Flammability of styrenic polymer clay nanocomposites based on a methyl methacrylate oligomerically-modified clay

Nanocomposites of polystyrene, high impact polystyrene, acrylonitrile-butadiene-styrene terpolymer, polypropylene, and polyethylene were prepared using a methyl methacrylate oligomerically-modified clay by melt blending and the thermal stability and fire retardancy were studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed morphology, depending on the polymer.     

Methacrylate modified clays and their polystyrene and poly(methyl methacrylate) nanocomposites

Two methacrylate‐modified clays have been prepared and used to produce nanocomposites of polystyrene and poly(methyl methacrylate) by in situ polymerization. These nanocomposites have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), cone calorimetry and the evaluation of mechanical properties. When the clay contains only a single methacrylate unit, the styrene system is exfoliated but methacrylate is intercalated. When two methacrylate units are present on the cation of the clay, both systems are exfoliated. TGA data show that the thermal stability of all the nanocomposites is improved, as expected. The relationships between the fire properties and nanostructure of the nanocomposites are complicated, as shown by cone calorimetry. The conclusions that one may reach using cone calorimetry do not completely agree with those from XRD and TEM. The evaluation of mechanical properties shows an increase in Young's modulus for all nanocomposites along with a decrease in elongation; tensile strength is decreased for methacrylate nanocomposites but increased for styrenics systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis,Characterization of Modified Graphene Oxide/Poly(methyl methacrylate) Composites

Graphene oxide was prepared by improving Hummers method and then modified by 4,4′-oxydianiline to get aminated graphene oxide, which was used to construct redox initiator system with dibenzoyl peroxide for synthesis of poly(methyl methacrylate) grafted to graphene oxide by in situ polymerization. Nanocomposites used grafted polymer as fillers with loadings from 0.5 to 1.0 wt % of poly(methyl methacrylate) were obtained by solution blending. The structures, properties and morphology of graphene oxide, grafted poly(methyl methacrylate) and composites are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectra, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical thermal analysis and bacterial adhesion examination respectively. The initial decomposition temperature and the glass transition temperature of the nanocomposites are improved by addition of grafted poly(methyl methacrylate). Furthermore, there is a significant enhancement of the decreasing of the surface bacterial adhesion of prepared nanocomposites.     

Fire properties of styrenic polymer-clay nanocomposites based on an oligomerically-modified clay

An oligomerically-modified clay has been used to fabricate nanocomposites with styrenic polymers, such as polystyrene, high-impacted polystyrene, poly(styrene-co-acrylonitrile) and acrylonitrile-butadiene-styrene by melt blending. The clay dispersion was evaluated by X-ray diffraction and bright field transmission electron microscopy. All of the nanocomposites have a mixed delaminated/intercalated structure. The fire properties of nanocomposites were evaluated by cone calorimetry a nd the mechanical properties were also evaluated.     

Synthesis of poly(methyl methacrylate) nanocomposites via emulsion polymerization using a zwitterionic surfactant

The synthesis of nanocomposites via emulsion polymerization was investigated using methyl methacrylate (MMA) monomer, 10 wt % montmorillonite (MMT) clay, and a zwitterionic surfactant octadecyl dimethyl betaine (C18DMB). The particle size of the diluted polymer emulsion was about 550 nm, as determined by light scattering, while the sample without clay had a diameter of about 350 nm. The increase in the droplet size suggests that clay was present in the emulsion droplets. X-ray diffraction indicated no peak in the nanocomposites. Transmission electron microscopy showed that emulsion polymerization of MMA in the presence of C18DMB and MMT formed partially exfoliated nanocomposites. Differential scanning calorimetry showed an increase of 18 degrees C in the glass transition temperature (Tg) of the nanocomposites. A dynamic mechanical thermal analyzer also verified a similar Tg increase, 16 degrees C, for the partially exfoliated nanocomposites over poly(methyl methacrylate) (PMMA). Thermogravimetric analysis indicated a 37 degrees C increase in the decomposition temperature for a 20 wt % loss. A PMMA nanocomposite with 10 wt % C18DMB-MMT was also synthesized via in situ polymerization. This nanocomposite was intercalated and had a Tg 10 degrees lower than the emulsion nanocomposite. The storage modulus of the partially exfoliated emulsion nanocomposite was superior to the intercalated structure at higher temperatures and to the pure polymer. The rubbery plateau modulus was over 30 times higher for the emulsion product versus pure PMMA. The emulsion technique produced nanocomposites of the highest molecular weight with a bimodal distribution. This reinstates that exfoliated structures have enhanced thermal and mechanical properties over intercalated hybrids.     

