PMMA Composites Research Articles

Preparation of Al(OH)3/PMMA nanocomposites by emulsion polymerization

AbstractAl(OH)3/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface‐functionalized Al(OH)3 particles. Nanosized Al(OH)3 particles were previously functionalized with a silane coupling agent, 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), which was confirmed by FT‐IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m−2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)3 core were produced with stable latex emulsion when the weight percents of Al(OH)3 to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)3 nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.

Influence of the surface modification of alumina nanoparticles on the thermal stability and fire reaction of PMMA composites

AbstractNanometric aluminum oxide particles were modified by phosphonic acid‐based oligomers of aromatic polyester, polyether, or polydimethylsiloxane (PDMS). The grafting process was characterized by FTIR spectroscopy and thermogravimetric analysis (TGA) showing that covalent bonds must have formed between the oxide and oligomers. The highest yield of grafting was achieved in dichloromethane (CH2Cl2) solvent. Then, nanocomposites were prepared by melt‐blending in a poly(methyl methacrylate) (PMMA) matrix. The best results in terms of thermal stability and flammability were obtained with the bis‐phosphonicpolydimethylsiloxane‐based formulation. With this latter, the peak of heat released rate (pHRR) decreased during the combustion, whereas PyGC/MS experiments led to the conclusion that PDMS‐covered nanoparticles played a role in the composition of the gaseous phase as well. Copyright © 2008 John Wiley & Sons, Ltd.

Near-edge x-ray absorption fine structure measurements using a laboratory-scale XUV source

We present a compact setup for near-edge x-ray absorption spectroscopy at the carbon K-edge based on a laser-driven plasma source. To generate the required broad-band emission in the spectral range of the ‘water window’ (λ = 2.2–4.4 nm) a krypton gas puff target was used. The table-top setup consisting basically of the laser-plasma source and a flat-field spectrometer can be used for near-edge x-ray absorption fine structure experiments in transmission as well as reflection under grazing incidence conditions (ReflEXAFS). The latter method offers the advantage that thin film preparation is not necessary and that the surface sensitivity is strongly enhanced. The results obtained for thin polymer films show good agreement with synchrotron data. Furthermore, we use the ReflEXAFS method to investigate changes in the chemical composition of PMMA induced by extreme ultraviolet (EUV) radiation. The spectra indicate a loss of the carbonyl functional group upon irradiation as well as crosslinking effects at high EUV radiation doses.

Coating zinc oxide submicron crystals on poly(methyl methacrylate) chips and spheres via ultrasound irradiation

Ultrasound irradiation is used for anchoring zinc oxide submicron crystals with a main diameter and length of ∼280nm and 470nm, respectively, onto the surface of poly(methyl methacrylate) PMMA chips (2mm diameter), and zinc oxide crystals with a mean diameter and length of ∼150nm and 230nm, respectively, onto the surface of the PMMA spheres (1–10μm). The zinc oxide crystals were obtained by sonochemical irradiation of a mixture containing the PMMA, zinc (II) acetate dihydrate, ethanol, water, and 24wt.% aqueous ammonia for 2h, yielding a PMMA–zinc oxide composite. By controlling the atmosphere and reaction conditions, we could achieve well-adhered zinc oxide crystals on the surface of poly(methyl methacrylate). The resulting zinc oxide–PMMA composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis (EDX), high-resolution scanning electron microscopy (HRSEM), and photoluminescence (PL) spectroscopy. The zinc oxide-deposited PMMA chips (loaded with 0.03–1.0wt.% ZnO) were successfully homogenized in melt by extrusion and then injection molded into small, disc-shaped samples. These samples were analyzed with respect to their directional spectral optical properties in UV, Vis and IR spectroscopy.

A 12 month in vivo study on the response of bone to a hydroxyapatite–polymethylmethacrylate cranioplasty composite

We investigated the osteoconductivity and biocompatibility in vivo of a new hydroxyapatite–polymethylmethacrylate (HA–PMMA) composite developed for use as an implant material for cranioplasty, which is expected to have the good osteoconductivity of HA together with the strength and ease of handling of PMMA. The HA–PMMA composites were implanted in eight full-grown beagles and then 6, 12, 24 weeks and 1 year after implantation, the animals were sacrificed and the implanted materials removed along with the surrounding tissues. Extirpated specimens were studied using an optical microscope and micro-computed tomography (micro-CT). Fibrous connective tissue was prominent in the interface of the composite at 6 weeks. New bone formation was seen around the implant, 12 and 24 weeks after operation. At 1 year, new bone filled in the interface of the HA–PMMA composite and adhered to the surrounding autogenous bone. Mixing HA and PMMA did not interfere with the osteoconductivity of the HA component. In micro-CT findings, the new bone growing on the HA–PMMA composite could be seen attaching preferentially to HA particles exposed at the composite surface, rather than the PMMA. This study demonstrated that this HA–PMMA composite is a good candidate for cranial bone implants due to its good osteoconductivity and biocompatibility.

