Non-polar Matrix Research Articles

Conducting Graphite/Cellulose Composite Film as a Candidate for Chemical Vapor-Sensing Material

A type of conductive graphite/cellulose composite film used for chemical vapor-sensing material was prepared at room temperature in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIm]Cl). Graphite was pretreated with both oxidation and reduction processes. Due to the use of N,N-carbonyldiimidazole (CDI), as a covalent cross-linking agent in [BMIm]Cl, there were limited chemical bonds between the graphite and cellulose. The composite film was analyzed using Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XRD). When these conducting films were exposed to certain organic vapors, their electrical resistances quickly changed, showing gas sensitivity. The percolation threshold of the conducting film was about 5 wt%. The gas-sensing behavior of these films in solvent were the opposite of those gas-sensing materials based on a non-polar polymer matrix. A typical negative vapor coefficient (NVC) was observed when the film was placed in polar organic solvents such as methanol, ethanol, and acetone.

Acetylation and stepwise solvent-exchange to modify hydrophilic cellulose whiskers to polychloroprene-compatible nanofiller

The acetylation of cellulose nanofiber (CNF) introduced hydrophobicity to the surface making it compatible with non-polar matrix, and also making it an effective nanofiller for polychloroprene (PCR) composite. The CNF was extracted from oil palm empty fruit bunches. Previously, CNF was dispersed in water, and this water was subsequently substituted with N,N-dimethylacetamide, in which CNF was acetylated by acetic anhydride with a pyridine catalyst. IR spectroscopy revealed that the acetylation extent was controllable by the reaction time. After the reaction, the DMAc was replaced by dichloromethane, and finally mixed with PCR. The CNF–PCR mixture was cast and composite film was formed at room temperature. Structural analysis and mechanical tests indicated that acetylation treatment made CNF compatible with PCR, and that nano-dispersed CNF raised the mechanical strength of the PCR–CNF nanocomposite.

Enhancing the Tunability of the Open-Circuit Voltage of Hybrid Photovoltaics with Mixed Molecular Monolayers

The alignment between the energy levels of the constituents of an organic solar cell plays a central role in determining the open-circuit voltage. However, tuning the energy levels of electrodes and/or active components via molecular modifiers placed at interfaces is not straightforward. The morphology of organic materials is commonly controlled by the substrate onto which they are deposited, and differences in morphology often lead to differences in energetics. Such a change in morphology may reduce the effect of surface modifications, as the modified surface is part of an interface with the organic material. Here we show, in an experimental model system, that by using binary molecular monolayers, in which dipolar molecules are buried in a protective nonpolar matrix, we can transform changes in the electrode surface dipole into interface dipole changes without significantly affecting the growth of pentacene onto the molecular layer, thus enabling the use of the full range of dipolar-induced open-circuit-voltage tuning.

Effective and Reusable Monolith Capillary Trap of Nitrosamine Extraction by Superheated Water from Frankfurter Sausage

A novel, simple, rapid, and inexpensive method of extraction and cleanup of nitrosamines from frankfurter sausage was achieved with a capillary filled with monolith of either polystyrene-co-divinylbenzene (PS-DVB), Polydivinylbenzene (P-DVB), or silica that had been fabricated. The study of capability in trapping nonpolar matrix and monolith capillaries with varied lengths revealed that a silica monolith gave the best result for nitrosamine determination. With an online coupling between superheated water extraction (SWE) and silica monolith capillary connected to a 5% phenyl-methylpolysiloxane column, factors affecting the extraction and determination, namely, sensitivity with and without the monolith, reusability, injection-injection repeatability, capillary-capillary precision, and chromatographic separation, were investigated. This confirmed the feasibility of the method. The optimal length of silica monolith capillary was 30 mm, offering reuse more than 20 times. Separation and quantification of selected volatile nitrosamines were carried out using gas chromatography (GC) coupled with either a flame ionization detector (FID) or mass spectrometer (MS). The overall extraction and determination method determined by GC-MS allowed for a recovery of 75-88% with a <5% relative standard deviation (RSD) and detection limit of 2-5 ng of injected nitrosamine.

