Increasing Filler Content Research Articles

Preparation and characterizations of SiCw/SEBS-g-MAH composite film

Silicon carbide whiskers (SiCws) were modified with silane coupling reagent with the aid of ultrasonic agitation, and SiCw/SEBS (styrene-ethylene-butadiene-styrene) grafted with maleic anhydride(SEBS- g-MAH) composites were prepared by a solution method. The effects of modification on the SiCw and the structure morphology, mechanical property, thermal stability, and hydrophobicity of composites were studied. The results show that the tensile strength of composites increased gradually with increasing filler contents, ranging from 19.05 to 24.91 MPa. The pyrolysis temperature of composites to begin to lose mass increased gradually. Comparing with the pure SEBS- g-MAH film beginning to lose mass at 365°C, the composite with 2.5% modified SiCw lost mass at 402°C, which had improved by 37°C. With increasing content of SiCw, the hydrophobicity of composite was enhanced. Compared with the pure SEBS- g-MAH film, the water contact angle of composite with 2.5% SiCw had been enlarged by 40%, from 65.56° to 91.57°.

Carbon-Based Aeronautical Epoxy Nanocomposites: Effectiveness of Atomic Force Microscopy (AFM) in Investigating the Dispersion of Different Carbonaceous Nanoparticles.

The capability of Atomic Force Microscopy (AFM) to characterize composite material interfaces can help in the design of new carbon-based nanocomposites by providing useful information on the structure–property relationship. In this paper, the potentiality of AFM is explored to investigate the dispersion and the morphological features of aeronautical epoxy resins loaded with several carbon nanostructured fillers. Fourier Transform Infrared Spectroscopy (FTIR) and thermal investigations of the formulated samples have also been performed. The FTIR results show that, among the examined nanoparticles, exfoliated graphite (EG) with a predominantly two-dimensional (2D) shape favors the hardening process of the epoxy matrix, increasing its reaction rate. As evidenced by the FTIR signal related to the epoxy stretching frequency (907 cm−1), the accelerating effect of the EG sample increases as the filler concentration increases. This effect, already observable for curing treatment of 60 min conducted at the low temperature of 125 °C, suggests a very fast opening of epoxy groups at the beginning of the cross-linking process. For all the analyzed samples, the percentage of the curing degree (DC) goes beyond 90%, reaching up to 100% for the EG-based nanocomposites. Besides, the addition of the exfoliated graphite enhances the thermostability of the samples up to about 370 °C, even in the case of very low EG percentages (0.05% by weight).

Waste marble dust‐filled glass fiber‐reinforced polymer composite Part I: Physical, thermomechanical, and erosive wear properties

This research article presents the fabrication and investigation of physical, thermomechanical, and erosive wear properties of glass fiber‐reinforced epoxy composites with and without waste marble dust. The composites were fabricated by vacuum‐assisted resin transfer molding (VARTM) technique under controlled operating condition. The filler material (marble dust) was varied in the range of 0–30 wt% in the composite at an interval of 10 wt% to find out the physical (density, void content, hardness and XRD), thermomechanical (storage modulus, loss modulus, damping factor, and thermal conductivity), and erosive wear rate, respectively. This study clearly demonstrated that with the increased filler content, the density, void content, and hardness of the composites were shown promising results along with the crystallinity of the composites. The storage modulus and loss modulus of the unfilled and particulate‐filled composites were shown positive effect up to a temperature range of 60°C and then observed decreased trend irrespective of change in filler content with the increased temperature. However, as far as erosion rate was concerned, the particulate‐filled composites were shown better wear resistance with the change in impact velocity as well as impingement angle in steady‐state operating condition as compared with unfilled composite. At the end, the obtained experimental results were compared with already reported theoretical model in order to validate the results along with the microstructural analysis of composites were also studied to understand the wear mechanism. POLYM. COMPOS., 40:4113–4124, 2019. © 2019 Society of Plastics Engineers

Manifestation of Interactions of Nano-Silica in Silicone Rubber Investigated by Low-Frequency Dielectric Spectroscopy and Mechanical Tests.

