The 50 most-cited articles in Journal of Applied Polymer Science, 2020

Abstract Hydrogels have been generated and explored for use in various applications. The main objective of this comprehensive review is to collate the fundamental concepts of hydrogels, and elaborate on knowledge gaps, and to provide a perspective on the future directions. This review includes details of constituent molecules (monomers, cross‐linkers, composite materials, etc.) and the methods used to prepare polymer networks. Moreover, the review highlights modifications of hydrogels that introduce new properties or enhance the existing features to suit the desired applications and challenges of synthetic polymer hydrogels. The other important topics covered in this review are the synthesis and applications of 3D printed hydrogels, nanocomposite hydrogels, injectable hydrogels, and self‐healing hydrogels.

ABSTRACT Polydimethylsiloxane (PDMS) is hailed as one of the foundational materials for microfluidics. Though a silicone‐based elastomer of many desirable properties, the emergence of microfluidic fabrication techniques, especially soft lithography, has elevated its status to an exceptional one. In this mini review, we look at the salient aspects that make PDMS so special in achieving such a coveted status in the microfluidics community. A methodical approach is followed to touch upon the application of PDMS in various aspects of microfluidics with the advantages, limitations, and some future directions. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48958.

Abstract This report traces the leading scientific endeavors to enhance the dielectric strength of polymer dielectrics for energy storage and electrical insulation applications. Remarkable progress has occurred over the past 15 years through nanodielectric engineering involving inorganic nanofillers, coatings, and polymer matrices. This article highlights the challenges of dielectric polymers primarily toward capacitors and cable/wire insulation. It also summarizes several major technical approaches to enhance the dielectric strength of polymers and nanocomposites, including nanoparticle incorporation in polymers, filler‐polymer interface engineering, and film surface coating. More attention is directed to interface contributions, including rational design of core‐shell structures, use of low‐dimensional fillers and thermally conducting fillers, and inorganic surface coating of polymer films. These efforts demonstrated the enhancement in dielectric strength by 40–160% when controlling the fillers below 5 wt% in polyvinylidenedifluoride (PVDF) composites. This article also discussed…

Abstract Many processing parameters can be adjusted to optimize the fused filament fabrication (FFF) process, a popular and widely used additive manufacturing techniques for plastic materials. Among those easily adjusted parameters are the nozzle temperature, printing speed, raster orientation, and layer thicknesses. Using poly(ether ether ketone) (PEEK) as the base material, a design of experiments analysis was performed on the main FFF parameters. A response surface methodology was applied to analyze the results and to maximize the output responses. Results have shown that the nozzle temperature is the most influential parameter on tensile properties and the crystallinity degree of printed PEEK by FFF process. Parts produced with optimized FFF parameters were then subjected to an annealing treatment to induce a relaxation of residual stress and to enhance crystallinity. The best properties for 3D printed PEEK parts were achieved with annealed parts prepared at 400°C with a printing speed of 30 mm/s, 0.15 mm layer thickness and raster orientation of [0°/15°/−15°]. The resulting…

ABSTRACT With rapid fossil fuel consumption and ecological concerns, alternative options of green energy development and its efficient storage technology is an emergent area of research. Nanocellulose is observed to be a very‐promising sustainable and environmentally friendly nanomaterial for green and renewable electronics for advanced electrochemical energy conversion/conservation devices. This review begins with a basic introduction on the sources and properties of nanocellulose. It provides an overview of the recent advancements made by researchers in integrating nanocellulose with active materials to form a flexible film/aerogel/3D structures as a substrate for powering portable electronics, electric vehicles, etc. The review highlights the use of nanocellulose‐based composites in energy conversion devices such as solar cells, piezoelectric materials, and lithium ion batteries. Recent research shows that the power conversion efficiency of solar cells and the piezoelectric performance of piezoelectric materials can be increased when the matrix is reinforced with nanocellulose.…

Abstract Synthetic polymers are ubiquitous materials widely used in construction, automotive, electronics, and countless commercial products. With the growing trend of polymer applications in everyday life, upholding the rigorous fire safety regulations has become a matter of concern. In this regard, numerous studies have been conducted for improving the fire retardancy of polymers, mainly through incorporating a diverse group of fire‐retardant compounds into polymer‐based composites. This review article aims to present a comprehensive overview of recent advances in the fire‐retardant categories for polymeric materials especially emphasizing the nanosized fire retardants. Along with an attempt to focus attention on the consumption of conventional and possibly harmful fire retardants, potential eco‐friendly alternatives are represented. A detailed discussion on the flame retardation mechanisms and conventional fire characterization techniques are also discussed.

