Good Filler Dispersion Research Articles

Aminated ZIF‐8 to facilitate CO2 sieving through polyvinyl alcohol/ionic liquid membranes

AbstractCO2 separation technology at low pressure is most desirable in carbon capture projects to mitigate global warming. Facilitated transport membranes offer selective and effective CO2 permeation using a wide range of carbon carriers at low pressure. Porous fillers were recently included as they can carry abundant fixed carriers besides offering open channels for CO2 permeation. This study investigates the effects of amine‐modified zeolitic imidazolate framework‐8 (ZIF‐8) with well‐defined micropores and gas sieving ability in polyvinyl alcohol (PVA) membranes containing an ionic liquid that worked as mobile carriers. The effects of amine‐modified ZIF‐8 and silica nanoparticles on membrane properties and separation performance were also compared. Fourier transform infrared spectra confirmed the incorporation of ZIF‐8, secondary amine, IL anions, and silica nanoparticles in PVA membranes. Energy dispersive analysis showed the good dispersion of inorganic fillers. The amine‐modified silica nanoparticles resulted in higher thermal stability compared to the amine‐modified ZIF‐8 in PVA membranes containing [bmin][Ac] ionic liquid, as shown in the thermogravimetric analysis. However, the CO2 separation performance of PVA membranes containing [bmim][Ac] ionic liquid was improved more significantly by the amine‐modified ZIF‐8 with microporous structure. A CO2/N2 ideal selectivity of 85.65 and CO2 permeance up to 4,502.91 GPU were attained. Unlike the CO2/N2 ideal selectivity, the CO2 permeance was not significantly affected either using [bmin][Ac] or [bmin][BF4]. The humid gas greatly enhanced the CO2 permeance without much changes in the CO2/N2 ideal selectivity due to the promotion of facilitated transport. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Protective graphene-based coatings for Zamak: Physical and electrochemical analysis

Concerns surrounding the widespread use of hazardous materials have increased over time and have led numerous states to implement regulations aimed at preserving human and environmental health. In response, industries like metallurgy have gradually transitioned from traditional, hazardous technologies to safer alternatives, such as using polymeric coatings to protect metals from corrosion. This study focuses on evaluating the protective properties of non-functionalized graphene oxide-based coating (GC) and functionalized graphene oxide-based coating (FGC) on the zamak samples. First, the powders were analyzed from structural, morphological, and spectroscopic perspectives. The formation of amino-silica groups on the graphene oxide sheets was confirmed through SEM-EDS, XRD, and FTIR analyses, validating the success of the functionalization process. Granulometric analysis demonstrated a good dispersion of fillers in the mixtures. Cross's theoretical model was applied to the rheological experiments to find the optimum way of coating application on metallic substrates. The corrosion resistance of the coatings was evaluated using OCP, LSV, PS, EIS, and salt spray experiments. The results revealed that the functionalized graphene oxide coating provided superior corrosion protection compared to other coatings on Zamak samples. AFM topographic images, along with roughness measurements, indicated a significantly less corroded surface when using the functionalized graphene oxide coating. Additionally, Raman spectroscopy confirmed the protective effectiveness of the FGC coating against corrosion.

Research Progress of Natural Rubber Wet Mixing Technology.

The performance of natural rubber (NR), a naturally occurring and sustainable material, can be greatly enhanced by adding different fillers to the NR matrix. The homogeneous dispersion of fillers in the NR matrix is a key factor in their ability to reinforce. As a novel method, wet mixing technology may effectively provide good filler dispersion in the NR matrix while overcoming the drawbacks of conventional dry mixing. This study examines the literature on wet mixing fillers, such as graphene, carbon nanotubes, silica, carbon black, and others, to prepare natural rubber composites. It also focuses on the wet preparation techniques and key characteristics of these fillers. Furthermore, the mechanism of filler reinforcement is also examined. To give guidance for the future development of wet mixing technology, this study also highlights the shortcomings of the current system and the urgent need to address them.

