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  • 1
    Online Resource
    Online Resource
    The role of nanofillers on the degradation behavior of polylactic acid
    Wiley ; 2012
    In:  Polymer Composites Vol. 33, No. 2 ( 2012-02), p. 282-294
    Details
    In: Polymer Composites, Wiley, Vol. 33, No. 2 ( 2012-02), p. 282-294
    Abstract: This study examines the effect of type and content of various nanofillers on the aging behavior of polylactic acid (PLA)/nanocomposites compared with that of pristine PLA, under specific environmental conditions, namely 80% relative humidity, 40°C temperature, and exposure time up to 6 months. Two different types of nanosized fillers (silica and montmorillonite, MMT) at three different weight fractions as well their mixtures were used for this purpose. The role of the various nanofillers on the aging of pristine PLA and its nanocomposites was investigated in terms of several experimental techniques including Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and tensile testing. All studied samples, except those of PLA/MMT/Si nanocomposites, exhibited the same trend in properties during aging. In particular, no significant changes are noted after 1 month of aging. The materials after 3 months of aging experienced a dramatic lowering of the stress–strain curve, whereas at 6 months a reverse effect was observed. Comparing the effect of nanofiller types on the degradation, one could conclude that PLA/MMT nanocomposites exhibit a more homogeneous degradation effect, having a higher impact on yield stress in comparison with silica. In contrast, silica has a greater effect in Young's modulus and strain at break, compared with MMT. The peculiar behavior of the PLA/MMT/Si nanocomposites during aging is explained by the hindering action of the mixture of the two nanofillers on the molecular reordering of the PLA chains in the amorphous region. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v33.2
    DOI: 10.1002/pc.21258
    Language: English
    Publisher: Wiley
    Publication Date: 2012
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  • 2
    Online Resource
    Online Resource
    Thermomechanical characterization of basalt fiber reinforced biodegradable polymers
    Wiley ; 2019
    In:  Polymer Composites Vol. 40, No. 11 ( 2019-11), p. 4340-4350
    Details
    In: Polymer Composites, Wiley, Vol. 40, No. 11 ( 2019-11), p. 4340-4350
    Abstract: In the present study the effectiveness of two different biodegradable polymers, namely Polylactic acid (PLA) and ECOVIO (EC), a blend of a copolyester and PLA, as matrix materials for basalt fiber composites, prepared with the “film stacking method” has been investigated. Comparison with composites based on glass fiber mat has also been performed. The addition of basalt fibers, leads to a significant improvement in tensile and flexural strength and stiffness. The ECOVIO/basalt fiber composites exhibited the highest percentage enhancement, while the failure strain decreased dramatically. Therefore, the basalt fabrics appear to have a competitive mechanical performance with the glass fiber mats employed.
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v40.11
    DOI: 10.1002/pc.25295
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 3
    Online Resource
    Online Resource
    Comparing the rheological and reinforcing effects of graphene oxide on glassy and semicrystalline polymers
    Wiley ; 2019
    In:  Polymer Engineering & Science Vol. 59, No. 9 ( 2019-09), p. 1933-1947
    Details
    In: Polymer Engineering & Science, Wiley, Vol. 59, No. 9 ( 2019-09), p. 1933-1947
    Abstract: In this work, a comparative study was performed on nanocomposites, based on three different polymeric matrices, namely polylactic‐acid (PLA), polystyrene (PS), and linear low‐density polyethyelene (mLLDPE), produced by metallocene catalyst. The reinforcing agent was graphene oxide (GO) at one percentage content (1 wt%) and the nanocomposites were prepared by the melt‐mixing procedure, whereas the matrix type employed was found to be decisive in the thermomechanical properties improvement. The thermomechanical performance of these material systems was studied by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, tensile testing, and creep and stress relaxation. The mechanical and rheological performance was comparatively studied, and an attempt was made to relate the macroscopic response with the nanocomposites micromorphology. Furthermore, the tensile response was analyzed by a viscoplastic model, introduced earlier, and the model parameters involved provide additional evidence about the nanocomposites micromorphology. The findings of the comparative study are encouraging, regarding the potential of PLA and mLLDPE as matrices for graphene‐based nanocomposites at higher GO loadings. POLYM. ENG. SCI., 59:1933–1947, 2019. © 2019 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0032-3888 , 1548-2634
    URL: Issue
    URL: Article
    DOI: 10.1002/pen.v59.9
    DOI: 10.1002/pen.25195
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 4
    Online Resource
    Online Resource
    Thermomechanical performance of biodegradable poly (lactic acid)/carbonaceous hybrid nanocomposites: Comparative study
    Wiley ; 2022
    In:  Polymer Composites Vol. 43, No. 4 ( 2022-04), p. 1900-1915
    Details
    In: Polymer Composites, Wiley, Vol. 43, No. 4 ( 2022-04), p. 1900-1915
    Abstract: In the present research, a series of hybrid nanocomposites based on polylactic acid (PLA) matrix and mixtures of graphene oxide (GO) with carbon nanotubes (CNTs) or carbon nanofibers (CNFs), at various loadings, were prepared and experimentally studied. Several experimental techniques were employed to analyze the morphology and the thermomechanical performance of the materials, as well as the dielectric properties. The related experimental data support the conclusion that a synergistic effect is exhibited by the PLA/GO/CNT nanocomposites. This effect was verified by the higher mechanical enhancement, the higher crystallinity and the development of conductive paths into the bulk matrix.
