Effect of tempo and periodate-chlorite oxidized nanofibrils on ground calcium carbonate flocculation and retention in sheet forming and on the physical properties of sheets

Nanofibrils (NFC) or microfibrils (MFC) are potential candidates for high filler-loaded papers and board as they are able to compensate for strength loss caused by the filler itself. However, the interaction of nanofibrils and the filler during sheet forming is not yet well understood. The aim here was to examine 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and periodate-chlorite oxidized (DCC) anionic nanofibrils during sheet forming in order to determine their effects on flocculation, filler retention and the strength and optical properties of the handsheets. The experiments were carried out by manufacturing filler-loaded sheets from refined kraft fibres and ground calcium carbonate (GCC) with various added levels of TEMPO and DCC nanofibrils. The results showed that both types of nanofibril caused pronounced agglomeration of the GCC filler, which increased its retention in the paper web. Given the same filler content, the strength properties were the same or slightly better than in a sheet formed without any chemical agent, while light scattering was slightly inferior. Poorer formation seemed to be the explanation for why the increased bonding induced by NFCs was not reflected in obviously better sheet strengths. The physical properties of sheets containing NFC were superior to those of sheets formed with cationic polyacrylamide as a retention aid with the same filler content and level of formation. Thus NFCs seem to be potential retention aids for use in fine paper production instead of traditional polymers.     

Combined effects of ceramic filler size and ethylene oxide length on the ionic transport properties of solid polymer electrolyte derivatives of PEGMEMA

In this work, the synthesis of a series of solid polymer electrolyte (SPE) derivatives of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA), homogenously dispersed with TiO₂ ceramic nano-filler, has been reported. The interactions between filler size and the length of the ethylene oxide (EO) polymer backbone are discussed, and transport properties such as ionic conductivity and cation transference number are determined. Results show that the improved performance of the SPE is due to an interaction between the ceramic filler and the entwining behavior of the PEGMEMA backbone. An optimal ceramic filler size and an appropriate length of EO have been suggested for the enhanced performance of SPE derivatives of PEGMEMA for a next-generation polymer battery.     

Nano-enabled microtechnology: polysulfone nanocomposites incorporating cellulose nanocrystals

Microchannel devices hold the potential to transform many separation processes. This preliminary study investigated the feasibility of incorporating cellulose nanocrystals (CNXLs) into polysulfone, a commonly used ultrafiltration membrane polymer. Incorporating CNXLs into non-water soluble polymers without aggregation has been problematic. A solvent exchange process was developed that successfully transferred an aqueous CNXL dispersion into the organic solvent N-methylpyrrolidone (NMP), which is a solvent for polysulfone (PSf). Films were prepared from the solution of PSf in NMP with dispersed CNXLs by a phase inversion process. Films were then examined by scanning electron microscopy and tested for their transport and mechanical properties. The interaction between the polymer matrix and the CNXL filler was studied by means of thermogravimetric analysis (TGA), which suggested a close interaction between the polymer and filler at the 2% filler loading. The tensile modulus showed a large increase beyond 1% filler loading, which could be due to a percolation effect. The water vapor transport rate increased with increase in filler loading. Agglomeration of the CNXLs seemed to be taking place at filler loadings >7%.     

Thermal stability of high density polyethylene–fumed silica nanocomposites

High-density polyethylene-based nanocomposites were prepared through a melt compounding process by using surface functionalized fumed silica nanoparticles in various amounts, in order to investigate their capability to improve both mechanical properties and resistance to thermal degradation. The fine dispersion of silica aggregates led to noticeable improvements of both the elastic modulus and of the stress at yield proportionally to the filler content, while the tensile properties at break were not impaired even at elevated filler content. Thermogravimetric analysis showed that the selected nanoparticles were extremely effective both in increasing the decomposition temperature and in decreasing the mass loss rate, even at relatively low filler loadings. The formation of a char enriched layer, limiting the diffusion of the oxygen through the nanofilled samples, was responsible of noticeable improvements of the limiting oxygen index, especially at elevated silica loadings. In contrast with commonly reported literature results, cone calorimeter tests also revealed the efficacy of functionalized nanoparticles in delaying the time to ignition and in decreasing the heat release rate values. Therefore, the addition of functionalized fumed silica nanoparticles could represent an effective way to enhance the flammability properties of polyolefin matrices even at low filler concentrations.     

