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In fiber reinforced composite materials, the interfacial strength between the fibers and the matrix plays a key role in controlling the stress transfer and damage mechanisms of the composite. In this study, CO2 laser surface treatment of the fibers was investigated as a potential sustainable substitute for conventional chemical treatments, that can be costly and have negative environmental effects. The influence of the laser treatment on basalt fiber fabric was comprehensively investigated. The fibers were subjected to different laser power levels and characterized from a morphological and mechanical point of view. From optical and scanning electron microscopy, it was observed that the treated fibers manifested increased surface roughness along with spots of fused and bonded fibers. Individual treated fibers exhibited improved tensile properties with increased values of scale parameter (by about 21%) in the case of a laser power equal to 1.04 W/mm2, and no substantial changes in Young's modulus. The treated fibers were subsequently used in the preparation of epoxy‐based microcomposites, and microdebonding tests revealed an increase in the interfacial shear strength (IFSS) up to 8%. Therefore, this work proved that a laser surface treatment of basalt fibers is a valid alternative to conventional fiber surface modification to enhance the mechanical compatibility between fibers and matrix, and therefore to improve the mechanical performances of basalt fiber composites. Highlights: Failure in composites due to weak interfacial adhesion with epoxy.CO2 laser treatment of basalt fibers to enhance interfacial adhesion.Treated fibers exhibit improved tensile properties.Treated fibers manifested improved interfacial shear strength (IFSS, +8%). [ABSTRACT FROM AUTHOR]

This study aims to investigate the electromagnetic interference shielding properties of composites based on immiscible polymer blends of poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) filled with carbon black doped with polypyrrole (CB‐PPy) prepared by compression molding and fused filament fabrication. Composites of PVDF/CB‐PPy and TPU/CB‐PPy were also prepared for comparison. Rheological measurements showed that although the rheological behavior of PVDF/TPU composites was an intermediate behavior between PVDF/CB‐PPy and TPU/CB‐PPy composites, the effect of the conductive filler was much more pronounced in PVDF than in TPU. Moreover, the addition of CB‐PPy was found to increase the storage modulus of the composites leading to more rigid materials, and to decrease the Tg values of the composites due to the reduction of the mobility of the polymeric chains. In addition, PVDF/TPU composites presented an intermediate behavior when compared to composites based on the neat polymers demonstrating that the addition of TPU to PVDF contributes to the development of composites with improved flexibility. Furthermore, the addition of CB‐PPy increased the electrical conductivity of all composites. However, the electrical conductivity of PVDF/TPU 50/50 vol% co‐continuous blends was higher than the electrical conductivity of PVDF/TPU 38/62 vol% composites with the same amount of conductive filler. Composites with higher electrical conductivity showed better shielding from electromagnetic radiation. As expected, composites based on the co‐continuous blend displayed higher EMI shielding efficiency than the 38/62 vol% composites. The main mechanism of shielding was absorption for all composites. Overall, composites based on the PVDF/TPU 50/50 vol% co‐continuous blend showed a better combination of EMI shielding efficiency and mechanical properties. Moreover, specimens prepared by fused filament fabrication displayed diminished electrical conductivity and EMI‐SE responses when compared to compression‐molded samples with the same composition. This difference is attributed to the presence of voids, defects, and overlapping layers, which can hamper the electron flow. [ABSTRACT FROM AUTHOR]

A mountain bike carbon reinforced polymeric frame failed in two pieces during cycling over a grass meadow at a speed of about 25 km/h. This has caused the shoulder dislocation of the driver, also last author of this paper. Here, we demonstrate evidence of macroscopic numerous pre‐existing and propagating defects, such as wrinkles, voids and delaminations, resulting in low mechanical properties of this frame. Numerical dynamic simulations conclude the paper and suggest a further cause of frame weakening, due to defect‐resonance interaction. The paper suggests that the design of carbon fiber reinforced plastic frame for mountain bikes may require new scientific and technological advancements for the safety of the riders, at least today carefully eliminating pre‐existing defects and tomorrow proposing bioinspired flaw tolerant solutions. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) composites filled with carbon‐black polypyrrole were prepared via melt compounding followed by compression molding and fused filament fabrication. CB‐PPy was added to the blends from 0 up to 15% to possible act as nucleating filler for PVDF β phase in order to increase its piezoelectric response. The influence of blending PVDF and TPU and of the addition of CB‐PPy on the overall crystallinity, content of β phase, and piezoelectric response of composites were investigated by differential scanning calorimetry (DSC), Fourier‐transformed infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and determination of the piezoelectric coefficient (d33). It was found that the addition of TPU to PVDF induced an increase of the crystallinity degree and content of β phase in PVDF. Moreover, although the degree of crystallinity of the composites decreased with the addition of CB‐PPy, the percentage of β phase in PVDF was increased. This effect is more significant in samples with filler concentration higher than 6 wt%. As expected, the d33 of the composites increased as the content of the β phase increased. Furthermore, 3D printed samples displayed lower content of β phase and reduced piezoelectric responses when compared to compression molded samples with same composition. [ABSTRACT FROM AUTHOR]