Abstract Thermoplastic vulcanizates (TPVs) are special classes of thermoplastic elastomers, in which dynamic vulcanization of the rubber phase takes place during melt mixing with a semicrystalline thermoplastic matrix phase at elevated temperature. This review article focus on the different types of thermoplastic vulcanizates (TPVs) from various elastomer and thermoplastic blends that are suitable for the automotive applications purpose. A detailed study of the various TPVs based on polypropylene‐ethylene propylene diene rubber (PP‐EPDM) and polypropylene‐ethylene α‐olefin has been focused and their application in the automobile sector has been summarized. Most of the commercially available TPVs are PP‐EPDM based. Limited applications of that TPVs in high heat and oil resistant application purposes requires new generation of TPVs. High performance TPVs or super TPVs are new generation TPVs that exhibit high heat resistance as well as excellent oil resistance property suitable for automotive under‐the‐hood applications. Therefore TPVs based on XNBR‐PA12, HNBR‐PA12 and FKM‐PA6 system…

Abstract Oil–water separation has attracted research interest due to the damages of oily wastewater caused to the environment and human beings. Electrospun fiber membrane has high oil–water separation performance. A nanofibers membrane with multi‐stage roughness was prepared by electrospinning using poly(vinylidene fluoride)(PVDF)‐silica blend solution as raw material. The result shows that the water contact angle (WCA) of the nanofibers membrane was promoted from 138.5 ± 1° to 150.0 ± 1.5° when the SiO2 content was increased from 0 to 3 wt%. The nanofibers membranes exhibited excellent separation efficiency (99 ± 0.1%) under gravity drive, with high separation flux of 1857 ± 101 L·m−2·h−1. More importantly, the obtained PVDF‐SiO2 nanofibers membranes showed excellent multi‐cycle performance and stable chemical resistance, which would make them great advantages for the practical application of oil–water separation.

ABSTRACT Mixed matrix membranes (MMMs), which combine the good separation performance of inorganic materials with the low cost of polymers, have emerged as a research hotspot for gas separation membranes. Zeolite imidazolate frameworks (ZIFs) are widely used as fillers to prepare MMMs owing to their advantageous characteristics, such as adjustable pore channels, unsaturated sites, and easy functionalization. For MMMs, three directions can be employed as criteria for improvement compared with pristine polymeric membranes. In this article, the progress of ZIF‐based MMMs is reviewed from the aspects of sole‐ZIF‐based MMMs and modified ZIF‐based MMMs. Both strategies improve the separation performance through different improvement directions and mechanisms. Our analysis shows that the synergistic effect of the modified filler can change the structure of the membranes, such as by improving the filler–polymer interface voids, which provides a foundation to overcome the trade‐off effect to a certain extent. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48968.

Abstract The purpose of present study is in the direction of development of an anticorrosive coating formulation of high durability for carbon steel corrosion in 3 wt% NaCl medium. The formulation comprises of a macromolecular epoxy coating (DGEDDS‐MDA) based bisphenol S diglycidyl ether (DGEDDS) cured with a methylene dianiline (MDA). The formulation was characterized by FT‐IR spectroscopy method. Performance of the epoxy coating was represented using PDP and EIS approaches. The formulation acts as effective anticorrosive coating for long durability (180 days). Surfaces of the specimens before and after 180 days exposure to UV radiation were examined using SEM. PDP, SEM, and EIS studies showed that DGEDDS‐MDA acted as highly durable and effective anticorrosive formulation. Results also showed that the formulation acts as interface type inhibitor and its presence enhances the polarization resistance ( R p ) value. DFT study suggests that the formulation DGEDDS‐MDA possesses strong ability to interact with metal surface through its several electron rich centers. MD and MC simulations…

Abstract Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi‐piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X‐ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field.

ABSTRACT A stable and scalable polymer‐stabilized liquid crystal window which electrically switches from transparent to opaque has been fabricated. Scanning electron microscope measurement shows that higher polymer concentration will induce denser polymer network in polymer stabilized liquid crystal system and then stronger anchoring force between polymer network and liquid crystal molecules, which resulting in larger operating voltage. The cell with larger cell gap has a lower saturated transmittance in the voltage‐on state, which attributed to a larger number of scattering domains in thick cell. The optimized cell exhibits a highly transparent voltage‐off state (3.5% haze) and a voltage‐on scattering state (98% haze) with the threshold voltage of around 20 V. The durability test shows that the optical device switches at least 100,000 times without degradation of optical contrast and shows a high temperature tolerance. Meanwhile, a 40 × 50 cm2 window has been developed in an industrial production line showing the same optical properties. Our results demonstrate the fabrication of…

Abstract Hydrogels were introduced as suitable materials for applications in, e.g., medical, agriculture, or daily life areas. Swelling characteristics of a hydrogel are important and must be precisely known for various fields of application. In medicine, where hydrogels are used as implants or drug delivery systems, precise knowledge of the swelling behavior is essential. Especially in ophthalmology as part of cataract surgery, the visco‐elastic properties of the hydrogels could even allow for the restoration of accommodation. The easiest way to describe the swelling is by measuring the swelling ratio, generally done by scaling. Besides that, it can also be done by volume investigations. The similarities and differences are studied on five hydrogel samples made of methyl methacrylate and N‐vinyl pyrrolidone. Additionally, a first camera‐based approach, potentially providing an automated, quasi‐continuous non‐contact method for swelling kinetics investigations, is described.