Ageing of filled polymers

It is tried to examine briefly all the aspects of filler interactions with polymer ageing, including direct chemical (catalysis of degradation, stabilising effects) and physical (screen and thermooptical effects, modification of transport properties) interactions as well as indirect ones such as stabiliser trapping, influence on the rate of mechanical properties change or interfacial phenomena.     

Percolation of carbon nanomaterials for high-k polymer nanocomposites

This review summarized the recent progress towards high-k polymer composites bases on the near-percolated networks of carbon nanomaterials by focusing on the effects of distinct network morphologies on the dielectric properties. It is expected to give guidance on designing new near-percolated networks in polymer matrices towards next-generation polymer dielectrics.     

Transport properties of graphite/epoxy composites: Thermal, permeability and dielectric characterization

In this study nanocomposites were prepared by dispersing three different grades of graphite particles, expanded graphite, commercial graphene nanoplatelets and natural graphite, in a commercial epoxy matrix. Dielectric properties, thermal conductivity and permeability to oxygen of the composites were studied and compared to those of the unfilled epoxy matrix. An increase of all properties is obtained using expanded graphite, suggesting the presence of a good dispersion of the filler in the matrix and a strong polar interactions of the filler with the matrix, attributed to the partially oxidised surfaces of the expanded graphite. All the measured transport properties were fitted with simple mathematical models obtaining good agreement between the experimental results and theoretical predictions. The model parameters were related to the aspect ratio of the filler, defined as the ratio between the in-plane average dimension and the thickness of the reinforcement. An aspect ratio between 1250 and 1550 indicates that graphite thin platelets (or graphene stacks), characterized by a thickness of the order of a few tens of nanometers, were dispersed in the epoxy matrix.     

Models for the Investigation of the Structure of Vulcanizates

For the investigation of vulcanizates structure, new models have been developed relating the modulus of vulcanizates and the volume fraction of filler. The parameters of the models are the filler distribution and the properties of the shell surrounding the filler particles. Three functions of filler distribution have been assumed. Dynamic mechanical properties of a series of vulcanizates were tested and the parameters of the models were computed. The obtained data allows estimating the properties of the shell formed around filler particles in vulcanizates and to distinguish the functions of filler distribution.     

Selective localization of organoclay and effects on the morphology and mechanical properties of LDPE/PA11 blends with distributed and co‐continuous morphology

A study was made on the effect of small amounts of organically modified clay on the morphology and mechanical properties of blends of low‐density polyethylene and polyamide 11 at different compositions. The influence of the filler on the blend morphology was investigated using wide angle X‐ray diffractometry, scanning and transmission electron microscopy and selective extraction experiments. The filler was found to locate predominantly in the more hydrophilic polyamide phase. Although such uneven distribution does not have a significant effect on the onset of phase co‐continuity of the polymer components, it brings about a drastic refinement of the microstructure for the blends both with droplets/matrix and co‐continuous morphologies. In addition to the expected reinforcing action of the filler, the resulting fine microstructure plays an important role in enhancing the mechanical properties of the blends. This is essentially because of a good quality of stress transfer across the interface between the constituents, which also seems to benefit for a good interfacial adhesion promoted by the filler. Our results provide the experimental evidence for the capabilities of nanoparticles added to multiphase polymer systems to act selectively as a reinforcing agent for specific domains of the material and as a medium able to assist the refinement of the polymer phases during mixing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 600–609, 2010     

