scholarly journals Thermal Properties of Multilayer Nanocomposites Based on Halloysite Nanotubes and Biopolymers

2018 ◽  
Vol 2 (3) ◽  
pp. 41 ◽  
Author(s):  
Vanessa Bertolino ◽  
Giuseppe Cavallaro ◽  
Stefana Milioto ◽  
Filippo Parisi ◽  
Giuseppe Lazzara
Keyword(s):  
Thermal Properties ◽  
Cellulose Degradation ◽  
Oxidative Degradation ◽  
Middle Layer ◽  
Halloysite Nanotubes ◽  
Hydroxypropyl Cellulose ◽  
Inert Atmosphere ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Kinetics Of

This paper reports a novel procedure to fabricate multilayer composite biofilms based on halloysite nanotubes (HNTs) and sustainable polymers. Among the biopolymers, the non-ionic (hydroxypropyl cellulose) and cationic (chitosan) molecules were selected. The nanocomposites were prepared by the sequential casting of ethanol solutions of hydroxypropyl cellulose and aqueous dispersions of chitosan/HNTs. The composition of the bio-nanocomposites was systematically changed in order to investigate the effect of the hydroxypropyl cellulose/HNTs ratio on the thermal properties of the films, which were investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). DSC studies were conducted in the static air (oxidative atmosphere), while TG measurements were carried out under nitrogen flow (inert atmosphere). The analysis of DSC data provided the enthalpy and the temperature for the oxidative degradation of the bio-nanocomposites. These results were helpful to estimate the efficacy of the well-compacted middle layer of HNTs as a flame retardant. TG experiments were performed at a variable heating rate and the collected data were analyzed by the Friedman’s method (non-isothermal thermogravimetric approach) with the aim of studying the kinetics of the hydroxypropyl cellulose degradation in the multilayer nanocomposites. This work represents an advanced contribution for designing novel sustainable nanocomposites with excellent thermal behavior as a consequence of their peculiar multilayer structure.

scholarly journals Isothermal Vulcanization and Non-Isothermal Degradation Kinetics of XNBR/Epoxy/XNBR-g-Halloysite Nanotubes (HNT) Nanocomposites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2872
Author(s):  
Seyed Mohamad Reza Paran ◽  
Ghasem Naderi ◽  
Elnaz Movahedifar ◽  
Maryam Jouyandeh ◽  
Krzysztof Formela ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Degradation Kinetics ◽  
Halloysite Nanotubes ◽  
Butadiene Rubber ◽  
Order Model ◽  
Scanning Calorimetry ◽  
Theoretical Methods ◽  
Vulcanization Kinetics ◽  
Kinetics Of ◽  
Thermal Stability Of

The effect of several concentrations of carboxylated nitrile butadiene rubber (XNBR) functionalized halloysite nanotubes (XHNTs) on the vulcanization and degradation kinetics of XNBR/epoxy compounds were evaluated using experimental and theoretical methods. The isothermal vulcanization kinetics were studied at various temperatures by rheometry and differential scanning calorimetry (DSC). The results obtained indicated that the nth order model could not accurately predict the curing performance. However, the autocatalytic approach can be used to estimate the vulcanization reaction mechanism of XNBR/epoxy/XHNTs nanocomposites. The kinetic parameters related to the degradation of XNBR/epoxy/XHNTs nanocomposites were also assessed using thermogravimetric analysis (TGA). TGA measurements suggested that the grafted nanotubes strongly enhanced the thermal stability of the nanocomposite.

Investigation in the kinetics of thermal and thermo-oxidative degradation of wood treated with fire-retardants and untreated wood

2020 ◽  
pp. 24-29
Author(s):  
Николай Петрович Копылов ◽  
Александр Евгеньевич Кузнецов ◽  
Елена Юрьевна Сушкина ◽  
Владимир Васильевич Яшин
Keyword(s):  
Forest Fires ◽  
Flame Retardants ◽  
Degradation Products ◽  
Cellulose Degradation ◽  
Oxidative Degradation ◽  
Fire Retardant ◽  
Untreated Wood ◽  
Fire Retardants ◽  
Kinetics Of ◽  
Thermo Oxidative Degradation

