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Polymers, Volume 10, Issue 7 (July 2018)

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Open AccessArticle Synthesis and Characterization of Fully Conjugated Ladder Naphthalene Bisimide Copolymers
Polymers 2018, 10(7), 790; https://doi.org/10.3390/polym10070790 (registering DOI)
Received: 8 July 2018 / Revised: 16 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
Fully conjugated ladder copolymers have attracted considerable attention due to their unique fused-ring structure and optoelectronic properties. In this study, two fully conjugated ladder naphthalene diimide (NDI) copolymers, P(NDI-CZL) and P(NDI-TTL) with imine-bridged structures are presented in high yields. Both of the two
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Fully conjugated ladder copolymers have attracted considerable attention due to their unique fused-ring structure and optoelectronic properties. In this study, two fully conjugated ladder naphthalene diimide (NDI) copolymers, P(NDI-CZL) and P(NDI-TTL) with imine-bridged structures are presented in high yields. Both of the two copolymers have good solubility and high thermal stability. The corresponding compounds with the same structure as the copolymers were synthesized as model system. The yields for each step of the synthesis of the model compounds are higher than 95%. These results suggest that P(NDI-CZL) and P(NDI-TTL) can be synthesized successfully with fewer structural defects. The structures and optoelectronic properties of compounds and copolymers are investigated by NMR, fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and cyclic voltammetry (CV). Both in solution and as a thin film, the two copolymers show two UV-vis absorption bands (around 300–400 nm and 400–750 nm) and a very weak fluorescence. The collective results suggest that the two fully conjugated ladder copolymers can be used as potential acceptor materials. Full article
(This article belongs to the Special Issue Synthesis and Application of Conjugated Polymers)
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Open AccessCommunication Controlling the Internal Structures of Polymeric Microspheres via the Introduction of a Water-Soluble Organic Solvent
Polymers 2018, 10(7), 789; https://doi.org/10.3390/polym10070789 (registering DOI)
Received: 25 June 2018 / Revised: 17 July 2018 / Accepted: 17 July 2018 / Published: 18 July 2018
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Abstract
Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in
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Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale. Full article
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Open AccessArticle Multi-Objective Optimization of Acoustic Performances of Polyurethane Foam Composites
Polymers 2018, 10(7), 788; https://doi.org/10.3390/polym10070788 (registering DOI)
Received: 22 May 2018 / Revised: 11 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
Polyurethane (PU) foams are widely used as acoustic package materials to eliminate vehicle interior noise. Therefore, it is important to improve the acoustic performances of PU foams. In this paper, the grey relational analysis (GRA) method and multi-objective particle swarm optimization (MOPSO) algorithm
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Polyurethane (PU) foams are widely used as acoustic package materials to eliminate vehicle interior noise. Therefore, it is important to improve the acoustic performances of PU foams. In this paper, the grey relational analysis (GRA) method and multi-objective particle swarm optimization (MOPSO) algorithm are applied to improve the acoustic performances of PU foam composites. The average sound absorption coefficient and average transmission loss are set as optimization objectives. The hardness and content of Ethylene Propylene Diene Monomer (EPDM) and the content of deionized water and modified isocyanate (MDI) are selected as design variables. The optimization process of GRA method is based on the orthogonal arrays L9(34), and the MOPSO algorithm is based on the Response Surface (RS) surrogate model. The results show that the acoustic performances of PU foam composites can be improved by optimizing the synthetic formula. Meanwhile, the results that were obtained by GRA method show the degree of influence of the four design variables on the optimization objectives, and the results obtained by MOPSO algorithm show the specific effects of the four design variables on the optimization objectives. Moreover, according to the confirmation experiment, the optimal synthetic formula is obtained by MOPSO algorithm when the weight coefficient of the two objectives set as 0.5. Full article
(This article belongs to the Special Issue Polymeric Foams)
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Open AccessArticle Dynamics of a Polymer Network Modeled by a Fractal Cactus
