Filled Polymer Nanocomposites Research Articles

Role of interface in highly filled epoxy/BaTiO3 nanocomposites. Part I-correlation between nanoparticle surface chemistry and nanocomposite dielectric property

The interface is critical for the design of polymer nanocomposites with desirable properties. The effect of interface behavior on the properties of polymer nanocomposites with low nanoparticle loading has been well documented. However, our understanding of the role of the interface in highly filled polymer nanocomposites is still limited because of the lack of comprehensive research work. In this contribution, by using BaTiO3 nanoparticles with six kinds of surface chemistry, we have prepared highly filled epoxy nanocomposites (50 vol% nanoparticle loading). The role of nanoparticle surface chemistry on the dielectric properties of epoxy nanocomposites is investigated at a wide frequency and temperature range by using broadband dielectric spectroscopy. Combining the microstructure analysis of the highly filled nanocomposites with a comprehensive X-ray photoelectron spectroscopy characterization of the surface chemistry of the BaTiO3 nanoparticles, an understanding is formed of the correlation between the nanoparticle surface chemistry and the dielectric properties of the nanocomposites. The functional group density, functional group type, and electrical properties of the modifier-the three parameters that are inherent from the nanoparticle surface modification-have a strong impact on the temperature and frequency dependence of the dielectric constant and dielectric loss tangent. This work demonstrates the great importance of surface chemistry in tuning the electrical properties of dielectric polymer nanocomposites.

Molecular dynamics simulation of dispersion and aggregation kinetics of nanorods in polymer nanocomposites

Nowadays, achieving a uniform dispersion of rod-like molecules (like carbon nanotube) in a polymer matrix is still a complicated and unsettled issue in polymer physics and chemical physics. It is very significant to fully understand the effects of deterministic factors on dispersion and aggregation processes of nanorods in the polymer matrix. Here, we adopt a coarse-grained molecular dynamics simulation to investigate the nanorod- filled polymer nanocomposites. It is found that the characteristic relaxation time of the end-to-end vector correlation exhibits an Arrhenius-like temperature-dependent behavior and both the rotational and translational diffusion coefficients have a linear relationship with temperature. By tuning the polymer–nanorod interaction in a wide range, we obtain the spatial organization of nanorods and the best dispersion state at the intermediate interfacial interaction. Meanwhile, we observe that grafting polymer chains on the nanorod surface could promote the dispersion. Moreover, a lower or higher temperature than glassy transition temperature can prevent the nanorod aggregation. The aggregation of nanorods can be significantly accelerated by nanorod–nanorod attraction, while inhibited by cross-linking of polymer chains and external shear fields. In short, by tailoring the deterministic factors above, we can effectively control the dispersion or even spatial organization of one-dimensional nanorods in polymer nanocomposites.

Fracture Toughness of Treated OPEFB Filled Polymer Nanocomposites at Different Clay Loading

Two different clay loadings were added to OPEFB/PP/MAPP which was 7 phr and 10 phr in order to see its effect on the fracture toughness. Standard dimension of samples was prepared for 180 μm, 355 μm and 355 μm treated with 1% NaOH. The result showed that 7 phr clay contents had the highest fracture toughness of 1.16 MPa.m1/2. Alkali treatment on OPEFB fiber gave 7% improvement of fracture toughness for samples with 7 phr PPnanoclay loading. SEM images show the improvement of bonding between the fibers and the matrix upon alkali treatment.

Effects of Oil Palm Empty Fruit Bunch (OPEFB) Fibre Size on Fracture Toughness of OPEFB Filled Polymer Nanocomposite

The effect of oil palm empty fruit bunch (OPEFB) fiber size on the fracture toughness of OPEFB/PP/PPnanoclay composites was investigated. Four fiber sizes ranging from 180 μm, 250 μm, 300 μm, and 355 μm were used to reinforce PP/PPnanoclay composites. The ratio of PP/PPnanoclay was 7:100 by weight (7 phr). Fracture toughness of the composite was determined according to ASTM D5045 and single edge notch bending (SENB) been employed during the test. The result indicates that the fracture toughness of OPEFB/PP/PPnanoclay composites has decreased as OPEFB fiber size increased. Fracture surfaces investigated through the scanning electron microscopy (SEM) showed that the bonding between fiber and matrix for OPEFB/PP/PPnanoclay composites with smaller OPEFB fibre size has better bonding as compared to OPEFB/PP/PPnanoclay composites with larger OPEFB fiber size.