Effects of clay‐modifying agents on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites synthesized via γ‐ray irradiation polymerization

Via γ‐ray irradiation polymerization, poly(methyl methacrylate) (PMMA)/clay nanocomposites were successfully prepared with reactive modified clay and nonreactive clay. With reactive modified clay, exfoliated PMMA/clay nanocomposites were obtained, and with nonreactive clay, intercalated PMMA/clay nanocomposites were obtained. Both results were confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. PMMA extracted from PMMA/clay nanocomposites synthesized by γ‐ray irradiation had higher molecular weights and narrow molecular weight distributions. The enhanced thermal properties of the PMMA/clay nanocomposites were characterized by thermogravimetric analysis and differential scanning calorimetry. The improved mechanical properties of PMMA/clay were characterized by dynamic mechanical analysis. In particular, the enhancement of the thermal properties of the PMMA/clay nanocomposites with reactive modified clay was much more obvious than that of the PMMA/clay nanocomposites with nonreactive clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3218–3226, 2003     

Highly enhanced electrical and mechanical properties of methyl methacrylate modified natural rubber filled with multiwalled carbon nanotubes

Developing conductive networks in a polymer matrix with a low percolation threshold and excellent mechanical properties is desired for soft electronics applications. In this work, natural rubber (NR) functionalized with poly(methyl methacrylate) (PMMA) was prepared for strong interfacial interactions with multiwalled carbon nanotubes (MWCNT), resulting in excellent performance of the natural rubber nanocomposites. The MWCNT and methyl methacrylate functional groups gave good filler dispersion, conductivity and tensile properties. The filler network in the matrix was studied with microscopy and from its non-linear viscoelasticity. The Maier-Göritze approach revealed that MWCNT network formation was favored in the NR functionalized with PMMA, with reduced electrical and mechanical percolation thresholds. The obvious improvement in physical performance of MWCNT/methyl methacrylate functionalized natural rubber nanocomposites was caused by interfacial interactions and reduced filler agglomeration in the NR matrix. The modification of NR with poly(methyl methacrylate) and MWCNT filler was demonstrated as an effective pathway to enhance the mechanical and electrical properties of natural rubber nanocomposites.     

Styrenic polymer nanocomposites based on an oligomerically-modified clay with high inorganic content

Clay was modified with an oligomeric surfactant containing styrene and lauryl acrylate units along with a small amount of vinylbenzyl chloride to permit the formation of an ammonium salt so that this can be attached to a clay. The oligomerically-modified clay contains 50% inorganic clay, and styrenic polymer nanocomposites, including those of polystyrene (PS), high-impact polystyrene (HIPS), styrene-acrylonitrile copolymer (SAN) and acrylonitrile-butadiene-styrene (ABS), were prepared by melt blending. The morphologies of the nanocomposites were evaluated by X-ray diffraction and transmission electron microscopy. Mixed intercalated/delaminated nanocomposites were formed for SAN and ABS while largely immiscible nanocomposites were formed for PS and HIPS. The thermal stability and fire properties were evaluated using thermogravimetric analysis and cone calorimetry, respectively. The plasticization from the oligomeric surfactant was suppressed and the tensile strength and Young's modulus were improved, compared to similar oligomerically-modified clays with higher organic content.     

Efficient photoinduced In situ preparation of clay/poly(glycidyl methacrylate) nanocomposites using hydrogen‐donor silane

Clay/poly(glycidyl methacrylate) nanocomposites (clay/PGMA) were prepared by in situ radical photopolymerization using N,N‐dimethylaminopropyltrimethoxysilane(DMA)‐modified bentonite clay acting as hydrogen donor for benzophenone in solution. This initiating system permits to photopolymerize glycidyl methacrylate between the lamellae of the DMA‐modified clay. The approach provides exfoliated nanocomposites as judged by the measurements of X‐ray diffraction. However, a low fraction of persistent intercalated clay regions was visible by transmission electron microscopy. X‐ray photoelectron spectra analyses indicate that the nanocomposites have PGMA‐rich surface. The clay/PGMA nanocomposites can be readily dispersed in ethanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 800–808     

Thermal and flame properties of polyethylene and polypropylene nanocomposites based on an oligomerically-modified clay

An oligomerically-modified clay was made using a surfactant which is the ammonium salt of an oligomer. The newly modified clay contains 37.5% inorganic clay and 62.5% oligomer. Polyethylene and polypropylene nanocomposites were made by melt blending the polymer with the oligomerically-modified clay in a Brabender mixer at various clay loadings. The structure of the nanocomposites was characterized by X-ray diffraction and transmission electron microscopy. Mechanical testing showed that the polyethylene nanocomposites had an enhanced Young's modulus and slightly decreased elongation, while the changes for polypropylene nanocomposites are small compared with the virgin polymers. The thermal stability and flame properties were evaluated using thermogravimetric analysis and cone calorimetry, respectively. The plasticising effect of the oligomer was suppressed because of the increased inorganic content. The maximum reduction in peak heat release rate is about 40%.     

