The 50 most-cited articles in Journal of Applied Polymer Science, 2019

ABSTRACT Wound healing is a complicated and continuous process affected by several factors, which needs an appropriate surrounding to achieve accelerated healing. Wound healing process recruits three different phases: inflammation, proliferation, and maturation. Due to the different types of wounds, as well as the advancement in medical technology, various products have been developed to repair different skin lesions. Our objective is to investigate the advancement in wound dressings from traditional to the current methods of treatment. The article presents the characteristics of an ideal wound dressing, the requirements for the appropriate selection of different types of wounds, and a detailed classification of wound dressings. Animal origin, herbal origin, and synthetic dressings are firstly introduced and reviewed. Then, nonmedicated dressings including alginate, hydrogel, and hydrocolloid dressings, as well as medicated dressings are discussed. Finally, the developmental prospectives of the new generations of wound dressings for future researches are presented. © 2019 Wiley…

ABSTRACT Shear‐thinning and self‐healing hydrogels are being investigated in various biomedical applications including drug delivery, tissue engineering, and 3D bioprinting. Such hydrogels are formed through dynamic and reversible interactions between polymers or polypeptides that allow these shear‐thinning and self‐healing properties, including physical associations (e.g., hydrogen bonds, guest–host interactions, biorecognition motifs, hydrophobicity, electrostatics, and metal–ligand coordination) and dynamic covalent chemistry (e.g., Schiff base, oxime chemistry, disulfide bonds, and reversible Diels–Alder). Their shear‐thinning properties allow for injectability, as the hydrogel exhibits viscous flow under shear, and their self‐healing nature allows for stabilization when shear is removed. Hydrogels can be formulated as uniform polymer and polypeptide assemblies, as hydrogel nanocomposites, or in granular hydrogel form. This review focuses on recent advances in shear‐thinning and self‐healing hydrogels that are promising for biomedical applications. © 2019 Wiley Periodicals, Inc.…

ABSTRACT Nanocellulose has received increasing attention in science and industry in recent years as a nanoscale material for the reinforcement of polymer matrix composites due to its superior mechanical properties, renewability, and biodegradability. New nanocellulose sources, modifications, and treatments are under development to reduce the high energy required during production and to create a more suitable industrial‐scale production process. Thus, this paper reviews plant‐based nanocellulose composites and their properties, with a focus on their thermal‐related characteristics. The purpose of this review is to establish for readers the impact of the incorporation of nanocellulose on the thermal and dynamic mechanical properties of nanocellulose composites. Understanding of the thermal properties is important for researchers to assess the suitability of the nanocomposites for a variety of applications in response to new and evolving societal requirements. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48544.

ABSTRACT Expanded polystyrene (EPS) is one of the building material capable of enhancing the design and structural integrity of the building. Since its recognition as conventional insulating material in 1950s, EPS has been experiencing swift progress in other new implementations. Currently, EPS is utilized in many building structures owing to its sustainability benefit and improvement in terms of energy efficiency, durability, and indoor environmental quality. This article provides an overview on the application of EPS as aggregates in lightweight concrete, decorative tiles and molding, panel application (structural insulated panels (SIPs) and composite SIPs), and embankment backfilling. Also, this article attempts to describe the properties of EPS in terms of fire behavior, mechanical properties, chemical resistant, water and moisture absorption, and their toxicity to the human and environment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47529.

ABSTRACT Material extrusion‐based additive manufacturing (ME‐AM) is an emerging processing technique that is characterized by the selective deposition of thermoplastic filaments in a layer‐by‐layer manner based on digital part models. Recently, it has attracted considerable attention, as this technique offers manifold benefits over conventional manufacturing technologies. However, to meet the challenges of complex industrial applications, certain shortcomings of ME‐AM still need to be overcome. A case in point is the limited amount of semicrystalline thermoplastics, which are still not established as reliable, commercial filament materials. Particularly, polypropylene (PP) offers attractive properties that are unique among the ME‐AM material portfolio. This review describes the current approaches of fabricating PP components by ME‐AM. Both commercial and scientific strategies to make PP 3D‐printable are elaborated and compared. As dimensional issues are especially problematic for PP, a comprehensive section of this review focuses on the strategies developed for mitigating warpage…

ABSTRACT The bio‐based environment‐friendly functional polymers are the most desired materials for the society. Thus, a superabsorbent hydrogel (SAH) of starch‐modified poly(acrylic acid) was reported and the concentrations of reactants, initiators, and crosslinkers were optimized to achieve the highest water absorption (>700 g/g). The chemical structure of SAH was supported by solid‐state 13C nuclear magnetic resonance and Fourier‐transform infrared spectroscopic studies. The hydrogels were found to be biodegradable and possess high water absorption capacity. After the addition of 0.25% of the hydrogel, water‐holding capacity of the soil was enhanced by 120%. Significant effect was also observed on bulk density and porosity of the soil after the addition of SAH. Furthermore, urea‐encapsulated SAH can be used as a controlled release fertilizer for crops, as indicated by a preliminary study on the growth rate of chick pea (Cicer arietinum) plant. Thus, SAH has the potential to be used as a controlled‐release carrier and water‐conserving agent in different fields. © 2019 Wiley…

ABSTRACT Dental composites are comprised of a polymerizable matrix and reinforcing fillers that can be hardened into a solid restoration in the prepared tooth cavity. Composites are becoming increasingly popular due to their esthetics and improved mechanical and physical properties. However, dental composites still encounter several problems, mainly secondary (recurrent) caries, restoration fracture, excessive wear, marginal degradation, and tooth sensitivity. Therefore, extensive efforts are underway to improve the composite compositions and microstructure, and enhance their clinical performance and longevity. Relying on advances in materials science and technology, dental composites have been continuously improved and their clinical applications have been expanded. In this review article, the development of dental composites was summarized, including compositional changes, performance improvements in key areas, current research hot spots, and outlook for future direction. The intention is to provide a review of the history and development of dental composites with a discussion of…

