Synthesis and characterization of monomer‐casting polyamide 6/polymethacrylic ionomer blends

Monomer‐casting polyamide 6 (MCPA6)/polymethacrylic ionomer blends were synthesized by the in situ anionic ring‐opening polymerization of ?‐caprolactam. The polymethacrylic ionomer used in this study was a copolymer of methyl methacrylate and sodium or zinc methacrylate. Because the polymethacrylic ionomer strongly interacted with polyamide 6 (PA6) chains, it influenced the alignment of the polyamide chains. The change in the degree of the order of hydrogen bonding in MCPA6 caused by the addition of the polymethacrylic ionomer was studied with Fourier transform infrared. The change in the interaction between PA6 chains was studied with rheological measurements. The influence of the polymethacrylic ionomer on the crystallization behavior of MCPA6 was also studied with differential scanning calorimetry. The isothermal crystallization and subsequent melting behavior were investigated at the designated temperature. The commonly used Avrami equation was used to fit the primary stage of the isothermal crystallization. The Avrami exponent (n) values were evaluated to be 2 < n < 3 for the neat MCPA6 and MCPA6/polymethacrylic ionomer blends. The polymethacrylic ionomer, acting as a stumbling‐block agent in the blends, decelerated the crystallization rate with the half‐time of crystallization increasing. The polymethacrylic ionomer made the molecular chains of MCPA6 more difficult to crystallize during the isothermal crystallization process. More less perfect crystals formed in the MCPA6/polymethacrylic ionomer blends because of the interaction between the MCPA6 molecular chains and polymethacrylic ionomer. The crystallinity of the blends was depressed by the addition of the polymethacrylic ionomer. The thermal stability was also studied with thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Use of a new natural clay to produce poly(methyl methacrylate)‐based nanocomposites

Nanocomposites of poly(methyl methacrylate) (PMMA) filled with 3 wt% of modified natural Algerian clay (AC; montmorillonite type) were prepared by either in situ polymerization of methyl methacrylate initiated by 2,2′‐azobisisobutyronitrile or a melt‐mixing process with preformed PMMA via twin‐screw extrusion. The organo‐modification of the AC montmorillonite was achieved by ion exchange of Na⁺ with octadecyldimethylhydroxyethylammonium bromide. Up to now, this AC montmorillonite has found applications only in the petroleum industry as a rheological additive for drilling muds and in water purification processes; its use as reinforcement in polymer matrices has not been reported yet. The modified clay was characterized using X‐ray diffraction (XRD), which showed an important shift of the interlayer spacing after organo‐modification. The degree of dispersion of the clay in the polymer matrix and the resulting morphology of nanocomposites were evaluated using XRD and transmission electron microscopy. The resulting intercalated PMMA nanocomposites were analysed using thermogravimetric analysis and differential scanning calorimetry. The glass transition temperature of the nanocomposites was not significantly influenced by the presence of the modified clay while the thermal stability was considerably improved compared to unfilled PMMA. This Algerian natural montmorillonite can serve as reinforcing nanofiller for polymer matrices and is of real interest for the fabrication of nanocomposite materials with improved properties. Copyright © 2009 Society of Chemical Industry     

Synthesis and properties of monomer casting polyamide 6/poly(methyl methacrylate) blends

We successfully synthesized monomer casting polyamide 6 (MCPA6)/poly(methyl methacrylate) (PMMA) blends in two steps: (1) radical polymerization of methyl methacrylate in ?‐caprolactam and (2) anionic ring‐opening polymerization of this ?‐caprolactam solution. The influence of PMMA on the crystallization behavior of MCPA6 was studied with differential scanning calorimetry and X‐ray diffraction, which showed that PMMA could act as a heterogeneous nucleation agent and favored the formation of the γ‐crystalline form. The rheological properties were also studied and indicated that PMMA reduced the interaction between MCPA6 chains by lowering the density of hydrogen bonding. This study used a novel and convenient method to prepare microporous MCPA6/PMMA particles that involved removing the continuous phase. Their surface area and thermal stability were characterized by the Brunauer–Emmett–Teller method and thermogravimetric analysis, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The effect of polyoxypropylene‐montmorillonite intercalates on polymethylmethacrylate

