scholarly journals The Effect of Substances of Plant Origin on the Thermal and Thermo-Oxidative Ageing of Aliphatic Polyesters (PLA, PHA)

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1252 ◽  
Author(s):  
Anna Masek ◽  
Malgorzata Latos-Brozio
Keyword(s):  
Color Change ◽  
Softening Temperature ◽  
Scanning Calorimetry ◽  
Aliphatic Polyesters ◽  
Plant Antioxidants ◽  
The Stability ◽  
Cie Lab ◽  
Hindered Amine Light Stabilizers ◽  
Hindered Amines ◽  
Temperature Surface

The stabilization efficiency of flavonoids (rutin and hesperidin) in polyester (polylactide (PLA) and polyhydroxyalkaonate (PHA)) composites under oxygen at high temperature was investigated. The polymer was homogenized with three antioxidants then processed by extrusion. The effects of stabilizers on the following physicochemical properties were investigated: melt flow, Vicat softening temperature, surface energy, and color change (Cie-Lab space). The aim of this study was to improve the stability of aliphatic polyesters by extending and controlling their lifetime. Differential Scanning Calorimetry DSC and Thermogravimetric analysis DTG methods were used to confirm the stabilizing effects (the inhibition of oxidation) of flavonoids (rutin and hesperidin) on the ageing process of biodegradable polymers. The levels of migration of plant antioxidants from PLA and PHA were determined and compared to the industrial stabilizer (Chimassorb 944 UV absorber). Based on this study, a comparable-to-higher efficiency of the proposed flavonoids for the stabilization of polyesters was found when compared to the commercial stabilizers. Thus, in the future, natural plant-derived substances may replace toxic hindered amines, which are commonly used as light stabilizers (HALS—Hindered Amine Light Stabilizers) in the polymer industry.

scholarly journals Integration of Stable Ionic Liquid-Based Nanofluids into Polymer Membranes. Part I: Membrane Synthesis and Characterization

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 607
Author(s):  
Carolina Hermida-Merino ◽  
Fernando Pardo ◽  
Gabriel Zarca ◽  
João M. M. Araújo ◽  
Ane Urtiaga ◽  
...  
Keyword(s):  
Polymer Membranes ◽  
Small Addition ◽  
Polymeric Membranes ◽  
Synthesis And Characterization ◽  
Complete Disappearance ◽  
Optical Profilometry ◽  
Scanning Calorimetry ◽  
Exfoliated Graphene ◽  
The Stability ◽  
Scanning Electron

In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer–IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer–IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNF.

scholarly journals Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 452 ◽  
Author(s):  
Waseem Saeed ◽  
Abdel-Basit Al-Odayni ◽  
Abdulaziz Alghamdi ◽  
Ali Alrahlah ◽  
Taieb Aouak
Keyword(s):  
Titanium Dioxide ◽  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Three Dimensional ◽  
Degree Of Crystallinity ◽  
Simultaneous Occurrence ◽  
Scanning Calorimetry ◽  
Isothermal Crystallization Kinetics ◽  
The Stability ◽  
Kinetics Of

New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading.

scholarly journals Desing of optical chemosensors for detection of cyanide ions in water environments

2019 ◽  
Vol 15 (1) ◽  
pp. 82-87
Author(s):  
Alexandra Alexandrovna Kudrevatykh ◽  
Lyubov Stepanovna Klimenko ◽  
Timofey Petrovich Martyanov
Keyword(s):  
Aqueous Medium ◽  
Absorption Spectra ◽  
Stability Constants ◽  
Molecular Interactions ◽  
Color Change ◽  
Cyanide Ion ◽  
Colorimetric Test ◽  
Optical Chemosensors ◽  
Aqueous Mixture ◽  
The Stability

Molecular interactions with various anions in the form of tetrabutylammonium salts in DMSO and DMSO-aqueous mixture were studied spectrophotometrically. It turned out that the solutions of 1-hydroxy-2-acylaminoanthraquinones in DMSO, originally yellow, became dark purple with the addition of cyanide, fluoride, phosphate, and acetate ions. The addition of other salts did not cause changes in the absorption spectra. When switching to aqueous DMSO, a contrasting color change in the solution was observed only with the addition of the cyanide ion. The stability constants of the complexes and the metrological characteristics of the processes were determined. On the basis of 1hydroxy-2-benzoylaminoanthraquinone, colorimetric test strips were made and tested for the detection of CN-ions in an aqueous medium.

