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CO2 laser micromachining provides a flexible and low-cost means for the rapid prototyping and manufacturing of miniaturized polymer systems such as polymethyl methacrylate (PMMA) microfluidic chip devices. In this paper, the relationships between the process variables (profile and depth of laser-ablated channels) and the process parameters (laser power and scanning velocity) are investigated. In contrast with the fabrication of 100–500 μm wide channels reported in previous work, we focus on the fabrication of narrower channels using low laser power which can reduce the cost of the fabrication system and low scanning speeds. In this work, the laser power used for channel fabrication ranged from 0.45 to 1.35 W and the scanning speeds ranged from 2 to 14 mm/s. The width of fabricated channels ranged from 44 to 240 μm and their depths ranged from 22 to 130 μm. Physical models were developed for predicting the depth and the profile of laser-ablated channels. The profile model incorporates the threshold fluence for CO2 laser ablation of PMMA to account for the partial ablation across the beam diameter. Our models are in excellent agreement with experimental results, with a maximum deviation of approximately 5%. [ABSTRACT FROM AUTHOR]

Five polymethyltrifluoropropylsiloxane (PMTFPS)–polyacrylate block copolymers (PMTFPS– b -polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n -butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10–50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at −15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS– b -polyacrylate copolymer can be used as icephobic coating materials potentially. [ABSTRACT FROM AUTHOR]

Abstract: A facile synthetic route for the preparation of magnetic poly(methyl methacrylate) (PMMA) core/polyethyleneimine (PEI) shell colloidal particles, possessing high saturation magnetization is reported. Bilayer oleic acid-stabilized iron oxide nanoparticles (bIOs) were designed to have both favorable encapsulation of iron oxide nanoparticles and interaction with protonated amine groups of PEI. The prepared particles had diameter ranging from 180 to 207 nm with narrow size distribution and displayed highly positive surface charges up to +47 mV. TEM revealed that the well-defined bIOs were successfully encapsulated inside the polymer core–shell colloids. Thermogravimetric analysis and magnetization study indicated that these colloidal particles had the magnetic material up to 80 wt % loading and exhibited superparamagnetic property with high saturation magnetization. Thus, they could be potentially useful in various applications, including magnetic separation, medical diagnostics, or drug delivery. [Copyright &y& Elsevier]

Abstract: New polarization and brightness curves as a function of scattering angle are studied at λ=632.8 and 543.5nm using PROGRA2 instruments (Propriétés Optiques des Grains Astronomiques et Atmosphériques) for four different kinds of soot and for two samples of carbon-black levitating in the cloud. The soot samples are also studied on the deposited surface. Two of the soot samples are issued from incomplete combustion of Toluene liquid solvent under two different combustion conditions. Two others are issued from a solid polymer. Polymethyl Methacrylate or PMMA under two different combustion conditions. These new studies are done using new more sensitive cameras than previous ones, allowing darker agglomerates to be detected. [Copyright &y& Elsevier]

Objective: To investigate mechanical properties of polymethyl methacrylate (PMMA) of different mixing ratios. Methods: At 25°C, self-curing denture acrylic and liquid dental base acrylic resin are mixed at mass-volume ratios of 1.5:1, 1:1, 1:1.25, 1:1.5, 1:1.75, 1:2 (g:ml) respectively, and stirred uniformly with a stirring speed of 60 revolutions per minute. A mould of 13 mm diameter and 100 mm length is filled with the mixture, and after it solidifies it is polished. The size of the model is accurate to 0.01 mm. A compression test, tensile test and three-point bending test are conducted. Results: The difference of compressive strength between groups with mixing ratios of 1.5:1 and 1:1 was not significant ( p = 0.326). However, the value of compressive strength of each of the first two groups was remarkably higher than that of the latter four groups ( p < 0.01). The difference of tensile strength among the first three groups was not significant ( p > 0.05), but the value of each groups was significantly higher than in the latter three groups ( p < 0.01). Deflection increased with the decrease of mixing ratio. For the first five groups, the value of elastic modulus decreased with the decrease of mixing ratio, which indicated that the rigidity of the test sample decreased accordingly ( p < 0.01). Conclusion: It can be concluded that PMMAs made from different mixing ratios of powdery polymer and liquid monomer has different mechanical properties. Therefore, during the preparation of PMMA, the mass-volume ratio of the reactants must be taken into precise consideration in order for the result to have optimum performance suitable for making bone substitutes and other applications in orthopaedic surgery. [ABSTRACT FROM AUTHOR]