Polymers 2018, 10(7), 787; https://doi.org/10.3390/polym10070787 (registering DOI)
Received: 27 June 2018 / Revised: 14 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
In this paper, we focus on the relaxation dynamics of a polymer network modeled by a fractal cactus. We perform our study in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. By performing real-space renormalization transformations, we
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In this paper, we focus on the relaxation dynamics of a polymer network modeled by a fractal cactus. We perform our study in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. By performing real-space renormalization transformations, we determine analytically the whole eigenvalue spectrum of the connectivity matrix, thereby rendering possible the analysis of the Rouse-dynamics at very large generations of the structure. The evaluation of the structural and dynamical properties of the fractal network in the Rouse type-approach reveals that they obey scaling and the dynamics is governed by the value of spectral dimension. In the Zimm-type approach, the relaxation quantities show a strong dependence on the strength of the hydrodynamic interaction. For low and medium hydrodynamic interactions, the relaxation quantities do not obey power law behavior, while for slightly larger interactions they do. Under strong hydrodynamic interactions, the storage modulus does not follow power law behavior and the average displacement of the monomer is very low. Remarkably, the theoretical findings with respect to scaling in the intermediate domain of the relaxation quantities are well supported by experimental results from the literature. Full article
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Open AccessArticle Novel PSMA-Coated On-Off-On Fluorescent Chemosensor Based on Organic Dots with AIEgens for Detection of Copper (II), Iron (III) and Cysteine
Polymers 2018, 10(7), 786; https://doi.org/10.3390/polym10070786
Received: 9 June 2018 / Revised: 8 July 2018 / Accepted: 14 July 2018 / Published: 17 July 2018
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Abstract
Herein, a novel on-off-on fluorescent chemosensor for copper (II) ion (Cu2+), iron (III) ion (Fe3+) and cysteine is developed simply by the nano-precipitation method. The prepared organic dots with AIEgens (AIE dots) are advantageous over other metal ions in
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Herein, a novel on-off-on fluorescent chemosensor for copper (II) ion (Cu2+), iron (III) ion (Fe3+) and cysteine is developed simply by the nano-precipitation method. The prepared organic dots with AIEgens (AIE dots) are advantageous over other metal ions in detecting Cu2+, Fe3+ with high selectivity and sensitivity by forming agglomerations (on-off). The agglomerations formed by AIE dots and Cu2+ redistributed and the fluorescence was obviously recovered in the presence of cysteine (off-on). This sensor has a wide linear range for Cu2+, Fe3+ and cysteine. The fluorescent detection limits of AIE dots are calculated to be 107 nM for Cu2+, 120 nM for Fe3+ and 78 nM for cysteine, respectively. These results indicate that the AIE dots can be used as a potential probe for Cu2+, Fe3+ and cysteine detection. Full article
(This article belongs to the Special Issue Polymer Based Bio-Sensors)
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Open AccessArticle Poly(propylene 2,5-thiophenedicarboxylate) vs. Poly(propylene 2,5-furandicarboxylate): Two Examples of High Gas Barrier Bio-Based Polyesters
Polymers 2018, 10(7), 785; https://doi.org/10.3390/polym10070785
Received: 30 June 2018 / Revised: 12 July 2018 / Accepted: 13 July 2018 / Published: 17 July 2018
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Abstract
Both academia and industry are currently devoting many efforts to develop high gas barrier bioplastics as substitutes of traditional fossil-based polymers. In this view, this contribution presents a new biobased aromatic polyester, i.e., poly(propylene 2,5-thiophenedicarboxylate) (PPTF), which has been compared with the furan-based
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Both academia and industry are currently devoting many efforts to develop high gas barrier bioplastics as substitutes of traditional fossil-based polymers. In this view, this contribution presents a new biobased aromatic polyester, i.e., poly(propylene 2,5-thiophenedicarboxylate) (PPTF), which has been compared with the furan-based counterpart (PPF). Both biopolyesters have been characterized from the molecular, thermo-mechanical and structural points of view. Gas permeability behavior has been evaluated with respect to 100% oxygen, carbon dioxide and nitrogen at 23 °C. In case of CO2 gas test, gas transmission rate has been also measured at different temperatures. The permeability behavior at different relative humidity has been investigated for both