Thermal Stability Of Nanocomposites Research Articles

Effect of Amino alcohol functionalized polyethylene as compatibilizer for LDPE/EVA/clay/flame-retardant nanocomposites

The synergistic effect of organo-modified montmorillonite (Nanomer I28E and Cloisite 20A) and metal hydroxides (magnesium hydroxide MH and alumina trihydrate ATH) as flame retardants in LDPE/EVA nanocomposites compatibilized with amino alcohol grafted polyethylene (PEgDMAE) was studied. Morphological characterization of nanocomposites was carried out by means of X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Flame-retardant properties of nanocomposites were evaluated by the UL-94 horizontal burning and cone calorimeter tests and limiting oxygen index (LOI). Thermal degradation behavior was analyzed with a Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR). The XRD analysis showed a displacement of the d001 plane characteristic peak of clay to lower angles, which indicates an intercalated–exfoliated morphology. From STEM images it was observed a good dispersion of flame retardants (MH and ATH) throughout the polymer matrix which was reflected in flame-retardant properties. TG-FTIR showed a better thermal stability of nanocomposites and the gases evolved during combustion showed an important reduction. Based on thermal stability and thermal degradation results, the flame-retardant mechanism of LDPE/PEgDMAE/EVA/Clay/MH nanocomposites was proposed.

Synthesis of Highly Efficient Flame Retardant High-Density Polyethylene Nanocomposites with Inorgano-Layered Double Hydroxides As Nanofiller Using Solvent Mixing Method

High-density polyethylene (HDPE) polymer nanocomposites containing Zn2Al-X (X= CO3(2-), NO3(-), Cl(-), SO4(2-)) layered double hydroxide (LDH) nanoparticles with different loadings from 10 to 40 wt % were synthesized using a modified solvent mixing method. Synthesized LDH nanofillers and the corresponding nanocomposites were carefully characterized using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, etc. The thermal stability and flame retardancy behavior were investigated using a thermo gravimetric analyzer and microscale combustion calorimeter. Comparing to neat HDPE, the thermal stability of nanocomposites was significantly enhanced. With the addition of 15 wt % Zn2Al-Cl LDH, the 50% weight loss temperature was increased by 67 °C. After adding LDHs, the flame retardant performance was significantly improved as well. With 40 wt % of LDH loading, the peak heat release rate was reduced by 24%, 41%, 48%, and 54% for HDPE/Zn2Al-Cl, HDPE/Zn2Al-CO3, HDPE/Zn2Al-NO3, and HDPE/Zn2Al-SO4, respectively. We also noticed that different interlayer anions could result in different rheological properties and the influence on storage and loss moduli follows the order of SO4(2-) > NO3(-) > CO3(2-) > Cl(-). Another important finding of this work is that the influence of anions on flame retardancy follows the exact same order on rheological properties.

Investigation of Structural, Thermal, and Electrical Properties of Nanocomposites Based on SnO2 Nanoparticles Dispersed in Conducting Polypyrrole Matrix

Pyrrole was polymerized with various concentrations of SnO2 nanoparticles, using FeCl3 to obtain conductive polypyrrole (PPy)/SnO2 nanocomposites. Characterization of the nanocomposites by XRD, FTIR, TGA, SEM, and TEM showed that the polymerization of pyrrole has been successfully achieved on the surface of the SnO2 nanoparticles. Electrical conductivity measurements showed that the conductivity of nanocomposites increases with increasing contents of SnO2. SEM, and TEM pictures showed that the nanocomposites have a close packing globular structure with an average grain size in the range of 30–65 nm. TGA showed that with introducing SnO2 nanoparticles into PPy chains, thermal stability of nanocomposites increases.

Enhanced general analytical equation for the kinetics of the thermal degradation of poly(lactic acid)/montmorillonite nanocomposites driven by random scission

An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of nanocomposites, composed of poly(lactic acid) (PLA) and organo-modified montmorillonite (OMMT) nanoparticles. This improvement has consisted of replacing the n-order conversion function by a modified form of the Sestak–Berggren equation f(α) = c (1 − α)nαm that led to a better adjustment of experimental data and also adequately represented the conventional mechanisms for solid-state processes. The kinetic parameters so obtained have been compared to those determined by conventional differential and isoconversional methods. Given that the thermal degradation of PLA has been argued to be caused by random chain scission reactions of ester groups, the conversion function f(α) = L (L − 1)x(1 − x)L−1, corresponding to a random scission mechanism, has been tested. Once optimized the kinetic model, the thermal degradation kinetics of nanocomposites (0.5 and 2.5% of OMMT) was compared to that of the polymer matrix. Moreover, the thermal stability of nanocomposites was tested and compared to that of the polymer matrix.

