Synthesis and characterization of poly(butyl acrylate)/silica and poly(butyl acrylate)/silica/poly(methyl methacrylate) composite particles

Poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) core–shell particles embedded with nanometer‐sized silica particles were prepared by emulsion polymerization of butyl acrylate (BA) in the presence of silica particles preabsorbed with 2,2′‐azobis(2‐amidinopropane)dihydrochloride (AIBA) initiator and subsequent MMA emulsion polymerization in the presence of PBA/silica composite particles. The morphologies of the resulting PBA/silica and PBA/silica/PMMA composite particles were characterized, which showed that AIBA could be absorbed effectively onto silica particles when the pH of the dispersion medium was greater than the isoelectric potential point of silica. The critical amount of AIBA added to have stable dispersion of silica particles increased as the pH of the dispersion medium increased. PBA/silica composite particles prepared by in situ emulsion polymerization using silica preabsorbed with AIBA showed higher silica absorption efficiency than did the PBA/silica composite particles prepared by direct mixing of PBA latex and silica dispersion or by emulsion polymerization in which AIBA was added after the mixing of BA and silica. The PBA/silica composite particles exhibited a raspberrylike morphology, with silica particles “adhered” to the surfaces of the PBA particles, whereas the PBA/silica/PMMA composite latex particles exhibited a sandwich morphology, with silica particles mainly at the interface between the PBA core and the PMMA shell. Subsequently, the PBA/silica/PMMA composite latex obtained had a narrow particle size distribution and good dispersion stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3425–3432, 2006     

Latex interpenetrating polymer networks based on polyacrylates and poly(methyl methacrylate)

The effect of methacrylic acid (MAA) concentration in the polyacrylate seed on the formation of latex interpenetrating polymer networks (LIPNs) with poly(methyl methacrylate) (PMMA) as polymer II in the ratio of 65 : 35 (w/w) has been studied. LIPNs were prepared using three different seeds having the compositions of n-butyl acrylate (BA), methyl methacrylate (MMA), and tetra(ethylene glycol)dimethacrylate (TEGDM) in the ratio of 55 : 45 : 0.7 by weight and varying amounts of MAA (0, 2.5, and 6% by wt) at two different pH values (∼ 3.3 and 8.5). LIPNs prepared from seeds having MAA > 2.5% resulted in the formation of continuous films, whereas LIPNs without MAA in the seed yielded discontinuous films (i.e., films with many cracks). Characterization using differential scanning calorimetry (DSC) showed the presence of multiphase morphology in all the LIPNs, indicating better mixing of the two polymers. Another set of LIPNs using the seed of the composition BA : MMA : TEGDM in the ratio of 63 : 37 : 6 : 0.7 by wt, possessing a glass transition temperature of 0°C and PMMA as polymer II, was prepared at two different pH values, as mentioned earlier, and with two different initiators—namely, 2,2′-azobisisobutyronitrile (AIBN) and potassium persulfate (PPS)—for the polymerization of monomer II. The tensile strength and hardness of both the LIPNs processed at high pH (8.5) did not show significant differences, whereas the LIPNs prepared at low pH using the AIBN initiator showed an inverted core-shell morphology possessing very low hardness and tensile strength with high elongation. The PPS-initiated polymer showed core–shell morphology yielding film of poor strength. © 1996 John Wiley & Sons, Inc.     

Film formation of poly (methyl methacrylate) latex with pyrene functional poly (divinylbenzene) microspheres prepared by click chemistry

