Dynamic Mechanical Thermal Properties Research Articles

Injection-molded thermoplastic cassava starch modified with single and mixed polyol plasticizers.

Increasing interest in biodegradable and cost-effective materials derived from renewable resources has led to the development of injection-moldable thermoplastic starch (TPS). Plasticizers constitute an indispensable additive for manufacturing TPS, influencing both its thermomechanical processability and performance. The aim of the current work is thus to study the effect of single and mixed polyol plasticizers on the performance of injection-molded TPS. This study was carried out by using three types of polyols - glycerol, xylitol, and sorbitol- as single and equal-weight binary mixed plasticizers to modify cassava starch via extrusion. The resulting TPS extrudates were converted to test specimens via injection molding. Melt flow index, moisture content, water contact angle, and tensile and dynamic mechanical thermal properties of the materials were examined. In addition, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis were also conducted. The results show that the higher-molecular-weight polyols (xylitol and sorbitol) exhibited lower plasticizing efficiency but formed denser hydrogen-bonding interactions with starch molecules than the smaller-molecular-weight one (glycerol). In both single and mixed plasticizer systems, increasing the molecular weight of the polyol plasticizer led to enhancements of the tensile strength (up to 27MPa (200% increment) and 26MPa (115% increment) for single and mixed plasticizer systems, respectively), Young's modulus (up to 386MPa (240% increment) and 458MPa (185% increment) for single and mixed plasticizer systems, respectively), decomposition temperature (2-3°C), and glass transition temperature (30-50°C) of TPS and a reduction in its moisture content (60-80%) and surface stickiness, though disadvantages included poorer thermomechanical processability and higher melt viscosity and brittleness. In conclusion, using a co-plasticizer of glycerol and xylitol is appropriate for injection-molded TPS articles considering both processability and performance. The obtained TPS has potential applications in edible or single-use biodegradable rigid products, such as pet chew toys, chopsticks, cutlery, plant pots, etc.

4D Printing of Multifunctional and Biodegradable PLA-PBAT-Fe3O4 Nanocomposites with Supreme Mechanical and Shape Memory Properties.

4D printing magneto-responsive shape memory polymers (SMPs) using biodegradable nanocomposites can overcome their low toughness and thermal resistance, and produce smart materials that can be controlled remotely without contact. This study presented the development of 3D/4D printable nanocomposites based on poly (lactic acid) (PLA)-poly (butylene adipate-co-terephthalate) (PBAT) blends and magnetite (Fe3O4) nanoparticles. The nanocomposites are prepared by melt mixing PLA-PBAT blends with different Fe3O4 contents (10, 15, and 20 wt%) and extruded into granules for material extrusion 3D printing. The morphology, dynamic mechanical thermal analysis (DMTA), mechanical properties, and shape memory behavior of the nanocomposites are investigated. The results indicated that the Fe3O4 nanoparticles are preferentially distributed in the PBAT phases, enhancing the storage modulus, thermal stability, strength, elongation, toughness, shape fixity, and recovery of the nanocomposites. The optimal Fe3O4 loading is found to be 10 wt%, as higher loadings led to nanoparticle agglomeration and reduced performance. The nanocomposites also exhibited fast shape memory response under thermal and magnetic activation due to the presence of Fe3O4 nanoparticles. The 3D/4D printable nanocomposites demonstrated multifunctional multi-trigger shape-memory capabilities and potential applications in contactless and safe actuation.

Controllable fabrication of shape memory epoxy resin filament by polymerization-melting-mixing-drawing process and performance regulation

ABSTRACT This work controlled the polymerization reaction, melting, and mixing processing of a mixture including epoxy resin and polyethylene glycol (PEG) by a pulverizer, to effectively develop high-performance shape memory epoxy/PEG (EPP) filaments. The process parameters of polymerization-melting-mixing-drawing were determined through the extrusion force investigation. The results showed that EPP mixtures could be developed into filaments through polymerization-melting-mixing-drawing process, reducing the spinning temperature and filament diameter from 300°C and 31 mm to 235°C and 13 mm, respectively. The Fourier transform infrared spectra confirmed the complete polymerization of epoxy resin and the stable existence of PEG. EPP filaments developed through the polymerization-melting-mixing-drawing process have exhibited controllable dynamic thermal mechanical properties and Tg, excellent shape recovery effects, and adjustable stimulus temperature. This work developed shape memory EPP filaments through a polymerization-melting-mixing-drawing process, with controllable spinnability and adjustable stimulus temperature, providing a reference for high-performance filament fabrication and process optimization.