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v43.4
    DOI: 10.1002/pc.26506
    Language: English
    Publisher: Wiley
    Publication Date: 2022
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  • 5
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    Online Resource
    Model Simulation of Creep and Thermal Ratcheting of Engineering Polymers
    Wiley ; 2022
    In:  Macromolecular Theory and Simulations Vol. 31, No. 1 ( 2022-01)
    Details
    In: Macromolecular Theory and Simulations, Wiley, Vol. 31, No. 1 ( 2022-01)
    Abstract: In the present work, the creep response at specific temperatures and stress level of several polymers has been modeled by a viscoelastic model, analyzed in previous works. In particular, the experimental creep results under thermal cycling of polymers used in bolted flange connections, utilized as components of pressure vessel and piping are employed. The analysis is focused on the experimental results for polymeric flange materials like high density polyethylene and three types of gasket materials, namely poly‐tetrafluoroethylene PTFE (expanded e‐ and virgin v‐) and clickable nucleic acid. It has been proved that by the implementation of the model on a simple creep curve at a specific temperature, the model parameters could be evaluated. Hereafter, by imposing a thermal cycling process, two more parameters, associated with thermal ratcheting, could be acquired. It is found that the thermal ratcheting behavior exhibited by the employed materials, could be captured with a good accuracy. Given that the effect of thermal ratcheting on the long‐time performance of polymers in targeted applications is a crucial issue, the research findings in the present work are encouraging for the design of appropriate materials, and the prediction of thermal ratcheting.
    Type of Medium: Online Resource
    ISSN: 1022-1344 , 1521-3919
    URL: Issue
    URL: Article
    DOI: 10.1002/mats.v31.1
    DOI: 10.1002/mats.202100043
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1475028-4
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  • 6
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    Comparative study of PLA nanocomposites reinforced with clay and silica nanofillers and their mixtures
    Wiley ; 2011
    In:  Journal of Applied Polymer Science Vol. 122, No. 3 ( 2011-11-05), p. 1519-1529
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 122, No. 3 ( 2011-11-05), p. 1519-1529
    Type of Medium: Online Resource
    ISSN: 0021-8995
    URL: Article
    DOI: 10.1002/app.34234
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 1491105-X
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  • 7
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    Online Resource
    Structure–properties investigations in hydrophilic nanocomposites based on polyurethane/poly(2–hydroxyethyl methacrylate) semi‐interpenetrating polymer networks and nanofiller densil for biomedical application
    Wiley ; 2016
    In:  Journal of Applied Polymer Science Vol. 133, No. 11 ( 2016-03-15)
    Details
    In: Journal of Applied Polymer Science, Wiley, Vol. 133, No. 11 ( 2016-03-15)
    Abstract: Nanocomposites based on sequential semi–interpenetrating polymer networks (semi–IPNs) of crosslinked polyurethane and linear poly(2‐hydroxyethyl methacrylate) filled with 1–15 wt % of nanofiller densil were prepared and investigated. Nanofiller densil used in an attempt to control the microphase separation of the polymer matrix by polymer–filler interactions. The morphology (SAXS, AFM), mechanical properties (stress–strain), thermal transitions (DSC) and polymer dynamics (DRS, TSDC) of the nanocomposites were investigated. Special attention has been paid to the raising of the hydration properties and the dynamics of water molecules in the nanocomposites in the perspective of biomedical applications. Nanoparticles were found to aggregate partially for higher than 3 and 5 wt % filler loading in semi–IPNs with 17 and 37 wt % PHEMA, respectively. The results show that the good hydration properties of the semi–IPN matrix are preserved in the nanocomposites, which in combination with results of thermal and dielectric techniques revealed also the existence of polymer–polymer and polymer–filler interactions. These interactions results also in the improvement of physical and mechanical properties of the nanocomposites in compare with the neat matrix. The improvement of mechanical properties in combination with hydrophilicity and biocompatibility of nanocomposites are promising for use these materials for biomedical application namely as surgical films for wound treatment and as material for producing the medical devises. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 43122.