Influence of interaction between poly(methyl methacrylate) and clay on the properties of nanocomposites prepared by a heterocoagulation method

To have a better insight into the effect of interaction between polymer matrix and clay on the properties of nanocomposite, poly(methyl methacrylate)/clay nanocomposites were prepared by a heterocoagulation method. Using a reactive cationic emulsifier, methacryloyloxyethyltrimethyl ammonium chloride (METAC), a strong polymer–clay interaction was obtained with the advantage of keeping a consistent polymer matrix property. X‐ray diffraction and transmission electronic microscopy indicated an exfoliated structure in nanocomposites. The glass transition temperature (T_g) of the nanocomposites was measured by DSC and DMA. The DMA results showed that with a strong interaction, PMMA–METAC nanocomposite showed a 20 °C enhancement in glass transition temperature (T_g), whereas a slight increase in T_g was observed for PMMA–cetyl trimethylammonium bromide (CTAB)/clay nanocomposite with a weak interaction. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 733–738, 2010     

Synthesis and characterization of polymer/clay nanocomposites by intercalated chain transfer agent

In situ synthesis of poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanocomposites by free radical polymerization using intercalated chain transfer agent (I-CTA) in the layers of montmorillonite (MMT) clay is reported. MMT clay was ion-exchanged with diethyl octyl ammonium ethylmercaptan bromide, which acts both as suitable intercalant and as chain transfer agent. These modified clays were then dispersed in methyl methacrylate (MMA) or styrene (St) monomers in different loading degrees to carry out the in situ free radical polymerization. The intercalation ability of the chain transfer agent and exfoliated nanocomposite structure were evidenced by both X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied.     

Effect of Organic Nano Carboncapsule Incorporated Modified Clay on Fire‐Retardancy of PMMA Nanocomposites

Here we investigate a new type of highly flame retardant poly(methyl methacrylate) (PMMA) nanocomposite by bulk polymerization of methyl methacrylate (MMA) in the presence of organic nano carboncapsule (OCNC/NCNC)‐incorporated modified montmorillonites (CL120, CL42). The morphology of the modified clay was confirmed by X‐ray diffraction (XRD), and Fourier transform infrared (FT‐IR) spectroscopy was used to identify the functional groups in the clay. The nano morphological characterization of the clay in the PMMA matrix was confirmed by XRD and transmission electron microscopy (TEM). The thermal and mechanical properties of the PMMA nanocomposites were investigated by thermogravimetry and dynamic mechanical analysis, respectively. PMMA containing organo nano carboncapsule‐doped CL42 modified cocoamphodipropionate (K2) (P‐O‐CL42) could achieve very high thermal stability compared to pristine PMMA. The 5% thermal decomposition temperature (T _5d) increased by 63.2°C. Storage modulus of PMMA nanocomposites measured by DMA analysis. An enhancement of storage modulus and significant reduction in the peak heat release (PHR) rate were observed in the almost all PMMA nanocomposites as compared to pristine PMMA. Moreover, these results suggest that PMMA nanocomposites can have potential applications in the building industry and the medical field.     

Preparation of nano poly(phenylsilsesquioxane) spheres and the influence of nano-PPSQ on the thermal stability of poly(methyl methacrylate)

The nano poly(phenylsilsesquioxane) spheres (nano-PPSQ) were prepared by the sol?Cgel method and incorporated into poly(methyl methacrylate) (PMMA) by in situ bulk polymerization of methyl methacrylate. The structure of nano-PPSQ was confirmed by transmission electron microscope and thermogravimetry analysis (TG). The interaction between nano-PPSQ and PMMA was investigated by Fourier transform infrared spectra (FT-IR). The influence of nano-PPSQ on the thermal stability of PMMA was investigated by TG and differential scanning calorimetry (DSC) measurements. The results indicated that nano-PPSQ enhanced the thermal stability and the temperatures of glass transition (T _g) of nanocomposites. The effect of the heating rate in dynamic measurements (5?C30?°C?min^?1) on kinetic parameters such as activation energy by TG both in nitrogen and air was investigated. The Kissinger method was used to determine the apparent activation energy for the degradation of pure PMMA and nanocomposites. The kinetic results showed that the apparent activation energy for degradation of nanocomposites was higher than that of pure PMMA under air.     

