Miscibility studies on blends of polycarbonate with syndiotactic polymethyl methacrylate

Miscibility of bisphenol-A polycarbonate (PC) and syndiotactic polymethyle methacrylate (sPMMA) blends was investigated by differential scanning calorimetry (DSC) and small-angle light scattering. Cloud-point measurements indicated the existence of both a lower critical solution temperature and an upper critical solution temperature, forming an immiscibility loop. This immiscibility gap was observed for PC blends with sPMMA of various molecular weights ranging from 8,300 to 55,000. The DSC study on solvent-cast and coprecipitated PC/sPMMA blends from tetrahydrofuran solutions showed a single glass transition, shifting regularly with composition. The annealing of the 50/50 composition within the immiscibility loop exhibited dual glass transitions, but the system reverted to a single phase upon annealing above the loop. Phase dissolution took place during annealing above the loop, followed by thermoxidative branching (cross-linking) reaction. Dry pellets of PC and sPMMA were melt mixed above the loop in a Mini-Max mixer/molder; these molded blends exhibited a single phase. © 1993 John Wiley & Sons, Inc.     

Deposition of polymethyl methacrylate latex on fibers

Summary In order to study the deposition of polymethyl methacrylate latex on fibers,viz., polyamide (Nylon 6), polyacrylonitrile (Vonnel), polyester (Tetoron), and cotton, the amount of latex deposited was measured and the interaction energy between fiber and latex particles was determined from -potentials by the application of heterocoagulation theory. The amount of latex deposited decreased and the total interaction energy increased with increasing pH for all fibers. However, it was found that the deposition of latex on Vonnel and cotton could not be interpreted satisfactorily by only the interaction energy, because latex deposited on those fibers in spite of the large total interaction energy.From the observation of the state of deposition of latex particles in terms of scanning electron microscope, it was found that latex particles deposited on Nylon and Tetoron in a single particle layer, while those on Vonnel in a multiple or blocky layer. It was suggested that the deposition of latex on fiber was influenced by the surface roughness of fiber and the uniformity of the filament diameter.

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Zusammenfassung Um die Ablagerung von Polymethylmethacrylat auf Fasern Polyamid (Nylon 6), Polyacrylnitril (Vonnel), Polyester (Tetoron) and Baumwolle zu studieren, wurde die Menge des abgelagerten Latex gemessen, and die Wechselwirkungsenergie zwischen Faser and Latex-Teilchen wurde aus den -Potentialen durch die Anwendung der Heterokoagulationstheorie bestimmt. Die Menge des abgelagerten Latex nahm ab und die totale Wechselwirkungsenergie stieg mit steigendem pH für alle Fasern an. Jedoch zeigte sich, daß die Ablagerung von Latex an Vonnel und Baumwolle nicht zufriedenstellend allein durch die Wechselwirkungsenergie erklärt werden konnte, weil Latex sich an diese Fasern trotz der großen totalen Wechselwirkungsenergie ablagerte.Aus der Beobachtung des Ablagerungszustandes von Latex-Teilchen im Rasterelektronenmikroskop fand man heraus, daß Latex-Teilchen sich an Nylon und Tetoron in einer einfachen, an Vonnel aber in einer mehrfachen oder dickeren Schicht ablagerten. Es wurde darauf hingewiesen, daß die Ablagerung von Latex an Fasern durch die Oberflächenrauheit der Fasern und die Einheitlichkeit des Faser-Durchmessers beeinflußt wurde.

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With 7 figures     

Physico-chemical studies of gamma-irradiated polyester-impregnated cement mortar composite

The effect of impregnation time on the physico-chemical and mechanical properties of polyester-cement mortar composite has been investigated. The samples were soaked in unsaturated polyester resin containing 40% styrene monomer at impregnation times ranging from 1–15 hours and then exposed to 50 kGy of γ-irradiation. The effects on polymer loading, compressive strength, apparent porosity, and water absorption in addition to IR spectra and TGA of the samples were studied. It was found that, the polymer loading and compressive strength increase with the increased of soaking time up to 4 hours and there is no significant improvement of the polymer loading and compressive strength increase with the increased of soaking time up to 4 hours and there is no significant improvement of the polymer loading and strength. Whereas, the apparent porosity and water absorption behave in an opposite direction. These are attributed to the presence of polymer in the pores of the samples. IR spectra showed that, new bands appeared as result of the reaction between polyester and set cement. TGA showed that, the polyester cement composite has higher thermal stability as a compared to irradiated polyester.     