Multifunctional self‐healing composites have great potential in several applications, i.e., from automotive to aerospace. This study examines the self‐healing behavior of carbon fiber reinforced composites by depositing jet‐spun cyclic olefin copolymer (COC) meshes on dry carbon fiber plies before lamination with epoxy resin (EP). Three different laminates were prepared, including neat EP/CF and two composites with 4 wt.% and 8 wt.% of COC in the form of a jet‐spun network as a healing agent. The introduction of COC mesh reduced flexural stress by 26% and interlaminar shear strength by 50%. Mode I interlaminar fracture toughness (GI) was evaluated and specimens were mended at 110°C by resistive heating generated by an electrical current flowing within the samples. The laminates containing 8 wt% COC reported a healing efficiency, evaluated as the ratio between the GI and as the ratio of the maximum load (PMAX) of virgin and healed samples, of 9.4% and 33.7%, respectively. Fractography analysis highlighted the poor adhesion between the COC mesh and EP matrix, and several COC microfibers were trapped inside the epoxy matrix, hindering their diffusion inside the crack zone, which limited the healing capability of the prepared laminates. [ABSTRACT FROM AUTHOR]

Recently, drug personalization has received noticeable attention. Problems arising from standard generalized drug treatments have aroused over the years, particularly among pediatric and geriatric patients. The growing awareness of the limitations of the "one‐size‐fits‐all" approach has progressively led to a rethinking of the current medicine's development, laying the basis of personalized medicine. Three‐dimensional printing is a promising tool for realizing personalized therapeutic solutions fitting specific patient needs. This technology offers the possibility to manufacture drug delivery devices with tailored doses, sizes, and release characteristics. Among additive manufacturing techniques, fused deposition modeling (FDM) is the most studied for oral drug delivery device production due to its high precision and cheapness. By playing with factors such as drug loading method, filament production, and printing parameters, the medication release profile of a drug delivery device produced by 3D printing can be tailored depending on the patient's requirements. This review focuses on the applications of FDM in drug fabrication using poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) as drug‐loaded matrices. The authors aim to provide an overview of the current trends in this research field, with special attention to the effect of the printing parameters, tablet shape, and drug distribution and concentration on drug customization and personalized drug release. [ABSTRACT FROM AUTHOR]

This work aims at preparing bioderived polymer films by blending poly(lactic) acid (PLA) and poly(dodecylene 2,5‐furandicarboxylate) (PDoF) and containing reduced graphene oxide (rGO) as a multifunctional filler in variable weight fraction (from 0.25 to 2 phr). Although the PLA/PDoF blend results as immiscible, the addition of rGO leads to smaller (from 2.6 to 1.6 µm) and more irregularly shaped PDoF domains and to a better PLA/PDoF interfacial adhesion, which suggests that rGO may act as a blend compatibilizer. Dynamic mechanical thermal analysis (DMTA) shows that rGO shifts the glass transition of PDoF (≈5°C) to higher temperatures. The addition of 10 wt% PDoF in PLA increases the strain at break (+145%), and the addition of 0.25 phr of rGO to this blend increases its tensile strength (+13%), without significantly modifying the strain at break. Finally, rGO strongly decreases the diffusivity and permeability to O2, N2, and CO2 due to an increased diffusion path for gas molecules. These results highlight the positive and sometimes synergistic role of PDoF and rGO in tuning the thermomechanical and gas permeation properties of PLA. [ABSTRACT FROM AUTHOR]

Rigid cross‐linked interpenetrated network polyvinyl chloride (PVC) foams are widely used as core materials in the composite industry. Nevertheless, no recycling methods exist today for these materials that are currently landfilled at the end of life (EoL). In this work, various amounts of EoL PVC cross‐linked foams in the form of chips were mixed with ethylene–propylene diene monomer (EPDM) rubber and carbon black (CB) at 60°C for 15 min. The obtained rubber mixtures were vulcanized at 160°C for 20 min to create compacted square sheets of EPDM‐CB‐PVC composites using compression molding technique. Tensile tests revealed a progressive increase in modulus of EPDM‐CB with increasing PVC content while a subsequent decrease of the elongation‐at‐break values of the composites was noticed. Scanning electron microscopy revealed a homogeneous dispersion of PVC particles with the EPDM‐CB matrix. Improved interfacial adhesion of filler in the matrix was also observed at higher PVC content as well. Hardness tests revealed an increased Shore A values by 25% with added PVC waste in EPDM‐CB. Concurrently, a steady increase in compression set was observed in the rubber composites with the added PVC filler. Additionally, due to added filler, thermal conductivity was decreased by 35% compared to pure EPDM‐CB. [ABSTRACT FROM AUTHOR]

Materials able to store thermal energy can be a useful strategy to reduce energy consumption of buildings and to decrease greenhouse gases emissions. In this work, for the first time, the technique of salt leaching has been used to produce novel polyethylene foams containing different amounts of a microencapsulated phase‐change material (PCM) with a melting point of 24°C, to be potentially applied in building insulation. The microstructural, thermal, and mechanical properties of produced foams have been comprehensively investigated. The prepared foams were characterized by high values of open porosity (about 60%) and by density values around 0.4 g/cm3. Infrared thermography analysis demonstrated that the time required from the samples to reach a set temperature, thanks to the presence of PCM, was up to two times higher with respect to the reference foam. Therefore, these materials could store/release an interesting amount of thermal energy. Shore‐A measurements evidenced that the addition of PCM generally led to a softening of the foams. Tensile mechanical tests confirmed the softening effect provided by the addition of the microcapsules, with a decrease of the stiffness and of the strength of the material. Interestingly, strain‐at‐break values were considerably increased upon PCM introduction. [ABSTRACT FROM AUTHOR]

