scholarly journals Relaxation Dynamics in Polyethylene Glycol/Modified Hydrotalcite Nanocomposites

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1182 ◽  
Author(s):  
Rossella Arrigo ◽  
Diego Antonioli ◽  
Massimo Lazzari ◽  
Valentina Gianotti ◽  
Michele Laus ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Polymer Matrix ◽  
Complex Viscosity ◽  
Gas Chromatography Mass Spectrometry ◽  
Hydroxyl Groups ◽  
Thermal Treatments ◽  
Relaxation Dynamics ◽  
Unusual Behavior ◽  
Melt Mixing ◽  
Grafting Reactions

Polyethylene glycol-based nanocomposites containing an organo-modified hydrotalcite with loadings ranging from 0.5 to 5 wt.% were prepared by melt mixing performed just above the melting point of the polymer matrix. In these conditions, the dispersion of the nanofiller within the polymer matrix was quite homogeneous as revealed by TEM analyses. The effect of various thermal treatments and filler loadings was thoroughly investigated by means of rheological, morphological and gas chromatography-mass spectrometry, hyphenated to thermogravimetry analysis tests. Unfilled polyethylene glycol exhibited a continuous decrease in complex viscosity upon heating. In contrast, the complex viscosity of nanocomposites containing nanofiller loadings higher than 1 wt.% showed first a decrease, followed by an increase in the complex viscosity as the temperature increases, exhibiting a minimum between 130 and 140 °C. Annealing at 180 °C for different times further increased the viscosity of the system. This unusual behavior was explained by the occurrence of grafting reactions between the –OH terminal groups of the polyethylene glycol chains and the hydroxyl groups of the organo-modified filler, thus remarkably affecting the relaxation dynamics of the system.

scholarly journals Effect of Silane Functionalization on Properties of Poly(Lactic Acid)/Palygorskite Nanocomposites

Inorganics ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 3
Author(s):  
Anton Kasprzhitskii ◽  
Georgy Lazorenko ◽  
Alexander Kruglikov ◽  
Irina Kuchkina ◽  
Vadim Gorodov
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Polymer Matrix ◽  
Covalent Bond ◽  
Poly Lactic Acid ◽  
Hydroxyl Groups ◽  
Good Dispersion ◽  
Melt Compounding

Poly(lactic acid) (PLA)/palygorskite (Paly) nanocomposites were prepared using the melt compounding technique. Paly modified by 3-aminopropyltriethoxysilane (APTES) and vinyltrimethoxysilane (VTMS) was used as nanofiller for PLA with concentrations in the 1–7 wt% range. It has been found that the functionalization allows a covalent bond between the hydroxyl groups of the Paly and the PLA matrix, evidenced by the improvement in mechanical properties. Paly modification with VTMS has better properties compared with Pale modification with APTES. This indicates a better adhesion between the Paly-VTMS and PLA matrix, and a good dispersion of the nanofiller in the polymer matrix.

Enhanced dielectric performance and energy storage density of polymer/graphene nanocomposites prepared by dual fabrication

2018 ◽  
Vol 33 (2) ◽  
pp. 270-285 ◽  
Author(s):  
UO Uyor ◽  
API Popoola ◽  
OM Popoola ◽  
VS Aigbodion
Keyword(s):  
Energy Storage ◽  
Polymer Matrix ◽  
Vinylidene Fluoride ◽  
Energy Storage Materials ◽  
Energy Storage Density ◽  
Melt Mixing ◽  
Graphene Nanocomposites ◽  
Storage Density ◽  
Solution Blending ◽  
Dielectric Performance

Polymer/graphene nanocomposites (PGNs) have shown great potential as dielectric and energy storage materials. However, insolubility of graphene in most solvents, hydrophobic behaviour and poor dispersion in polymer matrix restrict wider fabrications and applications of PGNs. In this study, we present co-fabricated PGNs engineered by solution blending and melt compounding methods with improved dielectric performance. Further processing of PGNs by melt mixing after solution blending not only improved dispersion of graphene in the matrix but also ensured good interfacial interaction of the composites’ constituents and reduction of oxygen content in PGNs. Graphene nanoplatelets used in this study was slightly functionalized (fGNPs) to enhance dispersion in the polymer matrix. It was later characterized using Fourier transform infrared (FTIR) and Raman spectrometer. Scanning electron microscope (SEM) was used in morphological study of the fabricated composites. Dielectric properties, electrical conductivity, breakdown strength and energy storage capacity of the fabricated composites were investigated. The results obtained showed well-dispersed fGNPs in poly (vinylidene fluoride) (PVDF) matrix and improved dielectric performance. For instance, with 3.34 wt% and 6.67 wt% fGNPs co-fabricated composites, dielectric constant increased from about 9 for neat PVDF to 9930 and 38,418 at 100 Hz, respectively. While 7588 and 12,046 were respectively measured for solution blended-only composites at similar fGNPs content. These resulted to about 176.9% and 376.4% increase in energy storage density with 3.34 wt% and 6.67 wt% fGNPs co-fabricated composites when compared to their counterparts. These results were also credited to strong bonding, reduction of oxygen and recovered graphene structure by melt-mixing approach.