Characterization, charge transport and magnetic properties of multi-walled carbon nanotube–polyvinyl chloride nanocomposites

Multi-walled carbon nanotube (MWCNT)–polyvinyl chloride (PVC) nanocomposites, with MWCNT loading up to 44.4 weight percent (wt%), were prepared by the solvent mixing and casting method. Electron microscopy indicates high degree of dispersion of MWCNT in PVC matrix, achieved by ultrasonication without using any surfactants. Thermogravimetric analysis showed a significant monotonic enhancement in the thermal stability of nanocomposites by increasing the wt% of MWCNT. Electrical conductivity of nanocomposites followed the classical percolation theory and the conductivity prominently improved from 10−7 to 9S/cm as the MWCNT loading increased from 0.1 to 44.4wt%. Low value of electrical percolation threshold ~0.2wt% is achieved which is attributed to high aspect ratio and homogeneous dispersion of MWCNT in PVC. The analysis of the low temperature electrical resistivity data shows that sample of 1.9wt% follows three dimensional variable range hopping model whereas higher wt% nanocomposite samples follow power law behavior. The magnetization versus applied field data for both bulk MWCNTs and nanocomposite of 44.4wt% display ferromagnetic behavior with enhanced coercivities of 1.82 and 1.27kOe at 10K, respectively. The enhancement in coercivity is due to strong dipolar interaction and shape anisotropy of rod-shaped iron nanoparticles.

New photosensitive semi aramid/organoclay nanocomposite containing cinnamoyl groups: Synthesis and characterization

New poly(ether–amide)/layered silicate nanocomposites (PEAN) containing dibenzalacetone and cinnamoyl moieties were prepared via solution intercalation technique from poly(ether–amide) 6 and organo-MMT in a solution of N,N-dimethylacetamide (DMAc). New dicarboxylic acid 4 was synthesis from two step reactions. At first 4,4′-bis(1,4-diphenoxybutane) dialdehyde 3 was synthesized from 1,4-dibromobutane and 4-hydroxybenzaldehyde, then solvent free reaction using to synthesis 4,4′-bis(1,4-diphenoxybutane) diacrylic acid from dialdehyde 3 and malonic acid. Poly(ether–amide) (PEA) chains were synthesized from 4,4′-bis(1,4-diphenoxybutane)diacrylic acid 4 and 2,5-bis(4-aminobenzylidene)cyclopentanone 5 via a direct polycondensation reaction. The synthesized PEA was characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC) and UV–Vis spectroscopy. The distribution of organoclay and nanostructure of the nanocomposites were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The thermal properties and flammability of the nanocomposites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetric (DSC) and microscale combustion calorimeter (MCC). In the presence of organoclay shows a good effect on improving the flame retardancy of the PEA, reflecting the decrease in heat release rate (HRR) and the total heat release (THR) of the nanocomposites, while the thermal stability of nanocomposites only changed slightly compared to the neat polymer. With the increase of the loading of organoclay, the nanocomposites showed improved flame retardancy and higher char residues.

Exfoliation and dispersion of micrometer-sized LDH particles in poly(ethylene terephthalate) and their nanocomposite thermal stability

Effect of surface modification on exfoliation and dispersion of micrometer-sized layered double hydroxide (LDH) in poly(ethylene terephthalate) (PET) and the thermal stability of the resultant PET/LDH nanocomposites or composite have been studied. First, large micrometer-sized LDH with carbonate anions was prepared by urea hydrolysis method. Then, various anions including nitrate (NO3−), dodecyl sulfate (DS−) or dodecyl benzene sulphonate (DBS−) were intercalated into the interlayer space via anion exchange reaction. By solution intercalation process, PET/LDH_DS and PET/LDH_DBS nanocomposites were successfully obtained, while the LDH_NO3 could not be exfoliated enough in the PET matrix. Finally, the thermal stabilities of the PET/LDH nanocomposites or composite were investigated.

