Thermal degradation and combustion behavior of the polyethylene/clay nanocomposite prepared by melt intercalation

Studies of thermal and fire-resistant properties of the polyethylene/organically modified montmorillonite (PE/MMT) nanocomposites prepared by means of melt intercalation are discussed. The sets of the data acquired with the aid of non-isothermal TG experiments have been treated by the model kinetic analysis. The extra acceleration of thermal-oxidative degradation of the nanocomposite which has been observed at the first stage of the overall process has been analyzed and is explained by the catalytic effect of the clay nanoparticles. The results of cone calorimetric tests lead to the conclusion that char formation plays a key role in the mechanism of flame retardation for nanocomposites.     

Preparation of fluorinated methacrylate/clay nanocomposite via in‐situ polymerization: Characterization,structure, and properties

Novel fluorinated coating containing well‐dispersed silicate nanolayers is successfully produced via in‐situ free radical polymerization of 2,2,2‐trifluoroethyl methacrylate in the presence of vinylbenzyl‐functionalized montmorillonite with different loading. The organic modification of sodium montmorillonite is achieved through an ion exchange reaction with triphenylvinylbenzylphosphonium chloride as surfactant prepared before use by reaction with vinylbenyl chloride and phosphine. The following in‐situ polymerization in the presence of organomodified clay leads to fluorinated nanocomposites with of partially exfoliated and intercalated morphologies, as determined via XRD and TEM analysis. The nanoscale dispersion of clay layers is also evidenced by thermal analysis; a moderate decrease of the glass transition temperature about 2–8 °C compared to their virgin PMATRIF and an improvement of their thermal stability as evidenced by TGA. The wettability of the nanocomposite films is also studied by contact angle measurements with water. The incorporation of organomodified clays not only increases the hydrophobicity of the fluorinated polymers but also improves the surface properties of obtained nanocomposites. Compared the virgin homopolymer, the mechanical properties of the nanocomposites are reduced by addition of organomodifed clay at temperature from 30 to 60 °C, whereas this trend is gradually decreased at higher temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 411–418     

Synthesis of clay nanocomposite materials by light-induced crosslinking polymerization

Different types of nanocomposite materials have been synthetized within seconds at ambient temperature, by photoinitiated crosslinking polymerization of epoxy, vinyl ether and acrylate-based resins containing a small amount (3 wt%) of an organoclay filler. The curing process was followed quantitatively by infrared spectroscopy through the decrease upon UV exposure of the IR bands characteristic of the functional groups. The silicate nanoparticles were found to have no effect on the polymerization kinetics. The UV-cured nanocomposites proved to be more flexible and impact resistant than the corresponding microcomposites. This method of synthesis of nanocomposites presents the advantages associated with the UV-curing technology, namely a solvent-free resin transformed rapidly at ambient temperature into a chemically resistant material, with a minimum consumption of energy.     

Synthesis and characterization of exfoliated MEH-PPV/clay nanocomposites by in situ polymerization

In this article, we demonstrate the synthesis of a conjugated polymer, poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) in the presence of organophilic montmorillonite (OMMT) and the properties of the MEH-PPV/OMMT composites produced herefrom. By controlling the reaction conditions, such as the ratio of monomeric precursors to montmorillonite, exfoliated MEH-PPV/OMMT nanocomposites were synthesized via in situ polymerization. These materials exhibit higher electroluminescent properties and enhanced performance of thermal stability than that of the pure polymer. Additionally, based on the solid-state ¹³C NMR measurement results, the possible origin of the optoelectronic property improvement is discussed from the point of view of segmental mobility.     

Impact fracture behavior of nylon-6/ABS blends

Tensile and impact properties of uncompatibilized nylon-6/ABS blends have been studied over the entire range of compositions. The blends were prepared by extrusion and, subsequently, injection molded into tensile specimens and rectangular plaques. The impact fracture performance was characterized using recently proposed models based on fracture mechanics, for various fracture behaviors. The results showed that nylon-6 breaks in a brittle manner. With the addition of ABS, the blend exhibits the same behavior with a slightly lower impact resistance up to about 60 wt %. A sudden jump in the value of impact fracture energy is observed around 70 wt % ABS with a brittle—ductile transition in the mechanism of fracture. The transition in fracture mechanisms is confirmed through observation of the fracture surfaces by scanning electron microscopy (SEM). Tensile tests showed that the elongation at break increases only slightly between 0 and 50% ABS content, but a significant jump occurs around 70% ABS, reaching a 6-fold increase in comparison to that of the pure components. SEM observation of etched samples shows that a cocontinuous morphology occurs around 70 wt % ABS. The peak observed for the elongation at break and the jump in impact performance, as well as the onset of brittle–ductile transition, are attributed to this morphological effect. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2583–2592, 1997     

Thermal safety and performances analysis of gel polymer electrolytes synthesized by in situ polymerization for Li-ion battery

Journal of Solid State Electrochemistry - This work obtained gel polymer electrolytes (GPEs) via in situ polymerization of methyl methacrylate (MMA) in the environment of lithium...     

