complex crystallization behaviors of polymer materials, surfactants, and lipids. Therefore, a deeper investigation of normal alkane phase behavior in confinement will help scientists to understand the crystalline phase transition and ultimate properties of many polymeric materials, especially polyolefins. In this Account, we provide an in-depth look at the research concerning the confined crystallization behavior of n-alkanes and binary mixtures in microcapsules by our laboratory and others. Since 2006, our group has developed a technique for synthesizing nearly monodispersed n-alkane containing microcapsules with controllable size and surface porous morphology. We applied an in situ polymerization method, using melamine-formaldehyde resin as shell material and nonionic surfactants as emulsifiers. The solid shell of microcapsules can provide a stable three-dimensional (3-D) confining environment. We have studied multiple parameters of these microencapsulated n-alkanes, including surface freezing, metastability of the rotator phase, and the phase separation behaviors of n-alkane mixtures using differential scanning calorimetry (DSC), temperature-dependent X-ray diffraction (XRD), and variable-temperature solid-state nuclear magnetic resonance (NMR). Our investigations revealed new direct evidence for the existence of surface freezing in microencapsulated n-alkanes. By examining the differences among chain packing and nucleation kinetics between bulk alkane solid solutions and their microencapsulated counterparts, we also discovered a mechanism responsible for the formation of a new metastable bulk phase. In addition, we found that confinement suppresses lamellar ordering and longitudinal diffusion, which play an important role in stabilizing the binary n-alkane solid solution in microcapsules. Our work also provided new insights into the phase separation of other mixed system, such as waxes, lipids, and polymer blends in confined geometry. These works provide a profound understanding of the relationship between molecular structure and material properties in the context of crystallization and therefore advance our ability to improve applications incorporating polymeric and molecular materials.

α-Fe2O3 /(PVA + PEG) Nanocomposite films; synthesis, optical, and dielectric characterizations

Abstract: Hematite (α-Fe2O3) nanorods with an average diameter of 40 nm were prepared using a template-free sol–gel method. These nanorods then mixed with polyvinyl alcohol (PVA)/polyethylene glycol (PEG) blend at concentrations of 0.0, 0.5, and 1.0 wt.%. The transmittance percentage (T%) of the films showed a decrease from 80.26 to 33.24 %. The direct optical band gap also decreased from 5.28 to 4.83 eV whereas the refractive index significantly increased with increasing the hematite content. The dielectric measurements were performed in the temperature range 303–413 K and frequency range 30 kHz–3.0 MHz. According to the temperature dependence of the dielectric constant (e’), α a -relaxation peaks observed in all films and assigned to the micro-Brownian motion of the polymer blend chains. The behavior of the ac conductivity, σ ac (f), of the nanocomposite films indicated that the homogenous distribution of α-Fe2O3 nanorods allows the formation of conductive three-dimensional networks throughout the nanocomposite film. Also, indicated that the correlated barrier hopping is the most suitable conduction mechanism.

Cellulose nanocrystals/ZnO as a bifunctional reinforcing nanocomposite for poly (vinyl alcohol)/chitosan blend films: fabrication, characterization and properties

Abstract: In this study, cellulose nanocrystals/zinc oxide (CNCs/ZnO) nanocomposites were dispersed as bifunctional nano-sized fillers into poly(vinyl alcohol) (PVA) and chitosan (Cs) blend by a solvent casting method to prepare PVA/Cs/CNCs/ZnO bio-nanocomposites films. The morphology, thermal, mechanical and UV-vis absorption properties, as well antimicrobial effects of the bio-nanocomposite films were investigated. It demonstrated that CNCs/ZnO were compatible with PVA/Cs and dispersed homogeneously in the polymer blend matrix. CNCs/ZnO improved tensile strength and modulus of PVA/Cs significantly. Tensile strength and modulus of bio-nanocomposite films increased from 55.0 to 153.2 MPa and from 395 to 932 MPa, respectively with increasing nano-sized filler amount from 0 to 5.0 wt %. The thermal stability of PVA/Cs was also enhanced at 1.0 wt % CNCs/ZnO loading. UV light can be efficiently absorbed by incorporating ZnO nanoparticles into a PVA/Cs matrix, signifying that these bio-nanocomposite films show good UV-shielding effects. Moreover, the biocomposites films showed antibacterial activity toward the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The improved physical properties obtained by incorporating CNCs/ZnO can be useful in variety uses.

Manipulating dispersion and distribution of graphene in PLA through novel interface engineering for improved conductive properties.