Polymethylmethacrylate (PMMA)‐layered silicate nanocomposites have been prepared by in situ polymerization of commercial type of methylmethacrylate monomer (MMA), for denture base material, into organoclay. Organoclay was prepared through an ion exchange process between sodium cations in montmorillonite and NH₃⁺ groups in polyethertriamine hydrochloride and polyoxypropylene triamine hydrochloride with different molecular weight (5000, 440). X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the structure of the resulting composites. Both intercalated and exfoliated nanocomposites were obtained depending on the type and amount of organoclay. The thermal decomposition temperatures of the nanocomposites were found to be higher than that of pristine polymer. PMMA was strongly fixed to inorganic surfaces, due to cooperative formation of electrostatic bonding between NH₃⁺ group and negatively charged surface of layered silicate and amide linkage between PMMA and polyethertriamine or polyoxypropylene triamine. The effect of the organoclay on the hardness, toughness, tensile stress, and elongation at break of the polymer was studied and was compared with pristine polymer. The hardness and Izod impact strength of PMMA‐organoclay nanocomposites were enhanced with the inclusion of clay. Tensile properties appear to be enhanced at certain organoclay content. However, the water absorption is slightly higher than the pristine PMMA. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synthesis of Na+‐montmorillonite/amphiphilic polyurethane nanocomposite via bulk and coalescence emulsion polymerization

Polyurethane/clay nanocomposites have been synthesized using Na⁺‐montmorillonite (Na⁺‐MMT)/amphiphilic urethane precursor (APU) chains that have hydrophilic polyethylene oxide (PEO) chains and hydrophobic segments at the same molecules. Nanocomposites were synthesized through two different crosslinking polymerization methods. One is UV curing of melt mixed APU/Na⁺‐MMT mixtures; the other is coalescence polymerization of APU/Na⁺‐MMT emulsions. These two kinds of composites had intercalated silicate layers of Na⁺‐montmorillonite by insertion of PEO chains in APU chains, which was confirmed by X‐ray diffraction measurement and transmission electron microscopy. These composite films also showed improved mechanical properties compared to pristine APU films. Although the two kinds of nanocomposites exhibited the same degree of intercalation and were synthesized based on the same precursor chains, these nanocomposite films had the different mechanical properties. Nanocomposites synthesized using APU/Na⁺‐MMT emulsions, having microphase‐separated structure, had greater tensile strength than those prepared with melt‐mixed APU/Na⁺‐MMT mixtures. Location of intercalated Na⁺‐MMT by PEO chains at the oil–water interface also could be confirmed by rheological behavior of the APU/Na⁺‐MMT/water mixture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3130–3136, 2003     

Preparation and characterization of transparent poly(methyl methacrylate)/Na+‐MMT nanocomposite films by solution casting

Films of poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na⁺‐MMT) nanocomposites have been successfully prepared utilizing Na⁺‐MMT by N,N‐dimethylformamide solution casting. The nanocomposite films show high transparency, enhanced thermal resistance, and mechanical properties in comparison with the neat polymer film. The transparency of the films was investigated by UV‐vis spectra. The exfoliated dispersion of Na⁺‐MMT platelets in nanocomposites were investigated by X‐ray diffraction and transmission electron microscopy. The enhanced thermal resistance and mechanical properties of PMMA were studied by thermal gravimetric analysis and dynamic mechanical analysis, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nanoclay dispersion in a miscible blend: an assessment through rheological analysis

In this study, miscible polymer blend nanocomposite of Poly(ethylene oxide)/Poly(methyl methacrylate), (PEO/PMMA), with sodium montmorillonite (Na⁺-MMT) clay were prepared at a constant concentration of nanoparticles via different solution intercalation methods. The resultant nanocomposites possess different structure and dispersion of Na⁺-MMT clays which are assessed through a combination of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The rheology of the neat blend and two different layered silicate nanocomposites were investigated using linear viscoelastic measurements with a parallel plate rheometry at small strain amplitudes. It was found that regardless of the extent of dispersion, the storage and loss modulus increased by incorporating the nanoparticles into the matrix of PEO/PMMA. Moreover, at low frequencies the rheological response of the nanocomposite in which layered silicates benefit from a better dispersion becomes relatively invariant with frequency and represents a mediocre solid-like behavior in comparison to the nanocomposite in which the nanoparticles are intercalated or agglomerated.     