Abstract Characterized by its strength, durability, and thermal properties, epoxy resin has been widely used as an adhesive, paint, and coating in many applications in the aerospace, civil and automotive industries. Despite this, the thermoset polymer resin has been known for its brittleness and low fracture resistance. This study focuses on the reinforcement of an epoxy resin system (diglycidyl ether of bisphenol A) with zinc oxide (ZnO) nanoparticles in their pristine form and a further modified form. The modification took place in two ways: coating with polydopamine (PDA) and covalently functionalizing them with (3‐aminopropyl)triethoxysilane (APTES) and (3‐glycidoxypropyl)trimethoxysilane (GPTMS). Therefore, four different types of nanoparticles were used: pristine ZnO, ZnO/PDA, ZnO/GPTMS, and ZnO/APTES aiming to improve the interfacial bonding between the polymeric matrix and the reinforcement. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, and scanning electron microscopy characterization and imaging techniques were used to prove that the ZnO…

Abstract This review encompasses the research progress on self‐healing properties of epoxy polymers and is divided into two categories: material supplement and energy supplement. The central concept of material supplement revolves around the addition of functional composite materials, such as, hollow fiber and microcapsule, to repair the micro‐cracks of epoxy polymers. In contrast, the energy supplement is based on the concurrent incorporation of some functional groups into the thermosetting epoxy polymers. These functional chemical groups participate in the construction of a three‐dimensional network structure of thermosetting materials and successfully enter the block copolymer of epoxy polymers. When the micro‐cracks are developed in the resin upon exterior impact, these functional groups automatically absorb energy from the outside to perform chemical reactions and automatically repair their micro‐cracks following the self‐healing phenomenon. Five kinds of reversible reactions are introduced for energy supply and are discussed in detail. Finally, a summary and comparison of the…

Abstract Blends of an amorphous polylactide (PLA) with three different thermoplastic polyurethane (TPU) grades having various hard segment (HS) contents are prepared at the blending ratio of 85/15 wt% through a twin‐screw extruder (TSE) at processing temperatures of 150 and 190°C. Blends of a semicrystalline PLA with 15 wt% of the noted TPU grades are also processed in the TSE at 190°C to investigate the matrix crystallization effect on the morphology and property enhancements. The rheological experiments reveal that the increase in TPU HS content significantly increases the phase compatibility between PLA and TPU as also suggested by the finer morphology of the TPU phase, although the use of lower HS TPUs is more favorable to enhance the ductility and impact properties of the blends.

Abstract Epoxy resin, which is extensively used in civil and industrial applications, shows excellent comprehensive performance, especially as a polymer matrix used in fiber‐reinforced composites. A thermal latent initiator, used as an epoxy curing agent, has high storage stability and is widely applied in the preparation of epoxy‐based blends and fiber‐reinforced composites. In this review, the basic properties of epoxy resins and commonly used curing agents are discussed while progress on the synthesis of thermal latent initiators is reviewed in detail. Moreover, the curing mechanisms, thermal stability, and mechanical properties of epoxy resins with thermal latent initiators are also discussed.

Abstract In this study, an innovative in situ green strategy was applied to prepare bacterial cellulose/silver nanocomposites using green tea as a substrate for the fermentation ofAcetobacter xylinumbacteria and a reducing agent for the in situ synthesis of silver nanoparticles. The samples were analyzed by different characterization tests including field emission scanning electron microscopy (FESEM), X‐ray diffraction analysis (XRD), UV–vis spectroscopy, atomic absorption spectroscopy, and ATR. The results indicated the excellent antibacterial activities with 100% bacterial reduction percentage and inhibition zones of 2.6 and 2.8 cm againstS. aureusandE. coli, respectively. Moreover, water absorption percentage and vertical wicking measurements supported the hydrogel properties of the prepared bio‐cellulose/silver nanocomposites. Finding of this research suggested the potential of the proposed green route for preparing antibacterial BC which can be regarded as a candidate for future wound healing applications.

Abstract A novel polyvinylidene fluoride (PVDF) nanocomposite membrane containing graphene oxide nanoribbones (GONRs) as a new nanofiller and polyvinylpyrrolidone (PVP) as pore former agent was prepared via phase inversion method. GONRs were prepared by oxidative unzipping of multi‐walled carbon nanotubes (MWCNTs) via chemical approach. Chemical vapor deposition method was used to synthesis MWCNTs. The effects of adding GONRs and PVP into the casting solution on morphology, hydrophilicity and pure water flux (PWF) of the prepared nanocomposite membranes were explored. Antifouling experiments were also performed. It was found that compared to the neat PVDF membrane, PWF of the PVDF/PVP, PVDF/(0.5GONRs) and PVDF/(0.5GONRs)/PVP membranes were improved 80%, 44.9%, and 241.6%, respectively. The obtained results showed that GONRs and PVP exhibit synergistic effects in controlling the membrane properties. This work shows that GONRs can be suitable as nanofiller for preparation of high performance PVDF ultrafiltration membranes with improved antifouling properties.

Abstract In this study, polyurethane‐films loaded with diclofenac were used to analyze the drug release kinetics and mechanisms. For this purpose, the experimental procedures were developed under static and dynamic conditions with different initial drug loads of 10, 20, and 30%. In the dynamic condition, to better simulate the biological flow, drug release measurements were investigated at flow rates of 7.5 and 23.5 ml/s. These values indicate the flow rate of the internal carotid artery (ICA) for a normal state of a body and for a person during the exercise, respectively. The experimental data were analyzed and adjusted by Higuchi, Korsmeyer–Peppas, First‐order, zero‐order, and Peppas–Sahlin models in order to understand the mechanisms contributed. Finally, drug release mechanisms were specified by investigating the model correlation coefficients. Experimental results showed that increasing the flow rate and initial drug loads enhance drug liberation. In addition, the rate of release is more influenced by the drug dosage in the static state. The analysis revealed that diffusion,…