Mechanical properties and three-body abrasive wear behavior of 5 and 10% w/w bio-based coleus spent (CS) filled and unfilled semi interpenetrating polymer network composites of unsaturated polyester/polymethyl methacrylate (80/20) have been studied. The tensile strength and elongation at break has been evaluated using 4302 Hounsfield Universal testing machine. The effect of abrading distances viz., 150, 300, 450, and 600m and different loads of 22 and 32N at 200 rpm on the abrasive wear behavior have been studied using dry sand/rubber wheel abrasive test rig. The CS filler lowered the mechanical properties and improved abrasion resistance of USP/PMMA SIPN. The tensile strength of the composites lies in the range of 25.0-33.1 MPa. The wear volume loss and specific wear rate as a function of abrading distance and load were determined. The wear volume loss increases with increased abrading distance/load for all composites tested. However, the specific wear rate decreased with an increase in abrading distance/load. CS filled USP/PMMA SIPN composites showed better abrasion wear resistance as compared to unfilled USP/PMMA SIPN. The worn surface features have been examined using scanning electron microscope. Also, the wear volume loss was correlated with the product of tensile strength and elongation at break. [ABSTRACT FROM AUTHOR]

Abstract  Polymer systems have various contents of rhodamine (Rh6G) doped Polymethyl methacrylate (PMMA) prepared by solution cast method. The structural and morphological properties were studied by Differential Scanning calorimetry (DSC), Fourier Transform Infrared spectroscopy (FTIR) Scanning Electron Microscopy (SEM) and X-ray diffraction methods. The induced effect on the strength of rhodamine (Rh6G) doped Polymethyl methacrylate (PMMA) samples were studied by measuring the surface microhardness using the Vicker’s microhardness tester. Significant changes were observed in the Vickers microhardness number (Hv) [ABSTRACT FROM AUTHOR]

The role of applied mechanical stress on space charge breakdown in electron beam irradiated polymethyl methacrylate (PMMA) is investigated. Space charge is implanted into PMMA sheets by electron beam. Space charge is measured by laser induced pressure pulse technique to investigate injection, trapping and detrapping of charge. Mechanical stress is applied on PMMA sheet to study its influence on space charge behavior. Experimental results show that applied electric field is not a necessary condition for breakdown of insulating materials. The breakdown can be triggered during space charge detrapping. The detrapping of space charge can result in tree-like breakdown, wherein this phenomenon is termed as space charge breakdown. Effect of applied mechanical stress on the initiation of breakdown and the development of tree-like breakdown is discussed in this paper. [ABSTRACT FROM AUTHOR]

Abstract  A new side chain liquid crystalline polymers have been synthesized and characterized in which [geraniol-co-MMA] polymer are used as a backbone linked via polymethylene spacer to phenyl benzoate mesogenic group. The polymer exhibits enantiotropic liquid crystallinity with nematic phase and does not exhibit side chain crystallization .A clear difference between the nature of the mesophase is evidenced between [Geraniol-co-MMA] main chain and methacrylate polymers .The LC polymer exhibit glass transition at 40 °C. In a comparative analysis, we discuss the relevance of polymer backbone in the synthesis of side chain liquid crystalline polymers. [ABSTRACT FROM AUTHOR]

Abstract: We have prepared nanocomposites containing large amounts of superparamagnetic nanoparticles dispersed in a polymethyl methacrylate matrix. The preparation was divided into three steps. In the first step, maghemite nanoparticles were synthesized using coprecipitation from aqueous solutions, followed by coating with oleic acid (OA). In the second step, the OA-coated nanoparticles were dispersed in n-decane to prepare a stable, concentrated suspension. Finally, methyl methacrylate was added to the suspension and in situ polymerization was carried out at elevated temperatures. The content of nanoparticles was controlled by varying the nanoparticles/monomer ratio. The main focus was on controlling the nanocomposite''s homogeneity. The nanocomposites were characterized using X-ray powder diffractometry, TEM, SEM, thermogravimetry, FT-IR, NMR and magnetic measurements. The TEM analysis showed that the nanoparticles were well dispersed in the polymer matrix. They retained their superparamagnetic nature even when encapsulated by polymer with concentrations up to 48wt.%. The high loading of magnetic nanoparticles resulted in relatively high saturation magnetizations of the nanocomposites, up to 31emu/g. [Copyright &y& Elsevier]

Polymethyl methacrylate (PMMA)-BN nanotube (BNNT) composites were fabricated and their mechanical and thermal properties were analyzed. Using a 1wt.% BNNTs fraction in a polymer, the elastic modulus of PMMA was increased up to 19%. In addition, thermal stability and glass transition temperature of PMMA were also positively affected. The thermal conductivity of PMMA with BNNT additions increased three times. The resultant BNNT-PMMA composites possess the high electrical breakover voltages. Thus our studies clearly indicate that BNNTs are promising nanofillers for improvement of mechanical and thermal conductivity of dielectric polymers under preservation of their electrical insulation. [ABSTRACT FROM AUTHOR]