Synthesis and dielectric properties of poly(methyl methacrylate)–clay nanocomposite materials

Poly(methyl methacrylate) (PMMA)–clay nanocomposite (PCN) materials were synthesized through in situ intercalative polymerization. A cationic surfactant, [2(dimethylamino)ethyl]triphenylphosphonium bromide, was used as an intercalating agent with pristine Na⁺‐montmorillonite (MMT). The synthesized PCN materials were subsequently investigated by a series of characterization techniques, including wide‐angle powder X‐ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Compared to pure PMMA, the PCN materials exhibit higher thermal degradation temperatures and glass‐transition temperatures. The dielectric properties of PCN blending with a commercial PMMA material in film form with clay loading from 0.5 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 35–100°C. Significantly depressed dielectric constants and losses were observed for these PCN‐blending materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2175–2181, 2005     

Polymerization of ethyl methacrylate,methyl methacrylate,and vinyl acetate using sulfonated polystyrene as the initiator

Polymerization of ethyl methacrylate (EMA) and methyl methacrylate (MMA) was achieved in glass dilatometers, at 86°C, using polystyrene sulfonate (Na⁺ and H⁺ forms) as initiators. The conversion of EMA to PEMA and MMA to PMMA increased with the time of polymerization, quantity of initiator, and size of dilatometer but decreased with volume of water. The polymer yield was higher for the Na⁺ than for the H⁺ form of the resin initiator. The average degree of polymerization increased with increase in the volume of water, but decreased with the quantity of initiator. Vinyl acetate could not be polymerized using either the Na⁺ or H⁺ forms of the polystyrene sulfonate as the initiator under the conditions of EMA or MMA polymerization.     

Studies on synthesis and characterization of poly(methyl methacrylate)‐bentonite clay composite by emulsion polymerization and simultaneous in situ clay incorporation

Well‐dispersed poly(methyl methacrylate) (PMMA)–bentonite clay composite was synthesized by emulsion polymerization using methyl methacrylate (MMA) monomer and 3% sodium carbonate treated bentonite clay. The composite lost its transparency normally encountered with the neat PMMA. The composite was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), vicat softening point (VSP), dynamic mechanical thermal analysis (DMTA), and tensile studies. The morphology was investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM) as well. The crystallography was studied to estimate the changes in crystallographic planes by X‐ray diffraction (XRD) analysis. The particle size distribution was compared amongst neat bentonite clay, neat PMMA and the composite. The FTIR spectra reveal the fact that no new primary valence bond is formed between the clay and PMMA. The thermal stability of the composite is significantly improved, as indicated by the TGA and VSP studies. A substantial increase in glass transition temperature (T_g) approximately, 10°C was recorded from the DMTA as both the storage modulus and tan δ values underwent inflexion at higher temperatures in case of the composite compared with the pristine PMMA. The XRD pattern indicates increase in basal “d” spacing for the composite. The morphology from both the SEM and AFM is quite supportive to well‐dispersed exfoliation. The incorporation of nanosized activated clay particles in PMMA during its in situ polymerization from MMA led to the formation of nanocomposites. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Antimicrobial resistance of clay polymer nanocomposites

Antimicrobial-resistant polymeric Na⁺–bentonite nanocomposites were prepared by treating Na⁺–bentonite (Na⁺–Bent) with polymeric ultra-thin films of poly(diallyldimethyl ammonium chloride) (PDADMAC), poly(methylmethacrylate) (PMMA) and poly(vinylidene chloride) (PVDC) by admicellar polymerization technique. The clay polymer nanocomposites (CPNs) were characterized by several techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), BET surface analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). In additional, the antimicrobial resistance was studied by measuring the diameter of inhibition zone of growths of Escherichia coli and Salmonella typhimurium. The results showed an inhibitory effect of these CPN against microbial growth in inoculated samples. The CPN exhibited efficacy in the inhibition of bacterial growth.     