The Electromagnetic Shielding Properties of Biodegradable Carbon Nanotube–Polymer Composites

In this article, the electromagnetic shielding properties of carbon nanotube–polymer nanocomposites are presented. The composite fabrication technique is spray-drying, the usage of which leads to a uniform dispersion of carbon nanotubes (CNTs) in a polymer matrix. Obtaining good filler dispersion is necessary to form a continuous, electrically conductive network of CNTs inside the polymer matrix. In the described nanocomposites, the network of conductive filler particles acts as an electromagnetic radiation barrier. For this reason, developing a highly effective fabrication method is very important. Also, the method should be simple enough to be easily adopted in an industrial environment. The authors shows in this text that both goals mentioned are achieved. The obtained nanocomposite material not only has electrostatic shielding capabilities but comprises electromagnetic shielding properties, which fulfills the main goal of the presented work. It is also worth mentioning that the developed manufacturing method allows for the usage of different fillers and polymers and thus the fabrication of materials capable of meeting a wide range of requirements.

Multifunctional 3D-printed composites based on biopolymeric matrices and tomato plant (Solanum lycopersicum) waste for contextual fertilizer release and Cu(II) ions removal

The production of tomatoes faces significant challenges, including the high amount of waste generated during the harvest stage and copper-contaminated soil due to pesticide use. To address these issues and to promote a more sustainable agriculture, innovative biodegradable green composites for contextual controlled soil fertilization and Cu removal were produced by 3D-printing technology. These composites were made by incorporating NPK fertilizer flour and tomato plant waste particles (SLP) into three different biodegradable polymeric matrices: polylactic acid (PLA); a commercial blend of biodegradable co-polyesters (Mater-Bi®, MB) and their blend (MB/PLA, 50:50). Rheological characterization suggested the potential processability of all of the composites by FDM. Morphological analysis of printed samples confirmed the good dispersion of both filler and fertilizer, which also acted as reinforcement for MB and MB/PLA composites. SLP and NPK moduli were evaluated by powder nanoindentation and, for almost composites, the theoretical Halpin-Tsai model satisfactorily fitted the actual tensile moduli. The decrease in NPK fertilizer release rate and the increase in Cu(II) removal efficiency were achieved using whole 3D-printed composites. By selecting the appropriate matrix and incorporating SLP particles, it was possible to tune the NPK release rate and achieve copper absorption efficiency. Notably, MB samples containing SLP particles displayed the fastest release and the highest Cu(II) removal efficiency.Graphical abstract

Natural coal-derived graphite as rubber filler and the influence of its progressive graphitization on reinforcement performance

This study introduces a reinforcing rubber filler, natural coal-derived graphite (NCDG), evaluating how its progressive structural evolution from meta-anthracite (MA), semi-graphite (SG) to cryptocrystalline graphite (CG) during the natural graphitization process affects their reinforcing performance to styrene-butadiene rubber (SBR) composites. The highly graphitized NCDG fillers exhibit good filler dispersion, more bound rubber content, and well compatibility between filler and rubber matrix when compounded with SBR, and significantly enhance the mechanical properties of SBR composite (tensile strength can reach 22.8 MPa), as well as improving the storage modulus, wet-skid resistance, wear resistance, and electrical conductivity. The formation of microcrystalline multilayer graphene and graphene nanoplatelets exfoliated by mechanical shear stress during ball grinding and rubber compound mixing plays an important role in improving the reinforcement performance of rubber composites. This research provides valuable insights into the utilization of NCDG as a cost-effective and environment-friendly reinforcing filler for rubber composites.