Effect of Viscosity and Air Gap within the Spinneret on the Morphology and Mechanical Properties of Hollow-Fiber Polymer Membranes for Separation Performance.

Hollow-fiber membranes for nanofiltration were prepared from the blending of Poly (ethylene glycol) (PEG) with Poly (vinyl chloride) (PVC) with different PEG molecular weights (400 and 4000 g/mol) and PVC via a dry/wet spinning process. In the spinning process, the effects of air gap, wind-up speed, dope extrusion rate, and bore extrusion rate were examined. In addition, the different lengths of the center tube, which acted as the inner-side fiber diameter during the preparation of hollow-fiber membranes, were studied. This research was investigated in order to observe the morphological, dielectric, and dynamic mechanical thermal properties to identify a suitable preparation of a hollow-fiber membrane for feasible applications. The morphology of the PVC-580 blended PEG-400 5 weight percent hollow-fiber membrane was seen to have a dense skin on both the inner and outer fiber surface, along with a suitable dope viscosity. Moreover, it offered finger-like substructures that could provide a high applicable feed-stream permeability and selectivity. Finger-like substructures were present on the near inner fiber surface at the controlled center-tube length of 0.3 cm, more so than at the center tube of 1 cm. This was because the solvent and non-solvent in the lumen tube exchanged more quickly than they did in the coagulant bath. The effect of the wind-up speed during the spinning process was significantly influenced by an affordable hollow fiber that can be indicated by the drawing ratio (λ). It was found that the drawing ratio of 3.3 showed a thickness thinner than 2.6 and 2.0, respectively. In summary, a controlled wind-up speed, an acceptable dope viscosity, and-most importantly-an agglomerated time resulted in membrane preparation.

Preparation of Hydrophobic Modified Silica with Si69 and Its Reinforcing Mechanical Properties in Natural Rubber.

The inherent large number of hydroxyl groups of silica poses strong hydrophilicity, resulting in poor dispersibility in the natural rubber matrix. Here, the silica's surface was hydrophobically modified with [3-(triethoxysiliconyl) propyl] tetrasulfide (Si69) to improve the dispersibility and reinforce the mechanical properties of silica/natural rubber composites. The structure and morphology of modified silica were characterized by Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray electron spectroscopy (XPS), nuclear magnetic resonance spectroscopy and the contact angle. Further, the mechanical properties, dynamic mechanical properties and morphology of silica/natural rubber composites were studied with a universal electronic tension machine, dynamic thermal mechanical properties analyzer (DMA) and scanning electron microscope (SEM). The experimental results show that the Si69 was successfully grafted onto the surface of silica, thereby significantly improving the water contact angle (a 158.6% increase) and enhancing the mechanical properties of modified silica/natural rubber composites.

The effect of physical compatibilization and dynamic vulcanization on the properties of thermoplastic vulcanizates derived from polypropylene and natural rubber blends

This interesting study investigated the effect of Maleic Anhydride-grafted-Polypropylene/Epoxidized Natural Rubber (PP-g-MA/ENR) as a compatibilizing agent (CA) on the properties of a 30/70 Polypropylene/Natural Rubber PP/NR blends. The effect of dynamic vulcanization with sulfur-donors (i.e.: Tetramethyl thiuram disulfide (TMTD) and 4,4 Dithiodimorpholine (DTDM)) which were used as vulcanizing agents was also reported. Several formulations of TPVs with different concentrations of CA (from 5 to 15 phr) were prepared by mixing in the molten state using a Haake Rheocord 90. The structural analysis of dual compatibilizer was examined by FTIR spectroscopy. The rheological behavior was examined using Haake Rheocord 90. The mechanical properties were determined by the tensile measurements. The dynamic mechanical thermal properties were investigated by DMA. A morphological examination was conducted using SEM Microscopy, respectively. FTIR analysis confirmed reactions between the MA group in PP-g-MA and the epoxy groups in ENR, resulting in ENR-grafted PP with an ester and acid-based linkage. The Haake plastograms revealed a proportional increase in the final mixing torque value with the increasing content of CA. The mechanical results exhibited higher values in terms of tensile strength and Young’s modulus for the TPVs containing CA compared to un-compatibilized ones. The compatibilized TPV blends exhibited a noteworthy increase in storage modulus and a notable decrease in loss tangent values with the CA concentration increased. Furthermore, the TPVs show two distinct-phase morphologies. That is, the TPV with CA showed the presence of smaller vulcanized rubber particles dispersed within the PP matrix, a phenomenon that becomes more pronounced with higher CA contents.