Electrically conductive composites of thermoplastic polyurethane (TPU), poly(vinylidene fluoride) (PVDF), and carbon black‐polypyrrole (CB‐PPy) were prepared by melt compounding followed by compression molding or by filament production followed by fused filament fabrication (FFF). The storage modulus (G′) and complex viscosity (η*) of the composites increased with the addition of CB‐PPy leading to a more rigid material. The electrical and rheological percolation threshold of composites were 5 and 3 wt%, respectively. In fact, composites with 5 wt% or more CB‐PPy content display G′ higher than G″ indicating a solid‐like behavior. Furthermore, the addition of CB‐PPy increased the electrical conductivity of all composites. However, the electrical conductivity values of composites containing 5 and 6 wt% of CB‐PPy produced by compression molding are one and seven order of magnitude higher than those of FFF composites with same composition. Compression molded and 3D printed composites with 6 wt% of CB‐PPy displayed high sensitivity/gauge factor, large measurement range and reproducible piezoresistive response during 100 loading‐unloading cycles for both processing methods. The results presented in this study demonstrated the potential use of FFF for producing piezoresistive flexible sensors based on PVDF/TPU/CB‐PPy composites. [ABSTRACT FROM AUTHOR]

This work focus on the development of polymeric blends to produce multifunctional materials for 3D printing with enhanced electrical and mechanical properties. In this context, flexible and highly conductive materials comprising poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) filled with carbon black‐polypyrrole (CB‐PPy) were prepared by compression molding, filament extrusion and fused filament fabrication. In order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability, blends composition was optimized and different CB‐PPy content were added. Overall, the electrical conductivities of PVDF/TPU 50/50 vol% co‐continuous blend were higher than those found for PVDF/TPU 50/50 wt% (i.e., 38/62 vol%) composites at same filler content. PVDF/TPU/CB‐PPy 3D printed samples with 6.77 vol% filler fraction presented electrical conductivity of 4.14 S m−1 and elastic modulus, elongation at break and maximum tensile stress of 0.43 GPa, 10.3% and 10.0 MPa, respectively. These results highlight that PVDF/TPU/CB‐PPy composites are promising materials for technological applications. [ABSTRACT FROM AUTHOR]

Cyclic olefin copolymer (COC) is utilized as thermoplastic healing agent in an epoxy resin and the effect of mending temperature on the healing of resulting materials is investigated. Blends are prepared by adding 20 and 30 wt% COC powder in the epoxy resin. They are thermo‐mechanically characterized and fractured samples are thermally mended at various temperatures to evaluate the healing efficiency of the repaired samples. Optical microscopy reveals a homogenous dispersion of COC domains within epoxy matrix, while thermogravimetric analysis shows improved thermal stability of the samples. The immiscibility of the two phases in the blends lead to a decrease of the mechanical properties under flexural and tensile loading modes with respect to neat epoxy. The fracture toughness increases upon COC addition at elevated amounts. Healing efficiency values up to more than 80% are obtained at the lowest investigated temperature of 145°C for samples with 30 wt% of COC. [ABSTRACT FROM AUTHOR]

Various amounts of both devulcanized (DR) and non‐devulcanized (NDR) recycled rubber were melt compounded with a virgin ethylene‐propylene diene monomer (EPDM) rubber. The resulting compounds were then expanded by using azodicarbonamide. The role played by the presence of DR or NDR on the thermomechanical properties of the obtained materials was evaluated. Electron scanning microscope micrographs highlighted that DR particles were better encapsulated within the EPDM matrix with respect to the corresponding NDR ones. Moreover, a better interfacial adhesion was observed with DR, probably due the re‐vulcanization process in which the free crosslinking sites that typically characterize DR could form linkages with the EPDM matrix. Tensile impact behavior of expanded EPDM/recycled rubber blends highlighted a strong improvement of the normalized total absorbed energy, of the normalized impact strength and of the elongation at break with respect to the neat expanded EPDM for all the investigated compositions, and especially with a DR content of 20 wt%. The preparation of expanded EPDM containing considerable amounts of devulcanized rubber was, therefore, demonstrated to be a practical route to reduce the costs and improve the properties and the environmental sustainability of rubber products. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) materials constituted by a microencapsulated paraffin having a melting temperature of 6°C and a thermoplastic polyurethane (TPU) matrix were prepared through fused deposition modeling. Scanning electron microscope (SEM) micrographs demonstrated that the microcapsules were homogeneously distributed within the matrix, with a rather good adhesion within the layers of 3D printed specimens, even at elevated concentrations of microcapsules. The presence of paraffin capsules having a rigid polymer shell lead to a stiffness increase, associated to a decrease in the stress and in the strain at break. Tensile and compressive low‐cycles fatigue tests showed that the presence of microcapsules negatively affected the fatigue resistance of the samples, and that the main part of the damage occurred in the first fatigue cycles. After the first 10 loading cycles at 50% of the stress at break, a decrease in the elastic modulus ranging from 60% for neat TPU to 80% for composite materials was detected. This decrease reached 40% of the original value at 90% of the stress at break after 10 cycles. Differential scanning calorimetry tests on specimens after fatigue loading highlighted a substantial retention of the original TES capability, in the range of 80%–90% of the pristine value, even after 1000 cycles, indicating that the integrity of the capsules was maintained and that the propagation of damage during fatigue tests took probably place within the surrounding polymer matrix. It could be therefore concluded that it is possible to apply the developed blends in applications where the materials are subjected to cyclic stresses, both in tensile and compressive mode. [ABSTRACT FROM AUTHOR]