Abstract Extraction of lithium from high Mg 2+ /Li + ratio salt lake brine with the nanofiltration (NF) membrane is significantly challenging. Interfacial polymerization was utilized for the facile modification of NF membranes with polydopamine (PDA) and polyethylenimine (PEI) to enhance lithium separation efficiency. Comparing permeability and salts rejection (Li + and Mg 2+ ) of three NF membranes before and after PDA/PEI deposition, it was observed that separation efficiency was not only dependent on steric hindrance but also affected by Donnan exclusion mechanism. In the case of NF270 membrane after facile polymerization, due to small pore size distribution and low charge density confirmed by zeta potential measurements, Li + permeability was reached about 95% at a flux of 21.33 L·m −2 ·h −1 . Although with the DK membrane, separation factor SF Li/Mg was also increased up to 60 after modification, the pore narrowing effect significantly decreased lithium permeability and flux. Experimental results showed that facile modification not only enhanced stability and hydrophilicity but…

Abstract Green chemistry and green engineering concepts have been combined to develop novel sustainable polymeric materials. Solvent free photocurable acrylate resins with biorenewable carbon content of 75%–82% suitable for application in DLP 3D printing technology were composed by commercially available bio‐based materials, acrylated epoxidized soybean oil (AESO), isobornyl methacrylate (IBOMA), methacrylic ester (ME), tetrahydrofurfuryl acrylate (THFA), and tetrahydrofurfuryl methacrylate (THFMA). They demonstrated high printing accuracy and good adhesion between layers. The monitoring of photocross‐linking kinetics of high biorenewable content acrylate photoresins by the real‐time photorheometry and analysis of their rheological parameters was carried out. Synthesized polymers exhibited high yield of insoluble fraction and thermal decomposition temperature at the weight loss of 10% above 300°C. Polymers AESO/IBOMA and AESO/THFMA showed the highest values of tensile modulus and tensile strength. Biodegradability of the synthesized polymers AESO/ME, AESO/THFA, and AESO/THFMA was…

Abstract Today fused filament fabrication is one of the most widely used additive manufacturing techniques to manufacture high performance materials. This method entails a complexity associated with the selection of their appropriate manufacturing parameters. Due to the potential to replace poly‐ether‐ether‐ketone in many engineering components, polyphenylene sulfide (PPS) was selected in this study as a base material for 3D printing. Using central composite design and response surface methodology (RSM), nozzle temperature ( T ), printing speed ( S ), and layer thickness ( L ) were systematically studied to optimize the output responses namely Young's modulus, tensile strength, and degree of crystallinity. The results showed that the layer thickness was the most influential printing parameter on Young's modulus and degree of crystallinity. According to RSM, the optimum factor levels were achieved at 338°C nozzle temperature, 30 mm/s printing speed, and 0.17 mm layer thickness. The optimized post printed PPS parts were then annealed at various temperatures to erase thermal residual…

Abstract The most important polymer film used in commercial capacitors is biaxially oriented polypropylene (BOPP), which could be produced by sequentially or simultaneously biaxial orientation after the melt‐extrusion. In order to disclose the influence of the stretching technique on the properties of films, the BOPP films with varied thickness were fabricated by sequential and simultaneous orientation, respectively. Compared to the sequentially biaxially stretched films, the crystal grains in the simultaneously biaxially stretched films are more isotropically dispersed. As temperature increases, all the BOPP films exhibit similar dielectric constant, and the simultaneous films have much lower dielectric loss thanks to the finer blended crystalline and amorphous phases. When the film thickness is smaller than 5 μm, the breakdown field strength, energy density and discharging time of the simultaneous films can be increased by at least 10% comparing to the sequential ones, which is very important for reducing the volume of the film capacitors. All the results suggest the…

Abstract Thermoset resins generally lack the ability to be welded or reprocessed like thermoplastics because of their cross‐links. Increasing use of fiber‐reinforced composites in large structures, such as rail and aircraft parts, as well as wind blades, calls for better ways to repair damages and be compliant with recycling and environmental regulations. In this article, an epoxy resin containing disulfide bonds was prepared and characterized by Fourier transform infrared, 1H‐NMR, and 13C‐NMR. The dynamic nature of the disulfide bonds allowed the cured epoxy resin to be welded like thermoplastics, and the welded joints had strength that matched the resin's cohesive strength. It could also be reprocessed with 90% tensile strength retention after three reprocessing cycles, allowing the parts to be repaired instead of being replaced. In addition, the cured resin was chemically degradable in a thiol‐based solvent, allowing it to be recycled in closed‐loop processes. Moreover, the cured epoxy resin showed a glass transition temperature of 116°C, demonstrating its potential for advanced…

Abstract The flame retardant polypropylene containing the micro‐envelope core‐shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine‐formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon‐forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine‐formaldehyde resin and the micro‐envelope core‐shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char‐forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high…

Abstract Nematic monodomain liquid crystal elastomers (LCEs) undergo efficient temperature‐induced reversible shape‐shifting around the nematic‐isotropic transition temperature (Tni) due to the presence of the liquid‐crystalline order of mesogens. Usually, the Tni of nematic LCEs is much higher than the human body temperature, and therefore LCEs are not often considered for biomedical applications. This study describes an LCE system where the Tni is tuned by substitution of the rigid mesogens RM257 with a flexible backbone PEGDA250. By systematically substituting the RM257 with PEGDA250, the Tni of LCEs was observed to decrease from 66°C to 23°C. A rate‐optimized LCE material was fabricated with 10 mol % rigid mesogens substituted with a flexible backbone that demonstrated Tni at 32°C, in‐between the room temperature of 20°C and the body temperature of 37°C. The Tni allowed the programmed shape at room temperature, quick shape‐shifting upon exposure to body temperature, and before‐programmed shape when kept at body temperature. This LCE material displayed reversible length change of…