ABSTRACT Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self‐healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion‐based techniques such as emulsion polymerization and solvent evaporation from oil‐in‐water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the…

ABSTRACT Synthesis of organophosphorus compounds containing nitrogen as heteroatom and its application as a flame retardant (FR) have attracted much attention in the academic and industrial communities over the past decade. Such compounds are relatively easy to synthesize and offer advantages such as high thermal stability, which is useful for high temperature processing, improved char stability, density, and yield during the thermal decomposition of polymer, and release phosphorus species active in the flame inhibition process. Though a variety of phosphorus–nitrogen (P–N) compounds can be found in the literature, this review mostly summarizes the recent (since 2013) development in phosphorus (O)‐nitrogen containing flame retardants which have been published in peer‐reviewed journals. General strategies of synthesizing P(O)–N compounds as FRs from various phosphorus‐based starting materials are highlighted in this review. Some of the most common classes of researched P(O)–N containing compounds as FRs include the phosphinamides, phosphonamides, phosphoramides, phosphoramidates,…

ABSTRACT Carbon dots (CDs) are a kind of zero‐dimensional carbon‐based nanoparticles with superb light‐trapping ability, high optical absorption ability, and superior intrinsic catalytic activity. Due to these advantageous properties, they have received enthusiastic attention from researchers in the field of optical devices. The application of carbon dots in dye‐sensitized solar cells has increased with steady steps recently, especially as a substitute for precious Ru‐sensitizers and Pt counter electrodes. In this review, we classified the application of carbon dots in dye‐sensitized solar cells in recent years and explained the mechanisms of improving the performance of carbon dots. The significant impact of surface functionalization of CDs on the performance of dye‐sensitized solar cells was discussed. Lastly, some challenges and application prospects of carbon dots in the dye‐sensitized solar cell were proposed, which is meaningful for the further exploration and application of carbon dots as a new energy material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137,…

ABSTRACT The present study is focusing on evaluating theoretically and experimentally stability and type of interactions between the epoxy resin bisphenol A diglycidyl ether (DGEBA)‐polyaminoamide anticorrosive coating and high strength low alloy steel surface 15CDV6. The coated steel samples were subjected to a harsh environment of an electrolyte solution of 3 wt % NaCl to simulate the corrosive marine environment. The performance of the epoxy coating was investigated using electrochemical impedance spectroscopy (EIS). The EIS results revealed the occurrence of some deterioration in the film after subjecting it to a harsh environment for 4392 h, because the impedance of the coating dropped by about 1.4 kΩ.cm 2 . Surface morphological study of metallic specimens before and after exposing to the simulated marine environment (3 wt % NaCl) was carried out using scanning electron microscopy, energy dispersive spectroscopy (EDS), and optical microscope (OM) methods. The interactions between DGEBA‐polyaminoamide and the metallic surface were further carried out using computation modeling…

ABSTRACT A hybrid polymeric system containing carbon nanofillers with different geometrical dimensions is proposed for strategic applications, particularly for electrical properties. Two different carbon nanofillers including functionalized multiwalled carbon nanotubes (fCNTs) and functionalized graphene nanoplatelets (fGnPs) were added to thermoplastic polyurethane (TPU) to prepare single and hybrid nanofiller filled TPU through solution mixing. Sufficient exfoliation of the fGNPs in the single nanocomposites was confirmed by X‐ray diffraction, while single filler and hybrid TPU nanocomposites containing fCNTs showed some re‐aggregation of these nanofillers. Linear rheology together with scanning electron microscopy revealed a proper exfoliation and dispersion degree for fGnPs and fCNTs, respectively. We have shown that simultaneous addition of fCNTs–fGnPs in the form of a hybrid system into the TPU made a large surface area available and strong interfacial interactions were formed between the hybrid network and the TPU matrix. This in turn led to electrical, thermal and mechanical…

ABSTRACT In this work, chitosan–gelatin/zinc oxide nanocomposite hydrogel scaffolds (CS–GEL/nZnO) were prepared viain situsynthesis of ZnO nanoparticles (nZnO) to reach a scaffold with both inherent antibacterial and drug delivery properties. The prepared nanocomposite hydrogel scaffolds were characterized using scanning electron microscopy, transmission electron microscopy, atomic absorption spectrometer, Fourier transform infrared spectroscopy, and X‐ray diffraction. In addition, swelling, biodegradation, antibacterial, cytocompatibility, and cell attachment of the scaffolds were evaluated. The results showed that the prepared scaffolds had high porosity with a pore size of 50–400 μm and nZnO were well distributed without any agglomeration on the CS–GEL matrix. In addition, the nanocomposite scaffolds showed enhanced swelling, biodegradation, and antibacterial properties. Moreover, the drug delivery studies using naproxen showed that nZnO could control naproxen release. Cytocompatibility of the samples was proved using normal human dermal fibroblast cells (HFF2). In comparison to…

ABSTRACT Rigid polyurethane foam (RPUF) composites with triphenyl phosphate (TPhP), aluminum trihydrate (ATH), and zinc borate (ZnB) alone, as well as their binary blends, were prepared via a one‐shot process. The amount of flame retardant (FR) or FR blend was varied from 10 to 50% by polyol weight percentage, and the weight fraction of the blends was also fixed at 40%. The effects of additives on thermal insulation, mechanical, and flame retardancy properties of the composites were investigated. Thermal conductivity of the neat foam (RPUF) decreased from 22.53 to 21.04–21.58 mW m−1K−1. The compressive strength of foams displayed an increase with increasing the amount of TPhP, ATH, and ZnB till 40% by weight. The limited oxygen index values of all foams increased and the flame spread rates of all foams significantly decreased. It was also observed that the flame was self‐extinguished in some cases. The cone calorimeter test results indicated that the FR additives improved the flame retardancy of the RPUF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 47611.