This work reports on the application of steady state fluorescence (SSF) technique for studying film formation from poly(methyl methacrylate) (PMMA) latex and poly(divinylbenzene) (PDVB) microsphere composites. Pyrene (P) functionalized PDVB cross‐linked spherical microspheres with diameters of 2.5 μm were synthesized by using precipitation polymerization technique followed by click coupling reaction. The diameter of the PMMA particles prepared by emulsion polymerization were in the range of 0.5–0.7 μm. PMMA/PDVB composite films were then prepared by physically blending of PMMA latex with PDVB microspheres at various composition (0, 1, 3, 5, 10, 20, 40, and 60 wt%). After drying, films were annealed at elevated temperatures above T_g of PMMA ranging from 100 to 270°C for 10 min time intervals. Evolution of transparency of the composite films was monitored by using photon transmission intensity, I_tr. Monomer (I_P) and excimer (I_E) fluorescence intensities from P were measured after each annealing step. The possibility of using the excimer‐to‐monomer intensity ratio (I_E/I_P) from PDVB microparticles as a measure of PMMA latex coalescence was demonstrated. Diffusion of the PMMA chains across the particle–particle interfaces dilutes the dyes, increasing their separation. The film formation stages of PMMA latexes were modeled by monitoring the I_E/I_P ratios and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the PDVB composition in the studied range. SEM images of PMMA/PDVB composites confirmed that the PMMA particles undergo complete coalescence forming a continuous phase in where PDVB microspheres are dispersed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Effects of compatibilizing agents in poly(n-butyl acrylate)/poly(methyl methacrylate) composite latexes

Graft copolymers with poly(n-butyl acrylate) (PBA) backbones and poly(methyl methacrylate) (PMMA) macromonomer side chains are used as compatibilizing agents for PBA/PMMA composite latexes. The composite latexes are prepared by seeded emulsion polymerization of methyl methacrylate (MMA) in the presence of PBA particles. Graft copolymers were already incorporated into the PBA particles prior to using these particles as seed via miniemulsion (co)polymerization of n-butyl acrylate (BA) in the presence of the macromonomers. Comparison between size averages of composite and seed particles indicates no secondary nucleation of MMA during seeded emulsion polymerization. Transmission electron microscopy (TEM) observations of composite particles show the dependence of particle morphologies with the amount of macromonomer (i.e., mole ratio of macromonomer to BA and molecular weight of macromonomer) in seed latex. The more uniform coverage with the higher amount of macromonomer suggests that graft copolymers decrease the interfacial tension between core and shell layers in the composite particles. Dynamic mechanical analysis of composite latex films indicates the existence of an interphase region between PBA and PMMA. The dynamic mechanical properties of these films are related to the morphology of the composite particles, the arrangement of phases in the films, and the volume of the interphase polymer. © 1997 John Wiley & Sons, Inc.     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. I. Experimental investigation

In this work, methyl methacrylate (MMA) and styrene (ST) were used as monomers in the first stage and second stage of polymerization, respectively, and potassium persulfate (K₂S₂O₈) was used as the initiator to synthesize the poly(methyl methacrylate)-polystyrene (PMMA/PS) composite latex by the method of two-stage soapless emulsion polymerization, i.e., PMMA seeded soapless emulsion polymerization of styrene. The morphology of the latex particles was observed by transmission electron microscopy (TEM). It showed that the composite latex particles had a core–shell structure. The particlesize distribution of the composite latex was very uniform. The kinetic data of seeded soapless emulsion polymerization showed that the square root of polymer yield (Wp)^1/2 was proportional to the reaction time in the earlier period of the reaction. The slope of the line of (Wp)^1/2 vs. reaction time was independent of the content of the seed, but proportional to 0.5 power of the initiator concentration. The gel effect was apparent after monomer droplets disappeared. A glassy effect was found in the latter period of the reaction. The number-average molecular weight of the polymers increased but the weight-average molecular weight of the polymers decreased with decrease of the MMA/ST weight ratio. The number- and weight-average molecular weight increased with decreasing the temperature significantly. © 1995 John Wiley & Sons, Inc.     

Studies on damping properties of P(MMA‐AN)/P(EA‐nBA) LIPNs

Using a two‐stage emulsion polymerization method, a series of poly(methyl methacrylate‐acrylonitrile)/poly(ethyl acrylate‐n‐butyl acrylate) [P(MMA‐AN)/P(EA‐nBA)] latex interpenetrating polymer networks (LIPNs) were synthesized by varying AN content, ratio of network I/network II, crosslinker content, and introducing chain transfer agent. The damping properties of the LIPNs were investigated using a Rheovibron Viscoelastometer. The results indicates that a suitable content of AN can improve the damping properties of the LIPNs. Three kinds of fillers were incorporated into the LPINs, respectively, to measure the change in the damping properties. Mica and TiO₂ both increased the damping properties of the LIPNs over the wide temperature range. For TiO₂‐filled LIPNs, it was observed that the tan δ values exceeded 0.4 over 112.6°C temperature range from −50 to 72.6°C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 722–727, 2000     