Morphological Trends in Precise Acid- and Ion-Containing Polyethylenes at Elevated Temperature

The morphologies at elevated temperatures (T > Tg, Tm) of 12 precise, polyethylene (PE)-based copolymers with acrylic acid (AA), phosphonic acid (PA), and 1-methylimidazolium bromide (ImBr) groups were studied via X-ray scattering. These precise copolymers enable direct comparisons focusing on the length of the spacer between the functional groups and the type of functional group. The polar groups in these materials self-assemble into microphase-separated aggregates dispersed throughout the nonpolar PE matrix. At high temperatures the PE segments are amorphous, such that the aggregates are distributed in a liquid-like manner in 11 of these precise copolymers. The correlation distances between aggregates increase with the following: carbon spacer length between pendant groups, size and volume fraction of the pendant species, and functional group configuration (single vs geminal substitution). In addition, comparisons are made between precise copolymers and pseudorandom copolymers of the same pendant concen...

Investigation of strontium ferrite activity in different rubber matrices

The goal of the present work was to study the preparation and properties of rubber magnetic composites and investigation of strontium ferrite activity in examined materials. Three types of rubber matrices, namely butadiene rubber as non-polar elastomeric matrix, nitrile butadiene rubber (NBR) and NBR/poly(vinyl chloride) blend as polar elastomeric matrices, were compounded with strontium ferrite and other additives in order to prepare rubber magnetic composites. Ferrite dosage was given in modified and unmodified forms in concentration scale ranging from 0 to 100 phr. The influence of magnetic filler content on the mechanical properties of composites was investigated. Correlation between Wolf activity coefficient and Payne effect in relation to the mechanical properties of tested systems was discussed. The results revealed that the observed characteristics are dependent on the type of rubber matrix and also on the type of ferrite.

Effect of acetylation and additive on the tensile properties of wood fiber–high-density polyethylene composite

The wood plastic composites studied in this work are composed of high-density polyethylene matrix and Pinus pinaster wood fibers. Despite some interesting intrinsic properties, this wood plastic composite has limited mechanical properties because of the incompatibility between the polar hydrophilic fibers and the non-polar hydrophobic matrix. In this study, the effects of maleic anhydride-modified polyethylene additive, of carbon chains grafted by acetylation and of wood fiber contents on the tensile mechanical properties of the wood plastic composite were studied. Tensile tests were carried out using digital image correlation as an intrusiveness and robust method for strain measurements. Results showed first that the addition of wood fibers made the wood plastic composite stiffer but less flexible. Acetylation improved the interfacial adhesion properties: the Young modulus was increased and a lower strain at failure was reported. The coupling agent also increased the compatibility but mainly in the case where there was no grafted chain. With regard to the carbon chains, the number of grafts improved the elastic properties while their length did not appear to have any influence. Finally, a scanning electron microscope was used to characterize the post-mortem morphology of the fracture surfaces, the results of which supported the observations obtained from the tensile mechanical properties.

Thermal stability of surface-esterified cellulose and its composite with polyolefinic matrix

Thermal stability of hydrophobized cellulose powders was investigated from the perspective of potential use as filler in non-polar polyolefinic matrix. The hydrophobization was done by heterogeneous esterification with three carboxylic acids which differ in chain length (3, 10 and 18 carbons). Data measured by means of thermogravimetry (TG) were recalculated according to model-free isoconversional method to construct time–temperature plots. It was demonstrated that the esterification significantly decreases thermal stability of the material, which reduces feasible processing window. Under non-oxidative atmosphere, the single-step decomposition of materials is prevailing, while the process is more complex in air. In both cases the oleic acid esters showed the lowest stability and the original cellulose was the most stable. Finally, all powders were compounded with polyethylene or polypropylene. Obtained composites were then subjected to color measurement and TG. Even though the materials were partly degraded, which was indicated by the yellowish hue of the composites, virtually no impact of the filler pyrolysis on the polymer matrix decomposition was observed, particularly in case of decanoyl esters.

Improving the Capacity of Polypropylene To Be Used in Antioxidant Active Films: Incorporation of Plasticizer and Natural Antioxidants

Two types of active antioxidant food packages with improved release properties, based on polypropylene (PP) as one of the most common polymers used in food-packaging applications, were developed. Incorporation of catechin and green tea as antioxidant provided PP with 6 times higher stabilization against thermal oxidation. Release of natural antioxidants (catechins, gallic acid, caffeine, and quercetin) into various food simulants from that nonpolar matrix were improved by blending poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PPG-PEG-PPG) as plasticizer into the polymer formulation. Increasing release levels between 10- and 40-fold into simulant A and between 6 and 20-fold into simulant D1 resulted from the incorporation of catechin and green tea as antioxidants and PPG-PEG-PPG as plasticizer into the film formulation. The efficiency of the antioxidants in the food simulants after the release process was also corroborated through antioxidant activity tests. Therefore, the developed PPG-PEG-PPG-modified polypropylene resulted in a potential system to be used in active packaging.