scholarly journals A Robust, Tough and Multifunctional Polyurethane/Tannic Acid Hydrogel Fabricated by Physical-Chemical Dual Crosslinking

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 239 ◽  
Author(s):  
Jie Wen ◽  
Xiaopeng Zhang ◽  
Mingwang Pan ◽  
Jinfeng Yuan ◽  
Zhanyu Jia ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Polyethylene Glycol ◽  
Hydrogen Bonds ◽  
Tannic Acid ◽  
Hydroxyl Groups ◽  
Self Healing ◽  
Physical Chemical ◽  
Biomedical Field ◽  
Physical Crosslinking

Commonly synthetic polyethylene glycol polyurethane (PEG–PU) hydrogels possess poor mechanical properties, such as robustness and toughness, which limits their load-bearing application. Hence, it remains a challenge to prepare PEG–PU hydrogels with excellent mechanical properties. Herein, a novel double-crosslinked (DC) PEG–PU hydrogel was fabricated by combining chemical with physical crosslinking, where trimethylolpropane (TMP) was used as the first chemical crosslinker and polyphenol compound tannic acid (TA) was introduced into the single crosslinked PU network by simple immersion process. The second physical crosslinking was formed by numerous hydrogen bonds between urethane groups of PU and phenol hydroxyl groups in TA, which can endow PEG–PU hydrogel with good mechanical properties, self-recovery and a self-healing capability. The research results indicated that as little as a 30 mg·mL−1 TA solution enhanced the tensile strength and fracture energy of PEG–PU hydrogel from 0.27 to 2.2 MPa, 2.0 to 9.6 KJ·m−2, respectively. Moreover, the DC PEG–PU hydrogel possessed good adhesiveness to diverse substrates because of TA abundant catechol groups. This work shows a simple and versatile method to prepare a multifunctional DC single network PEG–PU hydrogel with excellent mechanical properties, and is expected to facilitate developments in the biomedical field.

Biocompatibility and Functional Performance of a Polyethylene Glycol Acid-Grafted Cellulosic Membrane for Hemodialysis

2000 ◽  
Vol 23 (6) ◽  
pp. 356-364 ◽  
Author(s):  
V. Sirolli ◽  
S. Di Stante ◽  
S. Stuard ◽  
L. Di Liberato ◽  
L. Amoroso ◽  
...  
Keyword(s):  
Polyethylene Glycol ◽  
Functional Performance ◽  
Sialyl Lewis X ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Dialysis Session ◽  
Cellulose Diacetate ◽  
Activation Markers ◽  
Surface Hydroxyl ◽  
Cellular Expression

In order to improve the biochemical reactivity of the cellulose polymer, which is mainly attributed to the presence of surface hydroxyl groups, derivatized cellulosic membranes have been engineered replacing or masking some or all of the hydroxyl groups in the manufacturing process of the membrane. The present study was set up to analyze both biocompatibility and functional performance of two different derivatized cellulosic membranes (cellulose diacetate; polyethylene glycol, PEG, acid-grafted cellulose) as compared to a synthetic membrane (polymethylmethacrylate, PMMA). Cellulose diacetate is prepared by substituting hydroxyl groups with acetyl groups; PEG cellulose is obtained by grafting PEG chains onto the cellulosic polymer with a smaller amount of substitution than cellulose diacetate. While the three dialyzers provided similar urea and creatinine removal, the dialyzer containing cellulose diacetate showed a reduced ability to remove β2-microglobulin compared to that containing PEG cellulose or PMMA. A transient reduction in leukocyte count was observed for both derivatized cellulosic membranes. The neutrophil and monocyte counts throughout the entire dialysis session showed a closer parallelism with the cellular expression of the adhesive receptor CD15s (sialyl-Lewis x molecole) than with CD11b/CD18 expression. Platelet activation, as indicated by the percentage of cells expressing the activation markers CD62P (P-selectin) and CD63 (gp53), occurred with all membranes at 15 min of dialysis and also with PMMA at 30 min. An increased formation of platelet-neutrophil and platelet-monocyte coaggregates was found at 15 and 30 min during dialysis with cellulose diacetate and PMMA but not with PEG cellulose. Generally in concomitance with the increase in platelet-neutrophil coaggregates, an increased hydrogen peroxide production by neutrophils occurred. Our results indicate that derivatizing cellulose may represent a useful approach to improve the biocompatibility of the cellulose polymer, though some homeostatic reactions remain activated. Our results also indicate that there may be a great variability in the biocompatibility profile of derivatized cellulosic membranes which most likely stem from the different type of structural modification rather than from the degree of hydroxyl group replacement.