Comparative study of the mechanical and wear performance of short carbon fibers and mineral particles (Wollastonite,CaSiO3) filled epoxy composites

To improve the mechanical and tribological performance, two kinds of wollastonite fillers (fine or coarse) and short carbon fibers (5–15 vol %) were, respectively, incorporated into an epoxy resin. Fine wollastonite fillers remarkably enhanced the flexural modulus, strength, and toughness of the resin at some filler contents (i.e., 10 vol %) simultaneously, while coarse wollastonite fillers and short carbon fibers impaired most of mechanical properties except the modulus. The small particle size, low aspect ratio as well as the good adhesion to the epoxy matrix of the fine wollastonite particles are believed to be responsible for the improved strength and toughness. Tribological tests were performed under sliding and low amplitude oscillating wear conditions. All fillers enhanced the wear resistance and reduced the sliding coefficient of friction but to a different extent. Under sliding wear conditions, fine wollastonite particle‐filled epoxy displayed the highest wear resistance because of the formation of an effective transfer film and the low abrasiveness of the fillers. Under low amplitude oscillating wear conditions, both wollastonite fillers showed much higher wear resistance than short carbon fibers regardless of the filler content. The better adhesion between the wollastonite fillers and the epoxy matrix is responsible for the higher wear resistance under oscillating conditions. The wear tracks were inspected by microscopy to analyze the corresponding wear mechanisms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 854–863, 2006     

The influence of non-rubber constituents on performance of silica reinforced natural rubber compounds

An in-rubber study of the interaction of silica with proteins present in natural rubber show that the latter compete with the silane coupling agent during the silanisation reaction; the presence of proteins makes the silane less efficient for improving dispersion and filler–polymer coupling, and thus influences the final properties of the rubber negatively. Furthermore, the protein content influences the rheological properties as well as filler–filler and filler–polymer interactions. Stress strain properties also vary with protein content, as do dynamic properties. With high amounts of proteins present in natural rubber, the interactions between proteins and silica are able to disrupt the silica–silica network and improve silica dispersion. High amounts of proteins reduce the thermal sensitivity of the filler–polymer network formation. The effect of proteins is most pronounced when no silane is used, but they are not able to replace a coupling agent.     

双组份室温加成型硅橡胶口腔印模材料的制备

以自制乙烯基硅油为基胶、自制含氢硅油为交联剂、铂配合物为催化剂、高纯度硅微粉为填料、多乙烯基化合物为抑制剂等,通过实验制得双组份室温加成型硅橡胶口腔印模材料.研究了各组分对硅橡胶印模材料硫化化时间、细微复制、力学性能的影响.并制备了与国外产品性能相当的产品.     

Charge transport properties in carbon black/polymer composites

The charge transport properties of polymer matrix–carbon black composites are investigated in this study. Direct current conductivity is examined with varying parameters: the temperature and the conductive filler content. Conductivity data are analyzed by means of percolation theory, and both percolation threshold and critical exponent are determined at each of the examined temperatures. The temperature dependence of conductivity and the agreement of experimental results with the variable range hopping model reveal hopping conduction as the predominant transport mechanism, below and in the vicinity of the critical concentration of carbon black particles. At higher concentrations, the contribution of hopping transport to the overall conductivity is reduced and a balance between hopping and conduction via geometrical contact occurs. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2535–2545, 2007     

Role,effect, and influences of micro and nano‐fillers on various properties of polymer matrix composites for microelectronics: A review

Ever since the discovery of polymer composites, its potential has been anticipated for numerous applications in various fields such as microelectronics, automobiles, and industrial applications. In this paper, we review filler reinforced polymer composites for its enormous potential in microelectronic applications. The interface and compatibility between matrix and filler have a significant role in property alteration of a polymer nanocomposites. Ceramic reinforced polymeric nanocomposites are promising candidate dielectric materials for several micro‐ and nano‐electronic devices. Because of its synergistic effect like high thermal conductivity, low thermal expansion, and dielectric constant of ceramic fillers with the polymer matrix, the resultant nanocomposites have high dielectric breakdown strength. The thermal and dielectric properties are discussed in the view of filler alignment techniques and its effect on the composites. Furthermore, the effect of various surface modified filler materials in polymer matrix, concepts of network forming using filler, and benefits of filler alignment are also discussed in this work. As a whole, this review article addresses the overall view to novice researchers on various properties such as thermal and dielectric properties of polymer matrix composites and direction for future research to be carried out.     