Разработана экспериментальная методика определения механизма огнезащитного действия антипиренов на основе изучения кинетики термической и термоокислительной деструкции древесины. Отработка методики проведена на антипирене MgCl (бишофит). Методика основывается на количественной оценке при термическом разложении древесины выхода продуктов деструкции: CO, CO, дымового аэрозоля. В качестве приборной базы используются хроматографы, фотометр фотоэлектрический для аэрозолей, спектрофотометр. Water with various additives is used during extinguishing forest fires. Fire-retardants are used as additives in most cases. The selection of fire-retardants depends on the level of increase in extinguishing effectiveness at their addition to water. The purpose of this work is to develop an experimental method for evaluating the fireproof effect of flame retardants solutions. This method is based on the investigation of the kinetics of thermal and thermo-oxidative degradation of treated wood with flame retardants and untreated wood. In practice, bischofite and diammonium phosphate are often used as additives. Investigations were conducted using MgCl (bischofite). The explanation of the fireproof effect of the bischofite solution is based on the study of the yield of decomposition products (CO, CO, smoke aerosol) of wood treated with fire-retardant and untreated wood. The instrument base includes chromatographs «Gasochrom 3101», «Tsvet 152», photoelectric photometer for aerosols, spectrophotometer IKS-29. Wood samples were subjected to thermal and thermo-oxidative degradation in nitrogen flow or air flow with a volume velocity of 60 ml · min. Pulse heating in the pyrolysis furnace was carried out in the temperature range from 350 to 550 °C. The significant increase in fire resistance of wood treated with fire-retardant was found as a result of researches using the proposed method. It was shown that the theory of the coating layer, thermal and gas theory of catalytic dehydration are not suitable for explaining the mechanism of fireproof action of an aqueous solution of magnesium halides. Although it is not excluded the inhibition of gas-phase oxidation of cellulose degradation products by hydrogen halides released when heating aqueous solutions of magnesium halides.

scholarly journals Enhancing the Mechanical and Thermal Properties of Epoxy Resin via Blending with Thermoplastic Polysulfone

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 461 ◽  
Author(s):  
Zeyu Sun ◽  
Lei Xu ◽  
Zhengguo Chen ◽  
Yuhao Wang ◽  
Rogers Tusiime ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Epoxy Resin ◽  
Mechanical Tests ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Curing Reaction ◽  
Dynamic Mechanical Thermal Analyzer ◽  
Ft Ir ◽  
Epoxy Blends

Efficient enhancement of the toughness of epoxy resins has been a bottleneck for expanding their suitability for advanced applications. Here, polysulfone (PSF) was adopted to toughen and modify the epoxy. The influences of PSF on the mechanical and thermal properties of the epoxy resin were systematically studied by optical microscopy, Fourier transform infrared spectrometer (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analyzer (TG), dynamic mechanical thermal analyzer (DMA), mechanical tests and scanning electron microscope (SEM). The dissolution experimental results showed that PSF presents a good compatibility with the epoxy resin and could be well dissolved under controlled conditions. The introduction of PSF was found to promote the curing reaction of the epoxy resin without participating in the curing reaction and changing the curing mechanism as revealed by the FT-IR and DSC studies. The mechanical properties of PSF/epoxy resin blends showed that the fracture toughness and impact strength were significantly improved, which could be attributed to the bicontinuous phase structure of PSF/epoxy blends. Representative phase structures resulted from the reaction induced phase separation process were clearly observed in the PSF/epoxy blends during the curing process of epoxy resin, which presented dispersed particles, bicontinuous and phase inverted structures with the increase of the PSF content. Our work further confirmed that the thermal stability of the PSF/epoxy blends was slightly increased compared to that of the pure epoxy resin, mainly due to the good heat resistance of the PSF component.

scholarly journals Effect of Surface Treatment of Halloysite Nanotubes (HNTs) on the Kinetics of Epoxy Resin Cure with Amines

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 930 ◽  
Author(s):  
Vahideh Akbari ◽  
Maryam Jouyandeh ◽  
Seyed Mohammad Reza Paran ◽  
Mohammad Reza Ganjali ◽  
Hossein Abdollahi ◽  
...  
Keyword(s):  
Activation Energy ◽  
Epoxy Resin ◽  
Low Cost ◽  
Halloysite Nanotubes ◽  
Diffusion Control ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Epoxy Amine ◽  
Amine System ◽  
Kinetics Of

