Increasing Filler Content Research Articles

Effects of non‐linear conductivity on charge trapping and de‐trapping behaviours in epoxy/SiC composites under DC stress

Gas-insulated switchgear (GIS) spacers are made of epoxy resin. However, the surface charge accumulation has been a great concern to the safe operation of GIS, which causes the frequent flashover faults on spacers. In this study, micro-silicon carbide (SiC) particles with non-linear conductivity were added into epoxy matrix and the filler content varied from 0 to 14 vol%. Then, the bulk conductivity and surface potential decay (SPD) tests were conducted. The obtained results showed that the epoxy/SiC composites have obvious non-linear conductivities and the non-linear-conductivity threshold decreases with the increasing filler content. The addition of SiC can effectively resist the rise of surface potential and enhance the surface charge dissipation process. From the trap energy distributions, it can be inferred that the deep traps of ~0.9 eV should be the intrinsic traps of epoxy and the shallow traps of ~0.8 eV are considered to be introduced by SiC. Furthermore, the simulation results confirmed that the sharp increase of carrier mobility in non-linear region significantly reduces the remaining time and possibility of a de-trapped charge being recaptured by traps before reaching the grounded electrode. Therefore, the high conductivity in non-linear region contributes a lot to the increase of SPD rate.

Filler bondability factor as a tool for maximizing the potential of mineral additives in paper production

Increasing filler content in paper while maintaining paper strength is a continuous need in the paper industry. The bonds between cellulosic fibers and fillers are essential to increase filler level in paper. Besides tensile strength, which traditionally has been used to investigate different fillers on fiber bonding, a new factor, i.e. a filler bondability factor, can be applied in evaluating the mitigation effect of filler addition on fiber bonding. This factor shows its effectiveness in optimizing the key parameters for filler modification and the choice of filler, and it helps to maximize the use of filler in the paper industry.

Effect of nano- and micro-alumina fillers on some properties of poly(methyl methacrylate) denture base composites

This research investigated the effects of alumina (Al2O3) micro- and nano-particles on poly(methyl methacrylate) (PMMA) denture base. Al2O3 was surface treated using (3-methacryloxypropyl)trimethoxysilane (?-MPS), added to methyl methacrylate (MMA), and mixed with PMMA powder. The filler volume fractions in the micro-composites were 0.5, 1, 2, 5 and 7 wt. %, whereas those in the nano-composites were 0.13, 0.25, 0.5, 1, 2 and 5 wt. %. The treated fillers were examined using Fourier transform infrared spectroscopy (FTIR). The influence of filler size and loading on mechanical properties was studied using fracture toughness and flexural tests. The thermal stability of the PMMA/Al2O3 composites was investigated using thermogravimetric analysis (TGA). In addition, the water absorption and solubility characteristic of the prepared composites was also investigated. The FTIR spectra showed new absorption bands, indicating the occurrence of surface modifications. Both micro- and nanoscale particles showed increased fracture toughness. The maximum value of 2.02 MPa?m1/2 was achieved with the addition of 0.5 wt. % nano-Al2O3, which accounts for a 39 % increase. In contrast to the flexural strength, the flexural modulus improved with increasing filler content. The micro-composites showed higher thermal stability than nano-composites. The water absorption and solubility of the prepared composites were slightly higher than those of the control. The use of low concentrations of Al2O3 nanoparticles may be of considerable interest in future studies to improve the mechanical properties of PMMA denture base.

Ways to improve physico-mechanical properties of polymer composites on the basis of secondary polypropylene and natural extenders