Effect of the Graphene Quantum Dot Content on the Thermal, Dynamic-Mechanical, and Morphological Properties of Epoxy Resin.

Different amounts of graphene quantum dots (CQDs) (0, 1, 2.5, and 5 wt%) were incorporated into an epoxy matrix. The thermal conductivity, density, morphology, and dynamic mechanical thermal (DMTA) properties were reused from the study of Seibert et al.. The Pearson plot showed a high correlation between mass loading, thermal conductivity, and thermal diffusivity. A poorer correlation with density and heat capacity was observed. At lower CQD concentrations (0.1 wt%), the fracture surface showed to be more heterogeneous, while at higher amounts (2.5 and 5 wt%), a more homogeneous surface was observed. The storage modulus values did not change with the CQD amount. But the extension of the glassy plateau increased with higher CQD contents, with an increase of ~40 °C for the 5 wt% compared to the 2.5 wt% and almost twice compared to the neat epoxy. This result is attributed to the intrinsic characteristics of the filler. Additionally, lower energy dissipation and a higher glass transition temperature were observed with the CQD amount. The novelty and importance are related to the fact that for more rigid matrices (corroborated with the literature), the mechanical properties did not change, because the polymer bridging mechanism was not present, in spite of the excellent CQD dispersion as well as the filler amount. On the other hand, thermal conductivity is directly related to particle size and dispersion.

The thermoplastic polyurethane coated-LZH nanohybrids as a strategy for epoxy resin flame retardancy

Over traditional flame retardants, the hybrid material technology of flame retardant combines separate constituents into an entirety, demonstrating the benefit of the simultaneous development in polymer flame retardant. Zinc-layered hydroxide, borate, and thermoplastic polyurethane were used to create LZH/B/TU, a new organic-inorganic composite flame retardant. The structure of LZH, LZH/B, and LZH/B/TU was studied after synthesis with analysis spectroscopy. The borate ion was effectively intercalated into the interlayer space of the LZH, according to the XRD and FTIR studies. Using EDS analysis, the chemical makeup of the materials was assessed. The morphology of the synthesized product was identified using FESEM. The dynamic mechanical thermal (DMT) properties of the optimum sample were evaluated with DMTA analysis. The fire risk of epoxy resin was considerably reduced by using a small amount of LZH/B/TU. According to the flammability test and plate temperature experiment, LZH/B/TU with 1% w/w led to the creation of the char layer’s capacity to insulate heat with strong thermal resistance, resulting in dramatically reduced fire hazards.

Preparation of modified CO2‐based polyurethane for wet‐type artificial leather with excellent alkali resistance

AbstractPoly (propylene carbonate) diol (PPCD) is one of the most attractive CO2 copolymers. PPCD‐based polyurethane has excellent mechanical properties and hydrophilicity, and is widely used in various fields. However, poor alkali resistance limits the application of PPCD‐based polyurethane in wet‐type artificial leather (WPL). In order to solve this problem, polyurethane solution (PUS) for wet‐type artificial leather was prepared by using PPCD and polytetramethylene ether glycol (PTMG) as soft segments. The chemical structure, viscosity, molecular weight and distribution, physical and mechanical properties, thermal properties and dynamic mechanical thermal properties of PUS were characterized. The changes of the physical and mechanical properties of PUS films and surface morphology of WPLs after soaking in 10 wt% NaOH solution at room temperature for 24 h were studied, so as to evaluate the alkali resistance of polyurethane. The retention of tensile strength and tearing strength of PUS films modified by PTMG increased from 80% to 96% and from 89% to 100%, respectively. The scanning electron microscopy results showed that appropriate PTMG was beneficial to the formation of microporous structure for CO2‐based polyurethane leather. The leather without PTMG showed agglomeration phenomenon, the micropores were not obvious, and the changes were obvious after soaking in alkali solution. After being modified by PTMG, the morphology of leather after soaking in alkali solution was basically unchanged. Polyurethane leather prepared with PTMG and PPCD as soft segments has excellent alkali resistance. These results suggest that PPCD could be a potential artificial leather material.