Graphitic nanofillers in PMMA nanocomposites—An investigation of particle size and dispersion and their influence on nanocomposite properties

AbstractMechanical, thermal, and electrical properties of graphite/PMMA composites have been evaluated as functions of particle size and dispersion of the graphitic nanofiller components via the use of three different graphitic nanofillers: “as received graphite” (ARG), “expanded graphite,” (EG) and “graphite nanoplatelets” (GNPs) EG, a graphitic materials with much lower density than ARG, was prepared from ARG flakes via an acid intercalation and thermal expansion. Subsequent sonication of EG in a liquid yielded GNPs as thin stacks of graphitic platelets with thicknesses of ∼10 nm. Solution‐based processing was used to prepare PMMA composites with these three fillers. Dynamic mechanical analysis, thermal analysis, and electrical impedance measurements were carried out on the resulting composites, demonstrating that reduced particle size, high surface area, and increased surface roughness can significantly alter the graphite/polymer interface and enhance the mechanical, thermal, and electrical properties of the polymer matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2097–2112, 2007

Studying polymer-on-metal friction by thermodesorption mass spectrometry

A method for determining the parameters of thermal decomposition of polymer layers transferred onto a metal counterbody surface in the course of friction has been developed on the basis of thermodesorption mass spectrometry (TDMS). The efficacy of the proposed method is demonstrated using experimental data for poly(tetrafluoroethylene), polystyrene, and poly(methyl methacrylate) (PMMA). Using TDMS, it is possible to distinguish between damaged and intact molecules transferred in the course of friction in a relatively soft regime. TDMS data revealed differences in the character of thermal decomposition in the layers transferred during the friction of pure PMMA and PMMA-fullerene (C60) composition on steel.

Facile preparation of conductive paint made with polyaniline/dodecylbenzenesulfonic acid dispersion and poly(methyl methacrylate)

AbstractWe investigated an easy way to prepare industrially a conductive paint made with polyaniline (PANI)/dodecylbenzenesulfonic acid (DBSA) dispersion and poly(methyl methacrylate) (PMMA) in organic media. First, water‐dispersible PANI doped with DBSA was chemically synthesized with aniline sulfate using ammonium persulfate in water, and the resulting PANI/DBSA was readily extracted from the reaction medium with a mixture of toluene and methyl ethyl ketone (MEK) (toluene:MEK = 1:1 (v/v)), which is useful for industrial applications. The obtained PANI/DBSA organic dispersion was mixed with PMMA organic solution to give the corresponding PANI/DBSA conductive paint containing PMMA. A film prepared with the resulting PANI/DBSA conductive paint was found to possess relatively good conductivity and low surface resistivity for a conductive paint utilized for an electrostatic discharge even at low PANI/DBSA content in the PANI/DBSA–PMMA composite film (the conductivity and the surface resistivity were 9.48 × 10−4 S cm−1 and 3.14 × 106 Ω cm−2, respectively, when the feed ratio of PANI/DBSA:PMMA was 1:39 (w/w)). Furthermore, it was found that the conductivity of the film composed of PANI/DBSA–PMMA composite can be readily and widely controlled by the PANI/DBSA content of the composite or by the amount of DBSA used during the PANI/DBSA synthesis. The highest conductivity of PANI/DBSA–PMMA composite film (7.84 × 10−1 S cm−1) was obtained when the feed ratio of PANI/DBSA:PMMA was 1:4 (w/w). Copyright © 2007 Society of Chemical Industry

Magnetotransport in La 0.7Ca 0.3MnO 3–PMMA composites synthesized by polymeric precursor route

A detailed investigation on the effect of PMMA on the structure, microstructure and magnetotransport properties of manganite La 0.7Ca 0.3MnO 3 (LCMO) is presented. LCMO–PMMA nano-composites have been synthesized by a unique polymeric sol–gel route, which leads to improved solubility of PMMA in the LCMO matrix. The LCMO phase is grown in the presence of varying PMMA concentration at ∼500 °C. This route yields single-phase material at significant lower temperature (∼500 °C) and the grain size is observed to decrease slightly with increasing PMMA concentration. On increasing the PMMA concentration, T C undergoes a small decrease, resistivity is observed to increase by two orders of magnitude, with a concomitant large decrease in T IM, e.g., from ∼218 K for virgin LCMO to ∼108 K for ∼50 wt% PMMA admixed LCMO. Low field magnetoresistance measured in the temperature range 77–300 K shows considerable enhancement as a function of the PMMA concentration. These phenomena are explained by taking into account the increased intergranular disorder as a consequence of PMMA admixture.

