Effect of nitrile butadiene rubber/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/YSZ fillers for PMMA denture base on the thermal and mechanical properties

This study is to investigate the effect of nitrile butadiene rubber (NBR as impact modifier) together with Al₂O₃/YSZ (toughening) as filler loading in PMMA denture base on the thermal and mechanical properties. PMMA matrix without fillers was mixed between PMMA powder and 0.5 mass% of BPO, and it is used as the control group. The liquid components consist of 90% of methyl methacrylate (MMA) and 10% as the cross-linking agent of ethylene glycol dimethacrylate. The denture base composites were fabricated by incorporating PMMA powder and BPO and fixed at 7.5 mass% NBR particles and filler loading (1, 3, 5, 7 and 10 mass%) of Al₂O₃/YSZ mixture filler by (1:1 ratio) as the powder components. The ceramic fillers were treated with silane (γ-MPS) and the powder/liquid ratio (P/L) according to dental laboratory practice. The TGA data obtained show that the PMMA composites have better thermal stability compared to unreinforced PMMA, while DSC curves show slightly similar Tg values. DSC results also indicated the presence of unreacted monomer content for both reinforced and unreinforced PMMA composites. The fracture toughness, Vickers hardness and flexural modulus values were statistically increased compared to the unreinforced PMMA matrix (P?<?0.05).     

Isothermal crystallization kinetics,morphology, and thermal conductivity of graphene nanoplatelets/polyphenylene sulfide composites

Graphene nanoplatelets (GNP) and polyphenylene sulfide (PPS) were used as filler and matrix, respectively, to produce composites. The PPS/GNP thermal composites were prepared via a melt blending method. The effects of GNP on crystallization behavior and kinetics, morphology, and thermal properties of PPS/GNP composites were investigated. To determine the isothermal crystallization kinetics parameters and isothermal crystallization activation energy, the Avrami model was used to comparatively analyze the relevant DSC experimental data. The results show that GNP provides an obvious heterogeneous nucleation effect on PPS to accelerate the crystallization and decrease isothermal crystallization activation energy. Thermal conductivity values of PPS/GNP composites with various GNP contents revealed that GNP remarkably increases thermal conductivity of composites mainly via a layered dispersion in PPS matrix. Thermal conductivity also increased with increasing GNP content, which was further improved at elevated temperatures. The thermal conductivities of PPS composite containing 30 mass% of GNP were 1.156 and 1.350 W m^?1 K^?1 at 30 and 110 °C, respectively, indicating an increase of more than 3 times compared with the neat PPS.     

The role of organoclay on the properties of Polymethylsilsesquioxane: A systematic study

In this study, an attempt is made to improve the properties of PMSQ, an organosilicone polymer which possesses distinguished properties, through an easy and facile route by the inclusion of organically modified montmorillonite clay. PMSQ-clay composites were prepared by solution blending of the components initially and then heat curing under load. The effect of clay content, varied at 5–40 wt.%, on mechanical, thermal and dynamic mechanical properties was evaluated and the optimum was obtained for 20%. Morphology investigation as well as microstructure analysis revealed intercalated to exfoliated morphology of PMSQ-clay composite. An appreciable improvement in mechanical properties of PMSQ, compressive strength and impact strength in particular, was achieved by clay inclusion up to 20%. The properties declined at ≥ 30% clay loading. The composites showed increased thermal stability compared to unmodified PMSQ up to 400 °C. Also, increase in clay content accelerated conversion to ceramic SiOC. PMSQ-clay composites exhibited good visco-elastic characteristics with higher T_g probably due to enhanced polymer-clay interactions. Thus, a simple and viable method to enhance the mechanical and thermal characteristics of PMSQ by way of preparing its composite with the reinforcing filler organoclay is demonstrated here.     

Thermal stability and conductivity of hot-pressed Si3N4–graphene composites

This study concerns new Si₃N₄–graphene composites manufactured using the hot-pressing method. Because of future applications of silicon nitride for cutting tools or specific parts of various devices having contact with high temperatures there is a need to find a ceramic composite material with good mechanical and especially thermal properties. Excellent thermal properties in the major directions are characteristic of graphene. In this study, the graphene phase is added to the silicon nitride phase in a quantity of up to 10 mass%, and the materials are sintered under uniaxial pressure. The mixture of AlN and Y₂O₃ is added as sintering activator to the composite matrix. The studies focus on thermal stability of produced composites in argon and air conditions up to the temperature of 1,000 °C. The research also concerns the influence of applied uniaxial pressure during the sintering process on the orientation of graphene nanoparticles in the Si₃N₄ matrix. The study also presents research on anisotropy of thermal diffusivity and following thermal conductivity of ceramic matrix composites versus the increasing graphene quantity. Most of the presented results have not been published in the literature yet.     