Flexural strength and ballistic performance of vinyl ester resin/aramid fiber composites toughened by graphene nanosheets

The fiber reinforced polymer (FRP) armor composites are kinds of composite materials specially designed and manufactured to prevent the penetration of high-speed bullets and fragments. The FRP composites are commonly composed of reinforcing fibers, resin matrix and their interfacial structures. The vinyl ester resin (VER) is a kind of thermosetting resin commonly applied in the field of high performance bulletproof composites. However, the VER has the problem of insufficient toughness after curing, which seriously limits its application. In this research, the graphene nanosheets were homogeneously dispersed into VER matrix by ultrasonic-assisted dispersing process. The effects of graphene content on the mechanical and dynamic mechanical thermal properties of VER castings were investigated. The graphene-toughened VER/aramid fiber (AF) composites were prepared by hand layup-vacuum bag molding process. The influences of graphene content on the flexural strength and ballistic resistance of VER/AF composites were investigated. The results showed that the tensile strength, elongation at break, flexural strength and non-notch impact strength of VER casting filled with 0.1 wt.% graphene increased by 5.6%, 27.6%, 11.7% and 90.5%, respectively, compared with those of unfilled VER casting. The glass transition temperature Tg of VER casting gradually increased with the increase of graphene content. The hand layup-vacuum bag molding process effectively reduced the filtering effect of the fiber fabrics on graphene sheets. When the amount of graphene was 0.1 wt.%, the flexural strength of VER/AF composite was increased by 34.2%. Due to the improvement of fracture toughness of the resin matrix, the ballistic limit velocity V 50 and specific energy absorption of the VER/AF composites were both improved.

The Aging Behavior and Life Prediction of CFRP Rods under a Hygrothermal Environment.

Carbon fiber-reinforced polymer (CFRP) composites have been widely used in civil engineering structures due to their excellent mechanical and durability properties. The harsh service environment of civil engineering leads to significant degradation of the thermal and mechanical performances of CFRP, which then reduces its service reliability, service safety, and life. Research on the durability of CFRP is urgently needed to understand the long-term performance degradation mechanism. In the present study, the hygrothermal aging behavior of CFRP rods was investigated experimentally through immersion in distilled water for 360 days. The water absorption and diffusion behavior, the evolution rules of short beam shear strength (SBSS), and dynamic thermal mechanical properties were obtained to investigate the hygrothermal resistance of CFRP rods. The research results show that the water absorption behavior conforms to Fick's model. The ingression of water molecules leads to a significant decrease in SBSS and glass transition temperature (Tg). This is attributed to the plasticization effect of the resin matrix and interfacial debonding. Furthermore, the Arrhenius equation was used to predict the long-term life of SBSS in the actual service environment based on the time-temperature equivalence theory, obtaining a stable strength retention of SBSS of 72.78%, which was meaningful to provide a design guideline for the long-term durability of CFRP rods.

Exploring Properties of Short Randomly Oriented Rattan Fiber Reinforced Epoxy Composite for Automotive Application

ABSTRACT The acrylic acid treated rattan fiber reinforced epoxy (RF/Epoxy) composite has been fabricated by taking various weight percentages (5, 10, 15, 20, and 25 wt%) of fibers using hand layup followed by compression molding technique. The optimum fiber loading has been determined by regression analysis and it is found that 18 wt% of rattan fiber gives maximum tensile strength. The interaction of rattan fiber with epoxy matrix has been studied by Fourier transform infrared spectroscopy and X-ray diffraction. Scanning electron microscope (SEM) has been used to study the morphology of chemically modified rattan fiber and RF/Epoxy composite. The mechanical, thermal, and dynamic mechanical thermal properties of 18 wt% RF/Epoxy composite have been studied as per ASTM standards. From the results, it is observed that RF/Epoxy composite gives best properties at optimum (18 wt%) fiber loading. The maximum tensile strength and flexural strength of the composite are found to be 47.5 and 121 MPa, respectively, which is better in comparison to other natural fiber composites used for manufacturing different automobile body parts. Hence, it can be concluded that 18 wt% RF/Epoxy composite can be considered as a potential candidate for automotive body parts.

Injectable and photocurable macromonomers synthesized using a heterometallic magnesium-titanium metal-organic catalyst for elastomeric polymer networks.

Injectable and in situ photocurable biomaterials are receiving a lot of attention due to their ease of application via syringe or dedicated applicator and ability to be used in laparoscopic and robotic minimally invasive procedures. The aim of this work was to synthesize photocurable ester-urethane macromonomers using a heterometallic magnesium-titanium catalyst, magnesium-titanium(iv) butoxide for elastomeric polymer networks. The progress of the two-step synthesis of macromonomers was monitored using infrared spectroscopy. The chemical structure and molecular weight of the obtained macromonomers were characterized using nuclear magnetic resonance spectroscopy and gel permeation chromatography. The dynamic viscosity of the obtained macromonomers was evaluated by a rheometer. Next, the photocuring process was studied under both air and argon atmospheres. Both the thermal and dynamic mechanical thermal properties of the photocured soft and elastomeric networks were investigated. Finally, in vitro cytotoxicity screening of polymer networks based on ISO10993-5 revealed high cell viability (over 77%) regardless of curing atmosphere. Overall, our results indicate that this heterometallic magnesium-titanium butoxide catalyst can be an attractive alternative to commonly used homometallic catalysts for the synthesis of injectable and photocurable materials for medical applications.