Preparation and rheological characterization of poly(methyl methacrylate)/functionalized multi-walled carbon nanotubes composites

A method to synthesize poly(methyl methacrylate) (PMMA)-modified multi-walled carbon nanotubes (MWNTs) via emulsion polymerization under high shear is presented. The modification of PMMA on MWNT surfaces was confirmed by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectra, transmission electron microscopy and thermogravimetric analysis. PMMA composites with MWNTs and PMMA-modified MWNTs were prepared through melt mixing, and their morphology and rheological behavior were investigated. PMMA/PMMA-modified MWNTs composites have the rheological percolation threshold of 1.5 wt% MWNTs, but PMMA/MWNTs composites have the rheological percolation threshold of 2.5 wt%. The difference in rheological percolation threshold is mainly attributed to the larger gap between nanotubes exited in the PMMA/PMMA-modified MWNTs composites.

Interferometric measurement of light scattering behavior in continuous SiO 2 fiber in PMMA matrix composite

Possibility of an interferometric method was examined for evaluating local light scattering behaviors in light transmitting materials. Phase profiles of wavefronts through a continuous SiO 2 glass fiber–PMMA composite was measured by detecting transmitted light though the composite using the interferometric system with a pair of interferometers. Wavefront though the composite shows an anisotropic phase profile, and the phase delay originates from local light scattering due to refractive index difference at an interface between SiO 2 fiber and PMMA matrix. Measured wavefronts demonstrated that the interferometric method is effective tool for an evaluation of local light scattering.

Preparation and Properties of Three-dimensional Braided UHMWPE Fiber Reinforced PMMA Composites

In this study, three-dimensional (3-D) braided UHMWPE fiber reinforced PMMA resin (UHMWPE3DPMMA) composites are prepared by the vacuum impregnation technique. Research has been carried out to determine the mechanical properties and investigate the effects of fiber surface treatment and fiber volume fraction on the mechanical properties of the compsites. The results show that the UHMWPE3DPMMA composites possess excellent impact strength. XPS analysis reveals that oxygen-containing functional groups on the fiber surface increase after fiber surface treatment. It is found that enhanced interface adhesion results in substantial improvement of the flexural and shear properties, but a reduction in the impact strength. The flexural strength and modulus and the longitudinal shear strength increase markedly with increasing fiber volume fraction, attain maximum values at a Vf of 38%, but then decrease. The transverse shear strength exhibits continuous increase with Vf.

Preparation of Clay/PMMA Nanocomposites with Intercalated or Exfoliated Structure for Bone Cement Synthesis

AbstractSummary: Clay/PMMA nanocomposites were prepared by melt blending of an organically modified MMT with PMMA under various process conditions. The MMT clay was initially cation exchanged with octadecylammonium to enhance its hydrophobicity and to expand the interlamellar space of the silicate plates. PMMA was then inserted into the inter‐lamellar space of the modified clay by melt blending at an elevated temperature. The effects of blending temperature, blending time, and clay/PMMA compositions on the level of expansion and homogenization were investigated. Composites with intercalated and/or exfoliated clay structure were obtained depending upon the process conditions, as confirmed by XRD diffractometry. The thermal decomposition temperature (Td) and glass transition temperature (Tg) of the composites were determined, respectively, by TGA and DSC analyses. Marked improvements, up to 35 °C, of the thermal stability (Td) with respect to pure PMMA were achieved for many of the composite samples. The Tg of the composites, however, does not increase accordingly. Furthermore, a novel type of bone cement was synthesized by applying the clay/PMMA nanocomposites as a substitute for PMMA in a typical formulation. These bone cements demonstrated much higher impact strength and better cell compatibility than the surgical Simplex P cement. Therefore, the bone cements with clay/PMMA nanocomposites meet the requirement for the architectural design of orthopedic surgery.TEM images of an OA‐clay/PMMA composite.magnified imageTEM images of an OA‐clay/PMMA composite.

Estimation of the Compatibility Between Poly(Methylmethacrylate) and Poly(Styrene Co Vinyl Phenol) Blends from Dilute Solution Measurements

The compatibility of poly(methyl methacrylate) (PMMA) with poly(styrene‐co‐vinyl phenol) (PS‐VPh) with two different contents of vinyl phenol, 5.8 and 7.2%, in dilute tetrahydrofuran solutions has been investigated by size exclusion chromatography and fluorescence spectroscopy at 25°C. The chromatographic technique permits the evaluation of the preferential solvation at different PMMA/PS‐VPh ratios. Changes in the fluorescence properties of PS‐VPh, caused by its association with PMMA, were used to obtain the fraction of copolymer bound to PMMA at diverse PMMA compositions. Both techniques agree quantitatively in every system, indicating that the association increases when the PMMA concentration and the content of the vinyl phenol in the copolymer increase.