The sequence length in polymethyl methacrylate

The sequence length and tacticity of methyl methacrylate polymers prepared at 303–363°K in the presence of trichlorobromomethane as a transfer agent were measured from NMR spectra. The lengths did not change appreciably but there was an increase in syndiotacticity with increasing concentration of transfer agent. There is no marked change in tacticity with molecular weight.     

Radiolysis of polymers on the surfaces of solids; polymethyl methacrylate and polymethyl acrylate on aerosil

The radiolysis of polymethyl methacrylate (PMMA) and polymethyl acrylate (PMA) on an aerosil surface has been studied. We have found substantial sensitization of PMMA radiation degradation under irradiation on aerosil compared to in-bulk irradiation; this is determined by the effective transfer of the energy absorbed by aerosil particles to their surface. The dependence of the main PMMA chains break yield on polymer synthesis conditions and polymer concentration on the surface has been studied. For PMA, considerable inhibition of gel formation is found for irradiation on aerosil surfaces, as compared with bulk irradiation.     

Diffusion of water vapour in polymethyl methacrylate

Certain aspects of the concentration dependence of the diffusion coefficient and on the mechanism of sorption of water vapour in PMMA are investigated. Early time integral sorption kinetics follow the Fickian pattern of initial linearity. Diffusion coefficients deduced from the slopes of these lines are independent of concentration and satisfactorily agree with those obtained from late-time analysis; however, desorption values are higher throughout the whole range of activities than the corresponding absorption ones. On the contrary, typical “non-Fickian” features are discerned in differential absorption kinetics on membranes of different thickness. These anomalies are attributed to rate-determining relaxation processes concurrent with diffusion, whereas other sorption models are incompatible with the general behaviour of this system. General trends of the equilibrium and kinetic data are compared with those of other polymer—water systems and the observed differences are interpreted in terms of the molecular relaxation model.     

The study of preparation and luminescence of polymethyl methacrylate/rare earth composite luminescent materials

The alkaline-earth–rare-earth–aluminate systems phosphors are the new types of phosphors, which process very bright, safer, and excellent photoluminescence. Because of hydrolysis, however, the capacity of luminescent materials will fall down and the use value of luminescent materials will also be lost. Water-resistant polymers, which can form a kind of water-resistant clad on the surface of luminescent material powder, will solve this problem and the significance of its application is important. In this study, the polymethyl methacrylate (PMMA)/rare earth composite luminescent materials were prepared through grafting emulsion polymerization of methyl methacrylate onto the surface of luminescent materials. To study the structure and properties of the PMMA/rare earth composite luminescent materials, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and photoluminescent properties were measured. From the curves of FTIR and TGA, we can find that the organic parts are attached with the inorganic parts in the PMMA/rare earth composite luminescent materials. The results of luminescent decay curves show that the resistance to water of the PMMA/rare earth composite luminescent materials is much better than that of the unmodified luminescent materials because the organic parts had been grafted on the luminescent materials.     

Photochemical reaction of nitroanthracene derivatives in polymethyl methacrylate

Irradiation of 9-cyano-10-nitroanthracene or 9-benzoyl-10-nitroanthracene in polymethyl methacrylate (PMMA), at room temperature, gives the 9-cyano- or 9-benzoyl-10-anthryloxy radical which disappears slowly after irradiation, following the second order dark reaction, and finally gives the substituted anthranol. In the presence of TEA, the corresponding anthryloxy anions are obtained and their absorption spectra are greatly red-shifted compared with those in fluid basic polar solutions. The existence of 9-benzoyl-10-anthryloxy anion in basic PMMA is very interesting, because 9-benzoyl-10-anthranol is obtained in methyl methacrylate monomer (MMA) even in the presence of TEA. This is explained in terms of the increase of the microscopic medium polarity of MMA by the polymerisation.     