Influence of nanozirconia on the thermal stability of poly(methyl methacrylate) prepared by in situ bulk polymerization

Nanozirconia (nano‐ZrO₂) was prepared by the sol–gel method and incorporated into poly(methyl methacrylate) (PMMA) by the in situ bulk polymerization of methyl methacrylate. The structure of the nano‐ZrO₂ was confirmed by X‐ray diffraction (XRD), transmission electron microscopy, and Fourier transform infrared (FTIR) spectroscopy. The structure of the nano‐ZrO₂ nanocomposites were studied by differential scanning calorimetry, FTIR spectroscopy, XRD, and scanning electron microscopy, and the results show that there were interactions between the nanoparticles and the polymer. The influence of the nano‐ZrO₂ on the thermal stability of PMMA was investigated by thermogravimetric analysis (TGA). The results indicate that nano‐ZrO₂ enhanced the thermal stability of the PMMA/nano‐ZrO₂ nanocomposites. The effects of the heating rate in dynamic measurements (5–30°C/min) on kinetic parameters such as apparent activation energy (E_a) in TGA both in nitrogen and air were investigated. The Kissinger method was used to determine E_a for the degradation of pure PMMA and the PMMA/nano‐ZrO₂ nanocomposites. The kinetic results show that the values of E_a for the degradation of the nanocomposites were higher than that of pure PMMA in air. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetic study on the poly(methyl methacrylate) seeded soapless emulsion polymerization of styrene. III. Seeds with crosslinking

In this work, a seeded soapless emulsion polymerization was carried out with crosslinking (XL) poly(methyl methacrylate) (PMMA) as seeds, styrene as monomer, and potassium persulfate (K₂S₂O₈) as initiator to synthesize the PMMA XL–PS composite latex, which we knew as the latex interpenetrating polymer network (IPN). The morphology of the latex IPN was observed by transmission electron microscopy (TEM). It showed a core–shell structure. The kinetic data from the early stages of the reaction of seeded soapless emulsion polymerization showed that the square root of polymer yield (W_p)^1/2 was proportional to the reaction time. The reaction rate decreased with the increase of crosslinking density of PMMA seeds. The core–shell model proposed in our previous work^1–2 was modified to predict the conversion of polymerization over the entire course of the synthesis of PMMA (XL)–PS composite latex. Our modified core–shell kinetic model fitted well with the experimental data. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:425–438, 1997     

Synthesis and structure of the poly(methyl methacrylate) microlatex

Microemulsion polymerization is a new approach for preparing nanosize polymer materials. In this article, a nanosize poly(methyl methacrylate) (PMMA) was prepared by a novel microemulsion polymerization. The kinetics of the polymerization and the effects of the temperature, the monomer, and emulsifier/water ratio on the polymerization were investigated by means of the conversion, the transmittance, and the refractive index measurements. The structure of the obtained PMMA microlatex was studied through transmission electron microscopy (TEM), nuclear magnetic resonance (¹H‐NMR), and differential scanning calorimetry (DSC). The results show that the polymerization exhibits typical kinetic characteristics of a microemulsion polymerization, i.e., there only exists two rate stages: a stage of increasing rate, and a stage of decreasing rate, and no constant rate stage is observed during the polymerization. The obtained PMMA microparticles are very uniform, regular, and small, being about 17–33 nm in the number‐average diameter. The polymer has higher molecular weight (1.71 × 10⁶ viscosity average molecular weight), higher tacticity (51% syndiotacticity), and higher glass transition temperature (127°C), much different from the commercial PMMA. Experimentally, a stable and transparent PMMA microlatex with higher polymer content (30–40 wt %), lower weight ratio of emulsifier to water (E/W ≤ 0.03) and emulsifier to monomer (E/M ≤ 0.05) as well as smaller particle size (d_p < 40 nm), has been prepared, which is very important for the industrialization of the microemulsion polymerization technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2839–2844, 2002     

Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. VI. Charge‐transfer complex (2)

The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (E_a) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent E_a's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), E_a's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, E_a's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, E_a's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005     

Degradation of poly(methyl methacrylate) (PMMA) with aluminum nitride and alumina

This paper deals with the thermal and thermal-oxidative degradation of pure poly(methyl methacrylate) (PMMA), PMMA/A1N and PMMA/Al₂O₃ composites. Kinetic parameters were determined from the weight loss data using non-isothermal Thermogravimetric Analysis (TGA). The amount and morphology of the carbon residue in the burnt samples under N₂ and air atmospheres were also investigated using a Leco combustion analyzer. This study also showed that the normally accepted three-stage polymer thermal degradation, and hence three regions of Arrhenius linearity, can be treated with one value of activation energy. This is a basic departure from the normally accepted three different regions and applying the same diffusion equation (such as Jander diffusion) separately to each region. In nitrogen atmosphere, the activation energy of pure PMMA was 129.4 kJ/mol; however, the activation energies of 14% PMMA/AlN and PMMA/Al₂O₃ were found to be 119.5 and 118.2 kJ/mol, respectively.     

Optical percolation and oxygen diffusion in poly(divinylbenzene) doped poly(methyl methacrylate) latex flms

A simple fluorescence technique is proposed for the measurement of the diffusion coefficient of oxygen into poly(methyl methacrylate) (PMMA) latex‐poly(divinylbenzene) (PDVB) composite films. Percolation model was used by using photon transmission (PT) technique to interpret the distribution of PDVB particles in PMMA lattice. Optical results were interpreted according to site percolation theory. The optical percolation threshold value and critical exponent were calculated as, R_c = 0.03 and, β = 0.34, respectively. PT measurements were performed for eight different PDVB content (0, 1.5, 3, 5, 10, 20, 40, and 60) wt%. Pyrene (P) functionalized PDVB cross‐linked spherical microspheres with diameters of 2.5 μm were synthesized by using precipitation polymerization technique followed by click coupling reaction. The diameter of the PMMA particles prepared by emulsion polymerization was in the range of 0.5–0.7 μm. PMMA/PDVB composite films were then prepared by physically blending of PMMA latex with PDVB microspheres at various compositions. The steady‐state fluorescence method was used to monitor oxygen diffusion into these (0, 5, 10, 20, and 40 wt%) latex films. Diffusion coefficients, D, of oxygen were determined by the fluorescence quenching method by assuming Fickian transport and were found to be increased from 1.8 × 10⁻¹¹ to 36.6 × 10⁻¹¹ cm² s⁻¹ with increasing PDVB content. This increase in D values was explained with formation of microvoids in the film by using PT technique. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Bulk and emulsion copolymerizations of n-butyl acrylate and poly(methyl methacrylate) macromonomer

Bulk and emulsion copolymerizations of an ω-unsaturated poly(methyl methacrylate) (PMMA) macromonomer with n-butyl acrylate (n-BA) were investigated. The reactivity of PMMA macromonomer in bulk copolymerization with n-BA was found to be lower than that of methyl methacrylate monomer with n-BA. The incorporation of PMMA macromonomer into poly(butyl acrylate) (PBA) latex particles by miniemulsion copolymerization was proved by high performance liquid chromatography-silica adsorption spectroscopy. Dynamic mechanical studies showed that PMMA macromonomer was grafted to the PBA backbone, and the degree of grafting increased as the ratio of PMMA macromonomer to n-BA increased. Microphase separation of the PMMA macromonomer grafts was observed at higher ratio of macromonomer (higher or equal to 10% weight of macromonomer based on total polymer phase). The n-BA/PMMA macromonomer copolymer behaved completely differently from the physical blend of PBA and PMMA macromonomer particles of the same composition. © 1996 John Wiley & Sons, Inc.     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

Thermo-oxidative stability of poly(methyl methacrylate)/poly(methyl methacrylate)-grafted SiO2 nanocomposites