Polymethyl methacrylate (PMMA) is a versatile thermoplastic that is well suited for engineering and many common applications. This article presents a study to evaluate the effect of the processing parameters (laser power and cutting velocity) under the quality of the cut of PMMA. A plan of experiments was established considering CO2 laser cutting with prefixed processing parameters in plates of PMMA with 6 mm thickness. The objective was to evaluate the quality of the cut (surface roughness, dimensional precision and heat affected zone-HAZ) in linear and complex 2D cutting. The obtained results show that PMMA in complex 2D cutting presents dimension of HAZ between 0.12 to 0.37 mm, without burr and low surface roughness Ra < 1 μm. The results present good repeatability. [ABSTRACT FROM AUTHOR]

Over the past years, a tremendous effort has been made to develop an intervertebral disc (IVD) prosthesis with suitable biological, mechanical and transport properties. However, it has been frequently reported that current prostheses undergo failure mainly due to the mismatch between the mechanical properties of the conventional device and the spine segment to be replaced. The aim of the present work was to develop a poly(2-hydroxyethyl methacrylate)/poly(methyl methacrylate) (PHEMA/PMMA) (80/20 w/w) semi-interpenetrating polymer network (s-IPN) composite hydrogel reinforced with poly(ethylene terephthalate) (PET) fibres, and to investigate the static and dynamic mechanical properties. Filament winding and moulding technologies were employed to obtain the composite IVD prostheses with the unique complex structure that is peculiar to the natural IVD. The compressive properties analysis showed the typical J-shaped stress-strain curve which is displayed by natural IVDs. Compressive modulus varied from 84 to 120 MPa, as a function of the strain rate, and stress was higher than 10 MPa. These values are in the range of those of the natural lumbar IVDs. No failure of the prostheses has occurred during fatigue test performed for ten million cycles in physiological solution. Dynamic mechanical tests have confirmed the composite IVD prostheses exhibited appropriate viscoelastic properties. [ABSTRACT FROM AUTHOR]

Abstract: Polymethyl methacrylate (PMMA) spheres synthesized at boiling temperature were used to fabricate non-close-packed arrays by vertical lifting method. Scanning electron microscope (SEM) images demonstrated that these spheres could stack with square lattices parallel to the substrate and the neighboring spheres in the same layer were not contacted each other. In addition, the distance between the spheres can be controlled by thermal treatment. The method gave a new approach for extending the possibility of nanospheres lithograph and the creation of photonic band gap materials. [Copyright &y& Elsevier]

The axisymmetric Laplace equation is solved numerically to extract contact-angle data for a flat liquid/vapor interface contacting a submerged hemispherical solid. The liquid/vapor interface is treated as a membrane, with a membrane tension equal to the surface energy of the liquid. By measuring the vertical displacement of the membrane and the projected contact area the membrane makes with the hemisphere, the contact angle and correspondingly the driving force for motion of the contact line can be measured. We show that characteristic receding and advancing contact angles can be obtained by measuring the contact radii formed upon initial contact between the interface and hemisphere and final contact just prior to detachment of the interface, respectively. Use of the technique is illustrated with a model experiment involving the contact of an air/water interface with a poly(methyl methacrylate) surface. [ABSTRACT FROM AUTHOR]

Abstract: Semi-interpenetrating polymer networks (SIPNs) of polyurethane (PU) and poly(methyl methacrylate) (PMMA) in different weight ratios viz., 90/10, 70/30, 60/40 and 50/50 were prepared. The SIPNs were characterized for physico-mechanical properties like density, tensile strength and elongation at break. Thermal stability of IPNs was measured using thermogravimetric analysis (TGA). From the TGA thermograms it was noticed that all IPNs are stable up to 325°C and undergo three-step thermal degradation in the temperature ranges 251–400, 378–508 and 445–645°C for first, second and third steps, respectively. Thermal degradation kinetic parameters like activation energy (E a) were calculated using Broido, Coats–Redfern and Horowitz–Metzger models. The values obtained by Broido and Horowitz–Metzger methods showed concurrency, whereas Coats–Redfern method showed relatively lower values. Surface morphology measured using scanning electron microscope (SEM) showed two-phase morphology for all the IPNs. [Copyright &y& Elsevier]