Construction of silver-epoxy adhesive with suppressed silver migration rate based on thiol-silver interaction

The silver migration limits the application of silver based conductive adhesives in wet environment. The existing methods for inhibiting silver migration in epoxy conductive silver adhesives involve one or more issues such as cost, complexity, and inhibition of conductivity. Moreover, there is currently a lack of strategies that can suppress the silver migration effect while ensuring good dispersion of silver fillers in the matrix and constructing a good filler matrix interface. Herein, a facile method was reported suppressing the silver migration in silver-epoxy conductive adhesive. Tetrafunctional thiopentaerythritol tetramercaptoacetate (PERTMA) was introduced into 1,4-cyclohexanedimethanol diglycidyl ether (CHDMGE) epoxy resin as the curing agent. This method utilized the strong interaction between silver and thiols, including coordination and covalent bonding, to achieve good compatibility between filler and matrix. By tightly combining silver with the resin system, the content of free silver atoms was reduced, capturing and inhibiting the hydrolysis of silver atoms and their migration with current, and the conductivity of the conductive silver adhesive was not greatly degraded due to the silver-thiol interaction. At the same time, the introducing of PERTMA was able to reduce the surface hydrophilicity of epoxy resin, which also helped suppressing the silver migration effect under humid circumstances. The interaction between silver and thiol was characterized, and the influence of silver content on the curing behavior, material mechanical performance, conductivity, resistivity on silver migration and flexibility was explored. The CHDMGE/PERTMA/Ag conductive adhesive based on strong thiol-silver interaction had excellent resistance to silver migration, which occurred after 3500s, which was 10.67 times longer than the control group. In addition, the silver filler enhanced the tensile strength of the matrix resin by this thiol-silver interaction. This study will provide new ideas for the design and development of silver migration resistant conductive adhesives based on matrix filler interaction.

Three-in-one novel flame retardant through grafting organophosphorus onto Fe-MOF functionalized Mg(OH)2 for improving fire safety and mechanical properties of PBS composites

As one typically sustainable polymer material, poly(butylene succinate) (PBS) is highly necessary to improve its flame retardancy and simultaneously maintain satisfied mechanical performances. In this study, “three-in-one” novel flame retardant was synthesized through grafting organophosphorus onto Fe-MOF functionalized Mg(OH)2 (labeled as MH@Fe-MOF-P), then it was introduced into PBS matrix to investigate its effect on flame retardancy and mechanical properties. The results indicated that PBS/20MH@Fe-MOF-P exhibited excellent flame retardancy, including that the LOI was 29.6%, the UL-94 rating reached to V0, and the peak of heat release rate (PHRR) decreased by 82.1%. The flame retardant mechanism was ascribed to the synergistic effect of Mg(OH)2, Fe-MOF and organophosphorus on delaying the decomposition and catalyzing the carbonization of PBS. Meanwhile, PBS/20MH@Fe-MOF-P presented better mechanical performances than PBS/20MH and PBS/20MH@Fe-MOF composites, resulting from the special structure of MH@Fe-MOF-P to achieve good dispersion of fillers and strong polymer-filler interface adhesion. This work provides a novel strategy to modify Mg(OH)2 with high flame retardant efficiency, and also broadens the practical applications of PBS materials with balanced comprehensive performances.

Thermal Properties of Epoxy-GNP Based Nano-Dielectrics

This study highlights the thermal properties of nano-dielectrics materials composed of epoxy resin host and Graphene nano-platelets (GnP) have been studied. The introduction of the GnP nano-platelets (0.5, 1, 2, 3 and 5wt %) into the epoxy resin by the three roll mill technique following the Caframo mechanical mixer method is described. Asilane Coupling Agent (SCA) was used for the surface modification for better dispersion of filler in organic polymer matrix and for better compatibility between nano-platelets and host material. Thermal conductivity, glass transition temperature and thermal stability of nano-dielectrics were investigated based on the filler content. The synergistic effect was observed due to the introduction of GnP. The high-k nano-dielectric materials show better thermal conductivity and stability than that of the pure epoxy resins. The best performance of the composite is observed with 3wt% of graphene nano-platelets.