Dry sliding wear and viscoelastic performance of aluminum-based hybrid composites reinforced with SiC and metallic glass particles

In this research, a new type of bulk hybrid composites containing different amounts of Fe-based metallic glass (FMG) and SiC particles were successfully produced. FMG and SiC particles with varying percentages of volume were mixed with pure Al matrix and integrated by spark plasma sintering (SPS) method. The dynamic mechanical thermal properties, coefficient of friction and wear rates, hardness, and density of the composite were investigated. The results showed that the addition of FMG and SiC particles improved the wear resistance, hardness value, and storage modulus and slightly decreased the [Formula: see text] and relative density of pure Al. Also, replacing some SiC particles with FMG particles in the hybrid samples, in addition to the change of the dominant wear mechanism, led to the higher storage modulus and hardness values. It was found that the formation of a mechanically mixed layer during the wear test resulted in a reduction in the coefficient of friction. Compared to pure Al, the amounts of the increase in storage modulus and hardness of samples reinforced with 3 vol. % of SiC and 7 vol. % of FMG particles were 24.70% and 68.40%, respectively. The morphological analysis of the hybrid composites demonstrated that the amorphous structure of the FMG particles was preserved.

Highly crystallized and tough polylactic acid through addition of surface modified cellulose nanocrystals

AbstractTo prepare a fully organic polylactic acid (PLA)‐based bio‐nanocomposite, cellulose nanocrystals (CNCs) were grafted by PLA through ring‐opening polymerization (ROP) of L‐lactide monomers onto CNCs. The grafting process was evaluated by 1HNMR and FTIR spectroscopic methods. The effect of surface‐modified CNCs (M‐CNCs) was investigated on thermal, mechanical, rheological, and dynamic mechanical thermal properties of PLA. The M‐CNCs were successfully dispersed in the PLA matrix. Isothermal and non‐isothermal DSC studies revealed that M‐CNCs caused an intensive increase in crystallization kinetics and therefore nucleation density and crystallization extent. DSC, XRD, and DMTA analyses indicated the formation of different crystal structures [α, α', β] in PLA after addition of M‐CNCs. Rheological analysis was carried out for microstructural investigation of the nanocomposites. Interestingly, after the addition of M‐CNCs not only the tensile strength and modulus of the samples increased but also the toughness of PLA was considerably improved.

Mechanical, thermal and microstructural studies of acrylonitrile butadiene styrene reinforced with rattan (Calamus beccarii) fiber composites

AbstractIn this research work, fibers from rattan plant stem (RA) were selected as reinforcing material with widely used thermoplastic polymer acrylonitrile butadiene styrene (ABS). The extracted fibers were chemically modified with NaOH followed by benzoylation and bleaching. Then they were used as reinforcement in ABS polymer matrix by different weight percentages (0, 10, 20, 30, and 40 wt%) for fabrication of composites. It was observed that chemical treatment changes the surface texture of the fibers enhancing the surface roughness which helps in proper fiber–matrix bonding. Various properties like static and dynamic mechanical properties, thermal and morphological properties were investigated. The mechanical properties of the composites were observed to increase at beginning phase with increase in filler content till optimum (24 wt%) fiber loading and from there on declines. Highest tensile strength of 74.98 MPa, 4.80 GPa of young's modulus, 90. A total of 10 MPa of flexural strength and 31.42 kJ/m2 of impact strength were obtained at optimum fiber loading. Further characterizations in terms of Fourier transform‐infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA) on composites with optimum fiber loading were conducted and compared with untreated composites. These fabricated composites can be an alternative material for automobile industries due to its high strength and low weight advantage.