Enhanced electric breakdown strength and high energy density of barium titanate filled polymer nanocomposites

We report improved electric breakdown strength, high energy density, and low dielectric loss of nanocomposites using surface modified BaTiO3 (BT) nanoparticles filling in poly(vinylidene fluoride) polymer matrix. Dielectric and electric breakdown properties of the nanocomposites have been investigated as a function of BT content. The electric breakdown strength of 285 MV/m has been achieved at the nanocomposite with 10 vol. % BT nanoparticles. The results indicate that functionalized and produced passivation layers on the surface of ceramic fillers can improve the homogeneity of the nanocomposites, promote space charge and interface effects, and significantly enhance electric breakdown strength of the nanocomposites.

Enhanced durability of silanized multi-walled carbon nanotube/epoxy nanocomposites under simulated low earth orbit space environment

Silane treated carbon nanotube filled polymer nanocomposites are suggested as a new alternative to reduce the degradation of polymer matrix composites (PMCs) exposed to the low earth orbit (LEO) environment. The silanization of multiwalled carbon nanotubes (MWCNTs) is conducted using 3-aminopropyltriethoxysilane (APTES). Nanocomposites filled with MWCNTs with and without silanization were prepared by the solution mixing method using mechanical/physical approaches to homogeneously disperse the MWCNTs into the polymer matrix. The samples were exposed to an accelerated low earth orbit simulated space environment for 20 h. The synergistic environmental factors used in the ground simulation systems were high vacuum, atomic oxygen (AO), ultraviolet (UV) radiation and thermal cycling. The material properties for nanocomposites reinforced with MWCNTs with and without silanization before and after exposure to the low earth orbit space environment were evaluated by total mass loss (TML), tensile test, thermo-gravimetric analysis (TGA), thermo-mechanical analysis (TMA), and thermo-optical analysis. Surface morphologies of the exposed samples were characterized through scanning electron microscopy (SEM). The results indicated that improvement of the interfacial bonding between the nanotubes and the matrix by the silanization of MWCNTs can considerably reduce the degradation rate and enhance the thermal stability, without sacrificing the thermo-mechanical properties of nanocomposites with very low MWCNT content under LEO space environmental conditions.

Functionalization and Polymerization on the CNT Surfaces

In this review we focus on the current status of using carbon nanotube (CNT) as a filler for polymer nanocomposites. Starting with the historical background of CNT, its distinct properties and the surface functionalization of the nanotube, the three different surface polymerization techniques, namely grafting “from”, “to” and “through/in between” were discussed. Wider focus has been given on “grafting from” surface initiated polymerizations, including atom transfer radical polymerization (ATRP), reversible addition fragmentation chain-transfer (RAFT) Polymerization, nitroxide mediated polymerization (NMP), ring opening polymerization (ROP) and other miscellaneous polymerization methods. The grafting “to” and “through / in between” also discussed and compared with grafting from polymerization. The merits and shortcomings of all three grafting methods were discussed and the bottleneck issue in grafting from method has been highlighted. Furthermore the current and potential future industrial applications were deliberated. Finally the toxicity issue of CNTs in the final product has been reviewed with the limited available literature knowledge. Keywords: Carbon nano tubes, Controlled radical polymerizations, Functionalization, Grafting from, Grafting to, Grafting through, Nanocomposite.

Effect of preliminary compression and uniform shear on the deformation behavior of a filled polymer nanocomposite in orientation stretching

Effect of preliminary compression and uniform shear on the deformation behavior of a filled polymer nanocomposite in orientation stretching

The Experimental and Theoretical Estimation of Interfacial Layer Thickness in Elastomeric Nanocomposites

The interfacial layer thickness and its elasticity modulus were determined experimentally for particulate- filled polymer nanocomposite. It has been found out that elasticity modulus of interfacial layer is 5 times greater than corresponding characteristic for bulk polymer matrix. It has been shown that the theoretical calculation of interfacial layer thickness within the frameworks of fractal model corresponds well to experimental data.

Graphene Oxide Filled Nanocomposite with Novel Electrical and Dielectric Properties

Graphene oxide filled polymer nanocomposites are found to possess excellent nonlinear electrical conductivity, low conductivity at low field and a good combination of increased dielectric constant and low loss factor. Those outstanding electrical properties are achieved at filler loading of 3% and controllable by adjusting the oxidation state of graphene oxide.