Thermal and Electrical Conductivities of Carbon Fibers and Carbon Nanotubes Incorporated Polyurethanes Composites

2010 ◽  
Vol 442 ◽  
pp. 349-355 ◽  
Author(s):  
Shahrul A. Abdullah ◽  
Lars Frormann ◽  
Anjum Saleem
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Carbon Fibers ◽  
Polymer Matrix ◽  
Filler Concentration ◽  
Melt Mixing ◽  
Electrical Conductivities ◽  
The Matrix ◽  
Polyurethane Composites

Single filler polyurethane composites with carbon fibers (CFs) and multi-walled carbon nanotubes (MWNTs) were prepared by melt mixing methods and its thermal as well as electrical resistivity characteristics were investigated. The influences of fillers and mixing methods on thermal and electrical conductivity of CF/- and MWNT/polyurethane composites were investigated and the result shows that the addition of carbon fillers improved the thermal conductivity of the polyurethane composites. Higher filler concentration results in better thermal conductivity because better formation of thermally conductive networks along polymer matrix to ensure the thermal was conducted through the matrix and the network along the polymer composites. The presence of carbon additives improves the electrical resistivity of the materials as well. The present study revealed the potential of carbon as agent for better thermal and electrical conductivities and their properties depend strongly on the dispersion and distribution of the fillers in the polymer matrix.

Electrical and rheological properties of carbon black and carbon fiber filled low-density polyethylene/ethylene vinyl acetate composites

2018 ◽  
Vol 25 (4) ◽  
pp. 715-723 ◽  
Author(s):  
Xingchi Xu ◽  
Tingwei Wang
Keyword(s):  
Carbon Fiber ◽  
Carbon Black ◽  
Vinyl Acetate ◽  
Great Influence ◽  
Complex Viscosity ◽  
Ethylene Vinyl Acetate ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Melt Mixing ◽  
Significant Difference

Abstract In this study conductive composites of low-density polyethylene (LDPE)/ethylene-vinyl acetate (EVA) filled with carbon black (CB) and carbon fiber (CF) were prepared by melt-mixing method. The morphological, rheological, and electrical properties of CB filled composites were compared with CF filled composites by digital multimeter, scanning electron microscope, rotational rheometer, etc. The composites filled with different fillers have same percolation threshold but the EVA concentration has different effect on the two systems. For CB filled composites the increase in EVA concentration decreased resistivity first and reached lowest point when the LDPE:EVA ratio was 70:30; then the resistivity increased, but for CF filled composites the resistivity continued to decrease. The differences were caused by the diverse morphological and filler distribution of two different composite systems. The rheological behaviors of two types of composites also had significant difference; the value of complex viscosity of CB filled composites was about two orders of magnitude more than CF filled composites in low frequency region. It was because CB particles was nano-scale and had large surface area, so it had great influence on the value of complex viscosity of composites.

scholarly journals Efecto de la adición de copolímeros reactivos a mezclas de PLA/ATP

2020 ◽  
pp. 20-26
Author(s):  
Maria Cristina KANTUN-UICAB ◽  
Isis RODRÍGUEZ-SÁNCHEZ ◽  
Francisco Javier RODRÍGUEZ-GONZÁLEZ ◽  
Juan Gregorio HORTELANO-CAPETILLO
Keyword(s):  
Epoxy Group ◽  
Thermoplastic Starch ◽  
Hydroxyl Groups ◽  
Melt Mixing ◽  
Acrylic Copolymer ◽  
Reactive Compatibilization ◽  
Torque Rheometry ◽  
Viscosity Increase ◽  
End Groups ◽  
Acrylic Copolymers