High filler content acrylonitrile‐butadiene‐styrene composites containing tungsten and bismuth oxides for effective lead‐free x‐ray radiation shielding

AbstractAcrylonitrile‐butadiene‐styrene (ABS) based composites with a high content of tungsten and bismuth oxide were developed using an innovative process to obtain lead‐free x‐ray shielding materials. ABS was chosen for its good mechanical properties and its widespread availability as a recycled material. The composites underwent flexural tests, Shore D hardness tests, thermogravimetric and morphological analysis, and their x‐ray attenuation properties were determined through numerical simulations and experimental measurements. Despite their high filler content (up to 75 wt%), the composites showed good filler dispersion within the polymeric matrix and maintained their mechanical properties. Across the investigated energy range (50–150 kV), the lead equivalence for x‐ray shielding was achieved with composite plates containing 75 wt% of tungsten and bismuth oxide, at thickness values corresponding to a weight increase of only 29% and 36%, respectively, in comparison to lead. These findings pave the way for a new generation of lead‐free x‐ray shielding materials. Moreover, their mechanical properties, including flexibility for potential application in wearable personal protective equipment, can be tailored by adjusting the filler content.Highlights High filler content lead‐free ABS composites with WO3 and Bi2O3 were developed. They show good polymer/filler interfacial adhesion and flexural properties. Numerical simulations of their x‐ray shielding properties were performed. Experimental tests with polychromatic sources confirmed good x‐ray attenuation. Results pave the way for the development of new lead‐free x‐ray shielding systems.

Polypyrrole-Tungsten disulphide 2D nanocomposites for ammonia sensing

An attempt was made to prepare nanocomposites of polypyrrole (PPy) and Tungsten disulphide (WS2) chalcogen as a matrix and filler, respectively. The aim of the current work is to develop a highly selective and response for ammonia gas sensor. The various physiochemical techniques like X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDS) has been used for the characterization of prepared nanocomposites. The good dispersion of WS2 filler in the matrix of PPy has been done by the in-situ chemical oxidative polymerization route. Further, the sensing of gas like Hydrogen, Ethanol, Carbon mono-oxide, Carbon dioxide and ammonia for PPy and PPy/WS2 (1 wt%, 5 wt%, 10 wt%, 20 wt% and 30 wt%) nanocomposites were carried out at room temperature. A superior sensing for ammonia gas has been observed for PPy/WS2-5 wt% sample with 3.04–30.10% response for 50–200 ppm concentration of ammonia. The recorded response and recovery time for this nanocomposites was 51 s and 79 s, respectively. In addition to this it shows good repeatability and high selectivity for the ammonia gas.

English

Starch fillers were extracted from three plant sources namely amora tuber, Tacca lentopeteloides; sweet potato, Ipomoea batatas; yam starch, Dioscorea rotundata and their particle size, pH, amylose, and amylopectin percentage decomposition determined accordingly. The starch was introduced into natural rubber in liquid phase (through gelatinization) by the latex compounding method and compounded according to standard method. The prepared starch/natural rubber composites was characterized by Instron Universal testing machine (UTM) for tensile mechanical properties. The composites was further characterized by x-ray diffraction and crosslink density analysis. The particle size determination showed that amora starch granules has the smallest particle size (156 × 47 μm) followed by yam starch (155 × 40 μm) and then sweet potato starch (153 × 46 μm) with the biggest particle size. The pH test also revealed that amora starch has a near neutral pH of 6.9, yam 6.8, and sweet potato 5.2 respectively. Amylose and amylopectin determination showed that yam starch has a higher percentage of amylose (29.68), followed by potato (22.34) and then amora starch with the lowest value (14.86) respectively. The tensile mechanical properties testing revealed that yam starch produced the best tensile mechanical properties followed by amora starch and then sweet potato starch. The structure, crystallinity/amorphous nature of the product composite was confirmed by x-ray diffraction, while the nature of crosslinking was confirmed by swelling test in toluene solvent using the Flory-Rehner approach. The increasing values of crosslink density in the starch/rubber composite is a clear evidence of good interfacial adhesion between the starch fillers and the rubber, hence good dispersion of starch fillers in the rubber. This research has rendered a workable strategy for enhancing interfacial interaction between a hydrophilic filler (Starch) and hydrophobic polymeric matrix (natural rubber) yielding moderately good tensile mechanical properties with prospects for the rubber processing industry. The studied fillers can partially replace carbon black as natural rubber fillers with reduced cost, no risk to human health and also an environment friendly approach. Key words: Natural rubber, fillers, starch, amylose, amylopectin, crosslink density, mechanical properties.