Polymer-nanoparticle interfacial behavior revisited: a molecular dynamics study

By tuning the polymer-filler interaction, filler size and filler loading, we use a coarse-grained model-based molecular dynamics simulation to study the polymer-filler interfacial structural (the orientations at the bond, segment and chain length scales, chain size and conformation), dynamic and stress-strain properties. Simulated results indicate that the interfacial region is composed of partial segments of different polymer chains, which is consistent with the experimental results presented by Chen et al. (Macromolecules, 2010, 43, 1076). Moreover, it is found that the interfacial region is within one single chain size (R(g)) range, irrespective of the polymer-filler interaction and the filler size, beyond which the bulk behavior appears. In the interfacial region, the orientation and dynamic behaviors are induced by the interfacial enthalpy, while the size and conformation of polymer chains near the filler are controlled by the configurational entropy. In the case of strong polymer-filler interaction (equivalent to the hydrogen bond), the innerest adsorbed polymer segments still undergo adsorption-desorption process, the transport of chain mass center in the interfacial region exhibits away from the glassy behavior, and no plastic-like yielding point appears in the stress-strain curve, which indicates that although the mobility of interfacial polymer chains is restricted, there exist no "polymer glassy layers" surrounding the filler. In addition, it is evidenced that the filler particle prefers selectively adsorbing the long polymer chains for attractive polymer-filler interaction, validating the experimental explanation of the change of the bound rubber (BR). In short, this work provides important information for further experimental and simulation studies of polymer-nanoparticle interfacial behavior.     

An interlayer model for the complex dielectric constant of composites: An extension to ellipsoidally shaped particles

A theoretical interlayer model (IL) has been developed for the complex dielectric constant of a composite in which the filler particles are enveloped with a layer of interfacial material. The filler particles can be of any ellipsoidal shape. Special cases such as spherical particles, needles, and fabrics are shown to be covered by the model.The analytical formula as derived describes the composite properties as a function of the volume fractions of the filler, the layer and the matrix material, their dielectric properties and the filler particle shape factor.In the case of a two-phase composite the model reduces to the well-known Sillars relation for the complex dielectric constant of composite which contains filler particles of ellipsoidal shape.The effect of an interfacial layer on the static dielectric constant of the composite is discussed using the model. Next, the special case of a conductive interfacial layer in an otherwise non-conductive composite is discussed; it illustrates the effect of interfacially adsorbed water on the electrical properties of composites. Some practical examples are shown.     

Composites of Wood and Biodegradable Thermoplastics: A Review

This paper is an overview of current understanding in the areas of composites made from biodegradable thermoplastics and wood fillers. The review finds that the composite properties depend on the type of wood filler, the choice of polymer matrix, the wood filler content, the compatibilization technique used and the processing parameters. The extent of interfacial adhesion and the filler morphology are identified as the underlying factors that control the composite properties. Future research needs are identified, including establishment of fundamental relationships between quantified interfacial adhesion and end-use properties and advanced modelling of biodegradation processes.     