Thermo-oxidative stability of PMMA-grafted SiO₂ and PMMA/PMMA-grafted SiO₂ nanocomposites was investigated by conventional non-isothermal gravimetric technique. It was interesting to find that PMMA-grafted SiO₂ nanoparticles exhibited higher thermo-oxidative stability than that of PMMA. The apparent activation energy of PMMA-grafted SiO₂ nanoparticles increased with the grafting ratio of PMMA from SiO₂, which was estimated by Kissinger method. This indicates that the strong interactions existing between the grafted chains are responsible for the enhanced thermo-oxidative stability of PMMA-grafted SiO₂ nanoparticles. However, the grafting ratio of PMMA from SiO₂ in nanoparticles has only limited effect on the thermo-oxidative stability of PMMA/PMMA-grafted SiO₂ nanocomposites due to a much lower content of grafted PMMA in the nanoparticles relative to PMMA. The increased thermo-oxidative stability of PMMA/PMMA-grafted SiO₂ nanocomposites is possibly resulted from the increased SiO₂ content in the nanocomposites, in which the grafting ratio of PMMA in PMMA-grafted SiO₂ nanoparticles is kept almost as a constant. The glass transition temperature (T _g) of PMMA/PMMA-grafted SiO₂ nanocomposites is about 25 °C and is higher than that of PMMA. The grafting ratio of PMMA from SiO₂ in the nanoparticles has no qualitative effects on the T _g of the nanocomposites.     

Effects of a Hindered Amine Stabilizer (HAS) on radiolytic and thermal stability of poly(methyl methacrylate)

Commercial Poly(methyl methacrylate) (PMMA) containing Tinuvin 622, a Hindered Amine Stabilizer (HAS), in 0.3% (wt/wt) concentration was investigated. The samples were irradiated with gamma radiation (⁶⁰Co) at room temperature in air. The viscosity‐average molecular weight (M_v) was analyzed by viscosity technique. Both control PMMA (without HAS) and PMMA + 622 (with HAS) showed a decrease in molecular weight with the increase in dose, reflecting the random scissions that occurred in the main chain. The G value (scissions/100 eV of energy transferred to the system) was also obtained by viscosity analysis. G value results showed that the addition of Tinuvin 622 into the PMMA matrix significantly decreased the number of scissions/100 eV at dose range of 0–60 kGy. Analysis of infrared spectra showed a decrease in the carbonyl index (CI) in irradiated samples. However the CI decrease was found lower for PMMA + 622 than for control PMMA sample. Thermogravimetric analysis (TGA) revealed that maximum decomposition temperature of additive PMMA is 42°C higher than control PMMA for unirradiated system. On the other hand this difference is not significant in irradiated systems at 60‐kGy irradiation dose. The activation energy of the thermal degradation of PMMA was 165 kJ/mol, this activation energy increased 60 kJ/mol when Tinuvin 622 was added to PMMA matrix. Therefore Tinuvin 622 is a suitable radiostabilizing agent for commercial PMMA in a 0–60 kGy dose interval. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rheological properties of poly(methyl methacrylate)/rigid ladderlike polyphenylsilsesquioxane blends

A series of poly(methyl methacrylate) (PMMA) blends with rigid ladderlike polyphenylsilsesquioxane (PPSQ) were prepared at weight ratios of 100/0, 95/5, 90/10, 85/15, and 80/20 by solution casting and then hot‐pressing. Their rheological properties have been studied under both dynamic shear and uniaxial elongation conditions. Their rheological properties depend on the compositions. The storage modulus, G′, loss modulus, G″, and dynamic shear viscosity, η*, of the PMMA/PPSQ 95/5 blend were slightly lower than those of pure PMMA. However, the values of G′, G″, and η* for the other PMMA/PPSQ blends are higher than those of PMMA. The G′ values increase with an increase in PPSQ content from 5% through 15% PPSQ at low frequencies and then drop as the PPSQ content increases to 20%. Uniaxial elongational viscosity (η_E) data demonstrate that PMMA/PPSQ blends exhibit slightly weaker (5% PPSQ) and much weaker (10% PPSQ) strain‐hardening than PMMA. In contrast, the PMMA/PPSQ 85/15 blend shows strain‐softening. Neither strain‐hardening nor strain‐softening was observed in the 80/20 blend. The special rheological properties for the 95/5 blend is probably due to a decrease in PMMA entanglements brought by the specific PMMA–PPSQ interactions. Rheological properties of PMMA/PPSQ blends with higher PPSQ content (≥10%) are mainly affected by formation of hard PPSQ particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 352–359, 2007     