Creation of composition polymeric materials is one of the most perspective directions of the modern polymeric materials science. When developing such systems there can be problems of compatibility of components, for example between polymer and an excipient. Binding agents enter into composite structure for the purpose of ensuring connectivity of elements. The influences of part-time workers on rheological and physicomechanical behavior of polymeric composition on the basis of the secondary polymeric raw materials filled with natural components of a phytogenesis is studied in this work. It is shown that introduction of the part-time worker to composition affects MFR values - the more the part-time worker is in composition, the more MFR value, and so, and workability is easier. At the same time it should be noted that in case of use as part-time workers of EN13F1F3HH and SanUMBUGO F1 of regularity of change of the MFR a bit differents - increase of MFR values is observed only when content of the part-time worker in composition up to 1% of masses. Studying of rheological data demonstrates that introduction even of a small amount of the part-time worker leads to the fact that resilient properties at the composition containing the modifier are expressed less, the probability of formation of marriage at manufacture of products from these compositions respectively is less. Introduction of modifiers affects also physicomechanical properties of composition. Operation of SunUNBUGO F1 and EN13F1F3HM modifiers is close to each other, and MPP5X – differs. The lowest values of an elastic modulus take place when using as the SunUNBUGO F1 modifier. At the same time, increase filler content in composition reduces already not high values of an elastic modulus. Thus, during the research the basic possibility of regulation of rheological and physicomechanical behavior of polymeric composites not only by introduction of the part-time worker to composition playing a role superficially of the active material but also by regulation of conditions of receiving composites is shown.

Graphite nanosheets - polypropylene composites from in toluene delaminated graphite using atactic polypropylene as dispersant

Composites of polypropylene (PP) and graphite nanosheets (GN) are prepared by melt blending PP with a master batch of GN suspended in atactic polypropylene (Mw = 129.000 g/mol). aPP/GN master batches were obtained by wet ball-milling graphite in toluene using the aPP as dispersant. The procedure gives single flakes of GN with crystallite out-of-plane thickness as low as 17.7 nm. PP/aPP/GN composites were obtained with finely dispersed GN, predominantly as single nanosheets from master batches containing aPP dispersant and graphite. Crystallization of the iPP in the composites is facilitated by the presence of aPP and GN. PP spherulites are formed as the graphitic fillers act as strong nucleating agents: the dimensionality of the crystal growth (n = 2-3) and the crystallinity increases with increasing filler content in isothermal and non-isothermal crystallizations. The yield strength of the composites can be enhanced up to 20% by the presence of GN; the presence of aPP counteracts a decrease in elongation at break. Composites prepared from parent graphite or GN without aPP show larger aggregates of nanosheets in the composites.

Effect of fire retardant fillers on thermophysical properties of composite materials of ethylene-vinyl acetate copolymer

The influence of composite materials of ethylene-vinyl acetate copolymer that do not maintain combustion and fire-retardant fillers on thermophysical processes was explored. Ethylene-vinyl acetate copolymer was used in the studies. The content of vinyl acetate is 18 % and 28 %; MFI is 2.5 g/10 min. and MFI is 5 g/10 min. Fire retardant fillers included aluminum oxide trihydrates with average diameter of particles of 1.5 µm and 3.0 µm; magnesium oxide dihydrates with average diameter of particles of 3.0 µm and 3.7 µm and hydromagnesite with average diameter of particles of 1.4 µm. Using the method of thermogravimetric analysis and differential scanning calorimetry TGA/DSC, temperatures of vitrification, melting and decomposition, crystallinity degree, specific thermal capacity, and activation energy were determined. It was found that temperatures of physical transformations (temperatures of vitrification, melting, and decomposition) of polymer compositions that do not maintain combustion depend on properties of ethylene-vinyl acetate copolymer. They increase with decreasing of fluidity indicator of copolymer of ethylene vinyl acetate. EVA 1 has lower values of the indicator of melt fluidity and content of vinyl acetate than EVA 2. During an increase in content of fire retardant fillers, temperatures of physical transformations are shifted in the direction of increasing: vitrification temperature increases from – 85 °C to 53 °C, melting temperature – from 68 °C to 90 °C. At the same time, crystallinity degree decreases from 8.8 % to 1.0 % and specific thermal capacity increases from 0.4 to 8.6 J/gK. This is due to formation of supermolecular structure of the derived compositions. The influence of the polymeric matrix, composition and dispersity of fire retardant fillers on thermal-physical characteristics of polymeric compositions was determined. In case of using a polymer matrix with lower MFI and fire retardants fillers with smaller average diameter of particles, temperature characteristics are shifted towards higher temperatures than in the case of selection of polymer matrix with large MFI and fire-retardant fillers with a larger diameter of particles. Obtained results will be useful during development of formulations of polymer compositions that do not maintain combustion for cable products, considering their thermophysical characteristics.