Abstract: The relaxation properties of poly(methyl cyclohexyl methacrylate)s (P2MCHMA), (P3MCHMA), (P4MCHMA) were analyzed. Dielectric spectroscopy (DS) techniques were used for this purpose. These polymers exhibit prominent α peaks, associated to the dynamic glass transitions, and then poorly defined β-relaxations and two other relaxation zones labelled as γ- and δ-relaxation in order of decreasing temperatures. The α relaxation processes were analyzed by means of the free volume theory, using the Vogel–Fulcher–Tammann–Hesse (VFTH) equation and in terms of the Havriliak–Negami (HN) empirical equation. Previously to these analyses, conductive contributions to the loss permittivity were subtracted. The apparent activation energies for the secondary processes under study have been calculated by means of Arrhenius. Comparison with previous relaxation results of poly(cyclohexyl methacrylate) (PCHMA), i.e. the polymer without substituents in the cyclohexyl ring, has been also carried out. In this way, changes in the glass transition absorptions as well as in the secondary processes have been discussed. [Copyright &y& Elsevier]

This paper reports on the relationship between structure and mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with randomly oriented short poly(vinyl alcohol) (PVA) fibres. Special focus was on the effect of fibre content on the impact resistance of PMMAIPVA composites. Instrumented Charpy impact tests were carried out to characterize the impact resistance of PMMAIPVA composites. Linear elastics fracture mechanics was used to determine the dynamic critical strain energy release rate (Gid) and the critical stress intensity factor (Kid). Fracture surfaces were observed using scanning electron microscopy (SEM). Dynamic mechanical analysis was carried out to describe the viscoelastic response of the material. Finally, the behaviour of PMMAIPVA composites was interpreted using current short-fibre composite models. It was shown that a small amount of added PVA fibres (0.42 - 1.68 vol.-%) led to an increase of elastic modulus and yield stress under impact conditions. Gid was also slightly increased, but K-d remained unchanged. Good agreement was found between SEM observations and fracture toughness measured under impact loading. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe qualitatively and quantitatively the non-random scission of polymers by ultrasound. Scission experiments have been performed using monodisperse polymethyl methacrylate dissolved in methyl methacrylate, showing that fracture occurs close to the center of the polymer chain. A mechanism is proposed for this non-random fracture, from which it can be concluded that complete stretching of the polymer chains is required before breakage can occur. The developed model, which is a combination of strain rate and drag force calculations, predicts a limiting molecular weight, which has experimentally been confirmed. The scission rate depends almost quadratically on the molecular weight, which is derived by modeling the experimental time-dependent molecular weight distributions. This dependence supports the requirement of complete stretching of the polymer chain before breakage. The developed degradation model is also capable to describe the effects of various process variables on cavitation-induced polymer scission. [Copyright &y& Elsevier]

Two series of cross-linked polymers were examined by equilibrium swelling: poly(methyl methacrylate)cross-linked with different amounts of triethylene glycol dimethacrylate and poly(urethane dimethacrylate)s derived from dicarbamates of oligoethylene glycols monomethacrylates and aromatic diisocyanates. The method of estimation of the length of primary chains has been proposed based on the full form of the Flory-Rehner equation. This required comparing the network parameter values obtained by swelling and those derived from some other sources. In some cases the results had no physical meaning, whereas in others they appeared to be consistent. The latter for poly(urethane dimethacrylate)s yielded the length of poly(methacrylate)primary chains in the range of two to eight, which seemed to be a reasonable result. [ABSTRACT FROM AUTHOR]

The molecular basis of fracture of polystyrene and poly(methyl methacrylate) homopolymers and their latex blends was investigated with a custom-built dental burr grinding instrument (DBGI). About a third of the chains were cut several times, the remainder not at all. The number of chain scissions in polystyrene and poly(methyl methacrylate) was quantitatively interpreted by the microscopic parameters of craze fibrils and the energy balance between chain scission and chain disentanglement (chain pullout). The probability that a polymer strand in the craze fibrils is scissioned or disentangled was calculated from the fracture energy balance. In addition, the fracture energy of the latex blends of polystyrene and poly(methyl methacrylate) was studied. The large interface between the polystyrene and the poly(methyl methacrylate) did not lead to a small fracture energy, as initially expected. Rather, the latex blend of the two immiscible polymers primarily absorbs the fracture stress by strong co-continuous bulk phases. [ABSTRACT FROM AUTHOR]

Polymers, such as poly(methyl methacrylate) (PMMA), are important structural materials for microsystems because of their excellent mechanical properties; however, they suffer from severe problems of adhesion, friction, and wear [B. Bhushan, J. N. Israelachvili, and U. Landman, Nature (London) 374, 607 (1995)]. We report a simple process of O2 plasma treatment on a PMMA film, followed by overcoating with an ultrathin layer of perfluoropolyether (PFPE) which improved tribological performance of the film. O2 plasma on PMMA film has formed unique wavy nanotextured surface and increased the hardness and the elastic modulus of the film, which, together with the nanolurbication by PFPE, has increased the wear life of PMMA film by more than five orders of magnitude. [ABSTRACT FROM AUTHOR]