Effect of filler particle size on dynamic mechanical properties of poly(methyl methacrylate)

Dynamic mechanical properties of poly(methyl methacrylate) (PMMA) filled with mica flakes (M) or glass beads (G) were investigated as functions of particle size and filler concentration. With increasing particle size, dynamic modulus E′ slightly decreases for system G, while it increases rapidly at first and then approaches the limiting value for system M. Primary dispersion temperature T_α increases with increasing filler concentration. With increasing particle size, T_α decreases for system G but increases for system M. For the mica-filled system, the effect of particle size on the modulus can be explained in terms of orientation of the filler by comparing the experimental data with Wu's and Padawer and Beecher's predictions of the modulus. In order to explain the dependence of T_α on particle size and concentration, an equation for T_α has been proposed: where K_f is a constant and S is the specific surface area of filler per gram of polymer. For system G, T_α can be expressed by the above equation, irrespective of particle size and filler concentration. In the case of system M, it is suggested that T_α is affected also by orientation in addition to the surface area of the filler.     

Properties of mineral filled poly(lactic acid)/poly(methyl methacrylate) blend

This study examines the influence of three different minerals, that is, clay, calcium carbonate, and quartz on the physical, thermal, and mechanical properties of poly(lactic acid) (PLA)/poly(methyl methacrylate) blend. Rheological behavior and phase structure were initially studied by small-amplitude oscillatory shear rheology. Clay- and quartz-filled materials presented an increase in viscosity at low frequency associated with the presence of a yield stress. However, this behavior was not observed for calcium carbonate filled materials due to a matrix degradation effect. To elucidate this aspect, thermal stability and thermal properties were examined by thermogravimetric analysis and differential scanning calorimetry, showing that calcium carbonate promotes degradation of the PLA phase. No nucleating effect was observed in the presence of the minerals. Dynamical mechanical analysis and mechanical characterization revealed an increase of the overall softening temperature and, a reinforcing effect for clay- and quartz-based composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46927.     

Air plasma treatment of aluminium trihydrate filled poly(methyl methacrylate)

Air plasma treatments of aluminium trihydrate filled poly(methyl methacrylate) polymer (PMMA) composites were carried out in a dielectric barrier discharge. X-ray photoelectron spectroscopy (XPS) and attenuated total reflection – infrared spectroscopy have been employed to analyse the changes in chemical composition. Confocal laser-scanning microscopy and atomic force microscopy yielded the impact on surface structure and morphology. Surface free energy (SFE) measurements and adhesive bond strength tests were used to correlate the results to possible applications like gluing and lacquering. The plasma treatments resulted mainly in an etching of the matrix polymer and a minor chemical modification. An apparent contradiction of XPS, ATR and SFE results was attributed to a re-polymerization and re-deposition of the etched PMMA material as debris back onto the surface. This effect, which is seldom taken into account, annihilated the positive impact of the plasma treatment due to the debris acting as rated break point.     

Synthesis and characterization of poly(methyl methacrylate) star polymers

Star-branched poly(methyl methacrylate)s (PMMA) were synthesized by linking ‘living’ arms (produced by anionic polymerzation) with ethylene glycol dimethacrylate. Stars having arm molecular weights of 10000 and 40000 and between 4.9 and 18.7 branches were produced. The polymers were characterized using light scattering, size exclusion chromatography, and viscometry. It was found that well-defined PMMA stars were obtained only at the higher (40000) arm molecular weight. The stars prepared using the lower molecular weight (c. 10000) arms contained very high molecular weight gel components.     

The rheology of filled polymers

The flow properties of polymer melts containing fillers of various shapes and sizes have been examined. If there is no failure of either the filler or polymer in the solid state, then the modulus enhancement for randomly distributed filler is equal to the melt viscosity enhancement under medium shear stress conditions (10⁴ Nm^?2) in simple shear flow or in oscillatory shear flow. Submicron-size fillers, in particular, can form weak structures in the melt that greatly increase the low shear rate viscosity without changing the modulus of the solid proportionately. The highly pseudo-plastic nature of polymer melts at shear stresses of 10⁶ Nm^?2 means that, even without orientation of filler particles toward the flow direction, the viscosity enhancement is less than at lower shear stresses.     