Effect of the TiC content on microstructure and thermal properties of Cu–TiC composites prepared by powder metallurgy

Copper matrix with an individual addition of TiC particles was prepared by means of powder metallurgy and hot pressing process, and the effect of TiC addition on microstructure, thermal properties, and electrical conductivity of Cu–TiC composites was investigated. The TiC quantity was changed as 1, 3, 5, 10, and 15 Cu (in mass%), and Cu–TiC powder mixtures were hot-pressed for 4 min at 700 °C under an applied pressure of 50 MPa. Microstructure studies revealed that TiC particles were distributed uniformly in the Cu matrix. Thermal Analysis result showed that there were two exothermic peaks and with rising TiC rate, oxidation amount of Cu composite decreased. With the increasing addition of TiC, hardness of composites changed between 58.6 HV_0.1 and 87.8 HV_0.1. The highest electrical conductivity for Cu–TiC composites was obtained in the Cu-1 mass% TiC composite, with approximately 81.2 % IACS.     

Effect of nanosilica on thermal oxidative degradation of SBR

The effect of silica content on thermal oxidative stability of styrene–butadiene rubber (SBR)/silica composites has been studied. Morphologies of silica in SBR with different contents are investigated by scanning electron microscopy, which indicates that silica can well disperse in SBR matrix below the content of 40 %, otherwise aggregates or agglomerates will generate. Composites with around 40 % silica content show excellent mechanical properties and retention ratios after aging at 85 °C for 6 days. The values of activation energy (E _a) of pure SBR and its composites are calculated by Kissinger and Flynn–Wall–Ozawa methods based on thermogravimetric (TG) results, which suggests that composite with about 20 % silica has minimum E _a, and composite with 30–40 % silica has maximum E _a. According to TG curves, it is found that silica can suppress the formation of char leading to decline in stability to some extent. On the other side, silica also has positive effect on improving thermal stability of the matrix as filler. Thus, the SBR/silica composites with silica content of 30–40 % can possess both excellent resistance to thermal oxidative degradation and superior mechanical properties.     

Water sorption heats on silica-alumina-based composites for interseasonal heat storage

CaCl₂-containing composites have been prepared by depositing the hydrated salt (by incipient wetness impregnation) on three different silica-aluminas with various Si/Al ratios. The surface area and porosity of all the samples were determined by N₂-adsorption at ?196 °C, and their water sorption properties were investigated by thermogravimetry linked to differential scanning calorimetry (TG–DSC) in order to determine the quantity of adsorbed/desorbed water and the related heats. The heat released and the quantity of adsorbed water were found to depend on parameters such as the silica-alumina pore diameters, the Si/Al ratio, and the presence of accessible CaCl₂ active phase. The short-term stability of both supports and composites has been also checked by performing successive hydration–dehydration cycles. The sample with the lower Si/Al ratio provided the highest heat per surface area of material, and the heat released per mol of water increased with the amount of Al₂O₃ present in the samples. The deposition of CaCl₂ positively acted on the quantity of heat released during the water sorption, and the composite with the higher alumina content (75 mass% Al) showed the largest heat released per m² of material (2.4 J m^?2) compared to those containing 25 and 13 mass% Al (1.4 and 1.2 J m^?2, respectively).     

Thermogravimetry on wood powder-filled polyurethane composites derived from lignin

Novel polyurethane (PU) composites whose matrix is derived from lignin, molasses polyol and filler from wood powder were successfully prepared. Two kinds of polyol were mixed 0/100 to 100/0 in seven steps, and filler content was varied from 50 to 100 mass % to polyol content. Decomposition behaviour of PU composites was investigated by thermogravimetry. Apparent density and mechanical properties of the above composites were also measured. Surface texture was observed by scanning electron microscopy. Thermal decomposition of PU composites was found to occur in two stages. The first decomposition observed at 570–580 K (DT _d1, peak temperature of derivative curve) is attributed to the matrix of composites. The second stage decomposition depending on filler content, observed in a temperature range from 590 to 630 K (DT _d2), is attributable to filler homogenously associated with PU matrix. Marked differences were not found, when the kinds of lignin and molasses polyol composition were varied. The above PU composites were found to be thermally stabilised by the introduction of filler.     