Polystyrene nanocomposites based on an oligomerically-modified clay containing maleic anhydride

An oligomerically-modified clay containing maleic anhydride was used to prepare polystyrene-clay nanocomposites by melt blending and the effect of this modified clay on the thermal stability and fire performance was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed immiscible/intercalated/delaminated morphology. The maleic anhydride modified clay improved the compatibility between the clay and the polystyrene.     

Exfoliation of montmorillonite by the insertion of disklike micelles via the soap‐free emulsion polymerization of methyl methacrylate

Montmorillonites (MMTs) intercalating a potassium persulfate initiator were readily exfoliated in the presence of polymerizing methyl methacrylate during soap‐free emulsion polymerization. Because of the confined space, the polymerizing chains were aggregated into a disk form inside the clay interlayer regions for micellation. It was surprising to find from X‐ray diffraction analysis that the exfoliation of MMT was almost completed in the micellation stage. Further polymerization afforded latex particles of exfoliated poly(methyl methacrylate) (PMMA)–MMT nanocomposites. In addition, two kinds of MMT nanosheets were collected by the removal of PMMA with toluene: One was a single‐layer nanosheet with a thickness of 1.25 nm, and the other was a stacked sheet with an average thickness of 7.5 nm that may have consisted of six individual layers. Electron diffraction analysis revealed that if the individual layer of an MMT nanosheet were not a single crystal, it should contain an ultrathin layer of ice with a commonly occurring hexagonal phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5572–5579, 2006     

Exfoliated poly(methyl methacrylate) and polystyrene nanocomposites occur when the clay cation contains a vinyl monomer

The bulk polymerization of methyl methacrylate and styrene in the presence of an organically modified clay containing a vinyl group that can be involved in the polymerization produces exfoliated nanocomposites. These nanocomposites have been characterized by X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, mechanical properties, and cone calorimetry. The onset temperature of thermal degradation increases with the mechanical properties. The peak heat release rate is significantly reduced for nanocomposites containing 3 or 5% clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1124–1135, 2003     

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?Cvis 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.     

Investigating the effect of nanolayered silicates on blend segmental dynamics and minor component relaxation behavior in poly(ethylene oxide)/poly(methyl methacrylate) miscible blends

Polymer–silicate nanocomposites based on poly (ethylene oxide), PEO, poly(methyl methacrylate), PMMA, and sodium montmorillonite clay were fabricated and characterized to investigate the effect of nanolayered silicates on segmental dynamics of PEO/PMMA blends. X‐ray results indicate the formation of an exfoliated morphology in the nanocomposites. At low silicate contents, an enhancement in segmental dynamics of blend nanocomposites and also PEO, minor component in blend, is observed at temperature region below blend glass transition. This result can be attributed to the improvement of the confinement effect of rigid PMMA matrix on the PEO chains by introducing a low amount of layered silicates. On the other hand, at high silicate contents, an enhancement in segmental dynamics of blend nanocomposites and PEO is observed at temperature region above blend glass transition. This behavior could be interpreted based on the reduction of monomeric friction between two polymer components, which can facilitate segmental motions of blend components in nanocomposite systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

In situ Synthesis of Poly(methyl methacrylate)/Graphene Oxide Nanocomposites Using Thermal-initiated and Graphene Oxide-initiated Polymerization

A facile and cost-effective method to prepare poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposites was developed by in situ polymerization. By using thermal-initiated and GO-initiated polymerization of methyl methacrylate (MMA), no extra radical initiator was added during the reaction. Without any pre-functionalization of GO, PMMA chains were covalently bonded to its surface, which was confirmed by Fourier-transform infrared, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy investigations. TGA analysis showed that the mass ratio of grafted PMMA and GO was as high as 1.7. Transmission electron microscopy and X-ray powder diffraction investigations demonstrated that the grafting of PMMA chains to GO surfaces resulted in homogeneous dispersion of GO sheets in PMMA matrix, which led to a commendable performance on its mechanical and thermal properties. Dynamic mechanical analysis showed that, at a loading level of just 0.5 wt% for the nanocomposites, the storage modulus of the nanocomposites was improved 14%, and the glass transition temperature was increased 12°C in comparison with that of neat PMMA. Thermogravimetric analysis showed that the onset degradation temperature of the nanocomposites was increased 13°C with a GO content of 0.25 wt%.