The thermomechanical behavior of ethylene propylene diene monomer (EPDM) foams produced with the salt leaching method has been investigated and compared with the behavior of EPDM foams obtained from conventional blowing agents. Moreover, the salt‐leaching process has been optimized to minimize salt residues and the influence of different parameters (such as average particle size and particle size distribution) has been investigated. Scanning electron microscopy and density measurements highlighted that salt‐leaching leads to the formation of open‐cell porosity with cell dimensions of around 60 to 80 μm, while foams obtained with the two traditional foaming agents lead to closed‐cell porosity. Compression set values indicate that the behavior of the foams produced with salt leaching are more similar to the unfoamed rubber, characterized by higher elasticity and low residual deformation. Two theoretical models were successfully applied to the compression curves (Mooney‐Rivlin and Exponential‐Logarithmic) and they highlighted the effect of foaming on the properties of EPDM rubber and in particular the higher chain extensibility obtained through the salt leaching foaming method. [ABSTRACT FROM AUTHOR]

Microencapsulated phase change materials (PCMs) are being increasingly employed as functional fillers in polymer matrices for thermal management. Therefore, the effect of PCM microcapsules on the rheological, microstructural, thermal and mechanical properties of the host polymer matrices must be understood. This work concerned the preparation of epoxy polymers filled with PCM microcapsules (MC) in various concentrations and their subsequent characterization. The MC phase increases the viscosity of epoxy before curing, thereby reducing castability and hindering elimination of air bubbles. The latter was reflected in an increase in porosity for highly filled compositions, as elucidated by density measurements and microscopic investigation. SEM micrographs showed that the adhesion between the capsule shell and the epoxy matrix was not optimal. The interfacial weakness and the intrinsic low stiffness and strength of MC caused a reduction in mechanical properties, as evidenced by the Nicolais‐Narkis and Pukanszky models. On the other hand, at zero or low deformation levels, the interface presents no gaps and is able to transfer load and heat, as demonstrated by the data of elastic modulus, modeled with the Halpin‐Tsai and Lewis‐Nielsen models, and those of thermal conductivity, in excellent agreement with the Pal model. POLYM. ENG. SCI., 2020. © 2020 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

This work aims at developing multifunctional thermoplastic laminates combining structural and heat storage/management functions. The laminates are constituted by paraffin microcapsules as phase change materials (PCM), continuous carbon fibers, and a novel thermoplastic liquid methyl methacrylate resin (Elium), processable as a thermoset. The characterization aims to study how the paraffin microcapsules influence the thermo‐mechanical properties and thermal management performance of Elium and of the relative composite laminates. For the Elium/PCM systems, the phase change enthalpy increased with the experimental PCM concentration up to 101 J/g, but the mechanical properties decreased concurrently. The melting enthalpy of the laminates also increased with the microcapsule amount, up to 66.8 J/g, which indicates that the mild conditions applied in the processing of the liquid resin allow the integrity of the microcapsules to be preserved. This is also confirmed by the improved thermal management performance observed through thermal camera imaging measurements. Microscopy techniques showed that the PCM phase is preferentially distributed in the interlaminar region, which accounts for the observed decrease in the interlaminar strength and the flexural properties with an increase in the PCM content. These results show a potential for the future development of multifunctional thermoplastic composites with elevated thermal energy storage capabilities. POLYM. COMPOS., 40:3711–3724, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Aim of this work is to develop a novel epoxy based nanocomposite and to analyse its shape memory behavior. In particular, silver nanoparticles are in‐situ generated within an epoxy resin subsequently filled with both carbon black (CB) and carbon nanofibers (NFs) at different ratios and at a total amount of 4 wt%. Differential scanning calorimetry shows how the introduction of both CB and NF induces a slight decrease of the glass transition temperature (Tg) of the samples. The Tg drop due to nanofiller addition determines a decrease of both flexural modulus and stress at yield with respect to the neat resin, especially at elevated CB concentrations, while the presence of Ag nanoparticles plays a positive effect on the flexural properties. The best mechanical properties can be detected at a CF/NF ratio of 50%, coupled with a noticeable decrease of the electrical resistivity down to 102 Ω·cm and an interesting heating capability through Joule effect. The electro‐mechanical shape‐memory characterization under bending configuration demonstrates how it is possible to obtain an almost complete shape recovery after 60 s under an applied voltage of 220 V. POLYM. ENG. SCI., 59:694–703, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets (xGnP), expanded graphite (EG), multiwall carbon nanotubes (MWCNTs), and carbon black (CB) were dispersed in various amounts in a thermosetting polyurethane (PU) matrix derived from castor oil and composite plaques were obtained by compression molding. The electrical percolation threshold was found to be 0.1 vol% for MWCNT, 0.5 vol% for xGnP, 2.8 vol% for CB, and 2.7 vol% for EG‐filled systems. The relation between electrical conductivity, morphology, and electromagnetic interference shielding effectiveness (EMI SE) of the resulting composites was studied to understand how the EMI SE is influenced by morphology and electrical conductivity of each filler. The composites display significantly distinct EMI SE values, depending on the type of carbon filler and its volume fraction. Composite based in PU/EG and PU/xGnP exhibited the highest EMI SE values (70 and 47 −dB, respectively); however, PU/MWCNT composites showed higher EMI SE (24 −dB) value at the same filler content (3 vol%) than the other composite system. POLYM. COMPOS., 40:E78–E87, 2019. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Composite films based on sodium carboxymethyl cellulose (Na‐CMC) loaded with a ZnAl(OH)2CO3·yH2O hydrotalcite (ZnAl‐HTlc), were developed and characterized. The composites were mechanically more stable than the matrix alone: the noticeable enhancement of elastic modulus, creep resistance and failure properties, all proportional to the filler content, came at the expenses of a certain embrittlement. The filler tended to aggregate in the composites and the size of the aggregates increased with ZnAl‐HTlc amount. Contact angle measurements highlighted how ZnAl‐HTlc introduction in the polymeric matrix could strongly modify the wettability conditions of the films increasing their hydrophilicity. Bioadhesion tests showed that the adhesion behavior of the composites decreased as ZnAl‐HTlc amount increases, testifying the influence of the filler on the ability of the film to bind skin surface. Therefore, the developed films may find application as active wound dressings since ZnAl‐HTlc can be easily intercalated with an active pharmaceutical ingredient to be progressively released on the wound. POLYM. ENG. SCI., 59:E112–E119, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT: This work evaluates the influence of two types of carbonaceous fillers, carbon black (CB) and carbon nanotubes (CNTs), on the electrical, electromagnetic, and rheological properties of composites based on poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) prepared by the melt mixing. Electrical conductivity, electromagnetic shielding efficiency (EMI SE) in the X‐band frequency range (8–12.4 GHz), and melt flow index (MFI) results showed that ABS/CNT composites exhibit higher electrical conductivity and EMI SE, but lower MFI when compared to ABS/CB composites. The electrical conductivity of the binary composites showed an increase of around 16 orders of magnitude, when compared to neat ABS, for both fillers. Binary composites with 5 and 15 wt % of filler showed an EMI SE of, respectively, −44 and −83 dB for ABS/CNT, and −9 and −34 dB for ABS/CB. MFI for binary composites with 5 wt % were 15.45 and 0.55 g/10 min for CB and CNT, respectively. Hybrid composites ABS/CNT.CB with 3 wt % total filler and fraction 50:50 and 75:25 showed good correlation between EMI SE and MFI. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46546. [ABSTRACT FROM AUTHOR]

