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Polymers, Volume 10, Issue 9 (September 2018)

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Cover Story (view full-size image) A rhodamine (Rh) functionalized micellar hydrogel with excellent mechanochromic and [...] Read more.
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Open AccessArticle The Effect of Palm Oil-Based Hybrid Oils as Green Multifunctional Oils on the Properties of Elastomer Composites
Polymers 2018, 10(9), 1045; https://doi.org/10.3390/polym10091045
Received: 24 August 2018 / Revised: 14 September 2018 / Accepted: 18 September 2018 / Published: 19 September 2018
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Abstract
Hybrid oils in an elastomer matrix provide superior physical and chemical properties over conventional elastomer composites. In this study, we investigated the possibility of utilizing palm-based hybrid oil as a processing oil, with various other added oils such as methylester, palm monoglyceride and
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Hybrid oils in an elastomer matrix provide superior physical and chemical properties over conventional elastomer composites. In this study, we investigated the possibility of utilizing palm-based hybrid oil as a processing oil, with various other added oils such as methylester, palm monoglyceride and dammar, and their effects on the curing characteristics, mechanical, abrasion resistance and heat build-up properties of elastomer composites. The elastomer composites with the hybrid oils exhibit remarkable improvements in mechanical properties such as modulus, tensile strength, elongation and toughness, which were ascribed to the enhanced dispersion of the fillers in the elastomer matrix. Also, the hybrid oils in the elastomer matrix showed outstanding heat build-up, abrasion and rebound resilience properties at low loadings. The synergistic effects in the elastomer matrix achieved by the hybridization of palm oil and other oils represent a significant contribution to advanced, stronger elastomer composites in various applications. Full article
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Open AccessArticle Theoretical Study on the Grafting Reaction of Maleimide to Polyethylene in the UV Radiation Cross-Linking Process
Polymers 2018, 10(9), 1044; https://doi.org/10.3390/polym10091044
Received: 3 August 2018 / Revised: 6 September 2018 / Accepted: 6 September 2018 / Published: 19 September 2018
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Abstract
Theoretical investigation of the reaction of graft maleimide to polyethylene in the UV radiation cross-linking process is accomplished at the B3LYP/6-311+G(d,p) level for high-voltage cable insulation materials. The reaction potential energy surface of the nine reaction channels is identified.
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Theoretical investigation of the reaction of graft maleimide to polyethylene in the UV radiation cross-linking process is accomplished at the B3LYP/6-311+G(d,p) level for high-voltage cable insulation materials. The reaction potential energy surface of the nine reaction channels is identified. The results show that the N,N′-ethylenedimaleimide can connect two 4-methylheptane molecules and act as the cross-linking agent. The calculated reaction potential barrier of forming 4-methylheptane radical by maleimide is higher than that of maleic anhydride. The study is expected to provide a basis for optimizing the UV radiation cross-linking polyethylene process and development more than 500 kV high-voltage cable insulation materials in practical applications. Full article
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Open AccessArticle PBN11-8, a Cytotoxic Polypeptide Purified from Marine Bacillus, Suppresses Invasion and Migration of Human Hepatocellular Carcinoma Cells by Targeting Focal Adhesion Kinase Pathways
Polymers 2018, 10(9), 1043; https://doi.org/10.3390/polym10091043
Received: 12 March 2018 / Revised: 20 April 2018 / Accepted: 2 May 2018 / Published: 19 September 2018
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Abstract
The development of antitumor drugs has attracted cancer researchers and the identification of novel antitumor lead compounds is certainly of great interest. The fermentation broth of Bacillus sp. N11-8, which was isolated from the Antarctic waters, showed cytotoxicity towards different cells. A cytotoxic
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The development of antitumor drugs has attracted cancer researchers and the identification of novel antitumor lead compounds is certainly of great interest. The fermentation broth of Bacillus sp. N11-8, which was isolated from the Antarctic waters, showed cytotoxicity towards different cells. A cytotoxic polypeptide, PBN11-8, was purified from the fermentation broth of Bacillus sp. N11-8 using ultrafiltration, ammonium sulfate precipitation, anion exchange liquid chromatography and high performance liquid chromatography (HPLC). Cloning and sequence analysis showed that PBN11-8 polypeptide (MW: ~19 kDa by the electrospray-ionization (ESI)) displayed high similarity with peptidase M84 from Bacillus pumilus. PBN11-8 possessed moderate cytotoxicity towards several cancer cell lines with IC50 values of 1.56, 1.80, 1.57, and 1.73 µg/mL against human hepatocellular carcinoma cell line BEL-7402, human renal clear cell adenocarcinoma cell line 786-0, human hepatocellular carcinoma cell line HepG2, and human pancreatic cancer cell line Panc-28, respectively. Moreover, the polypeptide displayed weak cytotoxicity towards normal cell line renal tubular epithelial cell line HK2 and human normal liver cell line L02 cells. Wound healing migration and Transwell experiments demonstrate that PBN11-8 could inhibit the migration and invasion of BEL-7402. Further investigation revealed that PBN11-8 suppresses focal adhesion kinase (FAK)-mediated adhesion, migration, and invasion by disturbing FAK/extracellular regulated protein kinases (ERK) signaling and matrix metalloproteinase-2(MMP-2) and matrix metalloproteinase-9 (MMP-9) in BEL-7402 cells. Thus, PBN11-8 represents a potential novel anti-cancer lead compound. Full article
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Open AccessArticle Efficient Adsorption on Benzoyl and Stearoyl Cellulose to Remove Phenanthrene and Pyrene from Aqueous Solution
Polymers 2018, 10(9), 1042; https://doi.org/10.3390/polym10091042
Received: 31 July 2018 / Revised: 11 September 2018 / Accepted: 17 September 2018 / Published: 19 September 2018
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Abstract
Benzoyl and stearoyl acid grafted cellulose were synthesized by a simple chemical grafting method. Using these as chemical adsorbents, polycyclic aromatic hydrocarbons (PAHs), like pyrene and phenanthrene, were effectively removed from aqueous solution. The structural and morphological properties of the synthesized adsorbents were
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Benzoyl and stearoyl acid grafted cellulose were synthesized by a simple chemical grafting method. Using these as chemical adsorbents, polycyclic aromatic hydrocarbons (PAHs), like pyrene and phenanthrene, were effectively removed from aqueous solution. The structural and morphological properties of the synthesized adsorbents were determined through X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), FE-SEM, and NMR analyses. Through this method, it was confirmed that benzoyl and stearoyl acid were successfully grafted onto the surface of cellulose. The 5 mg of stearoyl grafted cellulose (St–Cell) remove 96.94% pyrene and 97.61% phenanthrene as compared to unmodified cellulose, which adsorbed 1.46% pyrene and 2.99% phenanthrene from 0.08 ppm pyrene and 0.8 ppm phenanthrene aqueous solution, suggesting that those results show a very efficient adsorption performance as compared to the unmodified cellulose. Full article
(This article belongs to the Special Issue Bio-Based Polymers for Engineered Green Materials)
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Open AccessPerspective 3D Printed Polymeric Hydrogels for Nerve Regeneration
Polymers 2018, 10(9), 1041; https://doi.org/10.3390/polym10091041
Received: 11 August 2018 / Revised: 12 September 2018 / Accepted: 14 September 2018 / Published: 19 September 2018
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Abstract
The human nervous system lacks an inherent ability to regenerate its components upon damage or diseased conditions. During the last decade, this has motivated the development of a number of strategies for nerve regeneration. However, most of those approaches have not been used
[...] Read more.