The transport of methyl methacrylate monomer in poly(methyl methacrylate)

The absorption kinetics and equlibria of methyl methacrylate monomer into poly(methyl methacrylate) were studied over a range of penetrant activities. The interval sorption kinetics at elevated activities were determined, compared, and contrasted with the integral sorption experiments in previously unpenetrated film samples. The sorption kinetics in previously unpenetrated films were predominantly case II or relaxation controlled at high activities. A Fickian contribution to the overall kinetics was apparent at lower activities. In contrast, interval sorption, at elevated activities in previously equilibrated and plasticized samples, followed Fickian kinetics rather closely, whereas resorption, over an activity range which involved a traversal of the effective T_g, was characterized by more complicated kinetics involving a super case II mechanism at long times. These composite results reinforce the notion that the kinetics describing penetration of a single penetrant into a single polymer are extremely sensitive to the boundary condition imposed upon the polymeric sorbent.     

Optical properties of particle‐filled polycarbonate,polystyrene, and poly(methyl methacrylate) composites

Transparency is a key material property of polycarbonate (PC), polystyrene (PS), and poly(methyl methacrylate) (PMMA). To study the optical properties of particle‐filled PC, PS, and PMMA, composites containing inorganic particles in different sizes and concentrations were produced by direct melt mixing in this work. The optical properties characterized by total light transmittance, haze, and clarity were studied. The results show that the optical properties of polymer composites are strongly affected by particle content, particle size, and especially by difference in refractive indices between polymer matrix and particles. It is also revealed that the light transmittance and haze of composites are mainly affected by difference in refractive indices, whereas the clarity is more affected by particle size. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Aging behavior of optically transparent poly (methyl methacrylate) composites

The thermal aging between 25 and 115°C of hot pressed glass fiber reinforced poly (methy1 methacrylate)(PMMA) transparent composites was studied as a function of the temperature and time of hot pressing. Thermal aging at near the T_g of the PMMA matrix caused dimensional changes and a reduction in optical transmission and clarity. The reduction in transmission was attributed to gas bubbles that formed in the matrix, which may be due to the evaporation of residual MMA monomer or low T_g (∼ 75°C) polymer in the composites during aging. Thermal cycling between 25 and 100°C by eliminating low T_g of the PMMA matrix establishes the upper temperature limit to which the composite can be exposed without seriously damaging its optical properties.     

Essential work of fracture of low‐filled poly(methyl methacrylate)/starch composites

In this study, poly(methyl methacrylate) (PMMA)/starch composites were prepared by a simple solvent casting method. The morphologies of the PMMA/starch composites were studied by scanning electron microscopy. The intermolecular interaction between PMMA and starch was investigated with Fourier transform infrared spectroscopy. The thermal properties of the PMMA/starch composites were compared with those of the pure PMMA sample. Thermogravimetric analysis showed that the thermal stability increased as the starch content increased in the composites. The biodegradability of the PMMA/starch composites was studied with a soil burial test. The degradability was measured in terms of mechanical strength, which increased as the starch content increased. The essential work of fracture (EWF) of the PMMA/starch composite films was investigated by the application of EWF theory under in‐plane (mode I) conditions, and we found that the toughness, in terms of the EWF of composites, increased compared to that of pure PMMA. The fracture of the composites was also evaluated by ANSYS software, and the results were compared to the experimental output. The increased toughness of these PMMA/starch composites may enable their application in the automobile and packaging industries. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical properties of drawn poly(methyl methacrylate) filled with ultrafine particles