Silicone rubber composites filled with nano-silica are currently widely used as high voltage insulating materials in power transmission and substation systems. We present a systematic study on the dielectric and mechanical performance of silicone rubber filled with surface modified and unmodified fumed nano-silica. The results indicate that the different interfaces between the silicone rubber and the two types of nano-silica introduce changes in their dielectric response when electrically stressed by a sinusoidal excitation in the frequency range of 10−4–1 Hz. The responses of pure silicone rubber and the composite filled with modified silica can be characterized by a paralleled combination of Maxwell-Wagner-Sillars interface polarization and DC conduction. In contrast, the silicone rubber composite with the unmodified nano-silica exhibits a quasi-DC (Q-DC) transport process. The mechanical properties of the composites (represented by their stress-strain characteristics) reveal an improvement in the mechanical strength with increasing filler content. Moreover, the strain level of the composite with a modified filler is improved.

Through-thickness thermal conductivity enhancement of carbon fiber composite laminate by filler network

This paper successfully introduces highly conductive filler network in composite laminate to enhance its through-thickness thermal conductivity (TC). The effects of filler type, filler content, filler dimension, and ply scheme on through-thickness TC are investigated. The results show that one-dimensional carbon fiber fillers occupy both interlaminar and inter-tow regions forming the river-pattern conductive network inside the modified composite. Hence, the through-thickness TC is enhanced effectively up to 2.21 W·m−1 K−1 for the carbon fiber filler modified composite, which increases with increasing filler content. The composites modified by shorter fiber fillers show higher through-thickness TCs than those modified by long fillers, due to relatively higher content of shorter fillers in inter-tow gap, easy orientation along through-thickness direction and higher filler volume faction in conductive path. These results prove the superiority of continuous conductive network with concentrated fillers, and guide the structural design of composite laminate to manage its through-thickness TC.

Preparation of high-performance cellulose composite membranes from LiOH/urea solvent system

New green solvent system alkali (such as NaOH and LiOH)/urea which could rapidly dissolve cellulose could be potentially used to prepare high-performance regenerated cellulose materials with low cost. Pure regenerated cellulose materials have relatively low strength inherent effects. In this work, we choose TEMPO-oxide cellulose nanofiber (CNF) and graphene oxide (GO) as fillers to prepare isotropic regenerated cellulose membrane (RCM) with significantly enhanced mechanical properties. Dynamic mechanical analyzer (DMA) test shows that RCM with content of 5 wt% CNF has the maximum enhancement value of 32.5% improvement comparing with pure RCM. And RCM with 0.4 wt% GO has the maximum improvement of 17.9%. Mechanical properties decrease with further increasing filler contents. We employ transmission electron microscopy to confirm the structure of fillers in solution and scanning electron microscopy to observe the microstructures of these RCMs. The results are consistent with DMA tests. In addition, XRD results confirm that the crystal structure of RCMs is the same with RCMs without filler. Thermogravimetric analyses results indicate that RCMs keep great thermal stability below 300 °C. Transmittance (Tr) property is carried out by UV–Vis spectroscopy. Pure RCMs and CNF/RCMs keep high transparency at the wavelength of 800 nm. Transparency of RCMs with GO decrease quickly when the content of GO increases. In conclusion, the enhancement mechanism is proposed as the addition of fillers makes up the defects in RCMs. Furthermore, CNF illustrates large aspect ratio which is beneficial for stress transfer. As for GO, polar groups on surface provide strong interaction with the matrix. This is the first time that the enhancement effects of different fillers are systematically analyzed and compared for RCMs system. Our work could benefit the selection of appropriate fillers for such green solvent system and expand its range of applications.

Rheological Properties and Thermal Conductivity of Epoxy Resins Filled with a Mixture of Alumina and Boron Nitride.

