Monomer Vapor Research Articles

Chronic inhalation toxicity and oncogenicity of methyl methacrylate in rats and hamsters

Male and female Fischer 344 rats were exposed to methyl methacrylate (MMA) monomer vapours at 0, 25, 100 and 400 ppm, 6 hr/day, 5 days/wk for 24 months and male and female Golden hamsters were exposed to similar vapour concentrations of MMA for 18 months. Parameters monitored throughout the study included clinical signs, individual body weights, haematology, clinical chemistry (rats only) and urinalyses (rats only). 10 rats per sex per exposure group were killed after 13 and 52 wk of exposure and all surviving rats were killed during wk 104–106. All surviving hamsters were killed at wk 78. Mortality and haematological, clinical chemistry and urinalyses parameters were not affected by MMA exposure. Body weights of male rats were not affected by exposure to MMA while body weights of female rats exposed to 400 ppm were lower than control values after wk 52. Male and female hamsters exposed to 400 ppm had body weight decreases ranging from 9 to 12% after wk 48. The nasal cavity was identified as the target organ for chronic toxicity in male and female rats exposed to 100 or 400 ppm. The microscopic nasal cavity changes occurred primarily in olfactory epithelium lining the dorsal meatus and consisted of degeneration of neuroepithelium, basal cell hyperplasia and atrophy of Bowman's glands. Hamsters did not have demonstrable nasal cavity microscopic changes. Chronic exposure to MMA vapour did not cause tumours in either rats or hamsters.

Surface Grafting of Nanometer Scale Hydrocarbon Films.

An organic monomer was grafted on a pulsed plasma polymerized film in a monomer vapor, where styrene (ST), methylmethacrylate(MMA) and others were used as a monomer. The processes were monitored by a quartz crystal microbalance. The grafting was not observed on a clean gold film. Time dependence of grafted film thickness showed a peak at the initial stage of grafting. Therefore it was supposed that some chaged sites traped monomers. The grafted thickness of a few nm suggests that the number of grafted monomer is a few. The initial stage of plasma polymerization and grafting were discuused in this paper.

The Chemistry of Paper Preservation Part 3. The Strengthening of Paper

The following study describes the parylene and graft copolymerization processes that have been developed to strengthen fragile or brittle paper artifacts. Theparylene process involves vaporizing di-para-xylylene at 150o - 250 oC and splitting the dimeric parylene gas at 650o - 690 oC to mono-para-xylylene. The monomer vapor collides with the surface of the paper sample at room temperature and penetrates the cellulose fibers. Polymerization of the monomeric units to poly- para-xylylenes then occurs with the deposition of a thin uniform film. This parylene film forms mechanical links with broken fibers and strengthening occurs. The graft copolymerization (British Library) method involves treating papers with gaseous monomeric ethyl acrylate and methyl methacrylate, and initiating copolymerization by irradiating the papers with low intensity gamma rays. Webs of long-chained polymers are deposited on and between the cellulose fibers thereby strengthening the papers. The chemistry as well as modifications to b...

Polytrimethylsylylpropyne Gas Separation Membranes Modified by Radiochemical Grafting of Divinylbenzene

A radiochemical method was employed to obtain poly(1-trimethylsilyl-1-propyne)(PTMSP)-divinylbenzene (DVB) grafted films. DVB monomer vapors were absorbed by the PTMSP, and the grafting reaction was thereafter accomplished by {sup 60}Co {gamma}-irradiation in a nitrogen atmosphere. The films so obtained were tested for nitrogen-oxygen separation. The performances of the membranes were studied as functions of time and percent of grafting. The DVB-grafted membranes show an increased selectivity factor and stability with time. The experimental data and some SEM observations confirm the presence of large voids in the PTMSP matrix. These voids are responsible for permeability changes during operation and disappear after the grafting procedure. 8 refs., 5 figs.