The elastic and yield properties of drawn poly(methyl methacrylate) (PMMA) filled with ultrafine SiO₂ are described as functions of filler content and size. The drawn PMMA composites were made by uniaxially drawing to x4.0 at 100°C and at a rate of 20 mm/min. Four compliance values, i.e., S₃₃, S₁₁, S₁₃, and S₄₄ were determined. These values decreased with filler content and decreasing filler size. The relative compliance values S^de/S^do(S^de is the compliance of drawn PMMA composites and S^do is that of drawn unfilled PMMA) are almost equivalently changed with changes in filler content. The elastic properties of drawn PMMA composites are thus reinforced isotopically. This is characteristic of PMMA which has a large side group. The yield behavior of drawn PMMA composites have similar filler size and content dependence to those of elastic properties except that the transverse yield stresses become more brittle with filler content. The anisotropy in yield stress is relatively larger than that of elastic properties. This is probably because the anti-reiforcing effect, such as fibrillation becomes prominent with increasing filler content in the perpendicular direction.     

Conducting property of carbon black filled poly(ethylene glycol)/poly(methyl methacrylate) composites as gas‐sensing materials

To reveal the role of crystalline polymers in carbon black (CB) filled amorphous polymer composites and improve the mechanical properties of composite films, CB/poly(ethylene glycol) (PEG)/poly(methyl methacrylate) (PMMA) composites were synthesized by polymerization filling in this work. The electrical conductive property and response to organic solvent vapors of the composites were investigated. The composites, characterized by a relatively low percolation threshold (～ 2.1 wt %), had lower resistivity than CB/PMMA composites prepared with the same method because of the different dispersion status of CB particles in the matrix polymer. The concentration and molecular weight of PEG notably influenced the electrical response of the composites against organic vapors. The drastic increase in the electrical resistance of the composites in various organic vapors could be attributed mainly to the swelling of the amorphous polymer matrix in the solvent but not to that of the crystalline polymer. These findings could help us to understand the conductive mechanism and electrical response mechanism of the composites as promising gas‐sensing materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation of poly(methyl methacrylate)/silicon particle composites and the study of the properties improvement

A flame retardants containing phosphorus-silicon, DOPO-VTS, was synthesized and incorporated into polymethyl methacrylate (PMMA) matrix through sol-gel process at different loadings. The results from Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM) and Differential Scanning Calorimetry (DSC) showed that silicon particle were formed and dispersed well in the PMMA matrix. The addition of DOPO-VTS can not only enhance the flame retardancy of PMMA but also improve the thermal stability of PMMA. When compared to PMMA, the addition of only 15wt% DOPO-VTS results in 28.5% decrease in pHRR. Moreover, 15.0 wt% DOPO-VTS results in 32.0 °C increase in half degradation temperatures (T_0.5). The results of Hot Stage Microscopy (HSM) and FTIR showed that phosphorus-containing compound and the silicon crystal were formed in the char layers during the pyrolysis process, and the char layers can effectively prevent the degradation of PMMA/silicon particle composites. It's believed that this research will stimulate further efforts in silicon particle as the based flame retardants in different polymers for the property reinforcements.     

Feather‐like morphology of poly(methyl methacrylate)/poly(ethylene oxide) blends: The effect of cooling rate and poly(methyl methacrylate) content

The effect of cooling rate on the crystallization morphology and growth rate of poly(ethylene oxide) (PEO) and PEO/poly(methyl methacrylate) (PMMA) blends has been observed by Hot Stage Polarized Microscopy (HS‐POM). The isothermal crystallization kinetics study was carried out by differential scanning calorimetry (DSC). The spherulite morphology has been observed for the neat PEO with molecular weight of 6000 g/mol. By adding of PMMA with molecular weight of 39,300 g/mol, the growth fronts become irregular. With the increasing of PMMA content, the irregularity of growth front becomes more obvious, and the feather‐like morphology can be observed. When PMMA content is 60%, the spherulite is seriously destroyed. This phenomenon is more obvious for the slow cooling process. Based on the measurement of spherulite, the growth rate curves were obtained. According to the curves, it can be seen that the growth rate decreases with the increasing of PMMA content, and the growth rate during the slow cooling process is higher than that of the fast cooling process. The isothermal crystallization experiment indicates that the crystallization rate decreases dramatically with the increasing of PMMA content. And the Avrami parameter n was obtained, which is non‐integral and less than 3. Finally, it can be concluded that the higher value of n can be obtained for the condition with low crystallization rate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41705.     