Formation of Network by Carbon Black，Silica and Their Mixing Fillers in Isoprene Rubber北大核心CSCD

The network formed by fillers has great influence on the mechanical properties of rubber materials. To understand the formation of network by carbon black,silica,and carbon black/silica mixing fillers in rubber and its influence on the properties of rubber,isoprene rubber/filler composites with different filler loadings are prepared and their micromorphology,rheological and tensile properties are investigated. It is found that the dispersion of fillers is better in rubber after cure than that in rubber before cure for all three rubber systems,and the filler size of silica is smaller than that of carbon black,but the aggregation is more severe in silica filled rubber system. In mixed filler system,the two fillers tend to aggregate separately, leading to the low modulus at small strain than that in single filler system. With the increase of the filler loading,the tensile strength increases first and then decreases,the elongation at break decreases,and the temperature rise in compression flexometer tests increases. Moreover,the temperature rise in mixed filler system is higher than that in single filler system at high filler loading. © 2022, Science Press (China). All rights reserved.     

Development of Natural Rubber-Fibrous Nano Clay Attapulgite Composites: The Effect of Chemical Treatment of Filler on Mechanical and Dynamic Mechanical Properties of Composites

Common nano clay fillers have layered structure. Some nano clays like Attapulgite (AT), Sepiolite have rod like fibrous structure. Compared to layered structured clay fibrous clay AT can undergo better dispersion in polymer matrix leading to better improvement in composite properties. Chemical modifications of AT are done through amine treatment as well as by amine+silane treatment to get chemically modified fillers AAT and SAT respectively. In the present investigation, nano composites are prepared using natural rubber (NR) filled with AT, AAT and SAT. Three different loadings of each filler are used namely 2.5, 5, and 10 phr (parts per hundred of rubber). Mechanical properties like tensile strength, elongation at break increase with the increase in filler loading up to 5 phr there after these properties marginally fall when loading is increased to 10 phr due to problem of filler dispersion at higher loading. However, modulus at 300% elongation and tear strength increases with the increase in filler loading up to 10 phr. Very similar trend can also be observed for composites with chemically modified fillers, AAT and SAT. But the degree of reinforcement is higher in the case of AAT and SAT compared to that of unmodified filler AT for the same filler loading. This difference is mainly due to better polymer-filler interaction and filler dispersion in the case of chemically modified clays AAT and SAT compared to unmodified AT. Tear strength of composites increases remarkably with the addition of AT and which is further enhanced when chemically modified clays AAT and SAT are added. Dynamic-mechanical analyses of different clay composites give idea about the difference in the degree of polymer–filler interaction due to chemical treatment of filler.     

Enhancement of proton mobility and mitigation of methanol crossover in sPEEK fuel cells by an organically modified titania nanofiller

An organically functionalized titania, TiO₂-RSO₃H, was evaluated as filler in sulfonated polyetheretherketone (sPEEK)-based composite membranes for application in high temperature direct methanol fuel cells. The presence of propylsulfonic acid groups covalently bound onto the TiO₂ surface and the nanometric nature of the additive were analyzed by Raman spectroscopy and transmission electron microscopy, respectively. The properties of the sPEEK/TiO₂-RSO₃H composite membranes were compared with those of the pure sPEEK membranes and those of the sPEEK/TiO₂ composite membranes containing pristine titania nanoparticles at same filler content. Water and methanol transport properties were investigated by NMR methods, including relaxation times and self-diffusion coefficients as function of temperature (up to 130 °C), and pressure (from 0 up to 2 kbar). The incorporation of the nanoadditivies in the sPEEK polymer demonstrates considerable effects on the morphology and stiffness of the membranes, as well as on the transport properties and barrier effect to the methanol crossover. In particular, the functionalization by propylsulfonic acid groups promotes a higher reticulation between the polymeric chains, increasing the tortuosity of the methanol diffusional paths, so reducing the molecular diffusion, while the proton mobility increases being favored by the Grotthus-type mechanism. Conductivity measurements point out that the filler surface functionalization avoids the reduction of the overall proton conduction of the electrolyte due to the embedding of the low-conducting TiO₂. Finally, remarkable improvements were found when using the sPEEK/TiO₂-RSO₃H composite membrane as electrolyte in a DMFC, in terms of reduced methanol crossover and higher current and power density delivered.