Porosity control in nylon-6/nylon-6, 6 membranes

The possibility of porosity control in N6/N66 membranes prepared from N6/N66 blend solutions of calcium chloride – methanol mixture was investigated. For N6/N66 blend solutions at 10 °C and 20 °C, the four-phase structure of solid, gel 1, gel 2 and solution was observed clearly in the pore formation process after adding water on a solution surface. In the boundary part between gel 1 and gel 2, the phase separation of N6 and N66 was predicted. The macroscopic pores of blend membranes prepared at 10°C and 20 °C were almost spherical.     

Synthesis of poly(2‐ethylhexyl acrylate)/clay nanocomposite by in situ living radical polymerization

This investigation reports the preparation of tailor‐made poly(2‐ethylhexyl acrylate) (PEHA) prepared via in situ living radical polymerization in the presence of layered silicates and characterization of this polymer/clay nanocomposite. Being a low T_g (?65 °C) material, PEHA has very good film formation property for which it is used in paints, adhesives, and coating applications. 2‐Ethylhexyl acrylate was polymerized at 90 °C using CuBr and Cu(0) as catalyst in combination with N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) as ligand. A tremendous enhancement in reaction rate and polymerization data was achieved when acetone was added as additive to increase the efficiency of the catalyst system. PEHA/clay nanocomposite was prepared at 90 °C using CuBr as catalyst in combination with PMDETA as ligand. Different types of clay with same loading were also used to study the effect on reaction rate. The molecular weight (M_n) and polydispersity index of the prepared nanocomposites were characterized by size exclusion chromatography. The active end group of the polymer chain was analyzed by ¹H NMR analysis and by chain extension experiment. Polymer/clay interaction was studied by Fourier Transform Infrared spectrometry and wide‐angle X‐ray diffraction analyses. Distribution of clay in the polymer matrix was studied by the transmission electron microscopy. Thermogravimetric analysis showed that thermal stability of PEHA/clay nanocomposite increases on addition of nanoclay. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Structure and mechanical performance of in situ synthesized hydroxyapatite/polyetheretherketone nanocomposite materials

Nano-hydroxyapatite (HA) particles were prepared by a sol–gel method and polyetheretherketone (PEEK) composite materials containing a various amount of lab-prepared HA fillers had been successfully synthesized via an in situ synthesis process. The materials structure was characterized by infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy and the mechanical performance was investigated by a tensile strength test. The tensile strength of HA/PEEK composites reaches an optimal 108 MPa at 6.1% HA content. The composites with HA content below 17.4% exhibit a plastic break mode, while a brittle break mode above 17.4%. The results exhibit that the strong bonding between hydroxyapatite fillers and PEEK matrix has been achieved. And it was proved that this strong bonding may be mainly attributed to the physical factors, such as mechanical interlock between PEEK molecules and HA surface. The study clearly demonstrates that in situ synthesized HA/PEEK composite materials have the potential for use as an alternative material for hard tissue replacement.     

A computationally efficient technique for the solution of non-isothermal nylon-6 polymerization in batch reactors

The kinetic scheme of nylon-6 polymerization consists of ring opening, polyaddition, step growth, reaction with monofunctional acids and cyclization. A set of ordinary differential equations (initial value problem) governing the concentrations and moments of the reacting species and the energy balance for batch reactors has been solved. We proposed a semianalytic technique somewhat similar to the finite element method in which the conversion domain has been divided into sequential subdomains. A series solution for the state variables has been assumed in terms of the incremental conversion of caprolactam in that domain. The coefficients are obtained using the balance equations. This technique of solution takes care of the nonlinearity of the problem in a natural way and involves the sequential evaluation of constant coefficients of the series. It gives comparable results with those from Gear's algorithm (which involves the evaluation of functions) in far fewer steps. Our scheme can be easily implemented on a PC-XT and is considerably faster and more efficient.     