In this work, thermoplastic polyurethane‐filled montmorillonite‐polypyrrole (TPU/Mt‐PPy) was prepared through melt mixing process for using in electromagnetic shielding applications. The effect of conducting filler content and type, sample thickness, and X‐band frequency range on the electromagnetic interference shielding effectiveness (EMI SE) and EMI attenuation mechanism was investigated. A comparative study of electrical and microwave absorption properties of TPU/Mt‐PPy nanocomposites and TPU/PPy blends was also reported. The total EMI SE average and electrical conductivity of all Mt‐PPy.Cl or Mt‐PPy.DBSA nanocomposites are higher than those found for TPU/PPy.Cl and TPU/PPy.DBSA blends. This behavior was attributed to the higher aspect ratio and better dispersion of the nanostructured Mt‐PPy when compared with neat PPy. Moreover, the presence of Mt‐PPy into TPU matrix increases absorption loss (SEA) mechanism, contributing to increase EMI SE. The total EMI SE values of nanocomposites containing 30 wt% of Mt‐PPy.DBSA with 2 and 5 mm thickness were approximately 16.6 and approximately 36.5 dB, respectively, corresponding to the total EMI of 98% (75% by absorption) and 99.9% (88% by absorption). These results highlight that the nanocomposites studied are promising materials for electromagnetic shielding applications. [ABSTRACT FROM AUTHOR]

The present work deals with the characterization of multi‐walled carbon nanotubes (MWCNTs) filled and unfilled short carbon fiber reinforced epoxy resin composites. Short carbon fibers (10 mm) were selected at various processing stages such as (i) white color polyacrylonitrile fibers (PAN); (ii) pre‐carbonized carbon fibers (Precarb‐CF); (iii) oxidized carbon fibers (OCF); (iv) fully carbonized carbon fibers (CF‐low); and (v) sized carbon fibers (CF Sized). The investigated composites were characterized by three points bending test, hardness test, dynamic mechanical thermal analysis (DMTA), electrical conductivity test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results show that the mechanical and electrical properties of the investigated materials markedly depend on the type of short carbon fibers and on the presence of MWCNTs. POLYM. COMPOS., 39:E817–E825, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Novel polyvinyl alcohol (PVOH) based biodegradable composites were prepared by a hand lay‐up process using ultrathin beech laminae cut by a specialized planer machine, and the resulting materials were thermo‐mechanically characterized. Density measured showed how the adopted procedure led to laminates having a high porosity degree (about 50% by volume) and an elevated wood concentration (about 80% by weight). In fact, because the wood fibers were perfectly cut (not pressed and abraded), wood porosity was partially filled by the PVOH resin, as documented by field emission scanning electron microscope (FESEM) micrographs. The occlusion of wood porosity by the PVOH matrix resulted to be beneficial for the tensile mechanical properties of the composites. In fact, quasi‐static tensile tests and DMTA analysis revealed how the stiffness (E, E′) and strength (σb) values of the composites both along longitudinal and transversal directions were considerably higher than those of the constituents. On the other hand, the values of the specific energy adsorbed under impact conditions by the composites samples were rather low, if compared to the neat matrix. POLYM. COMPOS., 39:1116–1124, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Electrically conducting fibers were prepared through in situ oxidative polymerization of pyrrole (Py) in the presence of peach palm fibers (PPF) using iron (III) chloride hexahydrate (FeCl3·6H2O) as oxidant. The polypyrrole (PPy) coated PPF displayed a PPy layer on the fibers surface, which was responsible for an electrical conductivity of (2.2 ± 0.3) × 10−1 S cm−1, similar to the neat PPy. Electrically conductive composites were prepared by dispersing various amounts of PPy-coated PPF in a polyurethane matrix derived from castor oil. The polyurethane/PPy-coated PPF composites (PU/PPF–PPy) exhibited an electrical conductivity higher than PU/PPy blends with similar filler content. This behavior is attributed to the higher aspect ratio of PPF–PPy when compared with PPy particles, inducing a denser conductive network formation in the PU matrix. Electromagnetic interference shielding effectiveness (EMI SE) value in the X-band (8.2–12.4 GHz) found for PU/PPF–PPy composites containing 25 wt% of PPF–PPy were in the range −12 dB, which corresponds to 93.2% of attenuation, indicating that these composites are promising candidates for EMI shielding applications. [ABSTRACT FROM AUTHOR]