ABSTRACT The pollution of heavy metal ions in water poses a serious threat to human being and ecosystems. Here, we report polyamidoxime (PAO) brush grafted graphene oxide (GO) as a highly efficient adsorbent for extraction of toxic metal cations from water. Surface‐initiated atom transfer radical polymerization was used to grow polyacrylonitrile (PAN) brushes on GO, followed by conversion of the nitrile groups in PAN into amidoxime groups, which had high binding affinity toward heavy metal cations. The PAO brush grafted GO demonstrated significantly fast adsorption kinetics and large adsorption capacity. At optimal pH 5, the PAO brush grafted GO can achieve maximum adsorption capacities of 116.7 mg g−1 for Pb(II), 258.6 mg g−1 for Ag(I), 192.2 mg g−1 for Cu(II), and 167.9 mg g−1 for Fe(III), which were significantly larger than those of small molecule functionalized GO. Mechanism analysis suggested that the enhanced adsorption performance was due to the myriads of functional groups in PAO brushes that were easily accessible to metal ions because of the swelling of the polymer…

ABSTRACT The versatility and applicability of thermoresponsive polymeric systems have led to great interest and a multitude of publications. Of particular significance, multifunctional poly(N‐isopropylacrylamide) (PNIPAAm) systems based on PNIPAAm copolymerized with various functional comonomers or based on PNIPAAm combined with nanomaterials exhibiting unique properties. These multifunctional PNIPAAm systems have revolutionized several biomedical fields such as controlled drug delivery, tissue engineering, self‐healing materials, and beyond (e.g., environmental treatment applications). Here, we review these multifunctional PNIPAAm‐based systems with various cofunctionalities, as well as highlight their unique applications. For instance, addition of hydrophilic or hydrophobic comonomers can allow for polymer lower critical solution temperature modification, which is especially helpful for physiological applications. Natural comonomers with desirable functionalities have also drawn significant attention as pressure surmounts to develop greener, more sustainable materials. Typically,…

ABSTRACT This work presents a comparative study on the formation of polyethersulfone ultrafiltration membranes via nonsolvent‐induced phase separation (NIPS) in two different solvent systems. N ‐methyl‐2‐pyrrolidone was chosen as conventional solvent and 2‐pyrrolidone as a greener alternative. The overall objective was to obtain a mechanistic clarification of the membrane formation process in dependence of the most important controlling parameters. By performing different series of experiments, it was possible to determine the differences between the two solvents regarding the effects of variations in nonsolvent additives, polymer concentration, and precipitation conditions. It was found that a raising concentration of several nonsolvents, the increase of the polymer concentration and changes in the precipitation conditions can suppress the formation of macrovoids, regardless of the applied solvent. In contrast, differences were observed with regard to the performance of the membrane prototypes. This study improves the understanding of membrane formation via NIPS and identifies the…

ABSTRACT It is well known that 3D printed parts prepared by fused deposition modeling (FDM) exhibit large anisotropy of mechanical properties. In this article, poly(lactic acid; PLA)/carbon fiber (CF) composites with different built orientations ( X , Y , Z ) were prepared by FDM. The effects of printing temperature, speed, orientations, and layer thickness on the mechanical properties of the composites were systematically investigated. The mechanical properties of PLA/CF composites show more significant anisotropy. The orientation of the fibers along the printing direction is displayed by scanning electron microscopy. Printing parameters bring almost no effect on mechanical properties of the X ‐construct oriented specimen, and bring obvious effect on those of the Y ‐construct oriented specimen and Z ‐construct oriented specimen. According to the analysis, carbon fiber can amplify this anisotropy from layer fashion, and the key factors from printing parameters are porosity and bond strength between fuses. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48786.

ABSTRACT Four‐dimensional (4D) printing of shape memory materials has attracted increasing interests for personalized structures. In this study, a biocompatible poly(d,l‐lactide‐co‐trimethylene carbonate) (PLMC) is utilized to fabricate 4D shape‐changing structures with customized geometries through direct ink writing. The printed objects show shape transformations at different dimensions under thermal programming. The influence of the printing parameters on the properties including rheological, solvent evaporation, and static mechanical behavior are systematically investigated. A printing map is further depicted to achieve high‐quality printing with high viscous ink flowed from micronozzle to construct various structures. The printed structures in one‐dimensional, two‐dimensional, and three‐dimensional (3D) exhibit shape‐changing behavior with fast response around body temperature. The fast responsive time shows potential in the field of surgical suture (4 s), nonwoven fabric (3 s), and self‐expandable stent (35 s). The feasibility of 3D printing of PLMC opens the way for…

ABSTRACT Hydrolyzed polyacrylamide (HPAM) is a polymer that extensively used in chemical industry and hydrocarbon extraction and refinery processes, but suffers a common problem of high‐temperature instability. This study improved high‐temperature rheological characteristics of HPAM by using novel graphene oxide (GO) nanosheets. Stable GO dispersions in aqueous HPAM were formulated, and their dynamic and viscoelastic behaviors were studied. The results showed that the addition of GO significantly increased the viscosities and high‐temperature stability of the base polymer fluid, as well as the elastic properties of the dispersion. Spectral data indicated the formation of covalent linkages and electrostatic hydrogen bonding between the GO and the HPAM functional groups, leading to enhanced stability and viscosity that is beneficial for high‐temperature oil recovery. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47582.