Preparation and Properties of α-Cellulose Short Fiber-Reinforced Poly(lactic Acid) Composites

The objective of this study is to fabricate the PLA/α-cellulose composites and to investigate the effect of α-cellulose short fibers on the toughness improvement of PLA. To homogeneously disperse the polar α-cellulose in the non-polar PLA matrix, the as-received α-cellulose was subjected to surface modification using stearic acid to impart the hydrophobic characteristics to the short fibers. The α-cellulose fibers dispersed more homogeneously in PLA through this modification, and consequently, the fiber pull-out and longer micro-crack length could improve the toughness and damping property of the resulting PLA composites. The inclusion of α-cellulose short fibers considerably decreased the spherulite dimension of the PLA/α-cellulose composites to accommodate larger deformation through grain boundary sliding. The PLA/α-cellulose composite improved its toughness by three times that of the neat PLA with low α-cellulose content (∼4 wt.%), and maintained its transparency.

Properties and nanoscale structure of polypropylene‐layered double hydroxide composites prepared by compatibilizer‐free way

ABSTRACTPolypropylene (PP) is the second most widespread commodity polyolefin. Even a small quantity of inorganic component is sufficient to achieve significant improvement of stiffness, strength, thermal stability, biodegradability, etc. The major drawback of inorgano‐organic composite materials is insufficient compatibility of the PP matrix with inorganic filler. A suitable choice of the layered double hydroxide‐modifying anion opens a possibility to obtain PP‐inorganic nanocomposites without a need to use compatibilizers like maleic anhydride grafted PP. The nanocomposites were prepared by melt blending in a twin‐screw mini‐extruder and characterized by dynamic mechanical thermal analysis, and electron microscopy. Nonpolar PP matrix mix uniformly with clay organophilized with functionalized surfactant acids, giving rise to composites with improved thermo‐mechanical properties. Influences of the anionic modifier and the filler content (2 or 5% w/w) on mechanical properties and nanoscale structure of the composites are discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2429–2438, 2013

Use of new synthetic talc as reinforcing nanofillers for polypropylene and polyamide 6 systems: Thermal and mechanical properties

New layered synthetic nanotalc prepared at a lab-scale by a conventional hydrothermal process and commercial natural fine talc were used in order to establish a comparative study in terms of their contributions on the improvement of the final properties of two different polymers: a nonpolar polyolefin matrix and a polyamide. All samples were prepared by melt extrusion in a co-rotating microcompounder. The surface properties of talc – surface energy and isoelectric point – were probed. The particles’ crystalline structure and the distribution/dispersion within the polymer matrix were performed using transmission electron microscopy and X-ray diffraction. The effect of talc particles on the crystallinity, the thermal and mechanical properties was highlighted as a function of the surface properties of talc. In the case of talc-filled PP systems, it seems that the incorporation of both natural and synthetic talc greatly improves the thermal stability of polypropylene matrix. The highest elastic modulus was obtained in presence of highly nucleating natural talc. Oppositely, the best ductility was observed for the synthetic talc-filled PP systems. For PA6/talc nanocomposites, a remarkable improvement in the dispersion of talc layers was shown and a significant increase in Young’s modulus was determined due to the closer affinity between the hydrophilic nanotalc lamellae and the polar PA6 matrix.

Anisotropic local correlations and dynamics in a relaxor ferroelectric.

Relaxor ferroelectrics have been a focus of intense attention due to their anomalous properties, and understanding the structure and dynamics of relaxors has been one of the long-standing challenges in solid-state physics. We investigate the local structure and dynamics in 75%PbMg(1/3)Nb(2/3)O(3)-25%PbTiO(3) using molecular dynamics simulations and the dynamic pair distribution function technique. We show that relaxor transitions can be described by local order parameters. The relaxor phase is characterized by the presence of highly anisotropic correlations between the local cation displacements that resemble the hydrogen bond network in water. This contradicts the current model of polar nanoregion inside a nonpolar matrix. We therefore suggest a new model of a homogeneous random network of anisotropically coupled dipoles.