The main focus of this study is to characterize the interfacial interactions between silica nanoparticles and polypropylene and to investigate how the surface properties and morphology of the silica nanoparticles affect the elastic response of the silica-polypropylene composites. The composites were prepared by melt compounding and injection molding. Both non-functionalized and dimethyldichlorosilane-functionalized silica nanoparticles were used. Three-component composites were also prepared by including selected formulations of both poly(propylene- g-maleic anhydride) copolymer (PPgMA) and different types of silica. It was found that both silica types are nucleating agents for PP and significantly alter its crystallization behavior. A strong correlation between the glass transition temperature ( Tg) and the tensile modulus in silica-PP nanocomposites indicated the presence of a secondary reinforcing mechanism that is the pinning of the polymer chains on the silica surface. The presence of a complex constrained phase, represented by immobilized amorphous and transcrystalline phases, forming at the filler surface, was assessed by modulated differential scanning calorimetry and dynamic mechanical analysis. Finally, the interfacial interactions were correlated to the tensile and viscoelastic properties using the theoretical models proposed by Pukanszky and Sumita et al., respectively, and comparing the predictions of the models to experimental results. POLYM. COMPOS., 37:2018-2026, 2016. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Viscoelastic properties of nanocomposite fibers of high density polyethylene (HDPE) and organically modified hydrotalcite were studied. Neat and nanofilled HDPE fibers (with nanofiller content between 0.5 and 3 wt%) were produced by melt spinning and hot-drawing at different draw ratios up to 20. Effect of temperature on storage modulus, loss modulus, and creep compliance were compared. Rising nanofiller content and/or drawing ratio accounted for an increase in storage modulus in the glassy (i.e., below the γ transition at 2100°C) as well as in the rubbery state of noncrystalline regions. The α relaxation temperature readoff for the maximum of the loss modulus peak ranged from 20 to 60°C being dependent on frequency, filler content and draw ratio. Sumita model was successfully applied to evaluate the effective volume fraction of the dispersed phase; maximum fraction of immobilized matrix was observed for the composite with 1 wt% of nanofiller. Creep behavior was evaluated by fitting experimental data with the Burgers model. The addition of a small amount of well-dispersed hydrotalcite (0.5-1 wt%) had a beneficial effect on the creep resistance of drawn fibers at room temperature as well as at 70°C. TEM analysis evidenced a good dispersion of 0.5% nanofiller in as-spun fibers and improved interfacial adhesion after drawing. The best mechanical properties were observed for the composition with 1 wt% of hydrotalcite, due to combined effects of nanofiller reinforcement and stiffening produced by hot drawing. [ABSTRACT FROM AUTHOR]

Thin adhesive composite films were prepared by melt-compounding and compression molding of a thermoplastic resin (Paraloid® B72) widely used for art protection and restoration with a microcrystalline cellulose powder (MCC). To simulate an oil painting restoration work, MCC-based composites were applied as lining adhesives on two kinds of canvases (English linen and woven polyester). Interestingly, single-lap shear tests both in quasi-static and creep conditions showed a remarkable stabilizing effect provided by MCC addition. Post-mortem microstructural analysis of the overlap adhesive area proved how MCC introduction did not change the fracture behavior of the bonded joints. The visual assessment of transparency and color measurements evidenced a chromatic variation of MCC-based films with a filler amount of 30 wt%, while, UV-vis analysis showed a decrease of relative transmittance in proportion to the MCC content. Additionally, rheological tests highlighted a viscosity increase for Paraloid B72 in both dry and wet conditions ( T = 23°C and RH = of 55%) as the MCC content increases. POLYM. ENG. SCI., 55:1349-1354, 2015. © 2015 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Linear low-density polyethylene (LLDPE)-based composites were prepared through melt compounding and hot pressing using both untreated and treated halloysite nanotubes (HNT) up to filler contents of 8 wt% to assess the role of the filler exfoliation and surface treatment on the thermal, mechanical, and rheological properties of the resulting composites. The addition of treated nanoparticles resulted in a better dispersion of the filler within the matrix, as confirmed by observations conducted at scanning and transmission electron microscopies. A decrease in both complex viscosity and shear storage modulus was recorded for all LLDPE-HNT nanocomposites in the molten state. Differential scanning calorimetry analysis evidenced that HNT addition produced an increase of the crystallization peak temperature, while thermogravimetric analysis showed a remarkable improvement of the thermal stability with the nanofiller content. The addition of treated HNT nanoparticles induced better improvements in elastic modulus and tensile properties at break without significant loss in ductility. The fracture toughness, evaluated by the essential work of fracture approach, showed remarkable improvements (up to a factor of 2) with addition of treated HNT. Conversely, incorporation of untreated HNT produced an adverse effect on the fracture toughness when considering the nanocomposite filled with 8 wt% HNT. Both creep tests and dynamic mechanical analyses showed an overall enhancement of the viscoelastic properties due to addition of HNT, revealing higher improvements in nanocomposites added with treated HNT. POLYM. COMPOS., 36:869-883, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, polypropylene (PP) composites reinforced with short glass fibers (GF) and exfoliated graphite nanoplatelets were obtained by melt compounding followed by injection molding. Morphological observations and quasi-static tensile tests were carried out in order to investigate how the morphology and the mechanical properties of the composites were affected by the combined effect of two fillers of rather different size scales (i.e., micro- and nanoscale). The results indicate that the dispersion of the nanofiller in the PP matrix promoted the formation of a stronger interface between the matrix and GF, as indicated by the increase of the interfacial shear strength determined by the single-fiber microdebonding test. Concurrently, a significant improvement of the tensile modulus and impact strength of the composites was observed, with small changes in the processability of hybrid composites compared to that of GF composites, as confirmed by rheological measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41682. [ABSTRACT FROM AUTHOR]