Nanocomposite films with enhanced radiometric properties for greenhouse covering applications

Nanocomposite films for covering applications were developed. Mechanical, radiometric and ultraviolet stability properties of the films were characterized. Nanocomposites were obtained by incorporating nanoadditives to a thermoplastic polymer matrix by melt-mixing in a corotating twin screw extruder. Three common polymers in cover applications were used as matrix: low-density polyethylene, linear low-density polyethylene and ethylene–butyl acrylate. Three different nanoparticles were used as fillers (2 wt%): titanium dioxide (rutile), silicon oxide and zinc oxide. All nanocomposites were processed in a blown film extrusion line, producing 200 µm thick films. The mechanical properties of the nanocomposite films were found to be slightly different than those of the neat films, whereby the optical and radiothermal properties changed dramatically. Titania nanocomposite containing films had high ultraviolet shielding, however, significantly reduced transparency. Zinc oxide introduced high ultraviolet-shielding capability preserving transparency. High infrared efficiency has been found in silica nanocomposite films, exhibiting efficiency values greater than 79%, and an increment greater than 100% for linear low-density polyethylene and low-density polyethylene nanocomposite films. The extent of ultraviolet degradation of the films was determined by elongation at break tests. Zinc oxide/low-density polyethylene film underwent less degradation than neat low-density polyethylene film after photoaging. Thus, zinc oxide–filled polymer nanocomposite films are suitable for transparent ultraviolet-shielding applications and present low degradation rates. Silica incorporation highly improves polyethylene infrared efficiency, rendering a low-cost high-thermicity transparent film.

Processing‐structure‐property relationships in solid‐state shear pulverization: Parametric study of specific energy

AbstractSolid‐state shear pulverization (SSSP) is a unique processing technique for mechanochemical modification of polymers, compatibilization of polymer blends, and exfoliation and dispersion of fillers in polymer nanocomposites. A systematic parametric study of the SSSP technique is conducted to elucidate the detailed mechanism of the process and establish the basis for a range of current and future operation scenarios. Using neat, single component polypropylene (PP) as the model material, we varied machine type, screw design, and feed rate to achieve a range of shear and compression applied to the material, which can be quantified through specific energy input (Ep). As a universal processing variable, Ep reflects the level of chain scission occurring in the material, which correlates well to the extent of the physical property changes of the processed PP. Additionally, we compared the operating cost estimates of SSSP and conventional twin screw extrusion to determine the practical viability of SSSP. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Glass Transitions in Highly Attractive Highly Filled Polymer Nanocomposites

Glass Transitions in Highly Attractive Highly Filled Polymer Nanocomposites

Colloidal synthesis of BaF2 nanoparticles and their application as fillers in polymer nanocomposites

Nanoparticles of pure and Eu-doped BaF2 have been prepared through sol-gel colloidal synthesis. In addition, BaF2-filled PMMA polymer nanocomposites were fabricated and dielectric properties were measured. The as-synthesized pure and Eu-doped BaF2 nanoparticles were analyzed by both X-ray diffraction and transmission electron microscopy and consisted of crystalline BaF2 particles with an average diameter of 13.6 nm with a standard deviation of about ±2.4 nm. The photoluminescence properties of the pure and Eu-doped (2%, 4% and 8%) nanoparticles showed characteristic emission of Eu3+ (5D0→7FJ (J=1–4) transitions). We also measured significantly enhanced dielectric breakdown strength of up to 30% for BaF2 nanocomposites over the unfilled PMMA polymer. This study thus offers some promise of sol-gel synthesis of nanocomposite dielectrics with great potential for use as electrical insulation materials in cryogenic high-voltage applications.

Improvement of tensile properties and tuning of the biodegradation behavior of polycaprolactone by addition of electrospun fibers

A novel approach to simultaneously improve the physical mechanical properties and tune the biodegradation of polycaprolactone (PCL)-based composites is presented. The viability of electrospun fibers as fillers for polymer nanocomposites is shown. Nylon was chosen as the reinforcing material, whereas polyvinylpirrolidone (PVP) was selected to calibrate the biodegradation rate. Nylon fibers were effective reinforcing fillers for the PCL matrix, also in co-presence with PVP fibers. PVP fibers were, on the other hand, critical in shaping the biodegradation behavior, because they were able to create channels by which water can easily penetrate within the bulk of the material. The cooperative effect of nylon and PVP fibers allowed to obtain composites able to degrade more quickly than the matrix or than the samples containing either of the two fibers, while retaining a remarkable dimensional stability even after 20% of the total mass had degraded.