Synthesis and characterization of UV-cured epoxy acrylate/POSS nanocomposites

In this study, epoxy acrylate (EA)/vinyl-polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared through in situ polymerization and by UV-curing technique. The vinyl-POSS monomers were added to EA matrix by physically blending at loadings between 0wt.% and 15wt.%. The microstructure of the EA/vinyl-POSS composites was studied by X-ray diffraction (XRD) measurements, and the result indicated that the separate POSS domains were present in EA/POSS composites. Aggregates were observed in the nanocomposites by SEM and the EDS results indicated that there were vinyl-POSS molecules existing in the EA matrix. TEM images further proved there were both POSS aggregates and monomers dispersed in the EA matrix. The kinetics of the photopolymerization was investigated by real time FTIR spectroscopy. The DSC analysis showed that the increasing POSS content caused a decrease on the composite's glass transition temperature. TGA measures confirmed that the degradation mechanism of EA was not affected by POSS and the nanocomposites thermal stability was slightly improved with the increasing of POSS loadings. It can be seen that the degradation rate slowed down with the increasing of POSS content and the 50% mass loss temperature of EA/POSS hybrids all increased conspicuously relative to plain EA.

Properties of Halloysite Nanotube (HNT) Filled SMR L and ENR 50 Nanocomposites

Various HNTs loading filled SMR L and ENR 50 were prepared. Addition of HNTs caused increments in scorch time, cure time, tensile modulus, and thermal stability of nanocomposites. Optimum tensile strength of nanocomposites was achieved at 20 phr loading. Elongation at break, swelling percentage, and fatigue life decreased with increasing HNTs loading. ENR 50 nanocomposites show shorter scorch time, longer cure time, and lower curing rate index than SMR L nanocomposites. ENR 50 nanocomposites also show higher tensile modulus and thermal stability than SMR L nanocomposites. SEM images show that HNTs can be dispersed more uniformly at lower filler loading.

Water absorption, mechanical, and thermal properties of halloysite nanotube reinforced vinyl-ester nanocomposites

Halloysite nanotube (HNT) addition to vinyl-ester resin (VER) is a field yet to contain an in-depth repository of information. This work represents the first study on the development and characterisation of HNT-reinforced VER nanocomposites, and presents findings on their water absorption, mechanical, and thermal properties. VER composites reinforced with HNTs (1, 3, and 5 wt%) were fabricated using high speed mechanical stirring. Weight gain and FTIR spectrum analysis indicated that the addition of 5 wt% HNTs gave perceptible reduction in the water absorption behavior of the samples. Results showed that elastic modulus increased with increasing HNT content. Strength and toughness were also found to steadily increase with increasing HNT content. Favorable strength can be attributable to the large aspect ratio of HNTs, favorable adhesion and dispersion, and the suitable extent of inter-tubular interaction while enhancements to toughness can be attributable to crack bridging, deflection, and plastic deformation mechanisms. Thermal stability of nanocomposites was found remarkably enhanced by the incorporation of HNTs. The thermal stability enhancement and decrease in flammability are attributable to HNT’s barriers for heat and mass transport, presence of iron, and hollow tubular structure.

Variously substituted phenyl hepta cyclopentyl-polyhedral oligomeric silsesquioxane (ph,hcp-POSS)/polystyrene (PS) nanocomposites

A comparative study concerning the thermal stability of polystyrene (PS) and six POSS/PS nanocomposites of general formula R7R′(SiO1.5)8/PS (where R = cyclopentyl and R′ = phenyl, 4-methoxyphenyl, 4-tolyl, 3,5-xilyl, 4-fluorophenyl, and 2,4-difluorophenyl) was carried out in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were prepared by in situ polymerization of styrene in the presence of 5 % w/w of POSS, but the actual filler concentration in the obtained nanocomposites, determined by 1H NMR spectroscopy, was in all cases slightly higher than that in the reactant mixtures. FTIR spectra of nanocomposites evidenced the presence of filler-polymer interactions. Inherent viscosity (ηinh) determinations indicated that the average molar mass of polymer in methylated and fluorinated derivatives was lower than neat PS, and were in agreement with calorimetric glass transition temperature (Tg) measurements. Degradations were performed into a thermobalance, in the scanning mode, at 10 °C min−1, and the temperatures at 5 % mass loss (T5 %), of various nanocomposites were determined. The effects of various substituents of the POSS phenyl group on the thermal stability of nanocomposites were evaluated. The results were discussed and interpreted.