Effect of rubber on properties of nylon-6/unmodified clay/rubber nanocomposites

Three nylon-6/unmodified clay/rubber nanocomposites with high toughness, high stiffness, high heat resistance and reduced flammability were studied in this paper, on basis of three compound powders of ultra-fine full-vulcanized powdered rubber (UFPR)/montmorillonite (UFPRM). It was found that all of the three UFPRs used in the study can help the silicate layers without organic treatment to be exfoliated in the nylon-6 matrix, despite some differences in compatibilities between them and nylon-6. Accordingly, the clay in different UFPRMs at the same loading content can lead to a similar improvement in stiffness and heat resistance of nanocomposites. In other words, UFPRs having different compatibilities with nylon-6 do not affect the stiffness and heat resistance of nanocomposites largely. However, the nylon-6 nanocomposites, modified with different UFPRMs, show different superior properties. Butadiene styrene vinyl-pyridine UFPRM (VP-UFPRM) is more effective in improving toughness of nylon-6. Nylon-6/silicone UFPRM (nylon-6/S-UFPRM) nanocomposite exhibits more reduced flammability, good flowability and high thermal stability. As for nylon-6/acrylate UFPRM (nylon-6/A-UFPRM) nanocomposite, it shows high toughness and thermal stability. Furthermore, the mechanism of unmodified clay exfoliation during the melt compounding and the effect of different UFPRs on the properties of the nylon-6/UFPRM nanocomposites are also discussed.     

Self assembled graphene/carbon nanotube/polystyrene hybrid nanocomposite by in situ microemulsion polymerization

Self-assembled graphene/carbon nanotube (CNT)/polystyrene hybrid nanocomposites were prepared by water-based in situ microemulsion polymerization. The resulting nanocomposites were used as filler in a host polystyrene matrix to form composite films. An admixture of the two types of carbon fillers provided better improvement in the thermal and mechanical properties compared to the neat polymer. The sheet resistance decreased progressively due to the formation of an extended conjugation network with the CNT bridging the gap between the graphene sheets coated with polymer nanoparticles. The details of the analysis are presented.     

Polymorphism of nylon-6 in nylon-6/nanoclay/functionalized polyolefin blends

The crystallization behavior of Nylon-6 and the interaction in Nylon-6/nanoclay/functionalized polyolefin blends were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. For samples without any thermal history, the interaction between Nylon-6 and nanoclay or the interaction between Nylon-6 and functionalized polyolefin favors the formation of γ form crystal. In contrast, the presence of both nanoclay and functionalized polyolefin together in Nylon-6 was found to have an antagonistic effect on each other's ability to promote the formation of γ form crystal. This was attributed to the complex interactions between the constituents. The crystallization behavior of Nylon-6 in Nylon-6/nanoclay/functionalized polyolefin blends is clearly affected by the cointeraction of these effects. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1494–1502, 2007     

Synthesis of exfoliated isotactic polypropylene/functional alkyl-triphenylphosphonium-modified clay nanocomposites by in situ polymerization

Diphenyl (4-hydroxyphenyl) hexadecyl phosphonium bromide (POH) -modified montmorillonite (POHMMT) was used to prepare a novel TiCl₄/MgCl₂/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiCl₄/MgCl₂/POHMMT compound catalyst. The POH surfactants don’t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na⁺MMT nanocomposites were produced with the TiCl₄/MgCl₂/Na⁺MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.     

Preparation and characterization of polypyrrole/magnetite nanocomposites synthesized by in situ chemical oxidative polymerization

This work describes the preparation and characterization of polypyrrole (PPy)/iron oxide nanocomposites fabricated from monodispersed iron oxide nanoparticles in the crystalline form of magnetite (Fe₃O₄) and PPy by in situ chemical oxidative polymerization. Two spherical nanoparticles of magnetite, such as 4 and 8 nm, served as cores were first dispersed in an aqueous solution with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form micelle/magnetite spherical templates that avoid the aggregation of magnetite nanoparticles during the further preparation of nanocomposites. The PPy/magnetite nanocomposites were then synthesized on the surface of the spherical templates. Structural and morphological analysis showed that the fabricated PPy/magnetite nanocomposites are core (magnetite)‐shell (PPy) structures. Morphology of the PPy/magnetite nanocomposites containing monodispersed 4‐nm magnetite nanoparticles shows a remarkable change from spherical to tube‐like structures as the content of nanoparticles increases from 12 to 24 wt %. Conductivities of these PPy/magnetite nanocomposites show significant enhancements when compared with those of PPy without magnetite nanoparticles, in particular the conductivities of 36 wt % PPy/magnetite nanocomposites with 4‐nm magnetite nanoparticles are about six times in magnitude higher than those of PPy without magnetite nanocomposites. These results suggest that the tube‐like structures of 36 wt % PPy/magnetite nanocomposites may be served as conducting network to enhance the conductivity of nanocomposites. The magnetic properties of 24 and 36 wt % PPy/magnetitenanocomposites show ferromagnetic behavior and supermagnetism, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1291–1300, 2008     