Mechanical and thermal investigation of thermoplastic nanocomposite films fabricated using micro- and nano-sized fillers from recycled cotton T-shirts

The thermal and mechanical performance of composites with nano-sized cotton fillers embedded in low-density polyethylene (LDPE) is investigated. Microfibrillated cotton was prepared by microgrinding mechanical treatment of pulverized cotton (pCot) derived from waste T-shirts, resulting in nano-sized fibrils of the cellulose that retain high crystallinity. Film composites of LDPE with pCot before and after microgrinding were fabricated through melt extrusion and the effect of filler size on mechanical, thermal and morphological properties of the composite was investigated. Compounding microfibrillated cotton with LDPE resulted in well-dispersed nanocomposites with no discoloration after 10 min of melt extrusion at 170 °C. At concentrations up to 10 % by weight, the composites showed increased modulus, increased tensile strength and a slight decrease in elongation to break. Further improvement in the dispersion and mechanical properties of the cotton-based fillers was realized by the use of LDPE powder instead of polymer pellets fed to the extruder. This research demonstrates the processing and applicability of the use of recycled cotton-based nano-sized fillers in melt-processing.     

Effect of AlN content on the performance of brominated epoxy resin for printed circuit board substrate

Polymer matrix composites, based on brominated epoxy, a type of material widely used in printed circuit boards (PCBs), as matrix and AlN particle as filler were prepared. The influences of AlN content on the mechanical, thermal, and electrical properties of the composites were investigated by uniaxial tensile test, TMA, thermal conductivity measurement, DMA, and dielectric properties measurement. It was found that the properties of composites monotonically varied with AlN content except that maximum tensile strength and strain of composites corresponded to a filler content of 10 wt %. The results of DMA also showed the AlN reinforcement was more pronounced above T_g, and the peak area of tan δ versus T curves decreased with AlN content, which implied the damping capacity of the composite gradually decreased. The increase in T_g and decrease in damping were probably due to strong interaction between the AlN and epoxy matrix inhibiting the mobility of the epoxy chain. In addition, different theoretical models reported in the literature were used to predict the E, CTE, k, and D_k, and compared with the experimental data. Finally, suitable models were recommended in the present materials system. For the significant improvement of performance of epoxy, we can conclude that these composite materials may be promising for PCB substrate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1662–1674, 2007     

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.     

Influence of barium titanate nanofiller on PEO/PVdF-HFP blend-based polymer electrolyte membrane for Li-battery applications

Organic-inorganic hybrid membranes based on poly(ethylene oxide) (PEO) 6.25 wt%/poly(vinylidene fluoride hexa fluoro propylene) [P(VdF-HFP)] 18.75 wt% were prepared by using various concentration of nanosized barium titanate (BaTiO₃) filler. Structural characterizations were made by X-ray diffraction and Fourier transform infrared spectroscopy, which indicate the inclusion of BaTiO₃ in to the polymer matrix. Addition of filler creates an effective route of polymer-filler interface and promotes the ionic conductivity of the membranes. From the ionic conductivity results, 6 wt% of BaTiO₃-incorporated composite polymer electrolyte (CPE) showed the highest ionic conductivity (6 × 10^?3 Scm^?1 at room temperature). It is found that the filler content above 6 wt% rendered the membranes less conducting. Morphological images reveal that the ceramic filler was embedded over the membrane. Thermogravimetric and differential thermal analysis (TG-DTA) of the CPE sample with 6 wt% of the BaTiO₃ shows high thermal stability. Electrochemical performance of the composite polymer electrolyte was studied in LiFePO₄/CPE/Li coin cell. Charge-discharge cycle has been performed for the film exhibiting higher conductivity. These properties of the nanocomposite electrolyte are suitable for Li-batteries.     

Nanoscale composite materials in the system SiO2–TiO2

Nanoscale composite materials based on the SiO₂–TiO₂ system were prepared in the form of co-precipitated composites and core SiO₂–shell TiO₂ composites, with specific surface area 150–650 m²/g and sorption volumes 0.1–1.0 cm³/g. It is shown that variation of phase composition and morphology permits to change their structural-adsorption properties and nanocrystallites size after thermal treatment. It is discovered that co-precipitated composite materials differ from core SiO₂–shell TiO₂ composites by a component interaction degree. It determines the difference of the titan-containing component crystallization process and alteration of their structural-absorption properties after thermal treatment. The results of the tests of composites as photocatalysts for Rhodamine B decomposition reaction, as catalysts of Hantzsch and Biginelli reaction, and as fillers in electrorheological fluids are shown.     