ABSTRACT In this study, aminopropyl trimethoxysilane as an interfacial modifier was introduced on the surface of graphene (Gr) nanoplatelets. The effects of the silane‐modified graphene (SGr) loading (0, 0.05, 0.1, 0.3, and 0.5 wt %) and silane modification on the tensile, compressive, interlaminar shear stress (ILSS), and tribological properties of the epoxy‐based nanocomposites were investigated. Out of these specimens, the highest values of ILSS and compressive strength were related to the 0.3 wt % SGr–epoxy nanocomposite. The addition of SGr enhanced the tensile strength and strain to failure only at low contents (i.e., 0.05 wt %). Also, the tensile and compressive moduli were improved, and the highest values were observed at a 0.5 wt % SGr loading. In addition, decreases of approximately 40 and 68% in the coefficient of friction and wear rate, respectively, were observed at a 0.3 wt % SGr loading. Enhanced tensile, compressive, ILSS, and wear properties in the SGr–epoxy specimens were observed compared to those in the Gr–epoxy specimens. © 2019 Wiley Periodicals, Inc. J. Appl.…

ABSTRACT Converting waste plastics into valuable carbon materials has obtained increasing attention. In addition, carbon materials have shown to be the ideal electrode materials for double‐layer supercapacitors owing to their large specific surface area, high electrical conductivity, and stable physicochemical properties. Herein, an easily operated approach is established to efficiently convert waste poly(ethylene terephthalate) beverage bottles into porous carbon nanosheet (PCNS) through the combined processes of catalytic carbonization and KOH activation. PCNS features an ultrahigh specific surface area (2236 m2 g−1), hierarchically porous architecture, and a large pore volume (3.0 cm3 g−1). Such excellent physicochemical properties conjointly contribute to the outstanding supercapacitive performance: 169 F g−1 (6 M KOH) and 135 F g−1 (1 M Na2SO4). Furthermore, PCNS shows a high capacitance of 121 F g−1 and a corresponding energy density of 30.6 Wh kg−1 at 0.2 A g−1 in the electrolyte of 1 M TEATFB/PC. When the current density increases to 10 A g−1, the capacitance remains at 95 F…

ABSTRACT This research discusses the mechanical behavior and the microstructure of high‐density polyethylene (HDPE)‐based composites, manufactured using the melt‐mixing and thermal‐pressing techniques, where HDPE is mixed with various percentages of either bulk lead monoxide (bulk PbO) or PbO nanoparticles (PbO‐NPs) acting as fillers. The scanning electron microscope and the field emission transmission electron microscope were utilized to identify the morphology of polymeric composites. Both showed the proper dispersion of PbO in the HDPE matrix without substantial agglomerations. The effect of PbO on the thermal behavior of the HDPE was studied using the thermogravimetric analysis. Tensile tests were implemented to find out how the mechanical characteristics of the composites were affected. Yield stress, % elongation at break, stiffness, tensile energy (toughness), ultimate tensile strength, and ultimate tensile strain were elucidated in this work. The values of stiffness, ultimate tensile strength, and yield stress increased by increasing either the bulk PbO or PbO‐NPs' loading up…

ABSTRACT The work presents a fully degradable superabsorbent composite material to be used in agricultural and horticultural applications. It is designed to retain and release fertilizer solutions to the soil in a controlled manner, permitting resource optimization. Because of its ability to absorb and release large amounts of saline water, a natural superabsorbent hydrogel derived from cellulose was chosen. Potassium nitrate was chosen to model the fertilizer. Poly(lactic acid) was added to the final composition in order to delay solution release. The composite material was obtained using easily available and low‐cost starting materials and using a simple manufacturing process, using a standard mixer. After being analyzed for morphological (scanning electron microscopy), physical (X‐ray diffraction), chemical (energy‐dispersive X‐ray spectroscopy), and thermal properties (thermogravimetric analysis and differential scanning calorimetry), the material was tested using two different Mediterranean cultivations (Pomodoro di Morciano di Leuca and Cicoria Otrantina) and two different…

ABSTRACT Adsorptive membranes with filtration and adsorption functions are one of the best strategies to remove harmful cations from wastewater and drinking water. In view of adsorptive capacity and regeneration cost, the most promising application field of adsorption membrane is the production of drinking water at present. An overview is given about the research progress of adsorptive membranes for removing heavy metal ions from drinking water. The removal mechanism of adsorptive membranes is explained by a schematic representation of electrical double layer. The types of adsorptive membranes are summarized. Future research outlook regarding adsorptive membranes is also discussed in order to promote research and application in drinking water for adsorptive membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48579.

ABSTRACT Polylactic acid (PLA) is a biodegradable and biocompatible polymer. Melt‐blown PLA electret fabrics have become attractive materials for air filter applications. Its filtration performance mainly depends on the electrostatic effect originating from electrets. How to improve their electret behavior and then to enhance their filtration efficiency has always been challenging. In this article, three melt‐blown PLA fabrics with different morphological or crystal structure are made from different process conditions or ingredient. The electrets are formed by means of corona charging technology. Their crystalline and morphological structure was analyzed, and filtration performance was measured. Their charge‐trapping feature was studied by thermal stimulating discharge technology. The results proved that the air filtration efficiency of three melt‐blown samples improved a lot when electrets were formed. Different crystalline structures of PLA fabrics will result in differences in their electret charge‐trapping feature. The PLA fabrics with semi‐crystalline characteristics display a…