Development of modified expanded graphite-filled solution polymerized styrene butadiene rubber vulcanizates in the presence and absence of carbon black

Expanded graphite (EG) consists of a huge number of partially exfoliated graphite sheets with the thickness of most of the sheets in the nanometer range. This study analyses the effect of EG and modified EG (MEG) on the mechanical, thermal, and dynamic mechanical properties of solution styrene butadiene rubber (SSBR) with and without carbon black (CB). The surface of the EG was modified to enhance its dispersion in the SSBR matrix. In addition, oil-extended carboxylated styrene butadiene rubber (XSBR) was used as a compatibilizer to disperse MEG in the base nonpolar SSBR matrix. XSBR/MEG nanocomposites have been prepared by solution mixing. The obtained nanocomposites were incorporated into the SSBR matrix in the presence of CB by melt blending. Morphological properties of the nanocomposites revealed intercalation of MEG sheets in the SSBR matrix. Nanocomposites containing MEG in the presence of CB show improvement in mechanical, thermal, and dynamic mechanical properties. POLYM. ENG. SCI., 54:33–41, 2014. © 2013 Society of Plastics Engineers

Compatibilized ethylene-propylene-diene terpolymer nanocomposites containing different type of organoclays

Summary — The simple mixing of non-polar rubber and organically modified nanoclay may not lead to good dispersion of organoclay in the rubber matrix, which is due to the incompatibility between the rubber and the filler. Thus, the application of polar compatibilizer which is compatible with both the gum base and organically modified clay may help to increase the reinforcing efficiency of the organoclay. Oil extended carboxylated styrene-butadiene rubber (XSBR) was used as a compatibilizer for the dispersion of the organically modified clay (Cloisite 15A, Cloisite 20A and Cloisite 30B) in the ethylene-propylene-diene terpolymer (EPDM) matrix. The degree of dispersion of organoclays in non-polar EPDM matrix after application of polar compatibilizer as well as the influence of these organoclays on the properties of nanocomposites based on EPDM were analyzed in this study. The microstructure of the organoclay filled EPDM composites was studied by wide angle X-ray diffraction (WAXD) method and high resolution transmission electron microscopic (HR-TEM) analysis. Dynamic mechanical thermal analysis (DMTA), scanning electron microscopic (SEM) analysis, thermogravimetric analysis (TGA) and curing tests were conducted for each nanocomposite. Cloisite 30B filled EPDM composite showed best thermal, mechanical and dynamic mechanical properties compared to all other investigated nanocomposites.

Development of nanoscale polarization fluctuations in relaxor-based (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3ferroelectrics studied by Brillouin scattering

The precursor dynamics of ferroelectric phase transitions in relaxor-based ferroelectric ($1\ensuremath{-}x$)Pb(Zn${}_{1/3}$Nb${}_{2/3}$)O${}_{3}$-$x$PbTiO${}_{3}$ single crystals, with $x=0.07$, 0.10, and 0.12, were investigated using inelastic light scattering from a longitudinal acoustic phonon. An acoustic anomaly in a broad temperature range, which is characteristic of relaxor ferroelectrics, was observed. We describe the anomalies in the paraelectric phase by assuming local piezoelectric coupling inside polar nanoregions, which are surrounded by a nonpolar matrix. On the basis of local piezoelectric coupling, a relaxation time $\ensuremath{\tau}$ and a dynamic characteristic length $L$ of the order-parameter (polarization) fluctuations were determined to be in the order of 10${}^{\ensuremath{-}13}$ s and 10${}^{\ensuremath{-}9}$ m, respectively. The $\ensuremath{\tau}$ and $L$ values increase sharply upon cooling from high temperatures but more gradually below the intermediate temperature ${T}^{*}$ ($=493\ensuremath{-}510\phantom{\rule{0.28em}{0ex}}\mathrm{K}$). This result implies that the local polarization fluctuations grow rapidly upon cooling down to above ${T}^{*}$ and the growth rate decreases below ${T}^{*}$. The inflexion point of this growth process in the paraelectric phase is related to the characteristic properties of relaxor-based solid solutions.