Abstract The present investigation aims at the thermal conditions for the printability of nylon using fused deposition modeling (FDM). Dog‐bone like specimens are manufactured under two printing temperatures to measure the tensile performance of 3D printed nylon with respect to the feedstock material properties. Both Scanning Electron Microscopy (SEM) and X‐ray micro‐tomography analysis are conducted to shed more light on the microstructural arrangement of nylon filaments. Finite element computation based on microstructural implementation is considered to study the main deformation mechanisms associated with the nylon filament arrangement and the process‐induced porosity. The results show a narrow temperature range for printability of nylon, and a significant influence of the printing temperature on the thermal cycling, porosity content and mechanical performance. With the support of both numerical and experimental results, complex deformation mechanisms are revealed involving shearing related to the filament sequencing, compression at the junction points and tension within the…

Abstract In this work, lignin was used as a heterogeneous nucleating agent to increase polylactic acid (PLA) crystallinity. To enhance the gas barrier performance of PLA/LG composite films, two graft copolymers, polylactide‐graft‐glycidyl methacrylate (PLA‐g‐GMA) and polylactide‐graft‐poly (ethylene glycol) methyl ether methacrylate (PLA‐g‐PEGMA) were successfully synthesized and separately used as compatibilizers to modify PLA/LG composite properties such as interfacial adhesion, crystallinity, and mechanical properties. Since crystallites can act as obstacles to gas diffusion, the higher the crystallinity of the polymer matrix, the better gas barrier performance of the composite film will be. The crystallinity and crystalline structure of the PLA matrix was demonstrated by wide‐angle X‐ray diffraction and differential scanning calorimetry results. Since LG particles can act as efficient heterogeneous crystal nucleating agents, a roughly 50% reduction in oxygen permeability (PO2) was obtained by adding 1 phr LG to the PLA matrix (PLA/1LG). Following addition of 10 phr PLA‐g‐GMA to…

Abstract Fused deposition modeling (FDM) filaments made of recycled materials are desirable for environmentally friendly and sustainable manufacturing of prototypes and load‐bearing components in many applications. We investigate the effect of FDM process parameters on the mechanical properties of 3D‐printed parts made of recycled polyethylene terephthalate (rPET) filaments. Increasing the nozzle temperature from 230°C to 260°C improves the strength of the specimens by 100%. Using a raster orientation parallel to the loading direction improves the ductility by more an order of magnitude. Specimen orientation and infill ratio also influence the mechanical properties. The temperature and the orientation effects are related to the quality of fusion between the printed lines. A modified Gibson‐Ashby model correctly predicts the strength as a function of the infill ratio. Through the optimization of process parameters, the mechanical strength of 3D‐printed rPET structures can reach that of injection‐molded PET, making FDM a suitable manufacturing technique for load‐bearing applications.

Abstract Black seed (Nigella sativa [NS]) is used in traditional medicine as an antibacterial agent. In this study, novel hybrid scaffolds were manufactured from poly(ɛ‐caprolactone[PCL])/ Poly(lactic acid [PLA]) with NS extract by double‐nozzle electrospinning for wound healing application. Optimal conditions were found using response surface methodology including feed rate 0.8 ml/hr, voltage 20 kV and PLA 8% /PCL 10% concentrations. The effect of NS extract on the properties of the scaffold was evaluated by scanning electron microscopy, contact angle, and mechanical test. The PLA‐PCL/NS 20% beadles, and smooth nanofibrous web was obtained as the optimum scaffold with an average diameter of 638 ± 69 nm and the contact angle of 44°. In addition, the biological properties of the scaffolds such as antibacterial against Staphylococcus aureus (gram‐positive) and Escherichia coli (gram‐negative) bacteria, MTT assay, extract release, and cell growth (human mesenchymal stem cells) were examined. Incorporation of NS extract into the nanofibers caused to enhance the biological properties,…

ABSTRACT We report a systematic investigation on the structure–property relationships in glycerol‐plasticized poly(vinyl alcohol) (PVA)/cassava starch blends prepared via solution casting. In particular, PVA mixed with native, low‐oxidized, high‐oxidized, and pregelatinized cassava starches were characterized by means of SEM, XRD, FTIR, thermal analysis and mechanical testing and the immiscible systems were received. Burial tests over a period of several days suggested the preferential degradation of the starch and glycerol component (as indicated by the absence of FTIR signatures of those components) and the amorphous phase of PVA (as indicated by the enhanced crystallinity index of the degraded samples). The rheological properties of the blends seem to dictate their morphological characteristics that, in turn, have a profound impact on their mechanical properties. In that sense, the study highlights promising strategies for the development of a new family of polymeric materials that combine their biodegradable nature within superior mechanical properties. © 2020 Wiley Periodicals,…

Abstract Fused filament fabrication (FFF) is an additive manufacturing technique that is used to produce prototypes and a gradually more important processing route to obtain final products. Due to the layer‐by‐layer deposition mechanism involved, bonding between adjacent layers is controlled by the thermal energy of the material being printed, which strongly depends on the temperature development of the filaments during the deposition sequence. This study reports experimental measurements of filament temperature during deposition. These temperature profiles were compared to the predictions made by a previously developed model. The two sets of data showed good agreement, particularly concerning the occurrence of reheating peaks when new filaments are deposited onto previously deposited ones. The developed experimental technique is shown to demonstrate its sensitivity to changing operating conditions, namely platform temperature and deposition velocity. The data generated can be valuable to predict more accurately the bond quality achieved in FFF parts.