ABSTRACT In this study, synergy between graphene platelets (GnPs) and carbon nanotubes (CNTs) in improving lap shear strength and electrical conductivity of epoxy composite adhesives is demonstrated. Adding two‐dimensional GnPs with one‐dimensional CNTs into epoxy matrix helped to form global three‐dimensional network of both GnPs and CNTs, which provide large contact surface area between the fillers and the matrix. This has been evidenced by comparing the mechanical properties and electrical conductivity of epoxy/GnP, epoxy/CNT, and epoxy/GnP‐CNT composites. Scanning electron microscopic images of lap shear fracture surfaces of the composite adhesives showed that GnP‐CNT hybrid nanofillers demonstrated better interaction to the epoxy matrix than individual GnP and CNT. The lap shear strength of epoxy/GnP‐CNT composite adhesive was 89% higher than that of the neat epoxy adhesive, compared with only 44 and 30% increase in the case of epoxy/GnP and epoxy/CNT composite adhesives, respectively. Electrical percolation threshold of epoxy/GnP‐CNT composite adhesive is recorded at 0.41 vol…

ABSTRACT In this work, the effect of a biodegradable hydrogel as a seed coating on the early growth of corn seed was studied. The hydrogel was a succinate‐modified potato starch, and it had an equilibrium water absorption capacity of 260 g distilled water (DW)/g hydrogel. To coat corn seeds, the seeds were slightly wetted with an aqueous adhesive solution and then, in a closed container, mixed with a dry mixture of the modified starch (MS), bentonite, and talc. The damp coated seeds were air‐dried at 40 °C for 24 h. The seed emergence and postemergence growth of coated and uncoated seeds were assessed with respect to: (1) the amount of MS on coated seeds, and (2) the available water supply. At a water supply of 77% field capacity (FC), the coated seeds showed a significantly higher rate of emergence than uncoated seeds—however, only a minor improvement was observed at higher and lower water supply levels (92, 82, and 65% FC, respectively). This indicates that, while poor water absorption by hydrogel at low water supply (65% FC) has limited benefit to seed water availability, the…

ABSTRACT Weak mechanical strength and serious mechanical anisotropy are two key limiting factors for three‐dimensional (3D) parts prepared by fused deposition modeling (FDM) in industrial applications. In this work, we investigated the relationships between mechanical properties and surface quality of FDM parts with the properties of materials used. Three kinds of polylactide (PLA) filaments, composed of the same PLA matrix but different fillers (carbon fibers and talc), were used to prepare FDM specimens. Due to the nature of FDM process, FDM parts exhibited tensile properties weaker and more anisotropic than their injection‐molding counterparts. The presence of fillers affected the tensile properties of FDM parts, especially the degree of mechanical anisotropy. It is found that the interlayer bond governing the mechanical performance of FDM parts was improved since the fillers added in the polymer materials facilitates the molecular diffusion across the bond interface. Also, the surface quality of FDM parts varied with fillers. Neat PLA parts exhibited surface quality superior to…

ABSTRACT In this study, we designed a novel hydrogel composite membrane based on the combination of polyvinyl alcohol (PVA), agar, and maltodextrin through a facile solution‐casting router. From Fourier‐transform infrared spectroscopy, contact angle, scanning electron microscopy, and swelling analyses, the formation of hydrogen bonds between surface functional groups of PVA, agar, and maltodextrin was confirmed. As a result, the PVA/agar/maltodextrin membranes exhibited a more hydrophobic nature compared with pure PVA. The thermal stability and integrity of such obtained composite membranes were also elucidated by the evaluation of thermogravimetric analysis and mechanical behavior. Besides, the composite membrane exhibited high selective adsorption for cationic dyes, namely 20.2 mg g−1 for methylene blue and 19.17 mg g−1 for crystal violet at initial dye concentration of 100 mg/L, an adsorbent dosage of 0.1 g, contact time of 180 min, and solution pH 7, while anionic dyes such as congo red and methyl orange are approximately zero. The adsorption kinetics and isotherm of the…

ABSTRACT First, making from eucalyptus cellulose fiber, the influences of different compound enzymolysis conditions on the morphology of cellulose nanocrystals (CNCs) were studied. Under the actions of the compound enzyme composed of cellulase and xylanase with the concentration ratio of 9:1, total enzyme concentrations of 10 and 500 U mL−1 and the hydrolysis time of 12 and 5 h, the rod‐like CNCs (length 600 nm, width 30 nm) and the spherical CNCs (40 nm) were obtained, respectively. Subsequently, the crystallinities, chemical structures, and thermal stabilities of the rod‐like and spherical CNCs revealed that, the CNCs structures were still similar to those of the eucalyptus cellulose fiber, the thermal decomposition temperatures of the rod‐like and spherical CNCs (345, 343 °C) were a little lower than that of the eucalyptus cellulose fiber (364 °C). Lastly, the control mechanism of CNC morphology by the compound enzymatic hydrolysis was also discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48407.

ABSTRACT Biofilms are defined as flexible films prepared from biological materials such as proteins or polysaccharides, which act as barriers to external elements and can consequently protect the products and increase their shelf life. The objective of this study was to evaluate the effects of hydrophilic and hydrophobic plasticizers and mixtures thereof in the characterization of alginate biofilms. Films plasticized with glycerol were less hygroscopic than films plasticized with TC (tributyl citrate) or with TC/glycerol mixtures. The presence of TC in the plasticization of the films turn them more hygroscopic, thus confirming their excellent performance in protecting against dissolution and in water vapor permeability. Films plasticized with pure TC were the least water‐soluble and showed the higher tensile stress, having a globular microstructure, which was attenuated as the TC was partially substituted by glycerol, making the structure more compact but not as homogenous as films containing only glycerol as the plasticizer. Films plasticized with pure TC and with TC/glycerol…