The human nervous system lacks an inherent ability to regenerate its components upon damage or diseased conditions. During the last decade, this has motivated the development of a number of strategies for nerve regeneration. However, most of those approaches have not been used in clinical applications till today. For instance, although biomaterial-based scaffolds have been extensively used for nerve reparation, the lack of more customized structures have hampered their use in vivo. This highlight focuses mainly on how 3D bioprinting technology, using polymeric hydrogels as bio-inks, can be used for the development of new nerve guidance channels or devices for peripheral nerve cell regeneration. In this concise contribution, some of the most recent and representative examples are highlighted to discuss the challenges involved in various aspects of 3D bioprinting for nerve cell regeneration, specifically when using polymeric hydrogels. Full article
(This article belongs to the Special Issue Hydrogels in Tissue Engineering and Regenerative Medicine)
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Open AccessArticle Effect of Core-Shell Morphology on the Mechanical Properties and Crystallization Behavior of HDPE/HDPE-g-MA/PA6 Ternary Blends
Polymers 2018, 10(9), 1040; https://doi.org/10.3390/polym10091040
Received: 9 August 2018 / Revised: 13 September 2018 / Accepted: 14 September 2018 / Published: 19 September 2018
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Abstract
In this paper, the high-density polyethylene/maleic anhydride grafted high-density polyethylene/polyamide 6 (HDPE/HDPE-g-MA/PA6) ternary blends were prepared by blend melting. The binary dispersed phase (HDPE-g-MA/PA6) is of a core-shell structure, which is confirmed by the SEM observation and theoretical calculation.
[...] Read more.
In this paper, the high-density polyethylene/maleic anhydride grafted high-density polyethylene/polyamide 6 (HDPE/HDPE-g-MA/PA6) ternary blends were prepared by blend melting. The binary dispersed phase (HDPE-g-MA/PA6) is of a core-shell structure, which is confirmed by the SEM observation and theoretical calculation. The crystallization behavior and mechanical properties of PA6, HDPE-g-MA, HDPE, and their blends were investigated. The crystallization process, crystallization temperature, melting temperature, and crystallinity were studied by differential scanning calorimetry (DSC) testing. The results show that PA6 and HDPE-g-MA interact with each other during crystallizing, and their crystallization behaviors are different when the composition is different. At the same time, the addition of core-shell particles (HDPE-g-MA/PA6) can affect the crystallization behavior of the HDPE matrix. With the addition of the core-shell particles, the comprehensive mechanical properties of HDPE were enhanced, including tensile strength, elastic modulus, and the impact strength. Combined with previous studies, the toughening mechanism of core-shell structure is discussed in detail. The mechanism of the core-shell structure toughening is not only one, but the result of a variety of mechanisms together. Full article
(This article belongs to the Special Issue Core-Shell Structured Polymers)
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Open AccessCommunication Protein Transduction Domain Mimic (PTDM) Self-Assembly?
Polymers 2018, 10(9), 1039; https://doi.org/10.3390/polym10091039
Received: 6 August 2018 / Revised: 12 September 2018 / Accepted: 14 September 2018 / Published: 19 September 2018
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Abstract
Intracellular protein delivery is an invaluable tool for biomedical research, as it enables fundamental studies of cellular processes and creates opportunities for novel therapeutic development. Protein delivery reagents such as cell penetration peptides (CPPs) and protein transduction domains (PTDs) are frequently used to
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Intracellular protein delivery is an invaluable tool for biomedical research, as it enables fundamental studies of cellular processes and creates opportunities for novel therapeutic development. Protein delivery reagents such as cell penetration peptides (CPPs) and protein transduction domains (PTDs) are frequently used to facilitate protein delivery. Herein, synthetic polymer mimics of PTDs, called PTDMs, were studied for their ability to self-assemble in aqueous media as it was not known whether self-assembly plays a role in the protein binding and delivery process. The results obtained from interfacial tensiometry (IFT), transmission electron microscopy (TEM), transmittance assays (%T), and dynamic light scattering (DLS) indicated that PTDMs do not readily aggregate or self-assemble at application-relevant time scales and concentrations. However, additional DLS experiments were used to confirm that the presence of protein is required to induce the formation of PTDM-protein complexes and that PTDMs likely bind as single chains. Full article
(This article belongs to the Special Issue Polymers: Design, Function and Application)
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Open AccessArticle Removal of Aromatic Chlorinated Pesticides from Aqueous Solution Using β-Cyclodextrin Polymers Decorated with Fe3O4 Nanoparticles
Polymers 2018, 10(9), 1038; https://doi.org/10.3390/polym10091038
Received: 20 July 2018 / Revised: 4 September 2018 / Accepted: 15 September 2018 / Published: 19 September 2018
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Abstract
This article describes the sorption properties of cyclodextrin polymers (nanosponges; NS) with the pesticides 4-chlorophenoxyacetic acid (4-CPA) and 2,3,4,6-tetrachlorophenol (TCF), including an evaluation of its efficiency and a comparison with other materials, such as granulated activated carbon (GAC). NS-pesticide complexes were characterized by
[...] Read more.