Study on the Preparation and Properties of Epoxy/PEI/Nano-Attapulgite Nanocomposites

Polyether imides (PEI) and nanoattapulgite particles organically synthesized by the active silane containing epoxide groups (OAT) were used to modify the epoxy resin (ER). The effect of the concentration of OAT on the morphology, thermal and mechanical properties of ER/PEI/OAT nanocomposites was explored in the present work. The microscopic structure of nanocomposites was investigated by Scanning electric microscopy (SEM). The results showed that a homogeneous nanoattapulgite organically-modified by silane in the polymeric matrix was obtained. SEM images showed that the morphology transformation increased with the increase of OAT content, which would lead the improvement of the impact strengths of nanocomposites. The results of mechanical and thermal measurements indicated that the introduction of PEI and OAT into the epoxy resulted in the great improvement of the impact strength and storage module. With the OAT concentration increasing, the glass translation temperature (Tg) value of nanocomposites was gradually increased. Additionally, the results of thermo-gravimetric analysis (TGA) revealed that thermal stability of nanocomposites was apparently improved in comparison to the epoxy resin systems.

Preparation and characterization of cellulose-ZnO nanocomposite based on ionic liquid ([C4mim]Cl)

Cellulose-ZnO composite was achieved by microwave assisted dissolution of cellulose in ionic liquid 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) followed by addition of premixed ground of Zn(CH3COO)2·2H2O and NaOH. Surface characterization, optical property and thermal stability of nanocomposite were determined by X-ray diffraction, scanning electron microscopy (SEM), UV–Vis spectroscopy and thermo gravimetric analysis. XRD patterns showed the ZnO in polymer matrix has the wurtzite structure. Presence of zinc oxide nanoparticles and cellulose fibers in the composites were observed by SEM. Band-edge transition of zinc oxide in the nanocomposite occurs in lower wavelength than bulk zinc oxide. Thermal stability of nanocomposite was lower than regenerated cellulose due to catalyst behavior of zinc oxide nanoparticles in cellulose matrix.

Thermal Stability of MWCNTs Reinforced Nanocomposites

The effect of functionalization of multi-walled carbon nanotubes (MWCNT) on the thermal stbility of MWCNT/epoxy nanocomposites was investigated. Epoxy-based nanocomposites reinforced with MWCNTs with and without functionalization were prepared. The thermal stability of nanocomposites was characterized using thermal gravimetric analysis (TGA). Experimental results showed that functionalization of MWCNTs enhanced the decomposition temperature of MWCNTs reinforced nanocomposite compared to those containing pristine MWCNTs.

Barrier Properties and Structural Study of Nanocomposite of HDPE/Montmorillonite Modified with Polyvinylalcohol

In this work was studied the permeation of CO2 in films of high‐density polyethylene (HDPE) and organoclay modified with polyvinylalcohol (MMTHDTMA/PVA) obtained from melt blending. Permeation study showed that the incorporation of the modified organoclay generates a significant effect on the barrier properties of HDPE. When a load of 2 wt% of MMTHDTMA/PVA was incorporated in the polymer matrix, the flow of CO2 decreased 43.7% compared to pure polyethylene. The results of TEM showed that clay layers were dispersed in the polymeric matrix, obtaining an exfoliated‐structure nanocomposite. The thermal stability of nanocomposite was significantly enhanced with respect to the pristine HDPE. DSC results showed that the crystallinity was maintained as the pure polymeric matrix. Consequently, the decrease of permeability was attributable only to the effect of tortuosity generated by the dispersion of MMTHDTMA/PVA. Notably the mechanical properties remain equal to those of pure polyethylene, but with an increase in barrier properties to CO2. This procedure allows obtaining nanocomposites of HDPE with a good barrier property to CO2 which would make it competitive in the use of packaging.

Polymer–clay nanocomposites thermal stability: experimental evidence of the radical trapping effect

The radical trapping flame retardant mechanism of polymer–clay nanocomposites is frequently claimed to be responsible for improving the thermal stability of polymers. However it had never been demonstrated. Herein using in situ time-resolved X-ray Absorption Spectroscopy (XAS) we present experimental evidence that Fe3+ embedded in the clay can act as electron acceptors during polymer thermal decomposition. Therefore it contributes to improve the polymer thermal stability.