In this work, the reactive compatibilization of Polylactic Acid/Thermoplastic Starch (PLA/TPS, 80/20% w/w) blends using acrylic copolymers of methyl methacrylate-glycidyl methacrylate (MMA-GMA) was examined. The compatibilization was studied using torque rheometry, thermal analysis (DSC), Scanning Electron Microscopy (SEM) and mechanical properties. During melt mixing, the torque of PLA/TPS blends decreased, this was related to the breakup of starch chains. The addition of MMA-GMA copolymer increased the torque during the mixing period. This torque increasing is evidence of a viscosity increase and it was related to the reactions between the epoxy group present in the acrylic copolymer, the end-groups of the PLA and TPS hydroxyl groups. The morphologies of the compatibilized blends showed a decrease in the particle size of the TPS domains and an increase in elongation of 30%. The reactive compatibilization is an interesting technique to expand the property range of PLA materials, which can potentially substitute oil-based materials.

scholarly journals Impact of the Graphite Fillers on the Thermal Processing of Graphite/Poly(lactic acid) Composites

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5346
Author(s):  
Daniel Kaczor ◽  
Kacper Fiedurek ◽  
Krzysztof Bajer ◽  
Aneta Raszkowska-Kaczor ◽  
Grzegorz Domek ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Polymer Matrix ◽  
Thermal Processing ◽  
Poly Lactic Acid ◽  
Expandable Graphite ◽  
Slight Reduction ◽  
Melt Mixing ◽  
Neat Polymer ◽  
Industrial Grade ◽  
The Impact

To assess the impact of graphite fillers on the thermal processing of graphite/poly(lactic acid) (PLA) composites, a series of the composite samples with different graphite of industrial grade as fillers was prepared by melt mixing. The average size of the graphite grains ranged between 100 µm and 6 µm. For comparative purposes, one of the carbon fillers was expandable graphite. Composites were examined by SEM, FTIR, and Raman spectroscopy. As revealed by thermogravimetric (TG) analyses, graphite filler slightly lowered the temperature of thermal decomposition of the PLA matrix. Differential scanning calorimetry (DSC) tests showed that the room temperature crystallinity of the polymer matrix is strongly affected by the graphite filler. The crystallinity of the composites determined from the second heating cycle reached values close to 50%, while these values are close to zero for the neat polymer. The addition of graphite to PLA caused a slight reduction in the oxidation induction time (OIT). The melt flow rate (MFR) of the graphite/PLA composites was lower than the original PLA due to an increase in flow resistance associated with the high crystallinity of the polymer matrix. Expandable graphite did not cause changes in the structure of the polymer matrix during thermal treatment. The crystallinity of the composite with this filler did not increase after first heating and was close to the neat PLA MFR value, which was extremely high due to the low crystallinity of the PLA matrix and delamination of the filler at elevated temperature.

Conductivity of Porous Phosphate-Silicate Glass Synthesized with Non-Ionic Surfactant

2019 ◽  
Vol 58 ◽  
pp. 118-124
Author(s):  
Xiao Ting Zhang ◽  
Fei Peng Zhang ◽  
Xiao Wang ◽  
Liu Shuan Yang
Keyword(s):  
Polyethylene Glycol ◽  
Pore Size ◽  
Silicate Glass ◽  
Volume Ratio ◽  
Adsorbed Water ◽  
Ionic Surfactant ◽  
Hydroxyl Groups ◽  
Phosphate Silicate ◽  
Porous Phosphate ◽  
Nano Size

Porous, phosphate-silicate glass with high-conductivity and nano-size pores was synthesized through a xero-gel route, using non-ionic surfactant polyethylene glycol monocetyl ether (Brij 56) to control pore size. The influences of Brij 56 concentration on pore size and conductivity under different humidity were studied by measuring conductivity and calculating the volume ratio of adsorbed-water to pore volume. Samples prepared with 0.1 wt% Brij 56 had 5.2 nm pore size, 0.91 volume ratio, and narrower pore size distribution than other samples. The nano-size pores were filled with water, which in pores of 5.2 nm is mostly chemically bonded with the hydroxyl groups on the pore surfaces, resulting in higher conductivity than other samples in high relative humidity (over 55%).

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