biopolyesters, the thiophen-containing sample demonstrating to be better than the furan-containing counterpart. PPF’s permeability behavior became worse than PPTF’s with increasing RH, due to the more polar nature of the furan ring. Both biopolyesters under study are characterized by superior gas barrier performances with respect to PEF and PET. With the simple synthetic strategy adopted, the exceptional barrier properties render these new biobased polyesters interesting alternatives in the world of green and sustainable packaging materials. The different polarity and stability of heterocyclic rings was revealed to be an efficient tool to tailor the ability of crystallization, which in turn affects mechanical and barrier performances. Full article
(This article belongs to the Special Issue Polymers for Packaging Applications)
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Open AccessArticle Modeling of Laser Beam Absorption in a Polymer Powder Bed
Polymers 2018, 10(7), 784; https://doi.org/10.3390/polym10070784
Received: 21 May 2018 / Revised: 28 June 2018 / Accepted: 16 July 2018 / Published: 17 July 2018
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Abstract
In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the
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In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for polymer powders and, therefore, can increase the energy density at the powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine powder distributions and high powder bed densities are discussed. Full article
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Open AccessArticle Enhancement of Colour Effects of Dyed-Yarn Mixed Fabrics Using Cramming Motion and Finer Polyester Yarns
Polymers 2018, 10(7), 783; https://doi.org/10.3390/polym10070783
Received: 10 June 2018 / Revised: 10 July 2018 / Accepted: 10 July 2018 / Published: 16 July 2018
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Abstract
This paper reports the study of the effects of cramming motion implemented during weaving and finer weft yarns used on dyed-yarn mixed woven fabrics produced by using raw white warps and multicolored-wefts. The cramming motion was used to increase the dyed-weft yarns cover
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This paper reports the study of the effects of cramming motion implemented during weaving and finer weft yarns used on dyed-yarn mixed woven fabrics produced by using raw white warps and multicolored-wefts. The cramming motion was used to increase the dyed-weft yarns cover factor of fabric, and thus, to reduce the negative effect of white warp floats at the fabric face on the color attributes of fabric. The surface structure of fabric was characterized by using several key geometrical parameters that determined the resultant fabric color attributes. The effects of fabric structure and density, weft yarn count, and the introduction of black yarn on the fabric face layer on the fabric surface geometrical parameters, physical properties, as well as color attributes were investigated under the implementation of cramming motion on the fabric. The color attributes of fabrics using cramming motion and finer yarns were also compared to the fabrics without cramming motion. The experimental results indicate that the weft yarn density and cover factor of fabric face layer are increased by applying cramming motion and finer yarns for fabricating the blue-red and/or black mixed fabrics. Consequently, the fabric lightness can be further reduced for achieving a better color effect on colorful and figured woven fabrics mainly using dyed-wefts for color mixing. Full article
(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)
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Open AccessArticle Synthesis of Benzene Tetracarboxamide Polyamine and Its Effect on Epoxy Resin Properties
Polymers 2018, 10(7), 782; https://doi.org/10.3390/polym10070782
Received: 12 June 2018 / Revised: 12 July 2018 / Accepted: 12 July 2018 / Published: 16 July 2018
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Abstract
Epoxy resins have found various industrial applications in high-performance thermosetting resins, high-performance composites, electronic-packaging materials, adhesives, protective coatings, etc., due to their outstanding performance, including high toughness, high-temperature performance, chemical and environmental resistance, versatile processability and adhesive properties. However, cured epoxy resins are