Color Stability Enhancement of Curcumin Bioplastic Films Using Natural Hybrid Fillers of Montmorillonite and Revalorized Cellulose

Naturally colored packaging systems with improved color stability are essential as alternatives to mainstay synthetic colored conventional plastics, which typically present high toxicity and environmental pollution challenges. Herein, we report a versatile all green fabrication process for colored bioplastic films. Curcumin (CUR), a model plant-based colorant, was incorporated with newly developed natural hybrid fillers of montmorillonite (MMT) and biomass waste-recovered cellulose (CEL) for improved color stability performance. The CUR-based hybrid fillers were compounded with polylactic acid (PLA) to fabricate sustainable, colored composite films via hot-melt extrusion. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) results indicated good compatibility between the filler counterparts. Macro- and microstructure analysis of the colored films confirmed the good dispersion of the natural hybrid fillers within the PLA matrix. No change was observed in the thermal properties of the colored films, while dynamic mechanical analysis (DMA) results demonstrated a moderate increase in the films’ elastic modulus, from 870 to 970 MPa. The color entrapment efficiency of the hybrid filler-based films was evaluated through a study of CUR release in ethanol. A sustained CUR release profile reaching around 50% after 48 h was observed in the hybrid filler-based films in contrast to 80% in the PLA–CUR film. This was correlated with the significantly improved color stability of the PLA films containing the hybrid fillers under weathering conditions of UV irradiation, high temperature, and humidity. Over a period of 10 days, the CUR-CEL-MMT-based films had relatively consistent color stability, showing a color shift value (ΔE*) of only 1.1 in comparison to 5.1 for the PLA film containing only CUR.

Seawater Biodegradable Poly(butylene succinate-co-adipate)—Wheat Bran Biocomposites

The present work focused on the development and characterization of biocomposites based on a fully bio-based polyester, poly(butylene succinate-co-butylene adipate) (PBSA), and wheat bran derived by flour milling. PBSA-bran composites containing 5, 10, 15, and 20 wt.% of wheat bran were produced via melt extrusion and processed by injection molding. Their thermal, rheological, morphological, and tensile properties were investigated. In addition, a biodegradation test in a natural marine environment was conducted on composite dog-bones to assess the capacity of the used filler to increase the PBSA biodegradation rate. The composites maintained similar melt processability and mechanical properties to virgin PBSA with up to 15 wt.% bran content. This result was also supported by morphological investigation, which showed good filler dispersion within the polymer matrix at low-mid bran content, whereas poor polymer-filler dispersion occurred at higher concentrations. Furthermore, the biodegradation tests showed bran's capacity to improve the PBSA biodegradation rate, probably due to the hygroscopic bran swelling, which induced the fragmentation of the dog-bone with a consequent increase in the polymeric matrix-seawater interfacial area, accelerating the degradation mechanisms. These results encourage the use of wheat bran, an abundant and low-cost agri-food by-product, as a filler in PBSA-based composites to develop products with good processability, mechanical properties, and controlled biodegradability in marine environments.

QUANTIFYING SULFUR DISPERSION USING POPULATION SURVIVAL ANALYSIS OF TENSILE STRENGTH

ABSTRACT High-performance rubber compounds require good dispersion of polymers, fillers, and other additives. However, fine powdery additives such as zinc oxide and insoluble sulfur (IS) are characteristically difficult to disperse, and poor dispersion may lead to large crosslink and modulus gradients in the final vulcanizate. IS dispersion can be assessed directly or indirectly, yet many techniques suffer from a lack of sensitivity and accuracy or are cost prohibitive. Herein, we describe the application of a two-parameter Weibull distribution and population survival analysis of cured rubber tensile strength as a simple technique to evaluate IS dispersion. We use statistical tools to determine the optimum number of sample replicates required to differentiate the quality of dispersion in rubber articles through the Weibull scale and shape estimates (α and β, respectively). We then demonstrate how mixing cycle time and intensity affect the dispersion of two IS grades and show that judicious choice of IS can lead to reduced cycle mix times, productivity improvements, and energy cost savings.