Abstract Cationic dye can cause severe damage to the environment due to their refractory degradation, complex composition and strong stability. Hydrogels as adsorbents have been widely used to treatment the wastewater with dyestuff for their low prices, simple operations, and high efficiency. This work uses poly(acrylic acid) (PAA)/poly(acrylamide)(PAM)/calcium hydroxide nanoparticles (CHN) polymeric hydrogel absorbent to eliminate methylene blue (MB) dye. First, PAM/PAA/CHN hydrogel is produced through copolymerization of acrylic acid monomer and acrylamide monomer using inorganic CHN as cross‐linker. And then, the adsorption performance of such PAM/PAA/CHN hydrogel adsorbent for adsorbing MB dye is explored at different conditions including pH, contacting time, adsorbent dosage, initial concentration of MB, and temperature. A maximum adsorption capability for adsorbing MB reaches 1,056 mg/g. Furthermore, the pseudo‐first‐order mode and Langmuir isotherm model can well describe adsorption behavior of MB dye onto such PAA/PAM/CHN hydrogel adsorbent. Thereby, as‐prepared PAA/PAM/CHN…

Abstract Harvesting biobased silane coupling agent to enhance the connection between fillers and epoxy matrix is vital to achieve sustainable and environmentally friendly products. In this work, a eugenol based epoxy silane‐coupling agent with high purity was prepared and used for the surface modification of nano‐sized silica particles. The surface structure composition and physical properties of the modified nano‐SiO 2 were characterized through nuclear magnetic resonance, Fourier transferred infrared spectrometer, X‐ray photoelectron spectroscopy, and thermal gravimetric analyzer. An epoxy nanocomposite was subsequently prepared by incorporating the resulting modified nano‐SiO 2 as an enhancing filler. The nanocomposites glass transition temperature, the morphology of fracture surface, dynamic mechanical properties, and thermostability were investigated. Results showed that the eugenol epoxy silane‐coupling agent bearing a long chain structure of benzene ring in the molecular structure could improve the compatibility of silica fillers with epoxy resin and contribute to a better…

Abstract A novel, small‐volume vertically arranged spin bath was successfully developed for an air gap lyocell‐type spinning process. A maximum regeneration bath length with a minimum free volume characterizes the concept of the new spin bath. Using the ionic liquid (IL) 1,5‐diazabicyclo[4.3.0]non‐5‐enium acetate [DBNH][OAc], the spin bath showed very good spinning performances of IL‐cellulose dopes at high draw ratios and spinning duration for single filament spinning experiments. Using this new device, it was possible to get a step further in the optimization of the Ioncell® process and simulate a process closed loop operation by performing single filament spinning in IL/H 2 O mixtures. Good dope spinnability and preserved fibers mechanical properties were achieved in a coagulation bath containing up to 30 wt% IL. It is only at 45 wt% of IL in the bath that the spinnability and fibers mechanical properties started to deteriorate. The fibers fibrillar structure was less pronounced in IL‐containing spinning bath in comparison to a pure water bath. However, their crystallinity after…

Abstract Electric power system applications demand for high‐temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in‐situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14…

Abstract Conductive polymer composites with positive temperature coefficient (PTC) effect have gained intensive attention for the potential application in the smart heating field. The PTC reproducibility is significantly essential to guarantee the security and utility of PTC composites. Regrettably, during the repeated temperature cycles, the irreversible self‐aggregation of conductive filler and the random reconstruction of conductive network lead to unsatisfactory performance of PTC reproducibility. Extensive efforts have been conducted to address this issue by strategies, including modification of fillers, cross‐linking of a polymer matrix, hybrids of fillers, and application of binary polymer matrix. Nevertheless, there are very limited reviews about this issue. In this review, the recent advances in fabricating PTC composites with the enhanced PTC reproducibility have been systematically summarized. Meanwhile, the current challenges and future prospects of PTC composite are also presented. We hope that this review will provide some inspirations for designing PTC materials of…

Abstract With the ever frequent of industrial organic solvent emissions and oil spillages, the development of high efficiency oil/water separation materials has attracted extensive attention. Here, PLA‐based nanofiber membranes modified with metal oxides (SiO2, TiO2, Al2O3, and CeO2) are fabricated through blow spinning the mixed solution of polylactic acid (PLA) and metal oxide nanoparticles (NPs). Results shows that the addition of SiO2 NPs significantly increases the hydrophobicity of the membranes, while maintaining the excellent superoleophilicity. The PLA/SiO2 nanofiber membranes demonstrate a higher separation performance than pure PLA, PLA/TiO2, PLA/Al2O3, and PLA/CeO2 nanofiber membranes with high separation efficiency (~100%) and permeation flux (17,800 L m−2 h−1 for n‐heptane), as well as prominent oil adsorption capacity (19.9 g/g for n‐hexane). The successful fabrication of metal oxides modified PLA nanofiber membranes with high separation and adsorption ability, and excellent durability hold great application potential in the field of oily wastewater treatment.