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Epoxy resins have found various industrial applications in high-performance thermosetting resins, high-performance composites, electronic-packaging materials, adhesives, protective coatings, etc., due to their outstanding performance, including high toughness, high-temperature performance, chemical and environmental resistance, versatile processability and adhesive properties. However, cured epoxy resins are very brittle, which limits their applications. In this work, we attempted to enhance the toughness of cured epoxy resins by introducing benzene tetracarboxamide polyamine (BTCP), synthesized from pyromellitic dianhydride (PMDA) and diamines in N-methyl-2-pyrrolidone (NMP) solvent. During this reaction, increased viscosity and formation of amic acid could be confirmed. The chemical reactions were monitored and evidenced using 1H-NMR spectroscopy, FT-IR spectroscopy, water gel-phase chromatography (GPC) analysis, amine value determination and acid value determination. We also studied the effect of additives on thermomechanical properties using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamical mechanical analysis (DMA), thermomechanical analysis (TMA) and by measuring mechanical properties. The BTCP-containing epoxy resin exhibited high mechanical strength and adhesion strength proportional to the amount of BTCP. Furthermore, field-emission scanning electron microscopy images were obtained for examining the cross-sectional morphology changes of the epoxy resin specimens with varying amounts of BTCP. Full article
(This article belongs to the Special Issue Hybrid Materials Based on Thermosets)
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Open AccessArticle The Synthesis of Low-Viscosity Organotin-Free Moisture-Curable Silane-Terminated Poly(Urethane-Urea)s
Polymers 2018, 10(7), 781; https://doi.org/10.3390/polym10070781
Received: 21 April 2018 / Revised: 4 July 2018 / Accepted: 6 July 2018 / Published: 16 July 2018
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Abstract
This work explores the possibility of synthesizing moisture-curable silane-terminated poly(urethane-urea)s (SPURs) of low viscosity. First, NCO-terminated urethane prepolymers were prepared, followed by silane end-capping. The impact of polyol molecular weight and the ratio of isocyanate to polyol (NCO/OH) on viscosity and the properties
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This work explores the possibility of synthesizing moisture-curable silane-terminated poly(urethane-urea)s (SPURs) of low viscosity. First, NCO-terminated urethane prepolymers were prepared, followed by silane end-capping. The impact of polyol molecular weight and the ratio of isocyanate to polyol (NCO/OH) on viscosity and the properties of SPUR were examined. As alternatives to the organotin catalysts traditionally used for the polyurethane synthesis and curing processes, bismuth carboxylate catalysts were evaluated. In addition, the effect of organofunctional groups in the aminosilane structure (R1–NH–R2–Si(OR3)3), i.e., R1 (alkyl, aryl or trimethoxysilyl-propyl), the spacer R2 (α or γ) and alkyl group R3 (methyl or ethyl), was examined. The chemical and physical structures of the SPUR were investigated by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and the mechanical properties were evaluated by tensile tests. The results reveal that silane-terminated, moisture-curable polyurethanes can be successfully synthesized and cured with bismuth carboxylate catalysts. SPUR exhibiting low viscosity, with adequate tensile strength and elongation can be prepared using environmentally benign bismuth carboxylate catalyst having a high metal content of 19%–21%, by utilizing secondary aminosilane end-cappers and an optimal combination of the polyol molecular weight and NCO/OH ratio. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessArticle Preparation of Molecularly Imprinted Microspheres as Biomimetic Recognition Material for In Situ Adsorption and Selective Chemiluminescence Determination of Bisphenol A
Polymers 2018, 10(7), 780; https://doi.org/10.3390/polym10070780
Received: 22 May 2018 / Revised: 3 July 2018 / Accepted: 13 July 2018 / Published: 16 July 2018
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Abstract
Bisphenol A (BPA) is an endocrine disrupter in environments which can induce abnormal differentiation of reproductive organs by interfering with the action of endogenous gonadal steroid hormones. In this work, the bisphenol A (BPA) molecularly-imprinted microspheres (MIMS) were prepared and used as biomimetic
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Bisphenol A (BPA) is an endocrine disrupter in environments which can induce abnormal differentiation of reproductive organs by interfering with the action of endogenous gonadal steroid hormones. In this work, the bisphenol A (BPA) molecularly-imprinted microspheres (MIMS) were prepared and used as biomimetic recognition material for in situ adsorption and selective chemiluminescence (CL) determination of BPA. Through non-covalent interaction, the BPA-MIMS was successfully prepared by Pickering emulsion polymerization using a BPA template, 4-vinylpyridine (4-VP) monomer, ethylene glycol dimethacrylate (EGDMA) cross-linker, and a SiO2 dispersion agent. The characterization of scanning electron