Fabrication of hydrophobic and enhanced anticorrosion performance of epoxy coating through the synergy of functionalized graphene oxide and nano-silica binary fillers

Two-dimensional graphene oxide (GO) nanosheets have emerged as ideal nano-fillers in anticorrosive epoxy coatings, but their poor dispersion because of π-π interaction, high hydrophilicity, and low compatibility with epoxy resin limit their application. In this work, to conquer these obstacles, the hydrophobic and anticorrosive GO based epoxy composite coating was developed via the synergistic enhancement effect of binary nano-fillers. To achieve this goal, the graphene oxide and nano-silica (SiO2) were hydrophobically functionalized by the 1H,1H,2H,2H-perfluoro-decyl triethioxy silane (PFDS) via a simple grafting method (SiO2-P: mSiO2:mPFDS=1:1), GO-P3: mGO:mPFDS=1:3), which were applied as binary fillers to reinforce the epoxy coating with enhanced dispersion and compatibility with matrix. Benefiting from the hierarchical micro-/nano- structure, regulated surface energy, good dispersion, and synergy of SiO2-P and GO-P3 binary fillers, the epoxy composite coating showed greatly enhanced hydrophobicity (The water contact angle increased from 70.45° to 126.84°) and anti-corrosion performance. With the synergetic enforcement of 1.5 wt % SiO2-P and 0.5 wt % GO-P3, the prepared epoxy composite coating exhibited the best anticorrosive performance with impedance of 2.74 × 109 Ω·cm2 (0.01 Hz) after immersion in 3.5 % NaCl medium for 30 days, which was confirmed by the salt spray test results. Meanwhile, the anti-corrosion mechanism including hydrophobicity and prolonged diffusion path of water-soluble corrosive medium was tentatively discussed.

Bioinspired Graphene Oxide-Magnetite Nanocomposite Coatings as Protective Superhydrophobic Antifouling Surfaces.

Antifouling (AF) nanocoatings made of polydimethylsiloxane (PDMS) are more cost-efficient and eco-friendly substitutes for the already outlawed tributyltin-based coatings. Here, a catalytic hydrosilation approach was used to construct a design inspired by composite mosquito eyes from non-toxic PDMS nanocomposites filled with graphene oxide (GO) nanosheets decorated with magnetite nanospheres (GO-Fe3O4 nanospheres). Various GO-Fe3O4 hybrid nanofillers were dispersed into the PDMS resin through a solution casting method to evaluate the structure-property relationship. A simple coprecipitation procedure was used to fabricate magnetite nanospheres with an average diameter of 30-50 nm, a single crystal structure, and a predominant (311) lattice plane. The uniform bioinspired superhydrophobic PDMS/GO-Fe3O4 nanocomposite surface produced had a micro-/nano-roughness, low surface-free energy (SFE), and high fouling release (FR) efficiency. It exhibited several advantages including simplicity, ease of large-area fabrication, and a simultaneous offering of dual micro-/nano-scale structures simply via a one-step solution casting process for a wide variety of materials. The superhydrophobicity, SFE, and rough topology have been studied as surface properties of the unfilled silicone and the bioinspired PDMS/GO-Fe3O4 nanocomposites. The coatings' physical, mechanical, and anticorrosive features were also taken into account. Several microorganisms were employed to examine the fouling resistance of the coated specimens for 1 month. Good dispersion of GO-Fe3O4 hybrid fillers in the PDMS coating until 1 wt % achieved the highest water contact angle (158° ± 2°), the lowest SFE (12.06 mN/m), micro-/nano-roughness, and improved bulk mechanical and anticorrosion properties. The well-distributed PDMS/GO-Fe3O4 (1 wt % nanofillers) bioinspired nanocoating showed the least biodegradability against all the tested microorganisms [Kocuria rhizophila (2.047%), Pseudomonas aeruginosa (1.961%), and Candida albicans (1.924%)]. We successfully developed non-toxic, low-cost, and economical nanostructured superhydrophobic FR composite coatings for long-term ship hull coatings. This study may expand the applications of bio-inspired functional materials because for multiple AF, durability and hydrophobicity are both important features in several industrial applications.