Electronic packaging materials with high thermal conductivity and suitable viscosity are necessary in the manufacturing of highly integrated electronic devices for efficient heat dissipation during operation. This study looked at the effect of boron nitride (BN) platelets on the rheology and thermal conductivity of composites based on alumina (Al2O3) and epoxy resin (EP) for the potential application as electronic packaging. The viscosity and thermal conductivity of the composite were increased upon increasing filler content. Furthermore, thermal conductivity of the BN/Al2O3/EP was much higher than that of Al2O3/EP at almost the same filler loadings. These unique properties resulted from the high thermal conductivity of the BN and the synergistic effect of the spherical and plate shapes of these two fillers. The orientation of BN platelets can be controlled by adjusting their loading to facilitate the formation of higher thermally conductive pathways. The optimal content of the BN in the Al2O3/EP composites was confirmed to be 5.3 vol %, along with the maximum thermal conductivity of 4.4 W/(m·K).

Considerations for readdressing theoretical descriptions of particle-reinforced composite food gels.

The aim of this work was to address the ability of established theoretical models to describe the small deformation mechanical properties of particle-filled food protein gels. To this end, the effect of incorporating glass microspheres on the elastic modulus of heat-set whey protein isolate/xanthan gum gels is reported. Filler size and polydispersity strongly influenced the observed reinforcement with increasing filler content; however, these effects were also strongly correlated to the ionic strength of the gelator phase (0-200 mM NaCl). Fillers with greater polydispersity provided less reinforcement at high filler content, which was associated with improved packing efficiency. Increasing ionic strength reduced the extent of filler/matrix binding, drastically reducing the impact of the smaller glass microspheres (4 μm, 7-10 μm). Larger particles increased the elastic modulus at high salt content due to interfacial stress concentration and particle-particle contacts. Theoretical fits could not satisfactorily describe the general trend in reinforcement observed with increasing filler content, despite employing various methods to account for the effects of filler self-crowding. Using an empirical approach, we propose an alternative functional form which provides improved fits over the entire range of filler content investigated. This general power law (GPL) model provided physically reasonable values for the maximum packing fraction through an empirically-derived expression for the scaling exponent. A weighted average approach was also proposed to incorporate effects of imperfect filler/matrix adhesion. This method incorporates contributions of both bound and unbound fillers, providing a means to model the effect of increasing ionic strength.

حساب الحجب الإشعاعي للأشعة السينية لبوليمر البولي اثيلين واطئ الكثافة والمطعم بمسحوق قشور المحار المستخرج من بحر قزوين

في هذا البحث تم دراسة حجب الأشعة السينية (توهين الأشعة) باستخدام عينات من بوليمر البولي اثيلين واطى الكثافة والمصنع في معمل البتر وكيمياويات في البصرة - العراق، والمضاف اليه مسحوق قشور المحار المستخرج من بحر قزوين في إيران كحشوات مالئة وبنسب وزنيه (2.5% ,5 % ,10 % ,15% ,20%) وعند حجم دقائق للحشوات مساو أو أقل من (0.25mm) إذ تمت دراسة معامل التوهين الخطي (μ) ومعدل المسار الحر (λ)، وبينت النتائج العملية بأن قشور المحار تعمل على تقليل الفراغات بين السلال البوليمرية وخاصة عند النسب العالية (%20-%10) مما يعكس إمكانية البوليمر مع المضاف عند هذه النسب بحجب قسم كبير من الأشعة السينية المسلطة على النماذج، حيث تمت الدراسة العملية بتسليط حزمة من الأشعة بطاقة مقدارها (30 KV) وباستخدام وحدة الأشعة السينية (x- ray unit) مع أنبوبتي توليد الأشعة ومنظومة كاشف عداد كايكر - موللر (G-M detector) وبطاقة مقدارها (V VG.M =600) ومن خلال القيم العلمية في هذا البحث نستنتج بأن قيم معدل المسار الحر (λ) تتناسب تناسبا عكسيا مع النسب الوزنية للمادة المتراكبة وان القيم العملية لمعامل التوهين الخطي (μ) تتناسب تناسبا طرديا مع النسب الوزنية للمادة المتراكبة (البوليمر المضاف إليه مسحوق قشور المحار) وخاصة عند النسب الوزنية العالية. فتم الحصول على أعلى قيمة لمعدل المسار الحر عند النسبة الوزنية (%2.5) وهي (2.1 cm (بينما كانت أقل قيمة لمعدل المسار الحر وهي (0.40 cm) عند النسبة الوزنية (%20). وتم الحصول على أعلى قيمة لمعامل التوهين الخطي وهي (2.44 cm-1) عند النسبة الوزنية للمادة المتراكبة وهي (%20)، وأقل قيمة كانت عند النسبة الوزنية (%2.5) وهي (0.49 cm-1).