Controlling the adhesion properties of high-filled polymethyl methacrylate composites

It has been determined that modification of high-filled polymethyl methacrylate composites that are intended for repair work on transportation facilities by hydroxypropyl methacrylate provides a significant (by 1.5–2.5 times) increase in the adhesion strength with cement concrete substrate, as well as durability of adhesion contact under various conditions of its formation.     

Problems of diffusion for polymethyl methacrylate/water systems

Summary In our research two types of polymethyl methacrylate have been used: theM-type with relatively high contents of monomer, and theT-type with small amounts of unpolymerisated monomer.Measuring the streaming potential versus time in polymethyl methacrylateM,T/water systems, it has been proved that the curves, characteristic for water diffusion, possess a common intersection point with the abscissaV _(w)z . This point is situated at some depth under the surface, this distance from the surface being denominated as the surface depth of the polymer.Basing on theoretical considerations, an equation has been deduced, which makes it possible to evaluate the surface depth of polymers.

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Zusammenfassung In unseren Untersuchungen wurden zwei Typen von Polymethylmethacrylat verwendet: dieM-Type mit relativ hohem Gehalt an monomerem und dieT-Type mit geringen Beträgen an unpolymerisiertem Polymeren. Durch Messung des Strömungspotentials als Funktion der Zeit in Systemen Polymethylmethacrylat-Wasser beider Typen läßt sich beweisen, daß die für Wasserdiffusion charakteristischen Kurven einen gemeinsamen Schnittpunkt mit der AbszisseV _(w)z besitzen. Dieser Punkt ist in gewisser Tiefe unter der Oberfläche zu finden, der Abstand von der Oberfläche wird als Oberflächentiefe bezeichnet.Auf Grund allgemeiner theoretischer Betrachtungen wird eine Gleichung abgeleitet, die die Oberflächentiefe der Polymeren zu ermitteln erlaubt.

     

XPS studies of Ni deposition on polymethyl methacrylate and poly(styrene‐co‐acrylonitrile)

Thin Ni layers were deposited onto clean polymethyl methacrylate (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) surfaces by a high vacuum thermal evaporation process. The resulting interfaces were studied by X‐ray photoelectron spectroscopy. The Ni deposition on PMMA changes the relative intensity of the C1s spectra associated with the O CO and C O carbon species, and modifies the shape of the O1s peak, while the Ni evaporation on SAN alters the C1s band intensity assigned to the CN moiety and gives a second N1s band at low binding energies. These observations suggest the formation of new chemical species at the interface between Ni and the PMMA ester group, and between Ni and the SAN nitrile group, which are the most reactive sites on these two polymers. Copyright © 2000 John Wiley & Sons, Ltd.     

On the kinetics of radical oxidation in polymethyl methacrylate films

Radical oxidation controlled by oxygen diffusion in a solid medium consisting of regions of size »» 60 with different diffusion coefficients, has been studied by computer simulation. It is shown that the rate constant distribution coincides with the diffusion coefficient distribution within a wide range of oxygen concentrations.     

Application of polymethyl methacrylate in cathode materials of lithium-ion batteries

A study of the Li₂FeSiO₄/C cathode material doped with Mn demonstrated that introduction of polymethyl methacrylate results in a substantial decrease in the particle size and increase in the specific surface area of the cathode material. Polymethyl methacrylate strongly improves the cyclic stability of the cathode material. The discharge capacity after the first cycle was 218 mA h g^–1, and that upon stabilization of the structure of the cathode material, 170 mA h g^–1.     