Abstract The effects of crosslinking densities on mechanical properties of nitrile rubber (NBR) composites before and after thermal oxidative aging are investigated. Tensile strengths of NBR composites are enhanced slightly at the initial aging stage, attributing to moderate increment of crosslinking densities. Continuous decrease with further aging is followed, resulting from over‐crosslinking and uneven distribution of crosslinking densities. The digital image correlation method is explored for large‐strain deformation measurement by displacement accumulation and establishing strain model, being promising in practical age detection and measurement of mechanical properties in complex environments. Compression sets are gradually increased with aging because of the destruction of the original crosslinking structures. The molecular chains fracture inhibits elastic recoveries of compressive NBR composites and results in residual deformation in thermo‐oxidative and compressive environment after unloading. This study provides new ideas for exploring mechanical properties of rubber‐based…

Abstract Silicone elastomers are used in a wide range of applications, including artificial muscles, biomedical devices, and soft robotics, for which chemical, thermal, and mechanical stability are important requirements that these elastomers must fulfill. However, to ensure that silicone elastomers' properties and performance remain constant under long‐term deployment, it is necessary to examine and account for the Mullins effect, which has the potential to significantly alter certain elastomer properties of interest. In this article, the mechanical properties of soft and hard commercial silicone elastomers and two blends of commercial silicone elastomers are investigated—specifically their softening behavior due to the Mullins effect. Ultimate stresses, ultimate strains, and Young's moduli are obtained from uniaxial tensile tests. Results show that the point of softening greatly depends on both the elastomer type and its strain history. Furthermore, a significant permanent set is observed in the softest commercial formulations.

Abstract A P/N‐containing flame retardant (PPT) constructed by phosphaphenanthrene, phosphonate, and triazole groups was successfully synthesized and used as a reactive co‐curing agent for epoxy resin (EP). The curing behavior, thermal property, combustion behavior, and flame retardant mechanism of EP thermosets were comprehensively investigated. According to the analysis of DSC and TGA, PPT accelerated the crosslinking reaction and enhanced the charring ability for EP thermosets at high temperature. The results of combustion test indicated that PPT endowed epoxy thermoset with outstanding flame retardancy. When the phosphorus content was 0.71 wt%, EP/DDS/PPT‐2 achieved a LOI value of 33.2% and passed V‐0 rating in UL‐94 test, and its peak heat release rate and total heat release were decreased by 63.7 and 30.5%, respectively, relative to EP/DDS. Moreover, the FIGRA of EP/DDS/PPT‐2 was reduced from 9.7 to 3.5 kW m−2 s−1, manifesting the significantly improved fire safety of EP thermoset. The flame retardant mechanism was summarized as two parts: (a) the barrier effect of continuous…

Abstract The aim of this research is to evaluate the effect of polyphosphoric acid (PPA) on the mechanical performance of styrene–butadiene–styrene (SBS) and styrene–butadiene–rubber (SBR) modified asphalt. Conventional properties, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS) tests were conducted to evaluate the performance characteristics of asphalt at different PPA inclusions. Gel‐permeation chromatography (GPC), saturates, aromatics, resins, and asphaltenes (SARA), and Fourier transform infrared (FTIR) were carried to reveal the molecular weight, component and infrared spectra of asphalt. Results showed that PPA hardened the asphalt, improved the rutting and fatigue performances of polymer modified asphalt (PMA) binder, but weakened the anti‐cracking performances. Besides, storage stability had a significant improvement as the addition of PPA. The addition of PPA brought more macromolecules into asphalt and led to more high‐average molecular weight compounds. Furthermore, PPA changed four component ratios of asphalt. Both…

Abstract The packing pattern of two‐dimensional (2D) sheet‐like fillers in membranes is relatively random, leading to the unfavorable permeability from tortuous diffusion pathway. A new strategy that using prestructured materials with uniform channels as fillers was proposed. In this work, Ti3AlC2is etched to prepare multilayered MXene (m‐MXene), the channels aggregate as a whole unit, ensure the impossibility of ineffective packing compared with traditional individual sheets, largely facilitating the selective permeation. Then, the m‐MXene/Poly (amide‐6‐b‐ethylene oxide) (Pebax) MMMs are synthesized. SEM images demonstrate the accordion shaped structure of filler, which is the multi‐channels laminates. Furthermore, the results of gas permeation test exhibit enhanced performance of m‐MXene/Pebax MMMs. MMM with 0.5 wt.% m‐MXene behaved best, CO2permeability of 86.22 Barrer as well as CO2/N2selectivity of 104.85, transcending the Robeson upper bound (2008). Having distinct enhancement for CO2separation, the m‐MXene/Pebax MMMs in this work offer prospective practical applications.