This study explores how the presence of nanofillers with different structural and chemical characteristics, specifically silica nanoparticles and exfoliated graphite nanoplatelets (GNP), alters the crystallization behavior and polymorphism of a semicrystalline polymer, such as polypropylene (PP). The main focus of this research is to investigate how silica and GNP affect the nucleation and growth of PP crystals during isothermal crystallization. The nonisothermal crystallization behavior, including crystal structures, crystallization temperature, and rate, is also determined. PP composites with nanomaterial content up to 7 wt% were produced by melt mixing and injection molding. Both silica and graphite were found to be effective nucleating agents, significantly increasing the crystallization rate during isothermal crystallization, with greater changes observed in case of GNP composites. The effect of filler type and amount on the PP polymorphism and lamella thickness was studied by X-ray diffraction and modulated differential scanning calorimetry. Both silica and graphite were found to be effective nucleating agents for the less common β-phase of PP crystals even at low nanomaterial concentration. α-−crystal perfection and the recrystallization of the β-form in the α-form and/or at the transcrystalline regime were found to be responsible for the recrystallization occurring upon melting in nanocomposites at high silica or medium GNP content. POLYM. ENG. SCI., 55:672-680, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT Thermoplastic composites based on a commercial acrylic matrix widely used in the field of art protection and restoration (Paraloid B72) and various concentrations (up to 30 wt %) of microcrystalline cellulose powder (MCC) were prepared by melt-compounding and compression molding. The mechanical behavior of the resulting materials conditioned at a temperature of 23°C and a relative humidity level of 55% was compared to that of the corresponding dried materials. Even though the moisture absorption of the filler was lower than the neat matrix, the maximum moisture content increased with the MCC amount, probably due to the preferential water diffusion path through the microvoids and/or the filler-matrix interface. Although the increase of moisture content for filled samples, DMTA analysis evidenced a stabilization upon MCC introduction, with an increase of the storage modulus and a decrease of the thermal expansion coefficient proportional to the filler loading. A similar trend was displayed by the corresponding dried materials. The tensile elastic modulus and the ultimate properties such as the stress at break and the tensile energy to break (TEB) of conditioned samples increased proportionally to the filler amount. On the contrary, the failure properties of dried composites were negatively affected by the presence of the microcellulose. It is worthwhile to report that a significant improvement of the creep stability was induced by MCC introduction both for dried and conditioned samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40741. [ABSTRACT FROM AUTHOR]

ABSTRACT Fibers of high density polyethylene (HDPE)/organically modified hydrotalcite (LDH) were produced by melt intercalation in a two-step process consisting of twin-screw extrusion and hot drawing. The optimum drawing temperature was 125°C at which the draw ratios up to 20 could be achieved. XRD analysis revealed intercalation with a high degree of exfoliation for the composites with 1-2% of LDH. Higher thermal stability of nanofilled fibers was confirmed by TGA analysis. DSC data indicated that dispersed LDH particles act as a nucleating agent. Crystallization kinetics of the HDPE matrix in the composite fibers is characterized by two transition temperatures, that is, for Regimes I/II at 123°C and for Regimes II/III ranging between 114-119°C as a function of the nanocomposite composition. Fibers with 1-2% of LDH show for the drawing ratios up to 15 a higher elastic modulus, 9.0-9.3 GPa (with respect to 8.0 GPa of the neat HDPE), maintain tensile strength of 0.8 GPa and deformation at break of 20-25%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40277. [ABSTRACT FROM AUTHOR]

ABSTRACT A polypropylene matrix was melt compounded with a given amount (2 vol %) of both untreated (hydrophilic) and surface treated (hydrophobic) fumed silica nanoparticles with the aim to investigate the influence of the time under processing conditions on the microstructure and thermo-mechanical properties of the resulting materials. Chain scission reactions induced by thermal processing caused a remarkable decrease of the melt viscosity, as revealed by the melt flow index values of both neat matrix and nanocomposites, but the degradative effect was significantly hindered by the presence of silica nanoparticles. It was observed that the size of nanofiller aggregates noticeably decreased as the compounding time increased, especially when hydrophobic silica nanofiller was considered. While the melting temperature seemed to be unaffected by the processing time, a remarkable embrittlement of the samples was observed for prolonged compounding times. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40242. [ABSTRACT FROM AUTHOR]