This article describes the sorption properties of cyclodextrin polymers (nanosponges; NS) with the pesticides 4-chlorophenoxyacetic acid (4-CPA) and 2,3,4,6-tetrachlorophenol (TCF), including an evaluation of its efficiency and a comparison with other materials, such as granulated activated carbon (GAC). NS-pesticide complexes were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRPD), proton nuclear magnetic resonance (1H-NMR), UV–VIS, and thermogravimetric analysis (TGA). This confirms the interactions of the guests with nanosponges and shows that the polymers have favorable sorption capacities for chlorinated aromatic guests. Our studies also show that the inclusion complex is predominantly favored for NS/CPA rather than those formed between TCF and NS due to the size of the adsorbate and steric effects. Sorption studies carried with repeated cycles demonstrate that NS polymers could be an improved technology for pollutant removal from aquatic environments, as they are very efficient and reusable materials. Our experiments and characterization by SEM, EDS, UV–VIS, and magnetization saturation (VSM) also show that NS is an optimal substrate for the deposition of magnetite nanoparticles, thus improving the usefulness and properties of the polymer, as the nanosponges could be retrieved from aqueous solution with a neodymium magnet without losing its efficiency as a pesticide sorbent. Full article
(This article belongs to the Special Issue Cyclodextrin-Containing Polymers)
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Open AccessCommunication Self-Assembly DBS Nanofibrils on Solution-Blown Nanofibers as Hierarchical Ion-Conducting Pathway for Direct Methanol Fuel Cells
Polymers 2018, 10(9), 1037; https://doi.org/10.3390/polym10091037
Received: 29 August 2018 / Revised: 17 September 2018 / Accepted: 17 September 2018 / Published: 19 September 2018
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Abstract
In this work, we reported a novel proton exchange membrane (PEM) with an ion-conducting pathway. The hierarchical nanofiber structure was prepared via in situ self-assembling 1,3:2,4-dibenzylidene-d-sorbitol (DBS) supramolecular fibrils on solution-blown, sulfonated poly (ether sulfone) (SPES) nanofiber, after which the composite PEM was
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In this work, we reported a novel proton exchange membrane (PEM) with an ion-conducting pathway. The hierarchical nanofiber structure was prepared via in situ self-assembling 1,3:2,4-dibenzylidene-d-sorbitol (DBS) supramolecular fibrils on solution-blown, sulfonated poly (ether sulfone) (SPES) nanofiber, after which the composite PEM was prepared by incorporating hierarchical nanofiber into the chitosan polymer matrix. Then, the effects of incorporating the hierarchical nanofiber structure on the thermal stability, water uptake, dimensional stability, proton conductivity, and methanol permeability of the composite membranes were investigated. The results show that incorporation of hierarchical nanofiber improves the water uptake, proton conductivity, and methanol permeability of the membranes. Furthermore, the composite membrane with 50% hierarchical nanofibers exhibited the highest proton conductivity of 0.115 S cm−1 (80 °C), which was 69.12% higher than the values of pure chitosan membrane. The self-assembly allows us to generate hierarchical nanofiber among the interfiber voids, and this structure can provide potential benefits for the preparation of high-performance PEMs. Full article
(This article belongs to the Special Issue Nanostructured Polymers and Nanocomposites)
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Open AccessArticle The Impact of Plasticizer and Degree of Hydrolysis on Free Volume of Poly(vinyl alcohol) Films
Polymers 2018, 10(9), 1036; https://doi.org/10.3390/polym10091036
Received: 22 May 2018 / Revised: 7 September 2018 / Accepted: 12 September 2018 / Published: 18 September 2018
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Abstract
The effect of plasticizer species and the degree of hydrolysis (DH) on the free volume properties of poly(vinyl alcohol) (PVA) were studied using positron annihilation lifetime spectroscopy. Both glycerol and propylene glycol caused an increase in the free volume cavity radius, although exhibited
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The effect of plasticizer species and the degree of hydrolysis (DH) on the free volume properties of poly(vinyl alcohol) (PVA) were studied using positron annihilation lifetime spectroscopy. Both glycerol and propylene glycol caused an increase in the free volume cavity radius, although exhibited distinct plasticization behavior, with glycerol capable of occupying existing free volume cavities in the PVA to some extent. The influence of water, normally present in PVA film under atmospheric conditions, was also isolated. Water added significantly to the measured free volume cavity radius in both plasticized and pure PVA matrices. Differences in plasticization behavior can be attributed to the functionality of each plasticizing additive and its hydrogen bonding capability. The increase in cavity radii upon plasticizer loading shows a qualitative link between the free volume of voids and the corresponding reduction in Tg and crystallinity. Cavity radius decreases with increasing DH, due to PVA network tightening in the absence of acetate groups. This corresponds well with the higher Tg observed in the resin with the higher DH. DH was also shown to impact the plasticization of PVA with glycerol, indicating that the larger cavities—created by the weaker hydrogen bonding acetate groups—are capable of accommodating glycerol molecules with negligible effect on the cavity dimensions. Full article
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Open AccessArticle Hydrophobic Modification of Nanocellulose via a Two-Step Silanation Method
Polymers 2018, 10(9), 1035; https://doi.org/10.3390/polym10091035
Received: 5 August 2018 / Revised: 6 September 2018 / Accepted: 12 September 2018 / Published: 18 September 2018
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Abstract
Dodecyltrimethoxysilane (DTMOS), which is a silanation modifier, was grafted onto nanocellulose crystals (NCC) through a two-step method using KH560 (ɤ-(2,3-epoxyproxy)propytrimethoxysilane) as a linker to improve the hydrophobicity of NCC. The reaction mechanism of NCC with KH560 and DTMOS and its surface
[...] Read more.
Dodecyltrimethoxysilane (DTMOS), which is a silanation modifier, was grafted onto nanocellulose crystals (NCC) through a two-step method using KH560 (ɤ-(2,3-epoxyproxy)propytrimethoxysilane) as a linker to improve the hydrophobicity of NCC. The reaction mechanism of NCC with KH560 and DTMOS and its surface chemical characteristics were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and HCl–acetone titration. These analyses confirmed that KH560 was grafted onto the surface of NCC through the ring-opening reaction, before DTMOS was covalently grafted onto the surface of NCC using KH560 as a linker. The grafting of NCC with DTMOS resulted in an improvement in its hydrophobicity due to an increase in its water contact angle from 0° to about 140°. In addition, the modified NCC also possessed enhanced thermal stability. Full article
(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)
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Open AccessArticle Sugar Functionalized Synergistic Dendrimers for Biocompatible Delivery of Nucleic Acid Therapeutics
Polymers 2018, 10(9), 1034; https://doi.org/10.3390/polym10091034
Received: 2 August 2018 / Revised: 14 September 2018 / Accepted: 15 September 2018 / Published: 18 September 2018
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Abstract
Sugars containing cationic polymers are potential carriers for in vitro and in vivo nucleic acid delivery. Monosaccharides such as glucose and galactose have been chemically conjugated to various materials of synergistic poly-lysine dendrimer systems for efficient and biocompatible delivery of short interfering RNA
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Sugars containing cationic polymers are potential carriers for in vitro and in vivo nucleic acid delivery. Monosaccharides such as glucose and galactose have been chemically conjugated to various materials of synergistic poly-lysine dendrimer systems for efficient and biocompatible delivery of short interfering RNA (siRNA). The synergistic dendrimers, which contain lipid conjugated glucose terminalized lysine dendrimers, have significantly lower adverse impact on cells while maintaining efficient cellular entry. Moreover, the synergistic dendrimers complexed to siRNA induced RNA interference (RNAi) in the cells and profoundly knocked down green fluorescence protein (GFP) as well as the endogenously expressing disease related gene Plk1. The new synergic dendrimers may be promising system for biocompatible and efficient siRNA delivery. Full article
(This article belongs to the Special Issue Polymers in Gene Delivery)
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Open AccessArticle Bioinspired Engineering towards Tailoring Advanced Lignin/Rubber Elastomers
Polymers 2018, 10(9), 1033; https://doi.org/10.3390/polym10091033
Received: 14 August 2018 / Revised: 13 September 2018 / Accepted: 14 September 2018 / Published: 18 September 2018
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Abstract
The pursuit of high volume and high value-added applications for lignin has been a long-term challenge. In this work, inspired by the energy sacrificial mechanism from biological materials, we developed high-performance lignin/carbon black (CB)/nitrile rubber (NBR) elastomers by constructing a dual-crosslinking network consisting
[...] Read more.