Development of mechanical properties in dental resin composite: Effect of filler size and filler aggregation state

The aim of this work was to study the effect of filler size and filler aggregation state on the mechanical properties of dental resin composites evaluated at filler loadings between 20 wt% and up to 76.5 wt%. Non-aggregated silica nanoparticles (SiNPMPS) (80 nm), doughnut-shaped silica nanoclusters obtained by spray drying (SDSiNPMPS) (3.5 μm) and amorphous barium-alumina borosilicate microparticles (BaAlBoSiMPS) (1.0 μm), functionalized by 3-methacryloxypropyl trimethoxysilane (MPS), were the fillers incorporated into resin matrix dental composites composed of triethylene glycoldimethacrylate (TEGDMA), urethane dimethylacrylate (UDMA), bisphenol A polyethylene glycol diether dimethacrylate (Bis EMA), and bisphenol A glycidyl methacrylate (BisGMA) (0.3:0.7:1:1 weight ratio, respectively). The mechanical properties developed in the resin composites were correlated with the formation of percolated-like particle networks, as observed by scanning electron microscopy (SEM), and volume fraction percolation thresholds (ϕc) calculated from a percolation model. Resin composites with non-aggregated SiNPMPS showed an apparent percolation threshold ϕc = 0.15 (i.e. 27 wt%); above this filler concentration and up to a volume fraction of particles (ϕP) of 0.24 (i.e. 40 wt%) there was an increase in the flexural modulus and the compressive strength of the resin composite. However, a further increase in filler concentration diminished all its mechanical properties due to a decrease in the particle-matrix adhesion strength, demonstrated by the increase in surface roughness and fracture steps as observed by SEM images. On the other hand, a resin composite filled with doughnut-shaped silica nanoclusters (SDSiNPMPS) showed an apparent percolation threshold ϕc = 0.41 (i.e. 60 wt%); increasing filler loading over this concentration generated an improvement in its mechanical properties, except the flexural strength also due to a decrease in the particle-matrix adhesion strength. The resin composites obtained with amorphous individual BaAlBoSiMPS microparticles (1.0 μm) and BaAlBoSiMPS microparticle aggregates (ca. 40.0 μm) showed an apparent percolation threshold ϕc = 0.41 (i.e. 64 wt%) that promoted an improvement in all their mechanical properties. SEM image of BaAlBoSiMPS resin composite at high filler loading (≥ 60 wt%) showed a decrease in fracture steps and no presence of voids, indicating a better adhesion between amorphous BaAlBoSiMPS particles and the polymeric matrix, which explains the improvement of mechanical properties. Resin composites filled exclusively with silica doughnut-shape nanoclusters or amorphous BaAlBoSiMPS microparticles could develop mechanical properties similar to or even better than those obtained by mixing nanofillers with spherical nanoclusters, which are commonly used in commercial resin composites.