The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) in the epoxy matrix, alkali surface-treated HNT (A-HNT) and epoxy silane functionalized HNT (F-HNT) were developed and cured with epoxy resin. Nonisothermal differential scanning calorimetry (DSC) analyses were performed on epoxy nanocomposites containing 0.1 wt.% of P-HNT, A-HNT, and F-HNT. Quantitative analysis of the cure kinetics of epoxy/amine system made by isoconversional Kissinger–Akahira–Sunose (KAS) and Friedman methods made possible calculation of the activation energy (Eα) as a function of conversion (α). The activation energy gradually increased by increasing α due to the diffusion-control mechanism. However, the average value of Eα for nanocomposites was lower comparably, suggesting autocatalytic curing mechanism. Detailed assessment revealed that autocatalytic reaction degree, m increased at low heating rate from 0.107 for neat epoxy/amine system to 0.908 and 0.24 for epoxy/P-HNT and epoxy/A-HNT nanocomposites, respectively, whereas epoxy/F-HNT system had m value of 0.072 as a signature of dominance of non-catalytic reactions. At high heating rates, a similar behavior but not that significant was observed due to the accelerated gelation in the system. In fact, by the introduction of nanotubes the mobility of curing moieties decreased resulting in some deviation of experimental cure rate values from the predicted values obtained using KAS and Friedman methods.

INVESTIGATION ON THE MORPHOLOGICAL AND THERMAL PROPERTIES OF POLYLACTIC ACID/POLYCAPROLACTONE LOADED WITH HALLOYSITE NANOTUBES AND BASALT FIBER

2022 ◽  
Author(s):  
A. ARUL JEYA KUMAR ◽  
NIRANJAN S. RAJ ◽  
C. SAIPRASAD ◽  
AGHALAYAM R. SUDHANVA
Keyword(s):  
Thermal Properties ◽  
Polylactic Acid ◽  
Basalt Fiber ◽  
Halloysite Nanotubes ◽  
Morphological Characterization ◽  
Degree Of Crystallinity ◽  
Thermal Testing ◽  
Scanning Calorimetry ◽  
The Matrix ◽  
Twin Screw

This paper is focused on the analysis of the morphological and thermal properties of the biomedical composites, polylactic acid (PLA) and polycaprolactone (PCL) matrix, reinforced with basalt fibers (BFs) and using halloysite nanotubes (HNT) as filler material. Four different composites, viz. PPHB 1, PPHB 2, PPHB 3 and PPHB 4, are obtained by varying the weight fractions of these materials using twin-screw extrusion followed by injection molding. The morphological characterization is performed on these composites using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. SEM reveals homogenous and strong bonding between the matrix, reinforcement and filler. The BF are well embedded in the matrix with a random orientation. No formation of voids and cracks is observed. The functional groups present and the types of vibration experienced by the chemical bonds were observed in the FTIR spectra. The composites are subjected to thermal testing such as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The PPHB 2, which contains 80% PLA, 10% BF, 7% PCL and 3% HNT, has the highest degree of crystallinity, as revealed by DSC, and exhibits the most optimum thermal degradation characteristics as indicated by TGA.

scholarly journals Statistical Copolymers of N-Vinylpyrrolidone and Isobornyl Methacrylate via Free Radical and RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 778
Author(s):  
Olga Kokkorogianni ◽  
Philippos Kontoes-Georgoudakis ◽  
Maria Athanasopoulou ◽  
Nikolaos Polizos ◽  
Marinos Pitsikalis
Keyword(s):  
Thermal Properties ◽  
Free Radical ◽  
Raft Polymerization ◽  
Structural Parameters ◽  
Reactivity Ratio ◽  
Sequence Length ◽  
Reactivity Ratios ◽  
Scanning Calorimetry ◽  
Reversible Addition ◽  
Kinetics Of

The synthesis of statistical copolymers of N-vinylpyrrolidone (NVP) with isobornyl methacrylate (IBMA) was conducted by free radical and reversible addition-fragmentation chain transfer (RAFT) polymerization. The reactivity ratios were estimated using the Finemann-Ross, inverted Fineman-Ross, Kelen-Tüdos, extended Kelen-Tüdos and Barson-Fenn graphical methods, along with the computer program COPOINT, modified to both the terminal and the penultimate models. According to COPOINT the reactivity ratios were found to be equal to 0.292 for NVP and 2.673 for IBMA for conventional radical polymerization, whereas for RAFT polymerization and for the penultimate model the following reactivity ratios were obtained: r11 = 4.466, r22 = 0, r21 = 14.830, and r12 = 0 (1 stands for NVP and 2 for IBMA). In all cases, the NVP reactivity ratio was significantly lower than that of IBMA. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length. The thermal properties of the copolymers were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and differential thermogravimetry (DTG). The results were compared with those of the respective homopolymers.