The pursuit of high volume and high value-added applications for lignin has been a long-term challenge. In this work, inspired by the energy sacrificial mechanism from biological materials, we developed high-performance lignin/carbon black (CB)/nitrile rubber (NBR) elastomers by constructing a dual-crosslinking network consisting of sulfur covalent bonds and dynamic coordination sacrificial bonds. Lignin was not only used for the substitution of half mass of CB in the NBR elastomer but also served as natural ligands for the Zn-based coordination bonds, providing a significant synergistic coordination enhancement effect. The mechanical performance of the elastomers can be easily manipulated by adjusting the proportion of non-permanent coordination bonds and permanent covalent bonds. Lignin/CB/NBR elastomers with a higher strength and modulus than CB-filled elastomers were obtained while maintaining excellent elasticity. The thermal stability and the high-temperature oil resistance of NBR elastomers were also improved by incorporation of lignin and metal coordination bonds. Overall, this work inspires a new solution for the design of high-performance lignin/rubber elastomers with a high lignin loading content. Full article
(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)
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Open AccessArticle Biomimetic Growth of Hydroxyapatite on Electrospun CA/PVP Core–Shell Nanofiber Membranes
Polymers 2018, 10(9), 1032; https://doi.org/10.3390/polym10091032
Received: 10 August 2018 / Revised: 12 September 2018 / Accepted: 13 September 2018 / Published: 17 September 2018
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Abstract
In this study, cellulose acetate (CA)/polyvinylpyrrolidone (PVP) core–shell nanofibers were successfully fabricated by electrospinning their homogeneous blending solution. Uniform and cylindrical nanofibers were obtained when the PVP content increased from 0 to 2 wt %. Because of the concentration gradient associated with the
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In this study, cellulose acetate (CA)/polyvinylpyrrolidone (PVP) core–shell nanofibers were successfully fabricated by electrospinning their homogeneous blending solution. Uniform and cylindrical nanofibers were obtained when the PVP content increased from 0 to 2 wt %. Because of the concentration gradient associated with the solvent volatilization, the composite fibers flattened when the PVP increased to 5 wt %. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results confirmed the existence of a hydrogen bond between the CA and PVP molecules, which enhanced the thermodynamic properties of the CA/PVP nanofibers, as shown by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results. To analyze the interior structure of the CA/PVP fibers, the water-soluble PVP was selectively removed by immersing the fiber membranes in deionized water. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the PVP component, which has a low surface tension, was driven to the exterior of the fiber to form a discontinuous phase, whereas the high-content CA component inclined to form the internal continuous phase, thereby generating a core–shell structure. After the water-treatment, the CA/PVP composite fibers provided more favorable conditions for mineral crystal deposition and growth. Energy-dispersive spectroscopy (EDS) and FTIR proved that the crystal was hydroxyapatite (HAP) and that the calcium to phosphorus ratio was 1.47, which was close to the theoretical value of 1.67 in HAP. Such nanofiber membranes could be potentially applicable in bone tissue engineering. Full article
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Open AccessArticle Microstructure Evolution of Immiscible PP-PVA Blends Tuned by Polymer Ratio and Silica Nanoparticles
Polymers 2018, 10(9), 1031; https://doi.org/10.3390/polym10091031
Received: 5 August 2018 / Revised: 11 September 2018 / Accepted: 14 September 2018 / Published: 17 September 2018
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Abstract
Composites of polypropylene (PP) and water soluble poly(vinyl alcohol) (PVA) can become an environmentally friendly precursor in preparing porous material, and their biphasic morphology needs to be manipulated. In this work, PP-PVA extrudates were prepared with a twin-screw extruder, and different PP/PVA ratios
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Composites of polypropylene (PP) and water soluble poly(vinyl alcohol) (PVA) can become an environmentally friendly precursor in preparing porous material, and their biphasic morphology needs to be manipulated. In this work, PP-PVA extrudates were prepared with a twin-screw extruder, and different PP/PVA ratios were employed to manipulate the morphology of the blends. Afterwards, different silicas were imbedded within the blends to further regulate the biphasic microstructure. PVA continuity, as a vital parameter in obtaining porous material, was determined by selective extraction measurement, and PP-PVA biphasic morphology was characterized by scanning microscopy analyses (SEM). Rheological measurement was also performed to correlate the microstructure evolution of the blends. First, it was found that with the increment of PVA proportion, PVA continuity is raised gradually, and the microstructure of blends containing 40–50 wt % of PVA is approaching co-continuous. Second, the localization of silicas was predicted based on the wettability of silica and polymers, and it was also confirmed by TEM that different silicas showed selective distribution. It is inspiring that R972 nanoparticles were found mainly distributed at the interface, which gives a possibility in preparing a surface-modified porous material. The shape distribution and average size of PVA nodules were examined by analyzing the SEM images. It is indicated that silicas with different wettabilities play disparate roles in tuning the biphasic microstructures, leading to heterogeneous PVA continuity. Full article
(This article belongs to the Special Issue Polymers: Design, Function and Application)
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Open AccessArticle Dyeing Property and Adsorption Kinetics of Reactive Dyes for Cotton Textiles in Salt-Free Non-Aqueous Dyeing Systems
Polymers 2018, 10(9), 1030; https://doi.org/10.3390/polym10091030
Received: 8 August 2018 / Revised: 8 September 2018 / Accepted: 13 September 2018 / Published: 15 September 2018
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Abstract
In recent years, new concepts in textile dyeing technology have been investigated which aim to decrease the use of chemicals and the emission of water. In this work, dyeing of cotton textiles with reactive dyes has been investigated in a silicone non-aqueous dyeing
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In recent years, new concepts in textile dyeing technology have been investigated which aim to decrease the use of chemicals and the emission of water. In this work, dyeing of cotton textiles with reactive dyes has been investigated in a silicone non-aqueous dyeing system. Compared with conventional aqueous dyeing, almost 100% of reactive dyes can be adsorbed on cotton textiles without using any salts in non-aqueous dyeing systems, and the fixation of dye is also higher (80%~90% for non-aqueous dyeing vs. 40%~50% for traditional dyeing). The pseudo-second-order kinetic model can best describe the adsorption and equilibrium of reactive dyes in the non-aqueous dyeing systems as well as in the traditional water dyeing system. In the non-aqueous dyeing systems, the adsorption equilibrium of reactive dyes can be reached quickly. Particularly in the siloxane non-aqueous dyeing system, the adsorption equilibrium time of reactive dye is only 5–10 min at 25 °C, whereas more time is needed at 60 °C in the water dyeing system. The surface tension of non-aqueous media influences the adsorption rate of dye. The lower the surface tension, the faster the adsorption rate of reactive dye, and the higher the final uptake of dye. As a result, non-aqueous dyeing technology provides an innovative approach to increase dye uptake under a low dyeing temperature, in addition to making large water savings. Full article