Energy dissipation accompanying Mullins effect of nitrile butadiene rubber/carbon black nanocomposites

Mullins effect of carbon black filled nitrile butadiene rubber compounds and vulcanizates during cyclic tensile deformation is investigated and the influences of thermal annealing of the stretched samples, the deformation velocity and history and the solvent swelling are discussed. The energy losses associated with recovery hysteresis and softening accompanying the Mullins effect at a given crosshead velocity are quantitatively analyzed. The results show that the recovery hysteresis involves in microscopic deformation of the rubber phase in the nanocomposites but it disappears in the swollen samples. On the other hand, the softening is associated with both the rubber and filler phases; its energy loss increases with increasing filler content and decreases significantly by swelling. Furthermore, the softening of samples stretched at room temperatures is recoverable after conditioning at 80 °C but the recovery is retarded significantly by filler. The investigation allows gaining recognition of the important role played by the viscoelastic rubber matrix and the influence of the filler.

Characterization of Highly Filled PP/Graphite Composites for Adhesive Joining in Fuel Cell Applications

In order to evaluate the suitability of graphite composite materials for use as bipolar plates in fuel cells, polypropylene (PP) was melt compounded with expanded graphite as conductive filler to form composites with different filler contents of 10–80 wt %. Electrical resistivity, thermal conductivity, and mechanical properties were measured and evaluated as a function of filler content. The electrical and thermal conductivities increased with filler content. Tensile and flexural strengths decreased with the incorporation of expanded graphite in PP. With higher graphite contents, however, both strength values remained more or less unchanged and were below the values of pure PP. Young’s-modulus and flexural modulus increased almost linearly with increasing filler content. The results of the thermogravimetric analysis confirmed the actual filler content in the composite materials. In order to evaluate the wettability and suitability for adhesive joining of graphite composites, contact angle measurements were conducted and surface tensions of composite surfaces were calculated. The results showed a significant increase in the surface tension of graphite composites with increasing filler content. Furthermore, graphite composites were adhesively joined and the strength of the joints was evaluated in the lap-shear test. Increasing filler content in the substrate material resulted in higher tensile lap-shear strength. Additionally, the influence of surface treatment (plasma and chemical) on surface tension and tensile lap-shear strength was investigated. The surface treatment led to a significant improvement of both properties.

Preparation of halloysite/polyvinylidene fluoride composite membrane by phase inversion method for lithium ion battery

In this paper, the composite membranes based on poly(vinylidene fluoride) (PVDF) with different amounts of halloysite (HNT) nano-filler were prepared by phase inversion method for the application of lithium ion batteries. The effect of the content of HNT on the crystallinity and morphology of the composite membranes were investigated. The results showed that the crystallization behaviors of the HNT/PVDF composite membranes were reduced with the increase of HNT filler content. Furthermore, the introduction of HNT into PVDF matrix remarkably affected the formation rate of nuclei which could evolve into pores to change surface morphology. The HNT/PVDF composite membranes showed the sufficient porosity and good affinity between the eletrolyte as well as the electrode, which led to superb electrolyte uptake and low interfacial impedance. Among HNT/PVDF composite membranes, in particular, the 4-HNT/PVDF composite membrane with 4 wt% HNT content had a great electrolyte uptake (430.2%), superior electrochemical stability window (4.5 V), high ionic conductivity (2.4 mS/cm), and low interfacial impedance (63Ω). The cells assembled with the 4-HNT/PVDF composite membranes obtain discharge capacities of 164.72 mAh/g (0.1C) and 134.88 mAh/g (2C), corresponding to 96.89% and 79.34% of the theoretical capacity of LiFePO4 (170 mAh/g), respectively, better cycle performance (with capacity retention 89.12% after 100 cycles) at 0.5C and excellent rate performance. It is concluded that the content of HNT deeply affects membrane performance. Therefore, the 4-HNT/PVDF composite membranes could be a good option of high performance lithium ion batteries.