Development of polyimide–nanosilica filled EPDM based light rocket motor insulator compound: Influence of polyimide–nanosilica loading on thermal, ablation, and mechanical properties

Thermal protection materials are necessary to protect structural components of launch vehicles during lift-off of launching system. The present study deals with the development of a novel thermally protected light rocket motor insulator compound (RMIC) of polyimide–silica filled EPDM nanocomposites. The insulation compound prepared for the studies comprised of aromatic polyimide and nanosilica particles. The addition of these materials in rocket insulator compound enhanced the multifunctional thermal and insulation characteristics. EPDM when grafted with maleic anhydride, contributed polarity in the non-polar EPDM matrix. Nanosilica contributes specifically better erosion resistance. SEM and TEM micrograph of EPDM nanocomposites exhibits good dispersion of nanosilica in polyimide–EPDM matrix. Nanocomposite formation was characterised by FTIR. Density, co-efficient of thermal expansion, thermal conductivity, ablation rate, specific heat, maximum thermal degradation, char yield and mechanical properties of the RMIC have been measured. This developmental study may find wide scope for commercial exploitation.

Influence of gamma radiation on compatibilized LLDPE/magnesium hydroxide/sepiolite composites

AbstractThe influence of gamma irradiation on the properties of compatibilized linear low‐density polyethylene/magnesium hydroxide (MH)/sepiolite composites has been investigated. Vinyl triethoxy silane and maleated polyethylene have been used as compatibilizers. The compatibilizing effect in the composites is confirmed by the Fourier transform infrared spectra, which showed the presence of additional chemical bonds, which are responsible for the enhanced polymer‐filler interaction. As a result, the miscibility of the polar additives into the nonpolar polymer matrix is enhanced. The scanning electron micrographs revealed that the additives are well embedded and uniformly dispersed in the polymer matrix without any voids. The known thermal decomposition temperature of MH (∼ 350°C) is also increased in the compatibilized composites. In addition, 150 kGy irradiated composite showed a remarkable improvement of 37°C in the onset degradation temperature of unirradiated composite. Furthermore, the formation of radiation crosslinked structure in the composites also improved the mechanical properties of the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Dielectric inspection of BaZr0.2Ti0.8O3 ceramics under bias electric field: A survey of polar nano-regions

The structure and dielectric properties of BaZr0.2Ti0.8O3 ceramics prepared by citrate method were investigated. Structural analysis of the ceramics indicated a cubic perovskite structure and a fine-grained (about 250nm) microstructure. The ceramics displayed a frequency dispersion of the dielectric loss and a slim polarization versus electric field (P–E) hysteresis loop. These results were related to the existence of polar nano-regions (PNRs) embedded in the non-polar matrix of the ceramics. The nonlinear dielectric properties under bias electric field were found to be dependent on holding time of applied bias field. The phenomenon was qualitatively explained with polarization reorientation of PNRs under the bias field. Fitting the dielectric constants under the bias field to a multipolarization mechanism model resolved the contribution of PNRs from the overall dielectric response. From the fitting, the polarization and size of PNRs in the ceramics were determined to be around 0.4μC/cm2 and 9nm, respectively.

Experimental and theoretical study on time dependence of the quasi-piezoelectric d33 coefficients of cellular piezoelectret film

The voided charged polymer film, also called piezoelectret, has a very large quasi-piezoelectric coefficient in the thickness direction, and has emerged as a new kind of electromechanical transducer materials. Piezoelectret film is usually prepared from polymer by means of biaxial stretching and electric charging process. Due to the inherent viscosity of polymer, the quasi-piezoelectric d33 coefficient of cellular piezoelectret film usually depends on the pressure and time of the measurement. In this article, experiments were carried out on the time spectra of quasi-piezoelectric d33 coefficient in the thickness direction for cellular linear Polypropylene piezoelectret film. To study the effect of void microstructures on the time-dependence of quasi-piezoelectric d33 coefficient, samples of three different thicknesses were tested under two different pressures. The micromechanical theory for viscoelastic composite was extended to predict the electromechanical properties of voided charged polymer film. The voids with surplus charges, which can be piezoelectriclike under deformation, are considered as ellipsoidal heterogeneous piezoelectric inclusions, while the viscous polymer is taken as the matrix. In Laplace transformed space, the generalized Eshelby tensor is formulated for the isotropic nonpolar matrix as well as for the anisotropic matrix. The Mori–Tanaka average scheme is used to find the overall electromechanical properties. Time dependence of the effective properties in real space can be studied by Laplacian inversion. Sensitivity analysis to various parameters is investigated for time dependence of the effective properties, including effective elastic moduli and the quasi-piezoelectric coefficients. Theoretical simulation was presented and comparison with experimental results was conducted. Both qualitative analysis and quantitative comparison with experiments show that this theoretical formulation can predict the time dependence of the effective properties of voided charged piezoelectret film.