ABSTRACT Despite the prosperity of membrane technology, the separation efficiency for Mg2+/Li+ mixture is still far from satisfactory. Herein, a novel thin‐film nanocomposite (TFN) membrane was developed by loading polyhydroxylated fullerene (PHF) via interfacial polymerization. The effects of the PHF dosages on the as‐developed membranes were investigated comprehensively by XPS, SEM, AFM, contact angle measurements, as well as nanofiltration tests. The results revealed the TFN membrane containing 0.01% (w/v) PHF exhibited the optimum performances. The membrane showed a pure water flux of 6.7 L·m−2·h−1·bar−1 and salt rejections with the order of Na2SO4 (95.6%) > MgSO4 (93.6%) > MgCl2 (89.9%) > NaCl (22.6%) > LiCl (16.3%). The membrane not only presented a separation factor of 13.1 in separating Mg2+/Li+ mixtures, but also demonstrated excellent antifouling ability, which enables membrane regeneration without operation break, suggesting its great potentials in the recovery of Li+ from brine or seawater. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48029.

ABSTRACT The bamboo fiber (BF)‐reinforced polylactic acid (PLA) composites were prepared using the twin‐screw extruder and injection molding. Thermal gravimetric analyzer results indicated the thermal stability of BF/PLA composites decreased with increasing BF content. Differential scanning calorimeter and X‐ray diffraction curves showed that BF played a role as a nucleating agent, but the crystallinity of composite materials decreased with the increasing BF content. The melt flow rate of composites reduced with the increase in BF content, resulting in a poorer processing property. The processability of the composites was improved with the addition of high molecular polyethylene glycol (PEG). Mechanics performance test showed that tensile strength and bending strength of composites increased at low loading with the BF content increased then decreased when the loading continued to increase. The tensile strength of the composite materials reached 65.46 MPa when alkali‐treated BF (ABF) content was 20 wt %. The flexural strength of the composites reached 97.94 MPa when ABF content was…

ABSTRACT In this article, we report an acrylate‐based three‐dimensional (3D) printing stereolithography rapid‐prototyping photosensitive resin with a low viscosity, small volumetric shrinkage, high photoreactivity, and excellent strength. The resin was a compound prepared with bisphenol A epoxy acrylate (BAEA) as the main matrix, 1,6‐hexanediol diacrylate (HDDA) and tri(propylene glycol) diacrylate (TPGDA) as reactive diluents, pentaerythritol triacrylate (PETA) as the crosslinking agent, and 2‐hydroxy‐2‐methyl propiophenone (1173) and diphenyl(2,4,6‐trimethyl benzoyl)phosphine oxide (TPO) as photoinitiators. The photocuring kinetics of the resins with different photoinitiator types and loadings were studied via real‐time IR spectroscopy, which provided insights into the optimization of photoinitiator composition and printing parameter settings. The results show that the content change of each component affected the viscosity of the photosensitive resin; this was accompanied by fluctuations in the volume shrinkage and mechanical strength of the cured products. Although an increase…

ABSTRACT This work provides a novel approach to improve not only water flux but also fouling resistance of Polyvinylidene fluoride (PVDF) membranes. PVDF/Poly(vinyl alcohol) (PVA)‐blended nanofiber membranes were prepared via electrospinning method. The structure and performance of blended nanofiber membranes were characterized by scanning electron microscopy (SEM), atomic force microscope (AFM), attenuated total reflection‐Fourier‐transform infrared (ATR‐FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), contact angle measurement, tensile mechanical measurement, and filtration experiments. These results indicate that PVA was uniformly blend in the PVDF matrix. This blended nanofiber membranes with the ridge‐and‐valley structure and bicontinuous phase exhibited the hydrophilic performance and super‐wettability, which is reflected in a drop of water fully spread within 1.44 s. Filtration experiments showed that the blended nanofiber membranes have ultrahigh flux and low irreversible fouling ratio. In general, this work enhances the possibility of hydrophilic modification of…

ABSTRACT This study presents the design of novel hydrogel films, based on low‐methoxyl (LM) pectin and NaA‐ or ZnA‐zeolite particles, to serve as wound dressing materials with controlled drug delivery properties. We studied the effects of the preparation method of hydrogels, the amounts of crosslinker, drug and zeolite, and the type of cation in zeolites on the drug release mechanisms from the hydrogels. Ionic strengths of both film and external medium dictated the drug release behavior of the films, while the other parameters also played essential roles. NaA‐zeolite hydrogels prepared using membrane diffusion controlled system, could reach a drug release ratio of 86% within 5 h. The drug‐free hydrogels displayed no cytotoxicity while supporting cell proliferation and migration. Our cost‐effective LM pectin–zeolite hydrogels promise to be effective wound dressing materials with controlled drug delivery ability, transparency, good swelling properties, ability to hold fluids, good oxygen transmission rate, and biocompatibility. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019,…

ABSTRACT Poly(lactic acid) (PLA) was first melt blended with five weight percentages (10–50 wt %) of poly(butylene adipate‐co‐terephthalate) (PBAT) on a twin‐screw extruder and then injection molded. The blend at 30 wt % PBAT exhibited the highest impact strength and elongation‐at‐break without phase inversion. The 70/30 (w/w) PLA/PBAT blend with high toughness improvement was selected for preparing both single and hybrid composites using an organic filler, wood fiber (WF) and inorganic filler, wollastonite (WT) with a fix total loading at 30 parts per hundred of resin (phr) throughout the experiment. Five WF/WT (phr/phr) ratios for the composites were 30/0, 10/20, 15/15, 20/10, and 0/30. The prepared composites were investigated for the mechanical and thermal properties, melt flow index (MFI), morphology, flammability, water uptake, and biodegradability as a function of composition. All the composites showed a filler‐dose‐dependent decrease in the impact strength, elongation‐at‐break, MFI, and thermal stability, but an increase in the tensile and flexural modulus, tensile and…