A new conception on the toughness of nylon 6/silica nanocomposite prepared via in situ polymerization

A novel method, in situ polymerization, was used for the preparation of nylon 6/silica nanocomposites, and the mechanical properties of the nanocomposites were examined. The results showed that the tensile strength, elongation at break, and impact strength of silica-modified nanocomposites exhibited a tendency of up and down with the silica content increasing, while those of silica-unmodified nanocomposites decreased gradually. It also exhibited that the mechanical properties of silica-modified nanocomposites have maximum values only when 5% silica particles were filled. Based on the relationship between impact strength of the nanocomposites and the matrix ligament thickness τ, a new criterion was proposed to explain the unique mechanical properties of nylon 6/silica nanocomposites. The nylon 6/silica nanocomposites can be toughened only when the matrix ligament thickness is less than τ_c and greater than τ_a, where τ_a is the matrix ligament thickness when silica particles begin to aggregate, and τ_c is the critical matrix ligament thickness when silica particles begin to toughen the nylon 6 matrix. The matrix ligament thickness, τ, is not independent, which related with the volume fraction of the inorganic component because the diameter of inorganic particles remains constant during processing. According to the observation of Electron Scanning Microscope (SEM), the process of dispersion to aggregation of silica particles in the nylon 6 matrix with increasing of the silica content was observed, and this result strongly supported our proposal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 789–795, 1998     

Transport properties of aluminophosphate nanocomposite membranes prepared by in situ polymerization

Nanocomposite membranes containing 5 wt% microporous layered aluminophosphate in a polymer matrix were fabricated using in situ polymerization. The gas transport properties of these membranes were evaluated. Polyetherimide was combined with aluminophosphate swelled with several different surfactants. The glass transition temperature of these membranes increased as a result of adding the layered aluminophosphate, however, gas pair selectivity was not improved. A second experiment involved the addition of as-synthesized layered aluminophosphate, which was ball milled to small sizes, to a linear and branched polyimide based on 4,4′-oxydiphthalic anhydride (ODPA), 2,4,6-triaminopyrimidine (TAP), and 4,4′-oxydianiline (ODA) via in situ polymerization. In some cases the gas pair selectivities were improved as a result of adding the layered aluminophosphate. DMTA data suggest no mechanical enhancement with the addition of AlPO, which means that the layers were likely not exfoliated. For this reason, it is most likely that the selectivity enhancements in these samples were not due to molecular sieving through the microstructure of the aluminophosphate.     

PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.     

Amphiphilic heteroarm star polymer synthesized by RAFT dispersion polymerization in water/ethanol solution

Well-defined amphiphilic heteroarm core cross-linked star (CCS) polymer was efficiently synthesized by RAFT-mediated arm-first strategy in dispersion polymerization, and its direct self-assembly in water was demonstrated.     

Studies on the conducting nanocomposite prepared by in situ polymerization of aniline monomers in a neat (aqueous) synthetic mica clay

The in situ polymerization of the anilinium‐intercalated synthetic mica clay can easily result in an intercalated polyaniline (PANI)/clay nanocomposite. The FT‐IR spectra demonstrated a significant shift for ν_{(C? N)} at 1292 cm^?1 of the templated polymerized and intercalated PANI molecules. A red shift of λ_max for PANI was found from UV–vis spectra. The intercalated PANI also expanded the clay basal spacing seen from WAXD patterns. The degradation rate and temperature of the nanocomposites were found to alleviate and increase compared to neat PANI, respectively. The microscopic examinations including TEM, SEM, and AFM pictures of the nanocomposite demonstrated an entirely different and more compatible morphology. Conductivity of nanocomposite gradually increased with PANI and apparent increase was found when intercalated PANI content reached 40.6 wt %, the possible percolation threshold. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1800–1809, 2008