(This article belongs to the Special Issue Polymer Processing for Enhancing Textile Application)
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Open AccessArticle Comparative Investigation of Thermal and Structural Behavior in Renewably Sourced Composite Films of Even-Even Nylons (610 and 1010) with Silk Fibroin
Polymers 2018, 10(9), 1029; https://doi.org/10.3390/polym10091029
Received: 1 September 2018 / Revised: 10 September 2018 / Accepted: 14 September 2018 / Published: 15 September 2018
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Abstract
As the average life expectancy continues to increase, so does the need for resorbable materials designed to treat, augment, or replace components and functions of the body. Naturally occurring biopolymers such as silks are already attractive candidates due to natural abundance and high
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As the average life expectancy continues to increase, so does the need for resorbable materials designed to treat, augment, or replace components and functions of the body. Naturally occurring biopolymers such as silks are already attractive candidates due to natural abundance and high biocompatibility accompanied by physical properties which are easily modulated through blending with another polymer. In this paper, the authors report on the fabrication of biocomposite materials made from binary blends of Bombyx mori silk fibroin (SF) protein and renewably sourced low molecular weight nylon 610 and high molecular weight nylon 1010. Films were characterized using scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Results of this study demonstrated that enhanced structural and thermal properties were achievable in composite films SF-N610/N1010 due to their chemical similarity and the possible formation of hydrogen bonds between nylon and silk molecular chains. This study provides useful insight into the sustainable design of functional composite materials for biomedical and green technologies. Full article
(This article belongs to the Special Issue Protein Biopolymer)
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Open AccessArticle A Geometry Effect of Carbon Nanomaterials on Flame Retardancy and Mechanical Properties of Ethylene-Vinyl Acetate/Magnesium Hydroxide Composites
Polymers 2018, 10(9), 1028; https://doi.org/10.3390/polym10091028
Received: 30 August 2018 / Revised: 11 September 2018 / Accepted: 12 September 2018 / Published: 14 September 2018
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Abstract
This study was aimed at investigating the effects of carbon nanomaterials with different geometries on improving the flame retardancy of magnesium hydroxide–filled ethylene-vinyl acetate (EM). The thermal stability and flame retardancy were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test,
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This study was aimed at investigating the effects of carbon nanomaterials with different geometries on improving the flame retardancy of magnesium hydroxide–filled ethylene-vinyl acetate (EM). The thermal stability and flame retardancy were studied by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test, and cone calorimeter test (CCT). The in situ temperature monitoring system and interrupted combustion offered direct evidence to link flame retardancy and composite structure. Results demonstrated that carbon nanomaterials enhanced the thermal stability and fire safety of EM. The geometry of carbon nanomaterials played a key role in synergistic flame retardancy of EM, with the flame-retardant order of carbon nanotube > nanoscale carbon black > graphene. Based on an online temperature monitoring system and interrupted combustion test, one-dimensional carbon nanotube was more inclined to form the network structure synergistically with magnesium hydroxide in ethylene-vinyl acetate, which facilitated the generation of more continuous char structure during combustion. In parallel, the mechanical property was characterized by a tensile test and dynamic mechanical analysis (DMA). The incorporation of carbon nanomaterials presented a limited effect on the mechanical properties of the EM system. Full article
(This article belongs to the Special Issue Multi-functional Polymer Composites and Structures)
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Open AccessArticle The Role of Rare Earth Lanthanum Oxide in Polymeric Matrix Brake Composites to Replace Copper
Polymers 2018, 10(9), 1027; https://doi.org/10.3390/polym10091027
Received: 3 August 2018 / Revised: 8 September 2018 / Accepted: 12 September 2018 / Published: 14 September 2018
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Abstract
The main focus of current research in polymeric matrix brake composites is on searching out a replacement for copper, which has been recently proved to be a hazard to human health and the environment. In this paper, rare earth lanthanum oxide was explored
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The main focus of current research in polymeric matrix brake composites is on searching out a replacement for copper, which has been recently proved to be a hazard to human health and the environment. In this paper, rare earth lanthanum oxide was explored for the replacement of copper in composites. The mechanism of the role of lanthanum oxide in brake composites to replace copper was analyzed. Four series of polymeric matrix brake composites with various amounts of copper (15, 10, 5 and 0 wt %) and rare earth lanthanum oxide (0, 5, 10 and 15 wt %) were developed, in which the copper was gradually replaced by lanthanum oxide in the formula. These series were characterized in terms of physical, thermo-physical and mechanical properties. The results show that lanthanum oxide can be successfully used as a replacement for copper in brake composites. Brake composites with 15 wt % lanthanum oxide that are copper-free are considered optimal, where tribo-properties are considered best. Compared with the addition of copper in brake composites, lanthanum oxide is more conducive to the formation of compacted friction films and transfer films, which is beneficial to the tribological properties of the brake composites. The addition of La2O3 to the brake composites can cause the reaction between La2O3 and Al2O3 to form LaAlO3, and the reaction between Al2O3 and BaSO4 can produce Ba18Al12O36 and Al2SO4 during the friction and wear processes, which can effectively improve the tribological properties of the brake composites at elevated temperature. This research was contributive to the copper-free, metal-free and eco-friendly brake composites. Full article
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Open AccessArticle The Low Velocity Impact Response of Shape Memory Alloy Hybrid Polymer Composites
Polymers 2018, 10(9), 1026; https://doi.org/10.3390/polym10091026
Received: 31 August 2018 / Revised: 13 September 2018 / Accepted: 13 September 2018 / Published: 14 September 2018
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Abstract