microscopy (SEM) and energy-disperse spectroscopy (EDS) showed that the obtained MIMS possessed a regular spherical shape and narrow diameter distribution (25–30 μm). The binding experiment indicated BPA could be adsorbed in situ on the MIMS-packing cell with an apparent maximum amount Qmax of 677.3 μg g−1. Then BPA could be selectively detected by its sensitive inhibition effect on the CL reaction between luminol and periodate (KIO4), and the inhibition mechanism was discussed to reveal the CL reaction process. The CL intensity was linear to BPA concentrations in two ranges, respectively from 0.5 to 1.5 μg mL−1 with a detection limit of 8.0 ng mL−1 (3σ), and from 1.5 to 15 μg mL−1 with a limit of detection (LOD) of 80 ng mL−1 (3σ). The BPA-MIPMS showed excellent selectivity for BPA adsorption and the proposed CL method has been successfully applied to BPA determination in environmental water samples. Full article
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Open AccessArticle Structure-Properties Relations for Polyamide 6, Part 2: Influence of Processing Conditions during Injection Moulding on Deformation and Failure Kinetics
Polymers 2018, 10(7), 779; https://doi.org/10.3390/polym10070779
Received: 30 May 2018 / Revised: 7 July 2018 / Accepted: 11 July 2018 / Published: 16 July 2018
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Abstract
The effect of processing conditions during injection on the structure formation and mechanical properties of injection molded polyamide 6 samples was investigated in detail. A large effect of the mold temperature on the crystallographic properties was observed. Also the the effect of pressure
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The effect of processing conditions during injection on the structure formation and mechanical properties of injection molded polyamide 6 samples was investigated in detail. A large effect of the mold temperature on the crystallographic properties was observed. Also the the effect of pressure and shear flow was taken in to consideration and analysed. The yield and failure kinetics, including time-to-failure, were studied by performing tensile and creep tests at several test temperatures and relative humidities. As far as mechanical properties are concerned, a strong influence of temperature and relative humidity on the yield stress and time-to-failure was found. A semi-empirical model, able to describe yield and failure kinetics, was applied to the experimental results and related to the crystalline phase present in the sample. In agreement with findings in the literature it is observed that for high mold temperatures the sample morphology is more stable with respect to humidity and temperature than in case of low mold temperatures and this effects could be successfully captured by the model. The samples molded at low temperatures showed, during mechanical testing, a strong evolution of the crystallographic properties when exposed to high testing temperature and high relative humidity, i.e., an increase of crystallinity or a crystal phase transition. This makes a full description of the mechanical behavior rather complicated. Full article
(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)
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Open AccessArticle Identification and Characterization of Novel Fc-Binding Heptapeptides from Experiments and Simulations
Polymers 2018, 10(7), 778; https://doi.org/10.3390/polym10070778
Received: 2 June 2018 / Revised: 11 July 2018 / Accepted: 12 July 2018 / Published: 16 July 2018
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Abstract
Purification of biologically-derived therapeutics is a major cost contributor to the production of this rapidly growing class of pharmaceuticals. Monoclonal antibodies comprise a large percentage of these products, therefore new antibody purification tools are needed. Small peptides, as opposed to traditional antibody affinity
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Purification of biologically-derived therapeutics is a major cost contributor to the production of this rapidly growing class of pharmaceuticals. Monoclonal antibodies comprise a large percentage of these products, therefore new antibody purification tools are needed. Small peptides, as opposed to traditional antibody affinity ligands such as Protein A, may have advantages in stability and production costs. Multiple heptapeptides that demonstrate Fc binding behavior that have been identified from a combinatorial peptide library using M13 phage display are presented herein. Seven unique peptide sequences of diverse hydrophobicity and charge were identified. All seven peptides showed strong binding to the four major human IgG isotypes, human IgM, as well as binding to canine, rat, and mouse IgG. These seven peptides were also shown to bind human IgG4 from DMEM cell culture media with 5% FCS and 5 g/L ovalbumin present. These peptides may be useful as surface ligands for antibody detection and purification purposes. Molecular docking and classical molecular dynamics (MD) simulations were conducted to elucidate the mechanisms and energetics for the binding of these peptides to the Fc region. The binding site was found to be located between the two glycan chains inside the Fc fragment. Both hydrogen bonding and hydrophobic interactions were found to be crucial for the binding interactions. Excellent agreement for the binding strength was obtained between experimental results and simulations. Full article