Erratum to: Nanoscale composite materials in the system SiO2–TiO2

Nanoscale composite materials based on the SiO₂–TiO₂ system were prepared in the form of co-precipitated composites and core SiO₂–shell TiO₂ composites, with specific surface area 150–650 m²/g and sorption volumes 0.1–1.0 cm³/g. It is shown that variation of phase composition and morphology permits to change their structural-adsorption properties and nanocrystallites size after thermal treatment. It is discovered that co-precipitated composite materials differ from core SiO₂–shell TiO₂ composites by a component interaction degree. It determines the difference of the titan-containing component crystallization process and alteration of their structural-absorption properties after thermal treatment. The results of the tests of composites as photocatalysts for Rhodamine B decomposition reaction, as catalysts of Hantzsch and Biginelli reaction, and as fillers in electrorheological fluids are shown.     

Measurement of thermal diffusivity of filler-polymide composites by flash radiometry

Thermal diffusivity D of filler-polyimide composites was investigated using flash radiometry. The fillers used were: diamond, alumina, boron nitride, aluminium nitride, silicon carbide, and silicon carbide whiskers, Composite films were prepared by casting a polyamic acid solution with dispersed filler on a glass plate and then annealing. The effects of filler type, size, content, and shape on D were studied. D increased with increasing average filler particle diameter and filler content. For the composite filled with fine Al₂O₃ whose average particle diameter is about 0.2 μm, aggregates of filler were observed with dimensions up to a few microns. The formation of thermal paths through this aggregate enhances thermal diffusion. For the composites filled with high thermal conductivity filler such as BN and AIN, there was a strong increase in D above a filler content of 20 vol %. D was ten times larger than that of unfilled polyimide when the BN content was 54 vol %. D of the SiC-whisker composite increased strongly up to a filler content of 18 vol %. Above this content D significantly decreased, probably because of interconnected voids formed by mold shrinkage.     

Mechanical,dynamic mechanical,and thermal analysis of Shorea robusta-dispersed polyester composite

The influence of Shorea robusta natural filler loading (5, 10, 15, 20, and 25 v/v%) on the mechanical, dynamic mechanical, biodegradability, and thermal stability of the polyester composite was analyzed. The composites were fabricated using hand lay-up method. The maximum mechanical properties, storage modulus, and glass transition temperature were observed for the composite with 20 v/v% filler. The peak height of Tanδ was found to be lesser for the same. Thermal analysis results revealed that the thermal stability of composite increased with the incorporation of Shorea robusta as natural filler. Biodegradability testing showed that the addition of filler resulted in weight loss of the composite under soil burial test.     

Thermal degradation of Pb(Zr0.53Ti0.47 )O3/poly(vinylidene fluoride) composites as a function of ceramic grain size and concentration

Poly(vinylidene fluoride)/Pb(Zr_0.53Ti_0.47)O₃,([PVDF]_1?x/[PZT]_x) composites of volume fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powders with average grain sizes of 0.2, 0.84, and 2.35 μm in different volume fraction of PZT up to 40 % were mixed with the polymeric matrix. The influence of the inorganic particle size and its content on the thermal degradation properties of the composites was then investigated by means of thermo-gravimetric analysis. It is observed that filler size affects more than filler concentration the degradation temperature and activation energy of the polymer. In the same way and due to their larger specific area, smaller particles leave larger solid residuals after the polymer degradation. The polymer degradation mechanism is not significantly modified by the presence of the inorganic fillers. On the other hand, an inhibition effect occurs due to the presence of the fillers, affecting particularly the activation energy of the process.     

The effect of granite powder on mechanical,structural and water absorption characteristics of alkali treated cordia dichotoma fiber reinforced polyester composite