Characterization of Nostoc muscorum NCCU-442 Derived Poly-3- hydroxybutyrate (PHB) and Polyethylene Glycol (PEG) Blends

2020 ◽  
Vol 10 (3) ◽  
pp. 200-207
Author(s):  
Sabbir Ansari ◽  
Tasneem Fatma
Keyword(s):  
Thermal Properties ◽  
Polyethylene Glycol ◽  
Morphological Properties ◽  
Morphological Alteration ◽  
Nostoc Muscorum ◽  
Microbial Culture ◽  
Polymer Science ◽  
Mixed Microbial Culture ◽  
Scanning Calorimetry ◽  
Casting Technique

Background: Poly-3-hydroxybutyrate (PHB) has attracted much consideration as biodegradable biocompatible polymer. This thermoplastic polymer has comparable material properties to polypropylene. Materials with more valuable properties may result from blending, a common practice in polymer science. Objective: In this paper, blends of PHB (extracted from cyanobacterium Nostoc muscorum NCCU- 442 with polyethylene glycol (PEG) were investigated for their thermal, tensile, hydrophilic and biodegradation properties. Methods: Blends were prepared in different proportions of PHB/PEG viz. 100/0, 98/2, 95/5, 90/10, 80/20, and 70/30 (wt %) using solvent casting technique. Morphological properties were investigated by using Scanning Electron Microscopy (SEM). Differential scanning calorimetry and thermogravimetric analysis were done for thermal properties determination whereas the mechanical and hydrophilic properties of the blends were studied by means of an automated material testing system and contact angle analyser respectively. Biodegradability potential of the blended films was tested as percent weight loss by mixed microbial culture within 60 days. Results: The blends showed good misciblity between PEG and PHB, however increasing concentrations of plasticizer caused morphological alteration as evidenced by SEM micrographs. PEG addition (10 % and above) showed significant alternations in the thermal properties of the blends. Increase in the PEG content increased the elongation at break ratio i.e enhanced the required plasticity of PHB. Rate of microbial facilitated degradation of the blends was greater with increasing PEG concentrations. Conclusion: Blending with PEG increased the crucial polymeric properties of cyanobacterial PHB.

Study of nickel-molybdenum catalysts for methanation of carbon monoxide

1980 ◽  
Vol 45 (3) ◽  
pp. 783-790 ◽  
Author(s):  
Petr Taras ◽  
Milan Pospíšil
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Mixed Oxides ◽  
Minor Component ◽  
Fast Neutrons ◽  
Scanning Calorimetry ◽  
Low Concentrations ◽  
Γ Rays ◽  
Molybdenum Catalysts ◽  
Kinetics Of

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.

scholarly journals Improved Processing and Properties for Polyphenylene Oxide Modified by Diallyl Orthophthalate Prepolymer

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2016
Author(s):  
Honghua Wang ◽  
Qilin Mei ◽  
Yujie Ding ◽  
Zhixiong Huang ◽  
Minxian Shi
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Phase Separation ◽  
Dilution Effect ◽  
Gradual Decrease ◽  
Gel Point ◽  
Dynamic Mode ◽  
Curing Process ◽  
Scanning Calorimetry ◽  
Polyphenylene Oxide

Diallyl orthophthalate (DAOP) prepolymer was investigated as a reactive plasticizer to improve the processability of thermoplastics. The rheology of blends of DAOP prepolymer initiated by 2,3-dimethyl-2,3-diphenylbutane (DMDPB) and polyphenylene oxide (PPO) was monitored during the curing process, and their thermal properties and morphology in separated phases were also studied. Differential scanning calorimetry (DSC) results showed that the cure degree of the reactively plasticized DAOP prepolymer was reduced with increasing PPO due to the dilution effect. The increasing amount of the DAOP prepolymer led to a gradual decrease in the viscosity of the blends and the rheology behavior was consistent with the chemical gelation of DAOP prepolymer in blends. This indicated that the addition of the DAOP prepolymer effectively improved processability. The phase separation occurring during curing of the blend and the transition from the static to dynamic mode significantly influences the development of the morphology of the blend corresponding to limited evolution of the conversion around the gel point.

Sign in / Sign up

Export Citation Format

Share Document