Study on superabsorbent composites. IX: Synthesis,characterization and swelling behaviors of polyacrylamide/clay composites based on various clays

A series of clay-based superabsorbent composite from acrylamide (AM) and various clays, such as attapulgite, kaolinite, mica, vermiculate and Na⁺-montmorillonite, was prepared by free-radical aqueous polymerization, using N,N′-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator, and then saponified with sodium hydroxide solution. In this paper, the reaction mechanism and thermal stability of the superabsorbent composites incorporated with various clays were characterized by FTIR, XRD and TGA, respectively. The effects of clay kind and clay content on equilibrium water absorbency of these composites were also investigated and compared. In addition, the influences of clay kind on comprehensive swelling behaviors of the PAM/clay superabsorbent composites were studied. The results indicated that the introduced clays could influence physicochemical properties of obtained superabsorbent composites. Mica could improve thermal stability of corresponding superabsorbent composites to the highest degree comparing with the other clays. The PAM/clay superabsorbent composites incorporated with 10 wt% clay of various kinds were all endowed with equilibrium water absorbency of more than 1300 g g⁻¹. The equilibrium water absorbency decreases with increasing clay content and correlates with the kind of clay. Attapulgite-based superabsorbent composite was endowed with higher water absorbency in univalent cationic saline solution, however, the vermiculite- and the kaolinite-based ones acquired the highest water absorbency in CaCl₂ and FeCl₃ aqueous solution, respectively. Moreover, the superabsorbent composites incorporated with Na⁺-montmorillonite have higher swelling rate and that of doped with mica was endowed with higher reswelling capability.     

Ionomers made from terpolymers with uniform poly(methyl methacrylate) grafts

Terpolymers with uniform poly(methyl methacrylate) (PMMA) grafts were prepared by terpolymerization of PMMA macromonomer, butyl acrylate, and acrylic acid in benzene using AIBN as initiator. During terpolymerization the macromonomer polymerizes faster than the monomers at the beginning but slower at the latter stage. The terpolymers were purified by solvent extraction and fractional precipitation. The average grafting number per chain of the terpolymers was determined to be 3–8. Ionomers were obtained by neutralization of the terpolymers with alkali hydroxide or metallic acetate. Dynamic mechanical spectrum of the ionomer shows the existence of two T_g's, which implies the occurence of microphase separation. The ionomer exhibits high damping over a temperature range from ?25 to 100°C. Both PMMA grafts and metallic carboxylate content raise the tensile strength of the ionomer and lower the ultimate elongation. The tensile strength of ionomers neutralized with different metallic ions decreases in the following order: Pb²⁺ > Zn²⁺ > Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. The ionomers with uniform PMMA grafts show much better mechanical properties than the terpolymer without neutralization or the ionomer without PMMA grafts.     

Synthesis and evaluation of high‐performance ethylene–propylene–diene terpolymer/organoclay nanoscale composites

The main objective of this study was to synthesize and characterize the properties of ethylene–propylene–diene terpolymer (EPDM)/clay nanocomposites. Pristine clay, sodium montmorillonite (Na⁺–MMT), was intercalated with hexadecyl ammonium ion to form modified organoclay (16Me–MMT) and the effect of intercalation toward the change in interlayer spacing of the silicate layers was studied by X‐ray diffraction, which showed that the increase in interlayer spacing in Na⁺–MMT by 0.61 nm is attributed to the intercalation of hexadecyl ammonium ion within the clay layers. In the case of EPDM/16Me–MMT nanocomposites, the basal reflection peak was shifted toward a higher angle. However, gallery height remained more or less the same for different EPDM nanocomposites with organoclay content up to 8 wt %. The nanostructure of EPDM/clay composites was characterized by transmission electron microscopy, which established the coexistence of intercalated and exfoliated clay layers with an average layer thickness in the nanometer range within the EPDM matrix. The significant improvement in thermal stability and mechanical properties reflects the high‐performance nanocomposite formation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2429–2436, 2004     

Morphology and Thermal Stability of Novolac Phenolic Resin/Clay Nanocomposites Prepared via Solution High‐Shear Mixing

Phenolic resin/clay composites were prepared by high‐shear mixing of clay suspended in CH₃OH solutions of Novolac resin and curing agent. Pure clay Cloisite Na⁺ and pillared clays Cloisite 10A, 30B, and Na⁺Cloisite that was pillared by 3‐hexadecyl‐1‐methylimidazolium bromide were studied. After CH₃OH evaporation, Novolac was cured at low temperatures. XRD showed that clay gallery d‐spacings decreased upon solvent evaporation and partial curing. Slight d‐spacing increases were sometimes observed from a partially cured stage to a further cured composite. Na⁺Cloisite gave the highest nanodispersion, Cloisites 10A and 30B the lowest. TGA revealed that Na⁺ clay or organoclay incorporation in partially cured and cured composites did not improve the thermal stability of Novolac.