ABSTRACT The preparation and characteristics of rigid polyurethane foams (RPUFs) based on recycled polyol obtained by glycolysis of waste RPUF scraps from end‐of‐life refrigerators were investigated. To deactivate the amine adducts derived from isocyanates, the recycled product obtained after depolymerization was chemically modified via addition polymerization of propylene oxide. Two kinds of recycled polyols with different hydroxyl values and viscosity were blended with conventional virgin polyether polyol to prepare the RPUFs. The effects of the recycled polyols on the physical properties of RPUFs such as cell structures, compressive strength, thermal conductivity, and limiting oxygen index were discussed. It was found that the RPUFs from recycled polyols showed superior compressive strength, thermal insulation property, and self‐extinguishing property compared with conventional control foam. The results of this study reveal that the recycled polyols could be used as feedstock for RPUFs with superior performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 ,…

ABSTRACT Biopolymers are very efficient for significant applications ranging from tissue engineering, biological devices to water purification. There is a tremendous potential value of cellulose because of its being the most abundant biopolymer on earth, swellability, and functional groups to be modified. A novel, highly efficient route for the fabrication of mechanically stable and natural hydrogels is described in which cellulose and glycine are dissolved in an alkaline solution of NaOH and neutralized in an acidic solution. The dissolving temperature and the glycine amount are essential parameters for the self‐assembly of cellulose chains and for tuning the morphology and the aggregate structures of the resulting hydrogels. Glycine plays the role of a physical crosslinker based on the information obtained from FTIR and Raman spectra. Among the prepared set of hydrogels, CL5Gly30 hydrogels have the highest capacity to absorb water. The prepared CL5Gly30 gels can absorb up to seven times their dry weight due to its porous 3‐D network structure. CL5Gly10 hydrogel exhibits 80%…

ABSTRACT Melamine–formaldehyde (MF) resins are widely used as adhesives and finishing materials in the wood industry. During resin cure, either methylene ether or methylene bridges are formed, leading to the formation of a three‐dimensional resin network. Not only the curing degree, but also the chemical species present in the cured resin determine the quality of the final product. Analytical methods allowing a detailed investigation of network formation are of great benefit to manufacturers. In the present work, resin cure of an MF precondensate is studied at different temperatures (100–200 °C) without considering the initial pH as a factor. Isoconversional kinetic analysis based on exothermal curing enthalpies enables calculation of the crosslinking degree at a given time/temperature regime. A semiquantitative determination of the chemical groups present is performed based on solid‐state nuclear magnetic resonance data. Fourier transform infrared spectroscopy has shown to be a fast and reliable analytical tool with high sensitivity toward functional groups and with great potential…

ABSTRACT Polymer composites, which are light in weight, cost effective, and less toxic, have potential applications in X‐ray and γ‐ray shielding and protection. In this work, we have explored the efficacy of poly(vinyl alcohol)–bismuth oxide composites as radiation shielding materials. Poly(vinyl alcohol) composites with different wt % (0–50) of bismuth were prepared by a simple solution casting technique. Structural and thermal characterization of these samples was carried out using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). TGA revealed the enhanced thermal stability of these composites. AC conductivity measurements and optical spectroscopy were used to analyze their electrical behavior. The composites showed low conductivity, and the energy gap obtained also showed their tendency to be insulators. The radiation attenuation properties were investigated using X‐ray (5.895 and 6.490 keV) and γ‐ray (59.54 and 662 keV) transmission measurements. The shielding efficiency of the composites…

ABSTRACT In this study, the mechanical properties of isotactic polypropylene (iPP) materials with different crystallinities at room and elevated temperatures were investigated. In order to obtain samples with a certain range of crystallinity, and to ensure a uniform microstructure of these samples, the iPP samples obtained by injection molding required melt compression molding and controlled annealing. In the macromechanical studies, the experimental results showed that the storage modulus and Young's modulus of polypropylene were sensitive to the service temperature. The crystallinity also had a great influence on this relationship. A function was proposed to evaluate the dependence of the Young's modulus of polypropylene on initial crystallinity and service temperature, and tested based on experimental data. The Young's modulus of iPP is reduced by about 90% when the service temperature rises from 25 to 125 °C. Moreover, the reduced value in Young's modulus between polypropylene having the highest and lowest crystallinity was reduced from 214.55 to 56.75 MPa. © 2019 Wiley…

ABSTRACT In this study, production of metal/polymer composites using polyethylene as the matrix with various contents of metal powder was investigated. Fused deposition modeling (FDM) process is one of the most popular and conventional additive manufacturing methods to produce three‐dimensional (3D) specimens from computer‐aided design data with complex geometry and lower prices in comparison with the alternative methods. Given the advantages of this process, it seems inevitable for the development of new materials. Utilizing semicrystalline plastics impose challenges for producing parts due to printing issues such as distortion and warpage. In this experimental work, a compounding production line was implemented to produce composite filaments with 25, 50, and 75 wt % of copper powder suitable for the FDM process. After dealing with printing issues, flexural, electrical conductivity, and bulk density tests were done. The micrographs of the specimens were examined via scanning electron microscopy to reveal the distribution of the copper particles. It is believed that the…