Preparation of Nickel/Poly(m-Toluidine) Composites and its Magnetic Properties

Ni/poly(m-toluidine)(PMT) nanocomposites were prepared by in situ chemical oxidative polymerization of m-toluidine (MT) monomer in the presence of Ni powder, with ammonium persulfate (APS) as oxidant and citric acid (C6H8O7) as dopant. The resultant products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and superconducting quantum interference device magnetometer (SQUID). The results exhibited that Ni/PMT nanocomposites show a ferromagnetic behavior with saturation magnetization strength (Ms) and coercivity of 28.4emu/g and 105.8Oe at room temperature. The prepared Ni/PMT composites were soft and ferromagnetic materials. Moreover, thermal Stability of nanocomposites was also investigated.

Effects of silver nanoparticles on thermal properties of DBSA-doped polyaniline/PVC blends

Dodecylbenzenesulfonic acid (DBSA)-doped polyaniline (PAND) has been synthesized by redoping (PANDR) and aqueous polymerization (PANDA) methods. Silver nanoparticles were incorporated into the PANDR/tetrahydrofuran solution (PANDS) and then mixed with poly (vinyl chloride) (PVC) solution to prepare PANDS/PVC nanocomposites. In the present study, effects of silver nanoparticles on thermal properties of PAND/PVC blends have been investigated by employing thermal gravimetric analysis and heat flow microcalorimetry techniques. From these results it has been observed that the thermal stability of blends have increased by increasing the concentration of PAND in blends and nanocomposites. Addition of silver nanoparticles has suppressed the dehydrochlorination process and evolution/degradation of DBSA in PANDS/PVC nanocomposites. Presence of silver nanoparticles in PAND/PVC nanocomposites has reduced the mobility of PANI chains which in turn inhibited the transfer of free radicals formed during degradation of PAND and PVC through inter-chain reactions; hence, degradation process has been slowed down and thermal stability has been improved. Embedment of silver nanoparticles has reduced thermal weight loss corresponding to polymer degradation step and attains lower heat flow level in inert atmosphere for nanocomposites in contrast to those with no nanoparticles, thereby further improving thermal stability of nanocomposites. The heats of oxidation measured for blends and nanocomposites were independent of PAND/PVC blends composition.

Properties of matrix-grafted multi-walled carbon nanotube/poly(methyl methacrylate) nanocomposites synthesized by in situ reversible addition-fragmentation chain transfer polymerization

Multi-walled carbon nanotubes (MWCNT)/poly(methyl methacrylate) (PMMA) nanocomposites were synthesized by the in situ reversible addition-fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) in the presence of MWCNTs, at which the bulk polymer was grafted onto the surface of nanotubes through the “grafting through” strategy. For this purpose, MWCNTs were formerly functionalized with polymerizable MMA groups. MMA and PMMA-grafted MWCNTs were characterized by Fourier-transform infrared spectroscopy, Raman, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). Dissolution of nanotubes was examined in chloroform solvent and studied by UV–vis spectroscopy. Thermogravimetric and degradation behavior of prepared nanocomposites was investigated by TGA. MWCNTs had a noticeable boosting effect on the thermal stability of nanocomposites. TGA thermograms showed a two-step weight loss pattern for the degradation of MWCNT-PMMA/PMMA nanocomposites which is contrast with neat PMMA. Introduction of MWCNTs also improved the dynamic mechanical behavior and electrical conductivity of nanocomposites. TEM micrograph of nanocomposite revealed that the applied methods for functionalization of nanotubes and in situ synthesis of nanocomposites were comparatively successful in dispersing the MWCNTs in PMMA matrix.

Preparation, structure and thermal properties of polylactide/sepiolite nanocomposites with and without organic modifiers

Polylactide-based nanocomposites containing unmodified and organic modified sepiolite were prepared through a solution casting method. The structure and properties of materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). From the results it can be concluded that the bundles of sepiolite have been dispersed into small aggregates containing several nanorods without destroying the crystal structure. Sepiolite nanofibers were well dispersed in the PLA matrix, exhibiting a randomly orientation with the contact among them in all cases. But the thermal stability of nanocomposites has been improved more by introducing unmodified sepiolite than that with organic modified sepiolite, which has also been confirmed by molecular dynamics simulation results that hydrophobic parts of organic modifiers could prevent the interaction between PLA molecules and sepiolite surface.