Graphene based composites prepared through exfoliation of graphite platelets in methyl methacrylate/poly(methyl methacrylate)

The use of methyl methacrylate/poly(methyl methacrylate) as a medium for the exfoliation of graphite platelets without any chemical treatment is reported. The dispersions, characterized by transmission electron microscopy and Raman spectroscopy, confirmed the obtainment of graphene sheets a few layers thick. We found that the electrical conductivity of such nanocomposites can be activated at temperature by the application of an external electric field, this effect being reversible after removal of the thermal stimulus. This result provides an initial understanding of how electric field assisted thermal annealing can be used to control the bulk physical properties of such composites. Copyright © 2012 Society of Chemical Industry     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(methyl methacrylate)

Summary Poly(n-propyl methacrylate) is known to be immiscible with poly(methyl methacrylate) (PMMA). However, we have found that poly(methoxymethyl methacrylate) is miscible with PMMA, indicating the importance of ether oxygen atoms in achieving miscibility. On the other hand, poly(methylthiomethyl methacrylate) is immiscible with PMMA.     

Stabilization of thermal degradation of poly(methyl methacrylate) by polysulfide polymers

The thermal degradation of poly(methyl methacrylate) (PMMA) in the presence of polysulfide polymers, namely, poly(styrene disulfide) (PSD) and poly(styrene tetrasulfide) (PST) was studied using thermogravimetry (TG) and direct pyrolysis-mass spectrometric (DP-MS) analysis. Both PSD and PST were found to stabilize the PMMA degradation, which was explained by both radical recombination and a chain-transfer mechanism. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2149–2156, 1997     

Plastic and fracture behavior of nanosilica‐filled poly(methyl methacrylate)

The plastic and fracture behavior of ‘model’ hybrid materials based on methyl methacrylate and methacryloxypropyl‐grafted nanosilica was investigated. A four‐step synthesis procedure allowed preparation of transparent nanosilica–poly(methyl methacrylate) networks of well‐defined architecture, of variable particle diameter, volume fraction of particles, number of methacryloyl units grafted per surface unit of silica particles and nature of the grafting agent. Plasticity behavior was investigated through compression tests. The evolution of yield stress with volume fraction of fillers can be understood by taking into account the undeformability of particles and using the geometrical Kerner approach. The reduction of plastic flow plateau by a substantial strain hardening was imputed to the presence of crosslinks on the particles. Fracture properties were deduced from three‐point bending experiments on notched samples. The effects on toughness of filler incorporation are tentatively related to plasticity and to the presence of crosslinks. Copyright © 2006 Society of Chemical Industry     

Dielectric analysis of poly(methyl methacrylate) zinc(II) mono-pinacolborane diphenylporphyrin composites

Poly(methyl methacrylate) (PMMA) composites were made from a polar metalloporphyrin [5-(4′,4′,5′,5′-tetramethyl[1′,3′,2′]dioxaborolan-2′-yl)-10,20-diphenylporphyrinato]zinc(II) (Zn(II)Bpin-DPP) in select weight % (wt%). Differential Scanning Calorimetry (DSC) showed that porphyrin acted as an antiplasticizer raising the glass transition (Tg) from 105 °C to 123 °C. Dielectric Analysis (DEA) was performed in the frequency range of 0.3 Hz to 100 kHz between −150 and 270 °C. Permittivity (?′), loss factor (?″) and dielectric response of beta (β), alpha beta (αβ), and conductivity relaxations were studied. Previous DEA data was limited to 190 °C. This study brings analysis to 270 °C which is start point for the first part of PMMA degradation. Thus forwarding DEA can be used to evaluate PMMA degradation. The electric modulus formalism is used to reveal the β and conductivity relaxations. The apparent activation energies (E_a) for the molecular relaxations are presented. AC (σ_AC) and DC (σ_DC) conductivity are also evaluated.