Thermal and electrical conductivities of epoxy resin-based composites incorporated with carbon nanotubes and TiO2 for a thermoelectric application

For a thermoelectric application, the thermal conductivity, electrical conductivity and figure of merit of epoxy resin-based composites incorporated with carbon nanotubes and TiO2 are investigated in this paper. First, the composite is prepared with a solution blending method. Then, the structure, thermal and electrical conductivities are characterized with experimental methods. Finally, the thermal conductivity, electrical conductivity and figure of merit are discussed. Results turn out that with an increasing content of carbon nanotube fillers, there are different changing trends of thermal and electrical conductivities because of large difference between thermal and electrical contact resistances in the composite. With the increasing filler content, the electrical conductivity increases exponentially while thermal conductivity saturates to be a constant value. Due to the large ratio of electrical to thermal conductivities, the figure of merit with 8 wt% of fillers is more than 50 times larger than that with a low content of fillers. Our results confirm that the recently proposed concept of ‘electron-percolation thermal-insulator’ is a feasible way to enhance the figure of merit of a polymer composite.

Effect of Coconut Shell Powder as Filler on the Mechanical Properties of Coir-polyester Composites

Coir mat was used as reinforcement, polyester resin was used as matrix and coconut shell powder (CSP) was used as filler material which was employed as 10, 20, 30, 40, 50, 60 and 100% by weight in the composites. Coir mat/polyester resin composites were made by hand lay-up technique. Mechanical properties such as tensile strength (TS), bending strength (BS), tensile modulus (TM), bending modulus (BM), elongation at break and impact strength (IS) were also investigated. The maximum increase of TS, BS, TM, BM and IS were found to be 44.44, 128.00, 17.96, 112.09 and 62.50% respectively for 30% filler content on the composites. It was revealed that the strength properties of the composites were increased with the increase in filler content up to 30% by weight, however, further increase in filler content the value decreased. Gamma radiation of 100, 250 and 300 krad doses were applied on 30, 40 and 60% filler content composites. Gamma radiation dose of 250 krad showed better result than that of other doses. IS of the composites improved 48.08, 26.67 and 17.50% for 30, 40 and 60% filler content respectively at 250 krad, where 30% filler content composites displayed the highest improvement. Degradation tests of the composites for up to 50 days were performed in a soil medium. It was revealed that BS decreased for all the composites.

Effect of the Addition of Carbon Nanomaterials on Electrical and Mechanical Properties of Wood Plastic Composites.

Wood Plastic Composites (WPCs) are a new generation of green composites that could optimize the use of harvested trees and increase the entire value chain. In this study, the electrical and mechanical properties of WPCs containing carbon blacks (CB), flake graphite (FG) and carbon nanotubes (CNTs) have been investigated. The electrical property of WPCs is improved significantly owing to the introduction of these carbon nanomaterial fillers. The volume and surface resistivity values of the investigated composites all obviously decreased with the increase in filler content, especially CNTs, which displayed the most satisfactory results. Based on a series of laboratory experiments carried out to investigate the mechanical performance, it can be concluded that the addition of the carbon nanomaterial fillers decreases the mechanical properties of WPCs slightly with the increase in filler content because of the weak interfacial interactions between the fillers and polymer matrix.

Magnetic, Electrical and Thermal Studies of Polypyrrole-Fe2O3 Nanocomposites

This research paper comprises of the synthesis of polypyrrole (PPy)-Fe2O3 nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H c ), saturation magnetization (M s ) and remanence (M r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites.