Diffusion-controlled penetration of polymethyl methacrylate sheets by monohydric normal alcohols

The kinetics of ethanol, n-propanol, and n-butanol penetration, sorption, and dimensional swelling in 2 mm poly(methyl methacrylate) sheets were determined over the temperature range 50–95°C. At 50°C, Case II relaxation-controlled transport dominated the observed sorption and penetration kinetics for all three alcohols. At higher temperatures, diffusion of swelling penetrant to the relaxing boundary contributes increasingly to the observed sorption kinetics. In addition, as the temperature is raised, the completion of sorption lags significantly behind the penetration of the relaxing boundary to the sheet midplane. p]The activation energy describing low temperature penetration is significantly higher than the activation energy describing the temperature dependence of high temperature penetration. A distinct transition in the penetration kinetics is apparent for all three alcohols at approximatively 65°C. Independent Clash—Berg determinations of the T_g of the alcohol-swollen sheets indicate that the transition in behaviour is not related to a thermal transition in the polymer, but rather to the generation of diffusional resistance in the high temperature penetration experiments which is comparable to the otherwise rate-determining Case II relaxations dominant in low temperature penetration. At high temperatures, the overall activation energy reflects the combination of diffusional absorption and the more highly activated relaxation-controlled transport. At low temperatures, diffusion of penetrant to the relaxing boundary is rapid compared with the slow, rate determining relaxations and, therefore, the concentration of penetrant is everywhere uniform within the already swollen shell. The extra-ordinarily high apparent activation energy describing the temperature dependence of the initial sorption rate at low temperature reflects the endothermic enthalpy of sorption of alcohols in PMMA as well as the strong coupling between relaxation rate and the penetrant concentration driving the rate determining relaxations. p]Clash—Berg measurements of the temperature dependence of the ten second shear moduli in partially swollen sheets, completely swollen sheets, and unswollen sheets suggest a T_g of approximatively 40°C in the alcohol-swollen PMMA. Moreover, an analysis of the Clash—Berg measurements suggests that the properties of the swollen regions of partially penetrated sheets are identical to the properties of the completely swollen sheets.     

Thermal degradation of gamma irradiated isotactic and atactic polymethyl methacrylate

Thermal behaviour of gamma irradiated free radical and isotactic polymethyl methacrylate has been studied at 256°.     

Optical and electrical analysis of blue polymethyl methacrylate for high-dose dosimetry

The response to gamma radiation of polymethyl methacrylate (“blue PMMA”) containing a blue dye was investigated, with the aim of providing a high-dose dosimeter based on either spectrophotometry or electrical-conductivity measurements. It is found that the 3-mm thick pieces of blue PMMA can be used for dosimetry in a range of absorbed doses from about 5-50 kGy, for which the changes in optical transmission density (absorbance) at different wavelengths in the visible region (402, 596, 612, and 643 nm) are linear functions of dose. Results also show that irradiation of thin 0.1 mm films of blue PMMA produces two components of radiation-induced conductivity: a transient component which can be used to determine the absorbed dose rate and a steady-state component which registers the total absorbed dose in the range 20–80 kGy as based on a suitable calibration. The effects of post-irradiation storage time, day light, and storage temperature on the radiation-induced visible spectrum were investigated. The storage-temperature effect on post-irradiation conductivity measurement was also evaluated.     

Mechanical characterization of polymethyl methacrylate composites reinforced with surface-coated carbon fibers

Using trihydroxy polyether polyol (PPG), diphenylmethane diisocyanate (MDI) as soft segment and hard segment, carbon fiber (CF) as reinforcement, and self-crosslinking CF/polymethyl methacrylate (PMMA) composite was prepared by prepolymer method. In this study, starch and octanoyl chloride were esterified to obtain esterified starch (SE). The fiber is then melt blended with PMMA matrix to prepare PMMA composite. Fourier-transform infrared spectroscopy (FTIR) and SEM were used to analyze and characterize the composites produced. The results show that the composite material was prepared by separately modifying the fiber with NaOH and SE, respectively. The mechanical properties of the composite materials prepared by the modified fiber are improved, and the fiber and the PMMA matrix showed better compatibility. The mechanism of comodified fiber enhanced the mechanical properties of its composites.