Stability of Ceftazidime and Vancomycin Alone and in Combination in Heparinized and Nonheparinized Peritoneal Dialysis Solution

1994 ◽  
Vol 28 (5) ◽  
pp. 572-576 ◽  
Author(s):  
Leigh M. Vaughan ◽  
Cathy Y. Poon
Keyword(s):  
Peritoneal Dialysis ◽  
Room Temperature ◽  
Color Change ◽  
Hplc Assay ◽  
Time Points ◽  
Stability Indicating ◽  
Dialysis Solution ◽  
Peritoneal Dialysis Solution ◽  
The Stability

OBJECTIVE: To examine the stability of ceftazidime, vancomycin, and heparin, alone and in combination, in dialysis solution over six days at three temperatures. DESIGN: Nine 250-mL Dianeal PD-2 dextrose 1.5% bags were prepared with ceftazidime, vancomycin, and heparin alone and in combination at set concentrations of 100 μg/mL, 50 μg/mL, and 1 unit/mL, respectively. Three bags of each mixture were stored at 4, 25, and 37°C. Duplicate samples for analysis were removed from each bag at the following time points: premix, 0, 12, 24, 48, 72, 96, 120, and 144 hours. MAIN OURCOME MEASURES: Each sample was examined visually for signs of cloudiness and precipitation. Each sample was analyzed by stability-indicating HPLC assay for ceftazidime and vancomycin, with stability defined as less than 10 percent degradation of drug overtime. RESULTS: No color change or precipitation was observed in any bag. Vancomycin with or without heparin was stable for 5–6 days at 4, 25, and 37°C. Ceftazidime with and without heparin was stable for 6 days at 4°C, 4 days at 25°C, and less than 12 hours at 37 °C. Vancomycin plus ceftazidime with and without heparin was stable for 6 days at 4 °C and 25°C, and 4–5 days at 37 °C, Ceftazidime plus vancomycin with or without heparin was stable for 6 days at 4°C, 2–3 days at 25°C, and 12 hours at 37 °C. CONCLUSIONS: Bulk preparations of ceftazidime and vancomycin, alone and in combination and with or without heparin in Dianeal PD dextrose 1.5% solution, are sufficiently stable for use up to 6 days under refrigeration or 48 hours at room temperature.

scholarly journals Study on the Structure and Dielectric Properties of Zeolite/LDPE Nanocomposite under Thermal Aging

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2108
Author(s):  
Bai Han ◽  
Chuqi Yin ◽  
Jiaxin Chang ◽  
Yu Pang ◽  
Penghao Lv ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Aging Time ◽  
Thermal Aging ◽  
Aging Treatment ◽  
Dielectric Strength ◽  
Breakdown Field ◽  
Scanning Calorimetry ◽  
Aging Resistance ◽  
The Stability ◽  
Breakdown Field Strength

Nanodoping is an effective way to improve the dielectric properties and the aging resistance of polyethylene. Nano-zeolite has a nano-level porous structure and larger specific surface area than ordinary nano-inorganic oxide, which can be used to improve dielectric properties of low-density polyethylene (LDPE) nanocomposite. The zeolite/LDPE nanocomposites were prepared and subjected to thermal aging treatment to obtain samples with different aging time. Using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the differential scanning calorimetry (DSC) test to study the microscopic and structure characteristics, it was found that nano-zeolite doping can effectively reduce the thermal aging damage to the internal structure of the nanocomposite; carbonyl and hydroxyl decreased significantly during the thermal aging time, and the crystallinity effectively improved. Nano-zeolite doping significantly improved the morphology and strengthened the aging resistance of the nanocomposite. In the dielectric strength test, it was found that nanodoping can effectively improve the direct current (DC) and alternating current (AC) breakdown field strength and the stability after the thermal aging. The dielectric constant of nanocomposite can be reduced, and the dielectric loss had no obvious change during the aging process. Moreover, the zeolite/LDPE nanocomposite with the doping concentration of 1 wt % had the best performance, for the nano-zeolite was better dispersed.