ABSTRACT Partially hydrolyzed polyacrylamide (HPAM) is the water‐soluble polymer most often used in flooding applications in the petroleum industry. However, in aqueous solutions at high temperatures, HPAM undergoes hydrolysis of the lateral amide groups, and the presence of salts in the solution can lead to precipitation of this polymer. Therefore, a method was developed to monitor the thermal stability of HPAM solutions in different saline environments and varying temperatures. The proposed test method involved measurements of intrinsic viscosity as a function of time and determination of the degree of hydrolysis of the HPAM by elemental analysis. The results obtained indicated that the presence of divalent cations (Ca +2 and Mg +2 ) negatively influenced the intrinsic viscosity of the solutions and in some systems led to precocious precipitation of the polymer in environments with higher concentrations of these cations. The hydrolysis reaction of the amide groups to the acrylate groups of the HPAM chain was significantly affected by rising temperature: at 50 °C, hydrolysis…

ABSTRACT Zwitterionic hydrogels have been explored for applications in electrochemical devices very recently due to their high water retention ability and interesting electrochemical properties. The use of zwitterionic hydrogels in devices requires them tough and recoverable or healable from fatigue damage. Herein, a double network zwitterionic hydrogel contains a reversible noncovalent interaction crosslinked polyvinyl alcohol (PVA) first network, together with a covalent/noncovalent hybrid crosslinked acrylamide and sulfobetaine methacrylate copolymer (P(AM‐ co ‐SBMA)) second network, was fabricated by a simple two‐steps methods of copolymerization and freezing/thawing. The reversible hydrogen bonds, crystalline domain, and electrostatic interactions in the double networks work as sacrificial bonds to dissipate energy and toughen the materials when hydrogel deforms. The broken bonds can reform upon unloading endowing the recovery of hydrogels' properties with the assistance of the elastic covalent network. The optimal hydrogels are highly stretchable (fracture strain 970%), tough…

ABSTRACT Possessing unique designs and properties absent in conventional materials, nanocomposites have made a remarkable imprint in science and technology. This is particularly true regarding the polymer matrix composites when they are further reinforced with nanoparticles. In this study, the effects of different weight percentages (0, 0.1, 0.2, 0.3, 0.4, and 0.5) of surface‐modified graphene nanoplatelets (GNPs) on the microhardness and wear properties of basalt fibers/epoxy composites were investigated. The GNPs were surface modified by silane, and the composites were made by the hand lay‐up method. The wear tests were conducted under two different loads of 20 and 40 N. The best wear properties were achieved at 0.3 wt % GNPs as a result of the GNPs' self‐lubrication property and the formation of a stable transfer/lubricating film at the pin and disk interface. Moreover, the friction coefficient was lower at the higher normal load of 40 N. The microscopic studies by FESEM and SEM showed that the presence of GNPs up to 0.3 wt % led to the stability of the transfer/lubricating film…

ABSTRACT Tire tread compounds based on various rubber types, that is, solution styrene‐butadiene rubber (SSBR), functionalized (propylamine and dimethoxysilane) solution styrene‐butadiene rubber (F‐SSBR), natural rubber (NR), chloroacetate‐modified natural rubber (CNR), and their blends, were prepared and used as raw rubbers. Properties of tire tread compounds and tire performance were then investigated. Due to the presence of chloroacetate group on its mainchains, CNR demonstrates increases in glass transition temperature and rubber‐filler interaction compared to NR leading to a significant improvement in tire performance, particularly wet grip (WG; ~88%), fuel‐saving efficiency (FSE; ~15%), and abrasion resistance (~11%). Similarly, F‐SSBR shows a greater tire performance than SSBR (~20, ~13, and ~7% improvements in WG, FSE, and abrasion resistance, respectively). Among the rubber blends, F‐SSBR/CNR gives the highest tire performance, followed by F‐SSBR/NR, SSBR/CNR, and SSBR/NR, respectively. The results suggest the significant enhancement in properties of tire tread compounds by…

ABSTRACT Recently, piezoelectric nanogenerators have received great interest as they can convert waste mechanical and radiative energy to electricity and can be used in self‐energy generating systems and sensor technologies. In this study, electrospun poly(vinylidene fluoride) (PVDF) nanofiber‐based piezoelectric nanogenerators with reduced graphene oxide (rGO), polyaniline (PANI), and PANI‐functionalized rGO (rGOPANI) have been developed. Two different types of nanofiber mats were produced: First, rGO‐ and rGOPANI‐doped PVDF nanofiber mats and second, rGO, PANI and rGOPANI‐spray‐coated PVDF nanofiber mats that have worked as nanogenerators' electrodes. Then, characterizations of samples were performed in terms of piezoelectricity, Fourier transform infrared (FTIR) spectrophotometric, X‐ray diffractions (XRD), and scanning electron microscopy analyses. FTIR and XRD results confirmed that piezoelectric β‐crystalline phase of PVDF occurred after the electrospinning process. Besides, maximum output voltages were obtained as 7.84 and 10.60 V for rGO‐doped PVDF and rGOPANI‐coated PVDF…

ABSTRACT In this study, a broadband, intense, novel, and promising microwave‐absorbing nanocomposite was prepared using graphite‐like carbon nitride (g‐C 3 N 4 )/CuS suspended in poly(methyl methacrylate) (PMMA) medium. The g‐C 3 N 4 nanosheets were synthesized by heating the urea as well as the CuS nanoparticles, and g‐C 3 N 4 /CuS nanocomposites were prepared using a solvothermal method and then were separately molded by a PMMA solution to investigate their microwave‐absorbing characteristics. The Fourier transform infrared and X‐ray powder diffraction were used to characterize the g‐C 3 N 4 , CuS, and CuS/g‐C 3 N 4 nanostructures, which confirmed that the pure structure of the nanomaterials has been synthesized. The optical properties of the nanostructures were also investigated by diffuse reflection spectroscopy analysis. Accordingly, the Kubelka–Munk theory suggested significant narrow band gap for g‐C 3 N 4 /CuS nanocomposite (0.27 eV), facilitating electron jumping and conductive loss. The morphology of the structures was examined using field emission scanning electron…