Environmental and societal concerns such as pollution, disposal of solid waste, requirement of different conflicting properties for materials in varied applications and cost are the main reasons for the development of new materials from the existing materials. The concerns may possibly be overcome by substituting natural fibers for synthetic fibers. In this study, a hybrid composite was developed by reinforcing the natural fiber “cordia dichotoma” and filler “granite powder” into polyester resin. This composite was fabricated using hand lay-up method. Cordia dichotoma fibers were surface treated with NaOH for reducing the hydrophilic nature of the fiber. Unused industrial waste in the form of granite powder obtained from the granite polishing industry is utilized as reinforcement in polymer composite. The hybrid composite was prepared by reinforcing a constant cordia dichotoma fiber content of 20 wt % and varying the granite powder weight (wt. %) percentages (0, 5, 10, 15, and 20) into polyester resin. Mechanical properties (tensile, flexural and impact) of hybrid composites were investigated. The novelty of this work lies in utilization of granite powder sourced from industrial waste utilized as filler material. Granite, as one of the hard materials, may improve wear and other mechanical properties. Following the results obtained, granite powder could be evidenced as a good filler material for the betterment of composites mechanical properties. Also, the ability of this filler material is proved in decreasing water absorption and chemical resistance. Scanning electron microscope (SEM) analysis was performed to investigate the bonding and distribution of granite powder within both the fiber as well as resin in the composite. Besides, the presence of chemical functional groups in the composite was traced by Fourier transform Infrared spectroscopy (FTIR). Also, Thermo-gravimetric analysis (TGA) was carried out and the composite was found to be thermally stable up to 415 °C.     

Investigation of the structure and swelling of poly(N-isopropyl-acrylamide-acrylamide) and poly(N-isopropyl-acrylamide-acrylic acid) based copolymer and composite hydrogels

We synthesized, thermo- and pH-sensitive gels and tested them as skin extenders. Our aim is the development of copolymer and composite hydrogels that, when implanted under the human skin, swell osmotically and thereby induce skin growth. In the course of the polymerization reaction, we produced copolymers with variable compositions, starting from different acrylic compounds [N-isopropyl-acrylamide (NIPAAm), acrylamide (AAm), and acrylic acid (AAc)]. The mechanical strength and the swelling stability of the gels are enhanced by the addition of fillers [Na-montmorillonite and Na-montmorillonites organophilized with alkylammonium ions (C_n-m.), n?=?4, 12, 18]. With this method we synthesized composite hydrogels. We observed that in the case of composites synthesized with the addition of fillers, relatively low filler contents (1–5 wt.%) resulted in more extensive swelling and stronger gel structure. During the experiments, the monomer composition (0/100–100/0 mol% NIPAAm/AAm or AAc) and the cross-link density (50–1500 mol%) of the gels (M/C ratio) and, in the case of composites, the quality and quantity of fillers are varied. The filler content of composites varies between 1 and 25 wt.%. The extent of swelling and the viscoelastic properties can be manipulated through the ratios of these parameters. In the case of certain copolymer and composite gels, values of desorption enthalpy (ΔH _m) corresponding to the actual water contents were also determined by thermoanalytical measurements (differential scanning calorimetry, DSC). Swelling values determined by gravimetry and enthalpies calculated from DSC measurements were found to be in good correlation. Even in the case of the relatively hydrophobic poly(NIPAAm)-based gels, an enthalpy value of 98.41 kJ/mol was obtained, which is twice the value measured in pure water (41.74 kJ/mol). Evaluation and comparison of the rheological and DSC results also allowed conclusions to be drawn concerning the types of interaction operating among the three components of the system, i.e., the polymer skeleton and the filler and water molecules.     

Amorphous Calcium Phosphate Based Composites: Effect of Surfactants and Poly(ethylene oxide) on Filler and Composite Properties

The uncontrolled aggregation of amorphous calcium phosphate (ACP) particulate fillers and their uneven distribution within polymer matrices can have adverse effects on the properties of ACP composites. In this article, we assessed the influence of nonionic and anionic surfactants and poly(ethylene oxide) (PEO) introduced during the preparation of ACP on the particle size distribution and compositional properties of ACP. In addition, the mechanical strength of polymeric composites utilizing such fillers with a photo‐activated binary methacrylate resin was evaluated. Zirconia‐hybridized ACP (Zr‐ACP) filler and its corresponding composite served as controls for this study. Surfactant‐ and PEO‐ACPs had an average water content of 16.8% by mass. Introduction of the anionic surfactant reduced the median particle diameter about 45% (4.1 µm versus 7.4 µm for the Zr‐ACP control). In the presence of PEO, however, the d_m increased to 14.1 µm. There was no improvement in the biaxial flexure strength (BFS) in any of the dry composite specimens prepared with the surfactant and/or PEO‐ACPs compared to those formulated with Zr‐ACP. The BFS of wet composite specimens decreased by 50% or more after a month‐long exposure to saline solutions. Other types of surfactants and/or polymers as well as alternative surface modification protocols need to be explored for their potential to provide better dispersion of ACP into the matrix resin and better mechanical performance ACP composites.