Sepiolite as a nanofiller to improve mechanical and thermal behavior of recycled high-density polyethylene

2020 ◽  
Vol 36 (3) ◽  
pp. 185-195 ◽  
Author(s):  
Negin Farshchi ◽  
Yalda K Ostad
Keyword(s):  
Thermal Behavior ◽  
High Density Polyethylene ◽  
Low Cost ◽  
Process Condition ◽  
Softening Temperature ◽  
High Density ◽  
Plastic Pollution ◽  
Scanning Calorimetry ◽  
Melt Flow Rate ◽  
Recycled Hdpe

Regarding the current demand for controlling plastic pollution, recycling of polymer sounds a promising solution. However, recycling causes mechanical and thermal shortcomings in polymers. Addition of nanoparticles to recycled materials may overcome these shortcomings. Nanocomposites can be achieved either by blending or through polymerization. Sepiolite as a nanoparticle enhances the thermal properties of polymers. In this study, the effect of sepiolite as a nanoparticle has been investigated on the thermal and mechanical behavior of recycled high-density polyethylene (HDPE). Hardness, density, Vicat softening temperature, melt flow rate (MFR), and differential scanning calorimetry has been investigated on recycled HDPE containing different amount of sepiolite. Results showed that both the amount of recycled HDPE and the sepiolite content affect the mechanical and thermal behavior of samples. Increasing the amount of recycled component resulted in increasing of MFR, a slight increase in density, and decrease in Vicat softening point, hardness, melting temperature, and degree of crystallization. As an opposite effect of these to factors on crystallinity of HDPE, sepiolite content has better effects to be considered separately for each recycle content. Sepiolite can be introduced as a low-cost reinforcement filler in recycling industry for tuning new compositions based on process condition, or vice versa.

Influence of epoxidation conditions on the rheological properties of gel-like dispersions of epoxidized kraft lignin in castor oil

Holzforschung ◽  
2017 ◽  
Vol 71 (10) ◽  
pp. 777-784 ◽  
Author(s):  
Esperanza Cortés-Triviño ◽  
Concepción Valencia ◽  
José M. Franco
Keyword(s):  
Power Law ◽  
Castor Oil ◽  
Complex Modulus ◽  
Softening Temperature ◽  
Gel Strength ◽  
Rheological Characterization ◽  
Scanning Calorimetry ◽  
Small Amplitude Oscillatory Shear ◽  
Power Law Equation ◽  
Power Law Parameters

Abstract The modification of castor oil (CO) with lignin was the focus of this research to create a lubricating medium with improved gel-like properties. Namely, an alkali lignin (L) was epoxidized with epichlorohydrin (EP) and the resulting LEPs were dispersed in CO. The parameters of LEP synthesis were varied and the epoxidation index (EPI) of the LEPs was determined. The LEPs were also submitted to thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. Rheological responses of the LEP/CO dispersions were investigated through small-amplitude oscillatory shear (SAOS) tests. Linear viscoelasticity functions are quantitatively affected by the epoxidation parameters, such as temperature, reaction time and L/EP and L/NaOH ratios. In general, lignins with higher EPI show higher values of the SAOS functions, which are indicative of better gel-strength due to a higher cross-linking density between the LEPs and CO. A power-law equation describes well the evolution of the complex modulus, G*, with frequency of gel-like dispersions, where the power-law parameters were found to increase almost linearly with the EPI. The thermo-rheological characterization provides a softening temperature beyond 50°C.

scholarly journals Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizers

2007 ◽  
Vol 57 (3) ◽  
pp. 287-300 ◽  
Author(s):  
Ravindra Dhumal ◽  
Shamkant Shimpi ◽  
Anant Paradkar
Keyword(s):  
Hydrogen Bonding ◽  
Solid Dispersion ◽  
Dissolution Profile ◽  
Scanning Calorimetry ◽  
Unit Operations ◽  
Bonding Interaction ◽  
Amorphous Drugs ◽  
The Stability ◽  
Amorphous Drug ◽  
Spray Dried

Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizersThe purpose of this study was to obtain an amorphous system with minimum unit operations that will prevent recrystallization of amorphous drugs since preparation, during processing (compression) and further storage. Amorphous celecoxib, solid dispersion (SD) of celecoxib with polyvinyl pyrrollidone (PVP) and co-precipitate with PVP and carrageenan (CAR) in different ratios were prepared by the spray drying technique and compressed into tablets. Saturation solubility and dissolution studies were performed to differentiate performance after processing. Differential scanning calorimetry and X-ray powder difraction revealed the amorphous form of celecoxib, whereas infrared spectroscopy revealed hydrogen bonding between celecoxib and PVP. The dissolution profile of the solid dispersion and co-precipitate improved compared to celecoxib and amorphous celecoxib. Amorphous celecoxib was not stable on storage whereas the solid dispersion and co-precipitate powders were stable for 3 months. Tablets of the solid dispersion of celecoxib with PVP and physical mixture with PVP and carrageenan showed better resistance to recrystallization than amorphous celecoxib during compression but recrystallized on storage. However, tablets of co-precipitate with PVP and carageenan showed no evidence of crystallinity during stability studies with comparable dissolution profiles. This extraordinary stability of spray-dried co-precipitate tablets may be attributed to the cushioning action provided by the viscoelastic polymer CAR and hydrogen bonding interaction between celecoxib and PVP. The present study demonstrates the synergistic effect of combining two types of stabilizers, PVP and CAR, on the stability of amorphous drug during compression and storage as compared to their effect when used alone.

Thermotoga neapolitana Homotetrameric Xylose Isomerase Is Expressed as a Catalytically Active and Thermostable Dimer in Escherichia coli

1998 ◽  
Vol 64 (7) ◽  
pp. 2357-2360 ◽  
Author(s):  
J. Michael Hess ◽  
Vladimir Tchernajenko ◽  
Claire Vieille ◽  
J. Gregory Zeikus ◽  
Robert M. Kelly
Keyword(s):  
Escherichia Coli ◽  
Differential Scanning Calorimetry ◽  
Gel Filtration ◽  
Xylose Isomerase ◽  
Thermotoga Neapolitana ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Catalytically Active ◽  
The Stability ◽  
Tetrameric Form

ABSTRACT The xylA gene from Thermotoga neapolitana5068 was expressed in Escherichia coli. Gel filtration chromatography showed that the recombinant enzyme was both a homodimer and a homotetramer, with the dimer being the more abundant form. The purified native enzyme, however, has been shown to be exclusively tetrameric. The two enzyme forms had comparable stabilities when they were thermoinactivated at 95°C. Differential scanning calorimetry revealed thermal transitions at 99 and 109.5°C for both forms, with an additional shoulder at 91°C for the tetramer. These results suggest that the association of the subunits into the tetrameric form may have little impact on the stability and biocatalytic properties of the enzyme.

Polypropylene/wood powder composites: Evaluation of PP viscosity in thermal, mechanical, thermomechanical, and morphological characters

2019 ◽  
pp. 089270571988095 ◽  
Author(s):  
Eduardo da Silva Barbosa Ferreira ◽  
Carlos Bruno Barreto Luna ◽  
Edcleide Maria Araújo ◽  
Danilo Diniz Siqueira ◽  
Renate Maria Ramos Wellen
Keyword(s):  
Softening Temperature ◽  
Morphological Characters ◽  
Environmental Benefits ◽  
Similar Data ◽  
Wood Powder ◽  
Scanning Calorimetry ◽  
Sem Images ◽  
Elongation At Break ◽  
Twin Screw ◽  
Powder Composites

Large waste amounts from wood industries as powder and sawdust are daily produced, and reusing these materials otherwise would be discharged to the environment has become an economically viable and environmentally friendly alternative to produce new materials. Based on these arguments, polypropylene (PP)/Jatobá wood powder composites upon addition of two types of PP were processed in a corotational twin screw extruder; specimens were injected and molded and their characterization was performed through differential scanning calorimetry, thermogravimetry, mechanical properties (impact, tensile, flexural, and hardness), heat deflection temperature (HDT), Vicat softening temperature, and scanning electron microscopy (SEM). Increased elastic modulus, shore D hardness, HDT, and Vicat related to neat PPs were reached. Nevertheless, losses in impact and tensile strength as well as in elongation at break were also verified. These lower data may be associated with the wood agglomeration, as shown in SEM images. Apparently, the investigated properties were not affected by PP viscosities, where both of them presented similar data. Summing up, presented results can be considered commercially feasible, focusing at economic and environmental benefits while producing higher performance products.

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