N-Type gas sensing characteristics of chemically modified multi-walled carbon nanotubes and PMMA composite

Multi-walled carbon nanotubes (MWCNTs) were chemically modified with hydroxylamine hydrochloride salt and formed a composite with poly(methyl methacrylate) (PMMA). The morphology observations by scanning electron microscopy (SEM) showed that MWCNTs were well dispersed in the PMMA film. The electrical responses of the composite to methanol vapor were investigated. The composite exhibited a decreased resistivity upon exposure to the reducing methanol vapor, denoting an n-type response which was fast, reversible and reproducible at room temperature. In addition, the response was free from the interference of humidity. It is proposed that the n-type, instead of the usually observed p-type, response of the MWCNT based composite, which is supported by its decreased resistivity in the reducing NH 3 vapor, is related to the modification of MWCNTs by the chemical treatment.

Temperature effects on the fatigue of highly filled PMMA

The modulus and fracture toughness of an ATH-filled PMMA composite are determined as a function of temperature. The modulus can be modelled as a series addition of the two phases, giving a decreasing modulus with temperature tending to zero at 110°C. The K1C value remains constant. Fatigue crack growth data in the form of da/dN versus K were obtained as a function of temperature and modelled using the Paris Law. The power index remained constant at 7.5, but the coefficient had a maximum at 50°C. It is suggested that this arises from microcracks generated by interparticle thermal stresses which are shown to have a maximum at the same temperature (50°C). A two-stage zone fatigue crack growth model was also applied to the data and gave a damage stress which correlated with the thermal stress and suggested a criterion based on achieving a constant energy per unit area.

Influence of dopant concentration on thermo-optic properties of PMMA composite

Thermo-optic (TO) coefficient (dT/dn ) as well as thermal expansion coefficients (β) of DR1/PMMA polymer film are measured for both TE (transversal electric) and TM (transversal magnetic) polarizations by using an attenuated total reflection (ATR) configuration at the wavelengths of 650, 832 and 1064 nm. Experimental results indicate that the absolute value of TO coefficient of DR1 (disperse red 1)/PMMA film does not always increase with the increasing wt.% of the dopant. The absolute value of TO coefficient of TE polarization is always larger than that of TM polarization due to the anisotropy of thermal expansion coefficient. Moreover, it is found that the found that the different values of TO coefficient at different wavelengths are mainly caused by the dispersion of the refractive index.

A Study on the Mechanical and Water Absorption Properties of Granite Powder/Epoxy Toughened with PMMA and Fly Ash/Epoxy Toughened with PMMA Composites

In this study, the properties of two particulate reinforced epoxy composites namely granite powder and fly ash have been assessed. An attempt has also been made to improve the pure matrix system epoxy resin using commercially available thermoplastic (polymethyl methacrylate). Pure blend matrix with different weight fractions of polymethyl methacrylate and epoxy are prepared and the blend matrix having the highest strength is selected for preparing composites. The composites are prepared with different weight percentages of granite powder and fly ash with the blend matrix, and their impact, compression, and water absorption properties are studied.

Cutting of carbon nanotubes by a two-roller mill

Cutting carbon nanotubes is an important issue encountered in many potential applications. It was found that multi-walled carbon nanotubes(MWNTs) could be cut short efficiently by a two-roller mill. The addition of poly (methyl methacrylate) (PMMA) could increase the cutting efficiency and make the lengths of as shortened carbon nanotubes more uniform. Both the milling times and MWNTs' content in PMMA composite had positive effects on the final lengths of as shortened MWNTs. The shortened MWNTs obtained from PMMA composites containing 25% MWNTs after being milled for 20 times showed a narrow length distribution of 250–300 nm and could form a homogeneous and stable dispersion in H 2CCl 2.

Low field magneto-transport in LBSMO–PMMA composite

The low field magneto-transport has been measured as a function of temperature in the range 77–300 K and magnetic field; H⩽3.6 kOe for La0.7Ba0.2Sr0.1MnO3 (LBSMO)–x wt% PMMA composites where x=0, 2, 6 and 10. The X-ray diffraction (XRD) study reveals that no structural modification has occurred in the LBSMO in the composite. Scanning electron microscopy (SEM) investigation shows PMMA getting dispersed through the sample volume and some LBSMO grains appear to be coated with the polymer. The metal-like transition observed at ∼150 K in the virgin LBSMO sample disappears in the composite samples and the resistance shows an increase of about three orders of magnitude as the polymer concentration is increased to 10 wt%. Despite this huge increase in the resistance, the low field magneto-resistance (LFMR) shows an enhancement although smaller than the values commonly observed for other manganite-polymer composite systems. Spin polarized tunneling that causes LFMR seems to be enhanced in the composites.