Polymer composites are sensitive to impact loading due to their low impact resistance. Shape memory alloy (SMA) wires have been used to improve the impact resistance of the polymer composite materials because of their unique superelasticity performance. In this study, a new SMA
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Polymer composites are sensitive to impact loading due to their low impact resistance. Shape memory alloy (SMA) wires have been used to improve the impact resistance of the polymer composite materials because of their unique superelasticity performance. In this study, a new SMA hybrid basalt fiber-reinforced polymer composite embedded with two perpendicular layers of superelastic SMA wires is designed and the low-velocity impact behavior is experimental investigated. For contrast, the conventional polymer composite without SMA wires is also tested as the reference laminate. The tests are carried out at three different impact energy levels (30, 60 and 90 J). Moreover, to find out indications for manufacturing of SMA hybrid composites with high impact resistance, four different SMA wires embedded modes are investigated. Visual inspection and scanning electron microscope methods are adopted to identify the damage modes of the impacted samples. Results show that the impact resistance of the hybrid laminates is improved due to the hybridization of SMA wires. The most effective impact resistance of the SMA hybrid composites can be obtained by incorporating the SMA wires with one layer between the front two plies and another layer between the bottom two plies into the composite structure. Full article
(This article belongs to the Special Issue Polymer Hybrid Materials)
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Open AccessArticle High-Strength Nanocomposite Hydrogels with Swelling-Resistant and Anti-Dehydration Properties
Polymers 2018, 10(9), 1025; https://doi.org/10.3390/polym10091025
Received: 2 July 2018 / Revised: 3 September 2018 / Accepted: 13 September 2018 / Published: 14 September 2018
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Abstract
Hydrogels with excellent mechanical properties have potential for use in various fields. However, the swelling of hydrogels under water and the dehydration of hydrogels in air severely limits the practical applications of high-strength hydrogels due to the influence of air and water on
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Hydrogels with excellent mechanical properties have potential for use in various fields. However, the swelling of hydrogels under water and the dehydration of hydrogels in air severely limits the practical applications of high-strength hydrogels due to the influence of air and water on the mechanical performance of hydrogels. In this study, we report on a kind of tough and strong nanocomposite hydrogels (NC-G gels) with both swelling-resistant and anti-dehydration properties via in situ free radical copolymerization of acrylic acid (AA) and N-vinyl-2-pyrrolidone (VP) in the water-glycerol bi-solvent solutions containing small amounts of alumina nanoparticles (Al2O3 NPs) as the inorganic cross-linking agents. The topotactic chelation reactions between Al2O3 NPs and polymer matrix are thought to contribute to the cross-linking structure, outstanding mechanical performance, and swelling-resistant property of NC-G gels, whereas the strong hydrogen bonds between water and glycerol endow them with anti-dehydration capacity. As a result, the NC-G gels could maintain mechanical properties comparable to other as-prepared high-strength hydrogels when utilized both under water and in air environments. Thus, this novel type of hydrogel would considerably enlarge the application range of hydrogel materials. Full article
(This article belongs to the Special Issue Smart and Functional Elastomers, Hydrogels, and Ionogels)
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Open AccessArticle Hyperbranched Liquid Crystals Modified with Sisal Cellulose Fibers for Reinforcement of Epoxy Composites
Polymers 2018, 10(9), 1024; https://doi.org/10.3390/polym10091024
Received: 15 August 2018 / Revised: 8 September 2018 / Accepted: 10 September 2018 / Published: 14 September 2018
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Abstract
Well-defined functionalized sisal cellulose fibers (SCFs) grafted on hyperbranched liquid crystals (HLP) were synthesized to improve the compatibility between SCFs and epoxy resin (EP). The influence of SCFs-HLP on the mechanical and thermal properties of SCFs-HLP/EP composites was studied. The results show that
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Well-defined functionalized sisal cellulose fibers (SCFs) grafted on hyperbranched liquid crystals (HLP) were synthesized to improve the compatibility between SCFs and epoxy resin (EP). The influence of SCFs-HLP on the mechanical and thermal properties of SCFs-HLP/EP composites was studied. The results show that the mechanical properties of SCFs-HLP/EP composites were enhanced distinctly. Particularly, compared with EP, impact strength, tensile strength, and flexural strength of composites with 4.0 wt % SCFs-HLP were 38.3 KJ·m−2, 86.2 MPa, and 150.7 MPa, increasing by 118.7%, 55.6%, and 89.6%, respectively. As well, the glass transition temperature of the composite material increased by 25 °C. It is hope that this work will inform ongoing efforts to exploit more efficient methods to overcome the poor natural fiber/polymer adhesion in the interface region. Full article
(This article belongs to the Special Issue Modification of Natural Fibres to Improve Biocomposites Performances)
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Open AccessArticle Conductive Cotton by In Situ Laccase-Polymerization of Aniline
Polymers 2018, 10(9), 1023; https://doi.org/10.3390/polym10091023
Received: 10 August 2018 / Revised: 10 September 2018 / Accepted: 12 September 2018 / Published: 14 September 2018
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Abstract
Conductive cotton fabrics were obtained via in situ aniline polymerization by laccase from Myceliophthora thermophila under mild reaction conditions without the addition of strong proton acids. The reactions were conducted using two types of reactors, namely a water bath (WB) and an ultrasonic
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Conductive cotton fabrics were obtained via in situ aniline polymerization by laccase from Myceliophthora thermophila under mild reaction conditions without the addition of strong proton acids. The reactions were conducted using two types of reactors, namely a water bath (WB) and an ultrasonic bath (US), and the role of a mediator, 1-hydroxybenzotriazol (HBT), on the laccase-assisted polymerization of aniline was investigated. A similar polymerization degree was obtained when using both reactors—however, the ultrasonic bath allowed the experiments to be conducted in shorter periods of time (24 h for WB vs. 2 h for US). The data obtained also revealed that the mediator (1-hydroxybenzotriazol-HBT) played a crucial role in aniline oxidation. A higher conversion yield and polymerization degree were obtained when the reaction was conducted in the presence of this compound, as confirmed by MALDI-TOF analysis. The cotton fabrics coated with polyaniline presented deep coloration and conductivity, especially when the mediator was included on the reactional system. The results obtained are a step forward in the enzymatic polymerization of aniline with the purpose of obtaining coloured conductive textile surfaces, with potential applications in wearable electronics. Full article