Dynamic Mechanical Thermal Analysis (DMTA) of Thermoplastic Natural Rubber (TPNR) Barium Ferrite (bafe12o19) Composites

filled with 0-6 volume percentage of barium ferrite was performed using a Polymer Laboratory- Dynamic Mechanical Thermal Analyser (PL-DMTA) over a range of temperature from -100 to 100°C at 10hz. The results showed that the storage modulus (E') of the composites below the transition temperature increase with filler content up to ~3-4 volume percentage. Incorporation of the filler does not change the matrix glass transition that occurs around -40°C but the damping curve becomes broader with increasing filler content. The addition of filler in the compositedoes not affect the glass transition and melting temperature. The blend of TPNR and barium ferrite powder is only a physical mixture that does not act chemically.

Food-grade filler particles as an alternative method to modify the texture and stability of myofibrillar gels

A series of food grade particles were characterized for their potential as fillers in myofibrillar gels. The fillers were separated into (i) hydrophilic, insoluble, crystalline particles and (ii) starch granules. The particles used were microcrystalline cellulose, oat fiber and walnut shell flour, as well as potato and tapioca starches. Crystalline particles increased hardness and decreased recovery properties. Although all of these fillers decreased the T2 relaxation time of water, this was dependent on particle type and size. An increase in gel strength was observed with increasing filler content, which was attributed to particle crowding. Native potato starch was the most efficient at increasing liquid retention, while native tapioca was the least effective. Gel strength increased significantly only for the native potato and modified tapioca starches, but no effect on recovery attributes were observed for any of the starch varieties. The potato starches became swollen and hydrated to a similar extent during the protein gelation process, while the native tapioca starch gelatinized at higher temperatures, and the modified tapioca showed little evidence of swelling. T2 relaxometry supported this finding, as the meat batters containing native potato starch displayed two water populations, while the remaining starches displayed only a single population.

Structural, Electrical and Dielectric Properties of Hexa-ferrite-Polyaniline Nano-composites

Ferrite-polyaniline (PANI) composites were prepared by in situ polymerization of polyaniline with the general formula (1 − x) ferrite + (x) PANI where x = 0, 0.25, 0.5, 0.75, 1. The samples were characterized by XRD, SEM, electrical resistivity, and dielectric measurements. X-ray diffraction reveals single phase formation of CaBaCo2Al0.5Fe11.5O22 Y-type ferrite, whereas polyaniline exhibits an amorphous nature. At room temperature, the resistivity of nano-composites increases with the increase of ferrite filler contents from 3.17 × 104 to 3.19 × 107 Ω cm. Real and imaginary parts of the complex permittivity of the PANI-ferrite composites follow the Maxwell-Wagner model. Based on the Jonscher Law, the AC conductivity of PANI-ferrite composites experiences an increase with the increase in frequency. The exponent calculated from AC conductivity reveals that the hopping is the likely conduction mechanism. The activation energy obtained from temperature-dependent measurements is consistent with room temperature resistivity. Due to the light weight, low cost and flexibility of design, the ferrite-polymer composites are considered useful for microwave devices.

THERMAL AND THERMOPHYSICAL PROPERTIES OF EPOXY-SILICA NANOCOMPOSITES OF CATIONIC POLYMERIZATION

The polymer and composites were received using epoxy resin EPONEX 1510 – diglycidyl ether of dicyclohexylolpropane and 15 % solution of boron trifluoride in diethylene glycol. The silica particles were formed in situ via the sol-gel method using hydrolytic polycondensation of tetraethoxysilane. The silica sol was obtained in acetone as the organic solvent. Silica filler content in the composites varied from 0.5 to 3 wt%. The effect of the nanofiller on the thermophysical and thermal properties of the obtained polymers was studied. Thermophysical characteristics were determined by differential scanning calorimetry on a TA Instruments DSC Q2000 apparatus at a rate of heating of 20 °С/min in the temperature range from 5 to 190 °C. With the objective of decreasing the influence of the technological (kinetic) and thermal prehistory of the sample on its thermophysical characteristics, the scanning was done twice. The glass transition temperature and heat capacity jump of the composite coatings based on epoxy-silica prepared by cationic polymerization were studied. It was established that with an increase of filler content the glass transition temperature of composites increases, and the value of the heat capacity jump remains almost unchanged. Parameters of thermostability of polymer and composites were determined by thermogravimetric analysis on a TA Instruments Q50 apparatus at a rate of heating of 20 °С/min in the temperature range from 20 to 1000 °C in an atmosphere of oxygen. The destruction process of epoxy-silica composites proceeds in several stages. In the deep stages of the thermo-oxidative destruction of obtained composites the effect of the silica filler is insignificant. The obtained polymer coatings were subjected to a long-term (100 hours) isothermal aging at 160 °C in an atmosphere of oxygen. It was determined that the maximum rate of mass loss rate of epoxy-silica composites is 1.5 times lower than that of unmodified polymer.