Water‐based amorphous carbon nanotubes filled polymer nanocomposites

AbstractA novel method of making water‐based amorphous carbon nanotubes (ACNTs) for advanced polymer nanocomposites is presented. In this approach, sodium dodecyl sulfate (SDS) is introduced onto the amorphous carbon nanotubes to improve the solubility in water and the dispersion in polyvinyl alcohol [PVA] matrix. As a result, the addition of 0.6 wt % ACNTs in the polymer resulted in the significant improvement (167.5 and 175.8%) in the tensile strength and modulus of the polymer, respectively. The improved mechanical property could be ascribed to the load transfer to the nanotubes in the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Characterization of Contact and Bulk Piezoresistive Properties of Carbon Nanotube/Styrene-Butadiene-Styrene Composite

Carbon nanotube (CNT) filled polymer nanocomposites are increasingly regarded as a realistic alternative to conventional smart materials. In this paper, we studied the contact and bulk piezoresistive properties of multi-walled carbon nanotube/styrene butadiene styrene (MWNT/SBS) composite. Measurements of resistance change under pressure utilizing an Au plate PCB electrode and a sputtered Au layer electrode for same samples were implemented to examine bulk piezoresistivity of the composites and the influence of contact resistance. The results showed that the contact resistance responses to stress for separated electrodes are more remarkable than bulk resistance responses in the MWNT/SBS composite films, but not so stable.

Localized In situ Polymerization on Graphene Surfaces for Stabilized Graphene Dispersions

We demonstrate a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets. Graphene sheets show great promise as strong, conductive fillers in polymer nanocomposites; however, difficulties in dispersion quality and interfacial strength between filler and matrix have been a persistent problem for graphene-based nanocomposites, particularly for pristine graphene. With this in mind, a physisorbed polymer layer is used to stabilize graphene sheets in solution. To create this protective layer, we formed an organic microenvironment around dispersed graphene sheets in surfactant solutions, and created a nylon 6, 10 or nylon 6, 6 coating via interfacial polymerization. Technique lies at the intersection of emulsion and admicellar polymerization; a similar technique was originally developed to protect luminescent properties of carbon nanotubes in solution. These coated graphene dispersions are aggregation-resistant and may be reversibly redispersed in water even after freeze-drying. The coated graphene holds promise for a number of applications, including multifunctional graphene-polymer nanocomposites.

Mechanical and Thermal Properties of Polyamide 6 Nanocomposite Toughened with Epoxidised Natural Rubber-25

Polyamide (PA6) is an engineering plastic with wide range of applications and the development in the field of montmorillonite (MMT) filled polymer nanocomposites has resulted in the development of PA6/MMT nanocomposites. However, MMT filled PA6 nanocomposites are notch sensitive and brittle at low temperatures, which posed as a major setback for many of its applications. The main objective of this study is to enhance the toughness of PA6/MMT (100/4) nanocomposites with epoxidised natural rubber-25 (ENR25). The ENR-25 content in the composites ranged from 15 to 30 wt%. The PA6/ENR/MMT nanocomposites were extruded and injection molded into tensile and impact test samples. The addition of ENR25 into PA6/MMT nanocomposites improved the impact strength of the nanocomposites while tensile modulus and tensile strength decreased with increasing ENR25 content. The thermal properties of PA6/ENR/MMT nanocomposites were also investigated via thermal gravimetric analysis (TGA). Both T10% and derivative thermal analysis (DTA) determined the lower thermal stability of PA6/MMT nanocomposites after addition of ENR.

Characterization of systematically selected organo-montmorillonites for polymer nanocomposites

Eight carefully selected organoclays from monoalkyl- to tetraalkylammonium type were prepared from a sodium-saturated < 2 μm fraction of Jelšový Potok bentonite (Slovakia). Four samples contained 1–4 octylammonium chains, from monooctylammonium (1C8) to tetraoctylammonium (4C8). Two cations had chains with 16 carbons each, hexadecylammonium (1C16) and dihexadecyldimethylammonium (2C16). Two cations contained a benzene ring, either without reactive bonds (benzyltrimethylammonium, C10) or with a double bond in 4-vinylbenzyl-trimethylammonium (C12). The d 001 values depended on the size and structure of the organocation. The height of the interlayer space in the 1C8–4C8-Mt series increased from 0.45 to 1.68 nm. 2C8 cation opened the interlayer space more than 1C16; 2C16 was more effective than 4C8. Expansion of only 0.55 nm was obtained with C10 and C12. Mass losses between 150 and 800 °C in N 2 flow were 13–38% for 1C8–4C8-Mt and 40% for 2C16-Mt. Infrared (IR) spectra were similar for 1C8–4C8-Mt but different for the samples with 16 C and 32 C atoms due to altered ratios of CH 3 and CH 2 groups. Downward shift of the CH 2 stretching bands with increasing size of the alkylammonium cation suggest that alkyl chains adopt more ordered structure. The suitability of the prepared materials to be used as fillers for polymer nanocomposites was assessed according to rheological measurements of dispersions in solvents taking solubility parameters as primary factors for comparison of particular solvent and polymer.