Study on Preparation, Thermal Conductivity, and Electrical Insulation Properties of Epoxy/AlN

High thermal conductive epoxy composites are particularly suitable for the impregnation process of superconducting power equipment due to their high electrical insulation property and low thermal expansion. In this study, the preparation and impregnation procedures of high thermal conductive epoxy (EP) composites were investigated first. Based on the orthogonal experiment results and the range analysis, the critical factors affecting on the thermal conductivity of final product in sequence were determined as aluminum nitride (AlN) filler content, filling ratio of AlN with different sizes, curing temperature, and surface modification method of AlN fillers. Through investigating the preparation factors of thermal conductive AlN/EP composites on their electrical insulation properties further, it was found that the increase of filler content, addition of nanofillers, and low curing temperature are advantageous for improving the electrical insulation property of composites. This study offers an experimental basis for the preparation and electrical application of dielectric polymer composites with high thermal conductivity in HTS equipment' manufacture.

Surface Discharge Behaviours, Dielectric and Mechanical Properties of EPDM based Nanocomposites containing Nano-BN

Surface discharge often occurs between a solid dielectric and high voltage conductor which is one of the major insulation failure modes. In this paper, surface discharge characteristics (phase resolved patterns, magnitude and repetition rate) of EPDM/BN nanocomposites are studied. Also investigated are the dielectric response, volume resistivity and mechanical properties. Surface modified boron nitride (BN: 50 nm) particles are procured for the fabrication of nanocomposites. Samples are exposed to surface discharges using the IEC (b) electrode configuration and partial discharge (PD) measurements are done according to IEC 60270 Standard. Experimental results proclaimed that PD behaviours depend on the nanoparticle loading in the EPDM. The PD inception voltage improves with increasing filler content up to 7 wt% and discharge integrated parameters are remarkably lower. Embedded nanoparticles strengthen the barrier resistance of the nanocomposites, which may help in reducing the net electric field in the air gap and thus mitigate the PD intensity. The permittivity value at power frequency follows a similar increasing trend up to 5 wt% then drops whilst the dielectric loss is the lowest for the 1 wt%. Consistent improvement in volume resistivity and mechanical tests results are observed with BN-contents.

Tribo-magnetization of the PTFE composites containing ferromagnetic fillers of Fe, Co, or Ni

In this paper, the tribo-magnetization and tribological performances of the Fe(or Co, or Ni)/PTFE composites were studied. The effects of sliding velocity, normal load, and filler content on the tribo-magnetization and tribological performances of the composites were mainly discussed. The micro-morphology of the worn surfaces was investigated by scanning electron microscopy (SEM) and optical microscopy (OM) to examine the wear behavior and transfer film of the friction couples. It was found that the magnetic flux density, induced by the friction of the composites, slowly increased with the increase of load, gradually decreased with the increase of velocity, and increased with the increasing filler content. The tribo-magnetization behavior of the PTFE composites containing ferromagnetic fillers will promote the aggregation of ferromagnetic particles on the surface. Moreover, the friction and wear of the composites are reduced due to the formation and stability of the frictional transfer film.

Mechanical and thermal properties of spent coffee bean filler/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biocomposites: Effect of recycling

Green composites were fabricated using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the matrix and spent coffee bean powder (SCBP) as a filler by simple solution casting method. The effect of varying concentrations (5–25 wt.%) of SCBP on the thermal and mechanical properties was studied. The SCBP filler had better thermal properties than the matrix and the composites. There was slight increase in the glass transition temperature of the composites with higher concentration of the filler when compared to the PHBV matrix. The weight remaining at endset temperatures of the composites was found to be higher than for the matrix indicating enhanced thermal stability. The contact angle of the composites increased with increasing filler content changing from 75.8° to 97°. The tensile strength and modulus of the composite films reduced with increasing filler concentration but a reverse trend was observed in case of the % elongation at break. However, the tensile properties were comparable with other synthetic polymers such as LDPE, HDPE etc. Furthermore, the recycling of films did not significantly affect the mechanical and thermal properties. Hence, with comparable thermal and tensile properties, these biocomposite films can be considered for replacing the conventional synthetic non-biodegradable polymers such as polyethylene and polypropylene for packaging applications.