This work aims to study the effects of date stone flour (DSF) on morphology, thermal, and mechanical properties of polypropylene (PP) composites in the absence and presence of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) used as the compatibilizer. DSF was added to the PP matrix at loading rates of 10, 20, 30, and 40 wt %, while the amount of compatibilizer was fixed to the half of the filler content. The study showed through scanning electron microscopy analysis that EBAGMA compatibilizer improved the dispersion and the wettability of DSF in the PP matrix. Thermogravimetric analysis (TGA) indicated a slight decrease in the decomposition temperature at onset ( Tonset) for all composite materials compared to PP matrix, whereas the thermal degradation rate was slower. Differential scanning calorimetry (DSC) data revealed that the melting temperature of PP in the composite materials remained almost unchanged. The nucleating effect of DSF was however reduced by the compatibilizer. Furthermore, the incorporation of DSF resulted in the increase of stiffness of the PP composites accompanied by a significant decrease in both the stress and strain at break. The addition of EBAGMA to PP/DSF composites improved significantly the ductility due to the elastomeric effect of EBAGMA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Two kinds of organo-modified (OM) clays were dispersed in an epoxy resin for the preparation of nanocomposite adhesives at various filler amounts. XRD tests evidenced the formation of intercalated structures, increasing the intercalation degree with the clay hydrophilicity. The original transparency of the samples was retained up to a filler content of 3 wt%, and then decreased due to filler agglomeration. The glass transition temperature of nanocomposites filled with the more hydrophilic clay (30B) raised up to a filler content of 3 wt% and then decreased, probably because of the concurrent and contrasting effects of the physical chain blocking and reduction of the cross-linking degree. Also elastic modulus, stress at break, and fracture toughness were sensibly improved by nanoclay addition up to filler loadings of 0.5-1 wt%. For higher concentrations the positive contribution of clay nanoplatelets was counterbalanced by the presence of agglomerated tactoids in the matrix. Mechanical tests on single-lap composite (epoxy/glass) bonded joints evidenced an enhancement of the shear strength by about 25% for an optimal filler content of 1 wt%. Therefore, it was concluded that the addition of a proper amount of OM clay to epoxy adhesives could represent an effective way to improve the shear resistance of adhesively bonded composite structures. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Interaction of the components and physical properties of the polypropylene (PP)/cycloolefin copolymer (COC) blends were studied by means of differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), Vicat softening temperature (VST), and measurements of the coefficient of linear thermal expansion (CLTE) and of the density. The attention was focused on the blends with 90-60% of PP by wt, where the COC minority component was present in the form of short fibers. DSC, DMTA, and density measurements concurrently prove the immiscibility of PP and COC. DSC measurements reveal that crystallinity and melting temperature of the PP component slightly decrease with the fraction of COC in blends, in the range of 56-47% and 164-161°C, respectively. Storage modulus and loss modulus of the blends are in a good accord with the model predictions based on (i) the equivalent box model (EBM) and on (ii) modified equations of the percolation theory. The dependence of the VST on the blend composition is in a good correlation with the previous morphological analysis. Measurements of the coefficient of thermal expansion provide useful data as the functions of temperature and blend composition. Density of the blends was found to obey the volume additivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined the properties of cycloolefin copolymer (COC)-polyhedral oligomeric silsesquioxanes (POSS) nanocomposites. Melt compounding was used in this study to prepare the nanocomposites. Results of the study showed that the optical transparency of the matrix has been retained by the composites. The study observed a significant drop in the glass transition temperature and the thermal decomposite rate of the POSS content.

The article presents the results of research into the the viscoelastic features of Poisson's ratio of polymeric materials. Measures of axial and transverse deformations under tensile testing conditions were conducted on two different crosslinked epoxy resins. In this context, Poisson's ratio appeared not as a constant, but as a viscoelastic function of time. An inverse relationship between the level of glass transition temperature and values of Poisson's ratio was noted. The ratio was particularly affected by strain which approached nonlinear viscoelasticity.

Examines the stress-strain linearity limit for short-term creep of heterogenous polymer blends. Characteristics of polymeric materials; Applicability of an empirical equation proposed by the author; Assessment on the percolation approach to the phase continuity in polymer blends.

Presents information on a study which investigated the nonlinear dynamic behavior of a vulcanized rubber compound employed in the production of tires. Methodology of the study; Results and discussion on the study; Conclusions.

This work focuses on the development of multifunctional thermoplastic composites with thermal energy storage capability. A polyamide 12 (PA12) matrix was filled with a phase change material (PCM), constituted by paraffin microcapsules (Tmelt = 43 °C), and reinforced with carbon fibers (CFs) of two different lengths (chopped/CF "long"[CFL] and milled/CF "short" [CFS]). DSC tests showed that the melting/crystallization enthalpy values increase with the PCM weight fraction up to 60 J/g. The enthalpy was 41–94% of the expected value and decreased with an increase in the fiber content, because the capsules were damaged by the increasing viscosity and shear stresses during compounding. Long CFs increased the elastic modulus (+316%), tensile strength (+26%), and thermal conductivity (+54%) with respect to neat PA12. Thermal imaging tests evidenced a slower cooling for the samples containing PCM, and once again the CFS‐containing samples outperformed those with CFL, due to the higher effective PCM content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47408. [ABSTRACT FROM AUTHOR]