Abstract: This study aimed to enhance the conductive properties of PLA nanocomposite by controlling the dispersion and distribution of graphene within the minor phase of the polymer blend. Functionalized graphene (f-GO) was achieved by reacting graphene oxide (GO) with various silanes under the aid of an ionic liquid. Ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer elastomer (EBA-GMA) was introduced as the minor phase to tailor the interface of matrix/graphene through reactive compatibilization. GO particles were predominantly dispersed in PLA in a self-agglomerating pattern, while f-GO was preferentially located in the introduced rubber phase or at the PLA/EBA-GMA interfaces through the formation of the three-dimensional percolated structures, especially for these functionalized graphene with reactive groups. The selective localization of the f-GO also played a crucial role in stabilizing and improving the phase morphology of the PLA blend through reducing the interfacial tension between two phases. The...

Towards tunable resistivity–strain behavior through construction of oriented and selectively distributed conductive networks in conductive polymer composites

Abstract: The resistivity–strain behavior of conductive polymer composites (CPCs) has gained intense interest due to its importance for various applications. The resistivity of CPCs often increases substantially and linearly under strain. To achieve constant resistivity under strain, a large filler content and special network configuration are often required. And a tunable step-wise resistivity–strain behavior has yet to be reported. Herein, a new method combining polymer blends and pre-stretching is introduced to modify the resistivity–strain behavior of CPCs based on thermoplastic polyurethane (TPU)/polyolefin elastomer (POE) with multi-walled carbon nanotubes (MWCNTs) selectively incorporated in the TPU phase. Depending on the compositions of blends and the intensity of pre-stretching, various interesting resistivity–strain behaviors have been achieved. The resistivity can be either linearly increasing or constant. Interestingly, two-stepwise resistivity–strain behavior has been achieved, with first an increase then a constant value. To understand this unique phenomenon, the phase morphology and conductive network structure are systematically characterized. It is observed that the orientation of MWCNTs is strongly correlated with overall resistivity. Finally, a mechanism involving fibrillization and “slippage” between conductive phases is proposed to explain the resistivity–strain dependency. This study provides guidelines for the preparation of high performance strain sensors as well as stretchable conductors.

Structural characterization of hydrophilic polymer blends/montmorillonite clay nanocomposites

Abstract: The nanocomposite films comprising polymer blends of poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), poly(ethylene oxide) (PEO), and poly(ethylene glycol) (PEG) with montmorillonite (MMT) clay as nanofiller were prepared by aqueous solution casting method. The X-ray diffraction studies of the PVA–x wt % MMT, (PVA–PVP)–x wt % MMT, (PVA–PEO)–x wt % MMT and (PVA–PEG)–x wt % MMT nanocomposites containing MMT concentrations x = 1, 2, 3, 5 and 10 wt % of the polymer weight were carried out in the angular range (2θ) of 3.8–30°. The values of MMT basal spacing d001, expansion of clay gallery width Wcg, d-spacing of polymer spherulite, crystallite size L and diffraction peak intensity I were determined for these nanocomposites. The values of structural parameters reveal that the linear chain PEO and PEG in the PVA blend based nanocomposites promote the amount of MMT intercalated structures, and these structures are found relatively higher for the (PVA–PEO)–x wt % MMT nanocomposites. It is observed that the presence of bulky ester-side group in PVP backbone restricts its intercalation, whereas the adsorption behavior of PVP on the MMT nanosheets mainly results the MMT exfoliated structures in the (PVA–PVP)–x wt % MMT nanocomposites. The crystallinities of the PEO and PEG were found low due to their blending with PVA, which further decreased anomalously with the increase of MMT concentration in the nanocomposites. The decrease of polymer crystalline phase of these materials confirmed their suitability in preparation of novel solid polymer nanocomposite electrolytes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40617.

PLA maleation: an easy and effective method to modify the properties of PLA/PCL immiscible blends

Abstract: In this study, maleic-anhydride-grafted polylactide (PLA-g-MA) was investigated as a potential compatibilizing agent for the polylactide (PLA)/poly(e-caprolactone) (PCL) system, with the aim of enhancing the final properties of the two polymer blends. Indeed, PLA-g-MA was prepared via reactive blending through a free radical process and characterized by means of 1H-NMR and titration measurements, which demonstrated that the employed procedure allows grafting 0.7 wt% of MA onto the polymer backbone, while avoiding a dramatic reduction of PLA molecular mass. The specific effect of the MA-grafted PLA on the features of the PLA/PCL system was highlighted by adding different amounts of PLA-g-MA to 70:30 (w/w) PLA/PCL blends, where the 70 % PLA component was progressively substituted by its maleated modification. The efficiency of PLA-g-MA as a compatibilizer for the PLA/PCL blends was assessed through SEM analysis, which showed that the dimensions of PCL domains decrease and their adhesion to PLA improves by increasing the amount of PLA-g-MA in the blends. The peculiar microstructure promoted by the presence of PLA-g-MA was found to enhance the mechanical properties of the blend, improving the elongation at break without decreasing its Young’s modulus. Our study demonstrated that not only the microstructure but also the thermal properties of the blends were significantly affected by the replacement of PLA with PLA-g-MA.