     

The disorderly exfoliated LDHs/PMMA nanocomposite synthesized by in situ bulk polymerization

A new nanocomposite—disorderly exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA)—was prepared by a two-stage process with an in situ bulk polymerization of methyl methacrylate (MMA) in the presence of 10-undecenoate intercalated LDH (LDH-U). The LDH-U was prepared using the co-precipitation method. The structural and compositional details of the LDH-U were determined by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), ²⁷Al and ¹³C magic-angle spinning nuclear magnetic resonance (²⁷Al and ¹³C MAS NMR), elemental analysis (EA), inductively coupled plasma-mass (ICP) and transmission electron microscopy (TEM). During the preparation of LDHs/PMMA nanocomposite, XRD and TEM were also employed to monitor the formation of the exfoliated LDHs/PMMA nanocomposite and the dispersion behavior of the LDH layers, respectively. The pre-polymerization process exfoliates LDH layers within pre-polymer, according to the XRD and TEM results. Additionally, the LDHs/PMMA nanocomposite contained 5 wt% LDH-U, indicating that the LDH layers were well exfoliated and dispersed in the PMMA matrix in a disordered fashion.     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

Controlled radical polymerization of poly(methyl methacrylate‐g‐epichlorohydrin) using N,N‐dithiocarbamate‐mediated iniferters

Poly(epichlorohydrin) (PECH) with pendent N,N‐diethyl dithiocarbamate groups (PECH‐DDC) was prepared by reaction of PECH with sodium N,N‐diethyl dithiocarbamate (DDC) in anhydrous ethanol, before being used as a macrophotoinitiator for the graft polymerization of methyl methacrylate. Photopolymerization was carried out in a photochemical reactor at a wavelength greater than 300 nm. Controlled radical polymerization was confirmed by the linear increase of the molecular weight of polymers with conversion. The polydispersity remained at 1.4–1.6 during polymerization. The formation of PMMA‐g‐PECH copolymer was characterized by GPC, ¹H‐NMR, FTIR spectroscopy, and DSC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of Calcium Silicate Hydrate in Highly Alkaline System

Synthesis of calcium silicate hydrate (C‐S‐H) was conducted over the range of 50°C–90°C and C/S ratio of 0.86–2.14 in the highly alkaline Na₂O–CaO–SiO₂–H₂O system for silicon utilization in high alumina fly ash. Structural change in C‐S‐H formed in the highly alkaline system was investigated using XRD and ²⁹Si MAS NMR spectra. X‐ray photoelectron spectroscopy was used to confirm the amount of sodium ions in C‐S‐H. Conversion of Si may reach 99% under optimum conditions. A higher degree of polymerization of silicate was obtained at lower temperature and C/S ratio. Na⁺ was confirmed to exist as Na–OSi and Na–OH. The amount of Na⁺ is the least at C/S ratio of 1.43, which conform to the prediction of topological constraint theory. High Ca/Si ratio leads to the increasing in Na⁺ combined in the interlayer. Increasing in the Na⁺ concentration in the system also increases the amount of Na⁺ combined in the interlayer and reduces the polymerization. Ion exchange was proven to be an effective way to remove Na⁺ combined in the interlayer of C‐S‐H.     

An investigation into the degree and rate of polymerization of poly(methyl methacrylate) in the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate

Room‐temperature ionic liquids (ILs), including 1‐butyl‐3‐methylimidazolium hexafluorophosphate, [bmim⁺][PF₆^?], were investigated as replacements for volatile organic compounds in the free‐radical solution polymerization of poly(methyl methacrylate) (PMMA). The latter was synthesized in benzene and [bmim⁺][PF₆^?] at 70 °C via a free‐radical process and the degree and rate of polymerization were compared based on the solvent used. The degree of polymerization was found to be five times higher in [bmim⁺][PF₆^?] than in benzene, while the rate of reaction was approximately four times faster in [bmim⁺][PF₆^?]. The results indicate the potential for using ILs to produce high‐molecular‐weight polymers and block structures based on the increased free‐radical stability in ILs. Copyright © 2004 Society of Chemical Industry