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Open AccessArticle Enhanced Mechanical and Water Absorption Properties of Rice Husk-Derived Nano-SiO2 Reinforced PHBV Composites
Polymers 2018, 10(9), 1022; https://doi.org/10.3390/polym10091022
Received: 14 August 2018 / Revised: 5 September 2018 / Accepted: 6 September 2018 / Published: 13 September 2018
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Abstract
Poly(3-hydroxybutyrate–co–3-hydroxyvalerate) (PHBV) is a biodegradable polymer and has several potential applications. Herein, we have used a rich biomass resource, rice husk, to obtain rice husk nano-SiO2 (RHNS) and prepared RHNS/PHBV composites by using hot-press molding. The results showed that the
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Poly(3-hydroxybutyrate–co–3-hydroxyvalerate) (PHBV) is a biodegradable polymer and has several potential applications. Herein, we have used a rich biomass resource, rice husk, to obtain rice husk nano-SiO2 (RHNS) and prepared RHNS/PHBV composites by using hot-press molding. The results showed that the amorphous nature of spherical nano-SiO2 particles with an average diameter of 40–80 nm was obtained. The tensile strength and flexural strength of the RHNS/PHBV-3 composite reached up to 23.515 and 75.669 MPa, respectively, corresponding to an increase of 33.65% and 15.54% as compared to pure PHBV. The enhanced mechanical properties of the RHNS/PHBV composite can be attributed to the uniform dispersion and strong interfacial bonding of RHNS with the PHBV matrix. In addition, the water absorption rate of the RHNS/PHBV composite increased from 0.26% to 0.35% and the water swelling ratio followed the given order in different directions: thickness > width > length. Furthermore, the initial degradation temperature and residual rate of combustion at 700 °C of the composites increased with higher content of RHNS, which represents the enhanced thermal stability of RHNS/PHBV composites. In summary, RHNS served as an excellent reinforcement and RHNS/PHBV composites have shown promising properties for various potential applications. Full article
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Open AccessArticle Preparation and Evaluation of Metronidazole-Loaded Pectin Films for Potentially Targeting a Microbial Infection Associated with Periodontal Disease
Polymers 2018, 10(9), 1021; https://doi.org/10.3390/polym10091021
Received: 20 August 2018 / Accepted: 4 September 2018 / Published: 13 September 2018
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Abstract
The objective of this study was to develop the metronidazole loaded high and low methoxyl pectin films (HM-G-MZ and LM-G-MZ) for the treatment of periodontal disease. The films were prepared by pectin 3% w/v, glycerin 40% w/v,
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The objective of this study was to develop the metronidazole loaded high and low methoxyl pectin films (HM-G-MZ and LM-G-MZ) for the treatment of periodontal disease. The films were prepared by pectin 3% w/v, glycerin 40% w/v, and metronidazole 5% w/v. The developed films were characterized by scanning electron microscope and evaluated for thickness, weight variation, and elasticity. The developed films showing optimal mechanical properties were selected to evaluate radial swelling properties, in vitro release of metronidazole and the antimicrobial activity against Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans by the disc diffusion method. The results demonstrated that LM-MZ and HM-G-MZ films were colorless and yellowish color, respectively, with the film thickness around 0.36–0.38 mm. Furthermore, both films exhibited good elasticity with low puncture strength (1.63 ± 0.37 and 0.84 ± 0.03 N/mm2, respectively) and also showed slight increase in radial swelling, so that they could be easily inserted and fitted into the periodontal pocket during a clinical use. However, HM-G-MZ showed a decrease in radial swelling after 1 h due to the film erosion. The in vitro release study of LM-G-MZ showed a burst release that was initially followed by a slow release rate profile, capable to maintain the therapeutic level in periodontal pocket for seven days, whereas HM-G-MZ showed an immediate release profile. The cumulative percentage of metronidazole release from HM-G-MZ was less than LM-G-MZ during the first 5 min as metronidazole was in a crystalline form inside HM-G-MZ film. For antimicrobial activity test, both films showed the inhibitory effect against P. gingivalis and A. actinomycetemcomitans, and there was no difference in the inhibition zone between LM-G-MZ and HM-G-MZ. The present study showed, for the first time, that low methoxyl pectin film containing glycerin and metronidazole could be potentially considered as a promising clinical tool for the drug delivery via intra-periodontal pocket to target an oral disease that is associated with polymicrobial infection. Full article
(This article belongs to the Special Issue Polymer-based Systems for Controlled Release and Targeting of Drugs)
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Open AccessCommunication Nanoscale Mechanical Properties and Indentation Recovery of PI@GO Composites Measured Using AFM
Polymers 2018, 10(9), 1020; https://doi.org/10.3390/polym10091020
Received: 24 August 2018 / Revised: 12 September 2018 / Accepted: 13 September 2018 / Published: 13 September 2018
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Abstract
Polyimide@graphene oxide (PI@GO) composites were prepared by way of a simple solution blending method. The nanoscale hardness and Young’s modulus of the composites were measured using nanoindentation based on atomic force microscopy (AFM). A nanoscale hardness of ~0.65 GPa and an elastic modulus
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Polyimide@graphene oxide (PI@GO) composites were prepared by way of a simple solution blending method. The nanoscale hardness and Young’s modulus of the composites were measured using nanoindentation based on atomic force microscopy (AFM). A nanoscale hardness of ~0.65 GPa and an elastic modulus of ~6.5 GPa were reached with a load of ~55 μN. The indentation recovery on the surface of PI@GO was evaluated. The results show that relatively low GO content can remarkably improve the nanoscale mechanical properties of PI. Full article
(This article belongs to the Special Issue Polymer Clay Nano-composites)
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Open AccessArticle Thermal Stability and Flame Retardancy of Polypropylene Composites Containing Siloxane-Silsesquioxane Resins
Polymers 2018, 10(9), 1019; https://doi.org/10.3390/polym10091019
Received: 30 August 2018 / Revised: 9 September 2018 / Accepted: 10 September 2018 / Published: 13 September 2018
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Abstract
A novel group of silsesquioxane derivatives, which are siloxane-silsesquioxane resins (S4SQ), was for the first time examined as possible flame retardants in polypropylene (PP) materials. Thermal stability of the PP/S4SQ composites compared to the S4SQ resins and neat PP was estimated using thermogravimetric