The Use of Waste Hazelnut Shells as a Reinforcement in the Development of Green Biocomposites

Biodegradable Mater-Bi (MB) composites reinforced with hazelnut shell (HS) powder were prepared in a co-rotating twin-screw extruder followed by compression molding and injection molding. The effects of reinforcement on the morphology, static and dynamic mechanical properties, and thermal and rheological properties of MB/HS biocomposites were studied. Rheological tests showed that the incorporation of HS significantly increased the viscosity of composites with non-Newtonian behavior at low frequencies. On the other hand, a scanning electron microscope (SEM) examination revealed poor interfacial adhesion between the matrix and the filler. The thermal property results indicated that HS could act as a nucleating agent to promote the crystallization properties of biocomposites. Furthermore, the experimental results indicated that the addition of HS led to a significant improvement in the thermomechanical stability of the composites. This paper demonstrates that the incorporation of a low-cost waste product, such as hazelnut shells, is a practical way to produce low-cost biocomposites with good properties. With a content of HS of 10%, a remarkable improvement in the elastic modulus and impact strength was observed in both compression and injection-molded samples. With a higher content of HS, however, the processability in injection molding was strongly worsened.

Effects of Wood Flour (WF) Pretreatment and the Addition of a Toughening Agent on the Properties of FDM 3D-Printed WF/Poly(lactic acid) Biocomposites.

In order to improve the properties of wood flour (WF)/poly(lactic acid) (PLA) 3D-printed composites, WF was treated with a silane coupling agent (KH550) and acetic anhydride (Ac2O), respectively. The effects of WF modification and the addition of acrylicester resin (ACR) as a toughening agent on the flowability of WF/PLA composite filament and the mechanical, thermal, dynamic mechanical thermal and water absorption properties of fused deposition modeling (FDM) 3D-printed WF/PLA specimens were investigated. The results indicated that the melt index (MI) of the specimens decreased after WF pretreatment or the addition of ACR, while the die swell ratio increased; KH550-modified WF/PLA had greater tensile strength, tensile modulus and impact strength, while Ac2O-modified WF/PLA had greater tensile modulus, flexural strength, flexural modulus and impact strength than unmodified WF/PLA; after the addition of ACR, all the strengths and moduli of WF/PLA could be improved; after WF pretreatment or the addition of ACR, the thermal decomposition temperature, storage modulus and glass transition temperature of WF/PLA were all increased, and water absorption was reduced.

Novel Conductive Polymer Composites for Asphalt Pavement Structure in Situ Strain Monitoring: Influence of CB/CNT and GNP/CNT Nano/Micro Hybrid Fillers on Strain Sensing Behavior

Sensing materials and devices with high sensitivity are necessary for engineering structure monitoring with the rapid development of intelligent infrastructure. This paper provides a novel approach to develop strain sensor with high sensitivity for pavement deformation monitoring by epoxying composites with hybrid nano/micro fillers. The effect of combined carbon black/carbon nanotubes (CB/CNT), graphene nanoplatelet/carbon nanotubes (CNT/GNP) fillers on the self-sensing behavior, morphology, dynamic mechanical performance and thermal properties of epoxy composites was discussed in detail. The incorporation of secondary CB results in significant improved self-sensing ability in micro-strain range. CB-CNT hybrid fillers show positive synergy effect on enhancement of piezoresistive response, while GNP show less positive effect on sensing behavior. The presence of CB forms the conductive core domain surrounded by CNT and constructs the multi scale conductive network of composites. The addition of two secondary fillers improves dynamic mechanical performance of composites. The self-sensing behavior of composites with combined filler was illustrated by SEM morphology and conductive pathway evolution during tensile deformation. Laboratory test showed that relative resistance changes have a linear relationship with the strain for developed sensor embedded in asphalt mixture. The polymer composite sensor shows strong sensing ability for asphalt concrete strain monitoring.

Nanofibrillated cellulose/nano SiO2/poly(vinyl alcohol) composite films: Evaluation of properties

Effects of nanofibrillated cellulose (NFC) and nano-silicon dioxide on dynamic mechanical thermal analysis and physical properties of nanocomposites films made of poly (vinyl alcohol) (PVOH) were investigated. For this purpose, the nanoparticles were mixed with PVOH at 0%, 5%, and 10% weight. Water absorption, dynamic mechanical thermal, transparency, and wettability properties were evaluated according to corresponding standard test methods. The morphology of nanocomposites was explored by using a field emission scanning electron microscope technique. The films became increasingly opaque with increasing nanoparticles contents, although the composites also retained moderate transparency. According to the results of the tests, the dynamic mechanical thermal (DMTA) properties of PVOH composite films were significantly improved with the increase of NFC and silica nanoparticles loading. The samples containing 20 wt% of nano-SiO2 exhibited higher hydrophobicity compared with that of 20 wt% NFC.