    Type of Medium: Online Resource
    ISSN: 0021-8995 , 1097-4628
    URL: Issue
    URL: Article
    DOI: 10.1002/app.v133.11
    DOI: 10.1002/app.43122
    Language: English
    Publisher: Wiley
    Publication Date: 2016
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  • 8
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    Aging of packaging films in the marine environment
    Wiley ; 2019
    In:  Polymer Engineering & Science Vol. 59, No. s2 ( 2019-03)
    Details
    In: Polymer Engineering & Science, Wiley, Vol. 59, No. s2 ( 2019-03)
    Abstract: The present article examines the aging behavior in the marine environment of some representative flexible plastic packaging films including supermarket plastic bags made of low‐density polyethylene (LDPE), polyethylene terephthalate (PET) films, polyamide–polyethylene (PAPE) films and films made of a material under the commercial name Mater‐Bi®. The effect of aging was studied by Fourier transform infrared spectroscopy, differential scanning calorimetry, and tension including creep‐recovery tests. The polyethylene films were not hydrolytically degraded during aging in seawater, and the polyethylene chains did not undergo any substantial chain scission. The PET films after exposure for 8 months in seawater did not suffer any substantial degradation, and the PET chains were plasticized by the absorbed water. After prolonged exposure to seawater (12 months), the PET films started to degrade. The PAPE film underwent extensive chemical and structural changes during aging in seawater as result of plasticization and hydrolysis of the polyamide (PA) component in combination with an eventual loosening of the tie layer. Mater‐Bi® film underwent a severe deterioration during aging in seawater due to the hydrolysis of the starch and polycaprolactone components. All films exhibited a marked degradation of their tensile properties after exposure to accelerating aging conditions under UV radiation. POLYM. ENG. SCI., 59:E432–E441, 2019. © 2019 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0032-3888 , 1548-2634
    URL: Issue
    URL: Article
    DOI: 10.1002/pen.v59.s2
    DOI: 10.1002/pen.25079
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 9
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    Online Resource
    Preparation and thermomechanical characterization of metallocene linear low‐density polyethylene/carbon nanotube nanocomposites
    Wiley ; 2019
    In:  Polymer Composites Vol. 40, No. S2 ( 2019-03)
    Details
    In: Polymer Composites, Wiley, Vol. 40, No. S2 ( 2019-03)
    Abstract: Nanocomposites, based on a metallocene linear low‐density polyethylene matrix (mLLDPE), reinforced with multiwalled carbon nanotubes (CNTs), at various CNT loadings, have been prepared and studied by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, tensile‐electrical testing, and Raman spectroscopy. The melt‐mixing procedure has been applied to prepare the nanocomposites, whereas the polyethylene matrix type (mLLDPE) employed was proved to be decisive in producing nanocomposites with improved thermomechanical/electrical properties, due to a good quality dispersion of the CNTs into the specific bulk matrix. Moreover, the electrical conductivity obtained at a specific CNT loading was analyzed by a model relating the electrical resistance of the CNT/nanocomposites with the effective length of CNTs, and the thickness of the interphase between matrix and CNTs. These quantities are parameters which participate in the tunnel effect. The simulated parameter values were in accordance with the results of the micromechanics modeling. POLYM. COMPOS., 40:E1263–E1273, 2019. © 2018 Society of Plastics Engineers
    Type of Medium: Online Resource
    ISSN: 0272-8397 , 1548-0569
    URL: Issue
    URL: Article
    DOI: 10.1002/pc.v40.s2
    DOI: 10.1002/pc.24961
    Language: English
    Publisher: Wiley
    Publication Date: 2019
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  • 10
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    Synthesis and characterization of polycyanurate/montmorillonite nanocomposites
    Wiley ; 2008
    In:  Journal of Polymer Science Part B: Polymer Physics Vol. 46, No. 11 ( 2008-06), p. 1036-1049
    Details
    In: Journal of Polymer Science Part B: Polymer Physics, Wiley, Vol. 46, No. 11 ( 2008-06), p. 1036-1049
    Abstract: The advantages of cyanate esters (CEs) versus competitor systems such as epoxies and polyimides, as well as the great reinforcing potential of organoclays properly dispersed into a polymeric matrix, have been examined in a series of polycyanurate (PCN)/montmorillonite (MMT) nanocomposites prepared under appropriate polymerization conditions. The curing schedule applied resulted in gradual propagation of polymerization. Through this procedure, the intragallery curing rate becomes comparable to the extragallery one, allowing intercalation before gelation. Systems with clay loadings from 1 to 3% per weight were synthesized, and their morphology and mechanical properties were studied by means of scanning electron microscopy (SEM), atomic force microscopy (AFM), wide angle X‐ray scattering (WAXS), dynamic mechanical analysis (DMA), and tensile tests. Microscopy investigations revealed better dispersion for the 3 wt % system compared to smaller concentrations, in which aggregation and, in some cases, agglomeration were the conspicuous features. Roughness and area analyses revealed more homogeneous dispersion for this nanocomposite. Topology and 3D‐phase images further suggested considerable reduction of the average particle diameters. WAXS analysis showed that the interlayer spacing of nanocomposites was increased compared to pristine MMT, indicating the formation of intercalated structures. On the other hand, tensile strength and elongation at break values displayed abrupt diminution with MMT addition, while Young's modulus exhibited a slight but systematic increment with MMT content. The decreasing glass transition tendency observed for small clay loadings was reversed in the case of 3 wt %, while secondary transitions were practically unaffected by the presence of MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1036–1049, 2008
    Type of Medium: Online Resource
    ISSN: 0887-6266 , 1099-0488
    URL: Issue
    URL: Article
    DOI: 10.1002/polb.v46:11
    DOI: 10.1002/polb.21436
    Language: English
    Publisher: Wiley
    Publication Date: 2008
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