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A novel group of silsesquioxane derivatives, which are siloxane-silsesquioxane resins (S4SQ), was for the first time examined as possible flame retardants in polypropylene (PP) materials. Thermal stability of the PP/S4SQ composites compared to the S4SQ resins and neat PP was estimated using thermogravimetric (TG) analysis under nitrogen and in air atmosphere. The effects of the non-functionalized and n-alkyl-functionalized siloxane-silsesquioxane resins on thermostability and flame retardancy of PP materials were also evaluated by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) and by cone calorimeter tests. The results revealed that the functionalized S4SQ resins may form a continuous ceramic layer on the material surface during its combustion, which improves both thermal stability and flame retardancy of the PP materials. This beneficial effect was observed especially when small amounts of the S4SQ fillers were applied. The performed analyses allowed us to propose a possible mechanism for the degradation of the siloxane-silsesquioxane resins, as well as to explain their possible role during the combustion of the PP/S4SQ composites. Full article
(This article belongs to the Special Issue POSS-Based Polymers)
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Open AccessArticle Alternating Magnetic Field-Triggered Switchable Nanofiber Mesh for Cancer Thermo-Chemotherapy
Polymers 2018, 10(9), 1018; https://doi.org/10.3390/polym10091018
Received: 31 July 2018 / Revised: 4 September 2018 / Accepted: 12 September 2018 / Published: 13 September 2018
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Abstract
We have developed a smart anti-cancer fiber mesh that is able to control tumor-killing activity against lung adenocarcinoma precisely. The mesh is capable of carrying large loads of chemotherapeutic drug, paclitaxel (PTX), as well as magnetic nanoparticles (MNPs). The mesh generates heat when
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We have developed a smart anti-cancer fiber mesh that is able to control tumor-killing activity against lung adenocarcinoma precisely. The mesh is capable of carrying large loads of chemotherapeutic drug, paclitaxel (PTX), as well as magnetic nanoparticles (MNPs). The mesh generates heat when the loaded MNPs are activated in an alternating magnetic field (AMF). The mesh is thermo-responsive, so the heat generated can be also used to trigger PTX release from the mesh. An electrospinning method was employed to fabricate the mesh using a copolymer of N-isopropylacrylamide and N-hydroxymethylacrylamide, the phase transition temperature of which was adjusted to the mild-hyperthermia temperature range around 43 °C. In vitro anti-tumor studies demonstrated that both MNP- and PTX-loaded mesh killed about 66% of cells, whereas only PTX-loaded mesh killed about 43% of cells. In a mouse lung cancer model, the thermo-chemotherapy combo displayed enhanced anti-tumor activity and the systemic toxic effects on mice were eliminated due to local release of the chemotherapeutic agents. The proposed fiber system might provide a blueprint to guide the design of the next generation of local drug delivery systems for safe and effective cancer treatment. Full article
(This article belongs to the Special Issue Polymeric Micro/Nanoparticles for Bio-Medical Applications)
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Open AccessArticle Mechanism of Yellowing: Carbonyl Formation during Hygrothermal Aging in a Common Amine Epoxy
Polymers 2018, 10(9), 1017; https://doi.org/10.3390/polym10091017
Received: 29 August 2018 / Revised: 8 September 2018 / Accepted: 12 September 2018 / Published: 13 September 2018
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Abstract
Epoxies are often exposed to water due to rain and humid air environments. Epoxy yellows during its service time under these conditions, even when protected from UV radiation. The material’s color is not regained upon redrying, indicating irreversible aging mechanisms. Understanding what causes
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Epoxies are often exposed to water due to rain and humid air environments. Epoxy yellows during its service time under these conditions, even when protected from UV radiation. The material’s color is not regained upon redrying, indicating irreversible aging mechanisms. Understanding what causes a discoloration is of importance for applications where the visual aspect of the material is significant. In this work, irreversible aging mechanisms and the cause of yellowing were identified. Experiments were performed using a combination of FT-NIR, ATR-FT-IR, EDX, HR-ICP-MS, pH measurements, optical microscopy, SEM, and DMTA. Such extensive material characterization and structured logic of investigation, provided the necessary evidence to investigate the long-term changes. No chain scission (hydrolysis or oxidation-induced) was present in the studied common DGEBA/HDDGE/IPDA/POPA epoxy, whilst it was found that thermo-oxidation and leaching occurred. Thermo-oxidation involved evolution of carbonyl groups in the polymeric carbon–carbon backbone, via nucleophilic radical attack and minor crosslinking of the HDDGE segments. Four probable reactive sites were identified, and respective reactions were proposed. Compounds involved in leaching were identified to be epichlorohydrin and inorganic impurities but were found to be unrelated to yellowing. Carbonyl formation in the epoxy backbone due to thermo-oxidation was the cause for the yellowing of the material. Full article
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Open AccessArticle Improve the Performance of Soy Protein-Based Adhesives by a Polyurethane Elastomer
Polymers 2018, 10(9), 1016; https://doi.org/10.3390/polym10091016
Received: 19 July 2018 / Revised: 9 September 2018 / Accepted: 11 September 2018 / Published: 13 September 2018
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Abstract
The purpose of this study was to improve the performance of soy protein isolate (SPI) adhesives using a polyurethane elastomer. Triglycidylamine (TGA), SPI, thermoplastic polyurethane elastomer (TPU), and γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) were used to develop a novel SPI-based adhesive. The residual rate, functional
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The purpose of this study was to improve the performance of soy protein isolate (SPI) adhesives using a polyurethane elastomer. Triglycidylamine (TGA), SPI, thermoplastic polyurethane elastomer (TPU), and γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) were used to develop a novel SPI-based adhesive. The residual rate, functional groups, thermal stability, and fracture surface micrographs of the cured adhesives were characterized. Three-ply plywood was fabricated, and the dry/wet shear strength was determined. The experimental results suggested that introducing 2% TGA improved the residual rate of the SPI/TGA adhesive by 4.1% because of the chemical cross-linking reaction between epoxy groups and protein molecules. Incorporating 7% TPU into the SPI/TGA adhesive, the residual rate of the adhesive increased by 5.2% and the dry/wet shear strength of plywood bonded by SPI/TGA/TPU adhesive increased by 10.7%/67.7%, respectively, compared with that of SPI/TGA adhesive. When using KH-560 and TPU together, the residual rate of the adhesive improved by 0.9% compared with that of SPI/TGA/TPU adhesive. The dry and wet shear strength of the plywood bonded by the SPI/TGA/TPU/KG-560 adhesive further increased by 23.2% and 23.6% respectively when compared with that of SPI/TGA/TPU adhesive. TPU physically combined with the SPI/TGA adhesive to form a interpenetration network and KH-560 acted as a bridge to connect TPU and SPI/TGA to form a joined crosslinking network, which improved the thermo stability/toughness of the adhesive and created a uniform ductile fracture section of the adhesive. Full article
(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)
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