Development of fiber-reinforced polypropylene with NaOH pretreated rice and coffee husks as fillers: Mechanical and thermal properties

Incorporation of agricultural wastes as fillers in fiber-reinforced plastics is gaining momentum in plastics engineering research. In this study, fiber-reinforced polypropylene (PP) with rice and coffee husks as filler material were developed. The effect of alkali (sodium hydroxide) pretreatment of the husks on mechanical and thermal properties of developed PP biocomposites was observed. Filler material loading was varied from 0% to 20% for rice husks and 0% to 10% for coffee husks. A twin-screw extruder was used for compounding the PP matrix with rice and coffee husk filler materials. Tensile strengths and percentage elongation results varied from 27.4 to 37.4 MPa and 2.4% to 70.3% (unmodified coffee husks), 31.1 to 37.4 MPa and 5% to 70.3% (unmodified rice husks), 30.7 to 37.4 MPa and 5.3% to 70.3% (modified coffee husks), and 30.7 to 37.4 MPa and 4.8% to 70.3% (modified rice husks). Young’s modulus ranged between 1656 and 2247.8 MPa for biocomposite PP samples with unmodified filler material. Young’s modulus ranged between 1740 and 2160 MPa after alkali treatment of the filler material. Charpy impact strengths ranged from 1.2 to 4 kJ/m2and 3.1 to 19.6 kJ/m2for samples containing unmodified and modified filler material, respectively. Thermogravimetric analysis showed that an increase in filler content resulted into delayed weight loss at high degradation temperatures. The results suggest that these developed fiber-reinforced plastics can be used in applications requiring high thermal stability and good mechanical properties.

Comparison of the carbon additives on the conductivity, thermomechanical, and corrosion properties for TEOS oligomer modified epoxy-amine coating systems

Four types of carbon filler, carbon black, mixture of carbon black and non-fullerene carbon nanotubes, non-fullerene carbon nanotubes, and purified fullerene carbon nanotubes were compared in a 2-K BPA-Epoxide-Amidoamne. The effect of carbon filler type and loading on the viscosity of coatings as well as mechanical, thermal, electrical, and general coating properties of the cured films were evaluated. General coating properties including pencil hardness, impact resistance, cross-hatch, and pull-off adhesion. Aggregation of carbon fillers at 1.0 wt% resulted in a decrease in film properties. Scanning electron microscope (SEM) was used to observe the surface morphology of a fracture film surface. The storage modulus and crosslink density increased and the maximum tan δ decreased with the increase of filler content. It was found that the most efficient material to enhance the electrical conductivity and anticorrosive properties of nanocomposite coating systems was fullerene CNT.

Preparation of cellulose nanofibers from Miscanthus x. Giganteus by ammonium persulfate oxidation

Carboxylic acid functionalized cellulose nanofibers (MxG-CNFA-CO2H) were successfully isolated from a sustainable grass hybrid Miscanthus x. Giganteus by a new two-step chemical oxidation, that involves bleach treatment and ammonium persulfate oxidation, followed by ultrasonication. The resulting MxG-CNFA-CO2Hs have ca. 1200 mmol/kg carboxylic acid surface groups, an aspect ratio of 230 (height of ca. 3.8 ± 0.8 nm and length of ca. 880 ± 300 nm) and 70% crystallinity. Interestingly, these MxG-CNFA-CO2Hs exhibit better thermal stability (as measured by thermal gravimetric analysis) and better dispersibility in DMF than corresponding cellulose nanocrystals (CNC) obtained from same biosource (MxG-CNC-CO2Hs) via acid hydrolysis. Poly(vinyl acetate):MxG-CNFA-CO2H composites show an increase in storage modulus (above Tg) with increasing filler content. Importantly, the mechanical properties of the poly(vinyl acetate):nanocellulose composites showed that the MxG-CNFA-CO2Hs exhibit significantly better reinforcement than the MxG-CNC-CO2H at the same weight percent filler content.