3D Printing of BaTiO3/PVDF Composites with Electric In Situ Poling for Pressure Sensor Applications

AbstractThis paper presents 3D printing of piezoelectric sensors using BaTiO3 (BTO) filler in a poly(vinylidene) fluoride (PVDF) matrix through electric in situ poling during the 3D printing process. Several conventional methods require complicated and time‐consuming procedures. Recently developed electric poling‐assisted additive manufacturing (EPAM) process paves the way for printing of piezoelectric filaments by incorporating polarizing processes that include mechanical stretching, heat press, and electric field poling simultaneously. However, this process is limited to fabrication of a single PVDF layer and quantitative material characterizations such as piezoelectric coefficient and β‐phase percentage are not investigated. In this paper, an enhanced EPAM process is proposed that applies a higher electric field during 3D printing. To further increase piezoelectric response, BTO ceramic filler is used in the PVDF matrix. It is found that a 55.91% PVDF β‐phase content is nucleated at 15 wt% of BTO. The output current and β‐phase content gradually increase as the BTO weight percentage increases. Scanning electron microscopy analysis demonstrates that larger agglomerates are formulated as the increase of BTO filler contents and results in increase of toughness and decrease of tensile strength. The highest fatigue strength is observed at 3 wt% BTO and the fatigue strength gradually decreases as the BTO filler contents increases.

Development of glass microballoon/HDPE syntactic foams by compression molding

Abstract Thermoplastic resins are widely used in consumer products and industrial components. There is a significant interest in weight reduction of many of those components. Although glass hollow particle filled lightweight syntactic foams with thermoset matrices have been studied in detail, studies on thermoplastic syntactic foams are scarce. The present study is focused on developing a compression molding based processing method for glass microballoon/high density polyethylene (GMB/HDPE) syntactic foams and studying their mechanical properties to develop structure-property correlations. Blending of GMB in HDPE is carried out using a Brabender mixer with processing parameters optimized for minimal filler breakage. Flexural and tensile test specimens are compression molded with 20, 40 and 60 vol% of GMB. Particle fracture increases with increasing GMB content due to increased particle to particle interaction during processing. Additionally, increasing wall thickness makes GMBs stronger and results in reduced particle fracture. Flexural modulus increases while strength decreases with increasing filler content. Tensile strength decreases with increasing filler content, while tensile modulus is relatively unchanged. GMB volume fraction has a more prominent effect than the wall thickness on the mechanical properties of syntactic foams. Specific moduli of GMB/HDPE foams are superior while specific strength is comparable to neat HDPE.

Experimental and theoretical studies on the adjustable thermal properties of epoxy composites with silver‐plated short fiberglass

ABSTRACTThis article investigates the evolution of the thermal conductivity and the coefficient of thermal expansion (CTE) of epoxy composites filled with different silver‐plated short glass fibers (Ag@GFs) treated by electroless plating. After electroless plating, the results of X‐ray diffraction and scanning electron microscopy showed that glass fibers were coated with pure silver shells whose thickness was controlled via the repetition of electroless plating cycle, and calculated by weighting method. The optical photographs showed that Ag@GFs are randomly oriented and uniformly dispersed in the composites. HotDisk thermal constant analyzer and dilatometer were used to further characterize the thermal conductivity and the CTE of the composites, respectively. The results revealed that the thermal conductivity of Ag@GF/epoxy composites increased with the increase of Ag@GF content, and was adjusted by changing the thickness of silver shell. But the CTE of the composites drops sharply as the Ag@GF content increases compared with neat epoxy. Based on Agari model with fitted factors of Cp and Cf, the calculated thermal conductivity values of Ag@GF/epoxy composites agreed well with the experimental results, and Cp kept almost unchanged, but Cf varied with the change of the thickness of silver shell, despite increasing filler content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45555.