Role of MWCNTs Loading in Designing Self-Sensing and Self-Heating Structural Elements.

This work proposes nanocomposites with carbon nanotubes characterized by self-sensing and self-heating properties. Recently, a growing interest in these two properties has been found in many industrial sectors, especially in the aerospace and automotive fields. While the self-sensing function allows diagnosing the presence of micro-damage in the material thanks to the detection of residual resistance, the self-heating function is exploited to properly tune the heating performance in terms of the heating rate and final temperature values. An electrical percolation value of around 0.5% by weight of carbon nanotubes was found by electrical characterization. The AC conductivity of the nanocomposites, in the range of 100 Hz to 1 MHz, evidences that beyond a CNTs amount of 0.5% wt/wt, they are characterized by a purely resistive behavior. The self-sensing analysis displayed a gauge factor value of 4.1. The solid thermal stability up to 300 °C makes the material suitable as a heating element at high temperatures. SEM investigations and temperature maps evidence a good dispersion of the conductive filler in the epoxy matrix and, consequently, good isotropy in heat distribution. As regards the trend of electrical resistance by varying the temperature, the electro-thermal investigation has shown the presence of both Positive Temperature Coefficient (PTC) and Negative Temperature Coefficient (NTC) behaviors with a predominance of NTC as soon as the temperature becomes closer to the glass transition temperature of the epoxy resin.

Sustainable Composites Based on Natural Rubber and Biomass Resources

Abstract: For the past two decades, environmentally friendly natural rubber composites and nanocomposites reinforced with renewable and biodegradable natural fillers has attracted increasing attention of polymer researchers from both industrial and environmental viewpoints. The use of bio-based fillers in rubber materials has emerged as extremely promising in the progress of green rubber technology. The dispersion of bio-based fillers within the rubber matrix is the key parameter that decides the overall performances of bio-based rubber composites. An important criterion for obtaining superior properties in rubber composites is good interfacial adhesion between natural fillers and natural rubber matrix, along with good dispersion and distribution of fillers within the matrix. Natural fillers represent materials that are environmentally friendly, easily available, comprising of valuable lignocellulosic fractions and are from a bio-based feedstock. Recent developments in this area focus on renewable fillers such as cellulose, chitin and lignin in its micro and nanoforms. Additionally, recent studies have focused on the use of different type of biomass residue wastes in rubber composites with a view to adapt to the recent circular economy principles. This review presents an overview of various studies and highlights in the area of bio-based filler reinforced natural rubber composites and also discusses the applications of such materials in industrial sectors.

The Influence of Different Sustainable Silk-Based Fillers on the Thermal and Mechanical Properties of Polylactic Acid Composites.

In this work, different silk fillers combined with maleinized corn oil (MCO), as environmentally friendly plasticizers, were used to modify the mechanical and thermal properties of polylactic acid (PLA) composites. Melt extrusion and injection were used to obtain samples with a content of 10 wt.% of MCO and 0.5 phr of different silk fillers: crushed silk (CS), silk fibroin microparticles (SFM), and silk fibroin nanoparticles (SFN). PLA formulation with 10 wt.% of MCO and 0.5 g of CS per hundred grams of composite (phr) showed the highest increase in mechanical ductile properties with an increase in elongation at break of approximately 1400%, compared with PLA. Differential scanning calorimetry (DSC) showed a decrease of 2 °C in their glass transition temperature with the addition of different silk fillers. In addition, SFM and SFN increase the degree of crystallinity of PLA. This increment was also confirmed by infrared spectroscopy analysis. Field emission scanning electron microscopy (FESEM) images revealed a good dispersion of the different silk fillers. Among them, PLA formulation with 10 wt.% MCO and 0.5 phr of SFN, showed an optimal balance between maximum resistance and elongation at break, with 52.0 MPa and 10.8%, respectively, improving elongation at break by 635%. Furthermore, all samples were satisfactorily disintegrated under composting conditions.