(This article belongs to the Special Issue Polymers for Bioseparations)
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Open AccessArticle In Situ Strain and Damage Monitoring of GFRP Laminates Incorporating Carbon Nanofibers under Tension
Polymers 2018, 10(7), 777; https://doi.org/10.3390/polym10070777
Received: 5 June 2018 / Revised: 4 July 2018 / Accepted: 10 July 2018 / Published: 16 July 2018
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Abstract
In this study, conductive carbon nanofibers (CNFs) were dispersed into epoxy resin and then infused into glass fiber fabric to fabricate CNF/glass fiber-reinforced polymer (GFRP) laminates. The electrical resistance and strain of CNF/GFRP laminates were measured simultaneously during tensile loadings to investigate the
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In this study, conductive carbon nanofibers (CNFs) were dispersed into epoxy resin and then infused into glass fiber fabric to fabricate CNF/glass fiber-reinforced polymer (GFRP) laminates. The electrical resistance and strain of CNF/GFRP laminates were measured simultaneously during tensile loadings to investigate the in situ strain and damage monitoring capability of CNF/GFRP laminates. The damage evolution and conduction mechanisms of the laminates were also presented. The results indicated that the percolation threshold of CNFs content for CNF/GFRP laminates was 0.86 wt % based on a typical power law. The resistance response during monotonic tensile loading could be classified into three stages corresponding to different damage mechanisms, which demonstrated a good ability of in situ damage monitoring of the CNF/GFRP laminates. In addition, the capacity of in situ strain monitoring of the laminates during small strain stages was also confirmed according to the synchronous and reversible resistance responses to strain under constant cyclic tensile loading. Moreover, the analysis of the resistance responses during incremental amplitude cyclic tensile loading with the maximum strain of 1.5% suggested that in situ strain and damage monitoring of the CNF/GFRP laminates were feasible and stable. Full article
(This article belongs to the Special Issue Multi-functional Polymer Composites and Structures)
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Open AccessArticle Confirmation of Bioinformatics Predictions of the Structural Domains in Honeybee Silk
Polymers 2018, 10(7), 776; https://doi.org/10.3390/polym10070776
Received: 21 June 2018 / Revised: 11 July 2018 / Accepted: 12 July 2018 / Published: 16 July 2018
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Abstract
Honeybee larvae produce a silk made up of proteins in predominantly a coiled coil molecular structure. These proteins can be produced in recombinant systems, making them desirable templates for the design of advanced materials. However, the atomic level structure of these proteins is
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Honeybee larvae produce a silk made up of proteins in predominantly a coiled coil molecular structure. These proteins can be produced in recombinant systems, making them desirable templates for the design of advanced materials. However, the atomic level structure of these proteins is proving difficult to determine: firstly, because coiled coils are difficult to crystalize; and secondly, fibrous proteins crystalize as fibres rather than as discrete protein units. In this study, we synthesised peptides from the central structural domain, as well as the N- and C-terminal domains, of the honeybee silk. We used circular dichroism spectroscopy, infrared spectroscopy, and molecular dynamics to investigate the folding behaviour of the central domain peptides. We found that they folded as predicted by bioinformatics analysis, giving the protein engineer confidence in bioinformatics predictions to guide the design of new functionality into these protein templates. These results, along with the infrared structural analysis of the N- and C-terminal domain peptides and the comparison of peptide film properties with those of the full-length AmelF3 protein, provided significant insight into the structural elements required for honeybee silk protein to form into stable materials. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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