Effect of filler content on the structure‐property behavior of poly(ethylene oxide) based polyurethaneurea‐silica nanocomposites

Poly(ethylene oxide) (PEO) based polyurethaneurea‐silica nanocomposites were prepared by solution blending and characterized by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Differential Scanning Calorimetry and tensile testing. The colloidal silica nanoparticles with an average size of 50 nm were synthesized by modified Stöber method in isopropanol. Silica particles were incorporated into three cycloaliphatic polyurethaneurea (PUs) copolymers based on PEO oligomers with molecular weights of 2,000, 4,600, and 8,000 g/mol. Hard segment content of PUs was constant at 30% by weight. Silica content of the PU nanocomposites varied between 1 and 20% by weight. Soft segment (SS) glass transition and melting temperatures slightly increased with increasing filler content for all the copolymers. Degree of SS crystallinity first increased with 1% silica incorporation and subsequently decreased by further silica addition. Elastic modulus and tensile strengths of PU copolymers gradually increased with increasing amount of the silica filler. Elongation at break values gradually decreased in PEO‐2000 based PU copolymer with increasing silica content, whereas no significant change was observed in PUs based on PEO‐4600 and PEO‐8000. Enhancement in tensile properties of the materials was mainly attributed to the homogeneous distribution of silica filler in polymer matrices and strong polymer‐filler interactions. POLYM. ENG. SCI., 58:1097–1107, 2018. © 2017 Society of Plastics Engineers

Investigation of the properties and production of sawdust ceiling tile using polystyrene as a binder

In this research, a production and properties investigation of wood sawdust ceiling tile using polystyrene as a binder was carried out. The content by weight of the wood sawdust was 5, 10, 15, 20, 25 and 30% consisting of three composite samples for each of the six filler content percentages. The samples were prepared in accordance with the American Standard for Testing and Material (ASTM) for wear resistance, flexural and tensile properties as well as water resistance. From the results, it was observed that with the exception of the wear loss, 5% sample gave the best values next to the control sample in almost all the properties. For wear resistance, the value was 0.4568 g and was the sample with the best wear resistance. The result revealed that curing rate is highly influenced by the filler since it decreases as the filler content increases. Higher resistivity was recorded as the filler content increased and this may not be unconnected to the fact that air, being a poor conductor, is more in the composite where we have more filler content.

Thermal, electrical, and mechanical properties of talc‐ and glass microsphere‐Reinforced Cycloaliphatic epoxy composites

Cycloaliphatic epoxy (CE) is used in high voltage and temperature applications because of its high glass transition temperature and resistance to ultraviolet, ozone, and hydrothermal aging mechanisms. Fillers can be used to increase the tensile modulus and thermal conductivity (TC) without a corresponding increase in electrical conductivity (1/electrical resistivity [ER]), which would be detrimental in a high voltage environment. In this study, two fillers were examined in a CE system: talc and glass microspheres (MS). Up to 20 wt% talc/CE and up to 40 wt% glass MS/CE composites were fabricated and tested for ER, TC, and tensile properties. As desired, all composites remained electrically resistive. Composite TC increased with increasing filler content from 0.15 W/m‐K for the neat epoxy to 0.25 W/m‐K for 20 wt% talc and for 40 wt% glass MS. This TC increase could be helpful to dissipate heat in high voltage and temperature applications. Tensile modulus increased from 2.7 GPa for the neat epoxy to 3.6 GPa for 20 wt% talc/CE and to 5.2 GPa for 40 wt% glass MS/CE composites. Increasing the tensile modulus is useful in the newly developed Polymer Core Composite Conductors that are used to transmit power. POLY COMPOS., 39:E1581–E1588, 2018. © 2017 Society of Plastic Engineers