Abstract The present research aims to improve the compatibility between relatively hydrophobic poly(lactic acid) (PLA) and hydrophilic thermoplastic starch (TPS) and the properties of the PLA/TPS blends by replacing TPS from native cassava starch (TPSN) with TPS from acetylated starch (TPSA). The effects of the degree of acetylation (DA) of acetylated starch, that is, 0.021, 0.031, and 0.074, on the morphological characteristics and properties of PLA/TPS blend are investigated. The melt blends of PLA and TPS with a weight proportion of PLA:TPS of 50:50 are fabricated and then blown into films. Scanning electron microscopy confirms the dispersion of TPS phase in the PLA matrix. Better dispersion and smaller size of the TPS phase are observed for the PLA/TPSA blend films with low DA of acetylated starch, resulting in improved tensile and barrier properties and increased storage modulus, thermal stability, and Tg, Tcc, and Tm of PLA. Elongation at break of the PLA/TPSA blend increases up to 57%, whereas its water vapor permeability and oxygen permeability decrease about 15%. The…

Abstract The chemically crosslinked network structures make epoxies, the most common thermosets, unable or hard to be recycled, causing environmental problems and economic losses. Epoxy‐based vitrimers, polymer networks deriving from epoxy resins, can be thermally malleable according to bond exchange reactions (BERs), opening the door to recycle epoxy thermosets. Here a series of experiments were carried out to study the effects of processing conditions (such as particle size distributions, temperature, time, and pressure) on recycling of an epoxy‐anhydride vitrimer. Polymer powders from the epoxy‐anhydride vitrimer with different size distributions were prepared and characterized, and the influence of particle size on the mechanical performance of recycled epoxy‐anhydride vitrimers was investigated by dynamic mechanical analysis and uniaxial tensile test. Experimental results demonstrated that finer polymer powders can increase the contacting surfaces of recycled materials and thus result in high quality of recycled materials. In addition, the influences of other treating…

Abstract A facile and inexpensive way have been developed to fabricate robust self‐cleaning superhydrophobic coating by depositing polymer layer on candle soot (CS) surface using dip coating method. The stability and robustness of the CS deposited superhydrophobic surface is much weaker due to weak interaction and nonchemical bonding with the substrate. We introduced a thin layer of polystyrene, polyethylene, polypropylene (PP), and polyvinylidene fluoride on CS surface in order to improve its mechanical properties. The fabricated surfaces with the use of respective polymers exhibited water contact angles of nearly 170, 174, 175, and 171° with sliding angles of 2, 1, 1, and 3°, respectively. Although, all the polymers used in this work exhibited excellent superhydrophobic and self‐cleaning surface property, we found that the PP deposited CS surface exhibit better stability against water jet hitting and water drop impact tests. The PP deposited CS surface almost maintained their surface properties even after 50 cycles of sandpaper abrasion and 20 cycles of adhesive tape peeling…

Abstract In this study, the synthesis of urea‐formaldehyde/polyurethane (UF/PU) microcapsules containing epoxy resin for self‐healing and anti‐corrosion coatings with good stability has been reported. Spherical microcapsules were prepared with a diameter of about 50–720 μm and a shell thickness of 0.6–0.7 μm via in situ polymerization in an oil‐in‐water emulsion using 2,4‐toluene diisocyanate‐based pre‐polymer along with the urea‐formaldehyde. Scanning electron microscopy (SEM) and optical microscopy (OM) were employed to evaluate the shape and morphology of the microcapsules. Fourier transform infrared (FTIR) spectroscopy showed the absence of free isocyanate groups within the microcapsule shell confirming the completion of shell formation reactions. OM illustrated that the microcapsules were stable over a period of 30‐days in toluene and xylene. Increasing microcapsule loading improved crack repairing and anti‐corrosion performance of the coating layer. Low‐carbon steel coupons coated with an epoxy resin containing 10 wt% microcapsules and scribed using a scalpel blade showed no…

Abstract Graphene quantum dots (GQDs) reinforced poly(vinyl alcohol) (PVA)/polypyrrole (WPPy) nanocomposite films with various GQDs loadings were synthesized using the versatile solvent casting method. The structural and morphological properties of PVA/WPPy/GQDs nanocomposite films were investigated by employing Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy. The thermogravimetric analysis revealed enhanced thermal stability of synthesized nanocomposites while enhanced dielectric properties were also observed. The maximum dielectric constant value for PVA/WPPy/GQDs nanocomposite films was observed to be ε = 6,311.85 (50 Hz, 150°C). The electromagnetic interference (EMI) shielding effectiveness (SE) of nanocomposite films was determined in the X‐band (8–12 GHz) and Ku‐band (12–18 GHz) frequency region. The EMI SE was found to be increased from 0.8 dB for the pure PVA film to 9.8 dB for the PVA/WPPy/GQDs nanocomposite film containing 10 wt% GQDs loading. The enhanced EMI shielding efficiency of nanocomposite films has resulted from the…

Abstract An array of highly conductive, lightweight and flexible cellulose nanopapers as effective attenuators of electromagnetic radiations within 8.2–12.4 GHz (X band) were formulated via in situ polymerization of pyrrole monomers on to cellulose nanofibers (CNFs). It is quite obvious that the free hydroxyl groups on the surface of CNFs facilitate the formation of intense intermolecular hydrogen bonding with PPy which is envisaged for its excellent electromagnetic shielding performance with an average shielding effectiveness of ca. –22 dB (>99% attenuation) at 8.2 GHz for a paper having 1 mm thickness. The fabricated papers displayed a predominant absorption mechanism (ca. 89%) rather than reflection (ca. 11%) for efficiently attenuating electromagnetic radiations, which has a considerable importance in the modern telecommunication sector. Thus, the designed PPy/CNF papers would replace the conventional metal‐based shields and pave way for the development of green microwave attenuators functioning via a strong absorption mechanism. The PPy/CNF nanopapers exhibited a DC…