Plasma etching durability of poly(methyl methacrylate)

The decomposition of poly(methyl methacrylate) (PMMA), as a positive resist, in CF₄/O₂ plasma etching has been studied in the thin film state in order to clarify the factors influencing the dry etching durability of resists. It becomes clear that the major PMMA decomposition in CF₄/O₂ plasma etching proceeds by the mechanism of random chain scission because very small kinetic chain lengths are estimated from the gel permeation chromatography data. The Arrhenius plots for the plasma etching rate of PMMA bend above about the glass transition temperature (T_g), where rapid increase of the etching rate and remarkable pattern deformation are observed. Activation energy of the PMMA etching rate which is changed by oxygen concentration and rf power indicates various values from 3.1 to 6.5 kcal/mol below about T_g. The result of molecular weight variation in the cross section of the film suggests that the active species permeate into the film with fairly large speed and the PMMA decomposition occurs not only at the film surface but also at deep layer of the film.     

Physical properties and crystallization behavior of poly(lactide)/poly(methyl methacrylate)/silica composites

Poly(lactide)/poly(methyl methacrylate)/silica (PLA/PMMA/SiO₂) composites were fabricated using a twin‐screw extruder. Nanosilica particles were incorporated to improve the toughness of the brittle PLA, and a chain extender reagent (Joncryl ADR 4368S) was used to reduce the hydrolysis of the PLA during fabrication. Highly transparent PLA and PMMA were designated to blend to obtain the miscible and transparent blends. To estimate the performance of the PLA/PMMA/SiO₂ composites, a series of measurements was conducted, including tensile and Izod impact tests, light transmission and haze measurements, thermomechanical analysis, and isothermal crystallization behavior determination. A chain extender increases the ultimate tensile strength of the PLA/PMMA/SiO₂ composites by ～43%, and both a chain extender and nanosilica particles increase Young's modulus and Izod impact strength of the composites. Including 0.5 wt % nanosilica particles increase the elongation at break and Izod impact strength by ～287 and 163%, respectively, compared with those of the neat PLA. On account of the mechanical performances, the optimal blending ratio may be between PLA/PMMA/SiO₂ (90/10) and PLA/PMMA/SiO₂ (80/20). The total light transmittance of the PLA/PMMA/SiO₂ composites reaches as high as 91%, indicating a high miscible PLA/PMMA blend. The haze value of the PLA/PMMA/SiO₂ composites is less than 35%. Incorporating nanosilica particles can increase the crystallization sites and crystallinities of the PLA/PMMA/SiO₂ composites with a simultaneous decrease of the spherulite dimension. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42378.     

Emulsion polymerization of methyl methacrylate in the presence of burnt mazote boiler deposit

The emulsion polymerization of methyl methacrylate (MMA) using different initiators was carried out in the absence and presence of burnt mazote boiler deposit (BMBD). When sodium persulfate or potassium persulfate was used, the initial rate of polymerization was found to decrease with increase of the burnt mazote boiler deposit concentration but to increase when sodium bisulfite was used as initiator. The initial rate of polymerization was found to be higher in nitrogen atmosphere than in air. The apparent activation energy (E_a) was found to be 12.4 × 10⁴ J/mol and 16.3 × 10⁴J/mol in the absence and presence of burnt mazote boiler deposit when potassium persulfate was used as initiator and 5.9 × 10⁴ J/mol and 5.1 × 10⁴ J/mol when sodium bisulfite was used as initiator, respectively. The mean average molecular weights for PMMA were found to increase with increase of the burnt mazote boiler deposit when sodium bisulfite was used as initiator.