Preparation of Polymer Particles in Aerosol-Phase Reaction

ABSTRACT Polymer (polysiloxane, polystyrene) particles were prepared by polymerizing droplets of monomer (methyltrichlorosilane, styrene) with vapor (water, trifluoromethanesulfonic acid) in aerosol reactor. The droplets were produced by either evaporation-condensation or nebulization. The applicability of the droplet production methods depends on the nature of the polymerization systems. In the step polymerization of polysiloxane, the evaporation-condensation route gave better results while, in the chain polymerization of polystyrene, the nebulization method was preferred to the other. The evaporation-condensation method was limited in its ability to produce appreciable amounts of polymer product due to its dependence on monomer vapor pressure. In the nebulization technique for the preparation of polystyrene particles, the addition of various volatile additives to the styrene monomer to be nebulized made it possible to change the average size, size distribution and surface characteristics of the particle...

Doppler-limited spectroscopy at cryogenic temperatures: Application of collisional cooling

A coolable gas cell for the measurement of mid-infrared spectra of gases at cryogenic temperatures as low as 77 K is described. The design of the cell allows it to be operated in collisional cooling (or diffusive trapping) mode to generate significant nonequilibrium pressures of monomer vapor for gases which would normally have vanishingly small vapor pressure at low temperatures. Fourier transform infrared spectra of carbon dioxide (CO2), nitrogen dioxide (NO2), and methyl silane (CH3SiH3) vapors cooled by collisions with helium gas at 77 K are reported. Sufficiently high concentrations of monomer gas may be produced at low total pressure conditions (<10 h Pa) to allow spectra to be recorded at the Doppler resolution limit. The resulting spectroscopic simplification indicates that efficient collisional cooling of the vibrational, as well as rotational, degrees of freedom occurs.

Binary nucleation kinetics. I. Self-consistent size distribution

Using the principle of detailed balance, we derive a new self-consistency requirement, termed the kinetic product rule, relating the evaporation coefficients and equilibrium cluster distribution for a binary system. We use this result to demonstrate and resolve an inconsistency for an idealized Kelvin model of nucleation in a simple binary mixture. We next examine several common forms for the equilibrium distribution of binary clusters based on the capillarity approximation and ideal vapor behavior. We point out fundamental deficiencies for each expression. We also show that each distribution yields evaporation coefficients that formally satisfy the new kinetic product rule but are physically unsatisfactory because they depend on the monomer vapor concentrations. We then propose a new form of the binary distribution function that is free of the deficiencies of the previous functions except for its reliance on the capillarity approximation. This new self-consistent classical (SCC) size distribution for binary clusters has the following properties: It satisfies the law of mass action; it reduces to an SCC unary distribution for clusters of a single component; and it produces physically acceptable evaporation rate coefficients that also satisfy the new kinetic product rule. Since it is possible to construct other examples of similarly well-behaved distributions, our result is not unique in this respect, but it does give reasonable predictions. As an illustrative example, we calculate binary nucleation rates and vapor activities for the ethanol–hexanol system at 260 K using the new SCC distribution and compare them to experimental results. The theoretical rates are uniformly higher than the experimental values over the entire vapor composition range. Although the predicted activities are lower, we find good agreement between the measured and theoretical slope of the critical vapor activity curve at a constant nucleation rate of 107 cm−3 s−2.

A Vacuum and/or Pressure Forming System Using a Prepreg Sheet of FRP with a Gel Coat Layer

This paper introduces a new vacuum and/or pressure forming system using a prepreg sheet which consists of two thickened layers of unsaturated polyester, i.e., FRP (Fiber Reinforced Plastic) and gel coat layers, sandwiched by two stretchable films. The efforts were focused on the development of sheet construction, material properties and processing conditions. The difficulties in the development of this system are found in; 1. uneven thickness distribution in a molding 2. vaporization of vinyl monomer 3. gel coat cracks These difficulties were solved by the chemical modifications of resin such as; 1. unifying the apparent tensile modulus of each layer by controlling the viscosity 2. reducing the maximum exothermal temperature 3. shortening the gel time and by the physical modifications of processing conditions such as selection of an appropriate forming rate. The expected application area of this new system is also mentioned briefly.

Enhancement of the monovalent cation perm-selectivity of Nafion by plasma-induced surface modification

In this paper, we focus on improvement of the monovalent cation perm-selectivity of a perfluorinated cation-exchange membrane, Nafion 117, by depositing an anion-exchange layer using a plasma surface modification process. The anion-exchange layer was deposited from 4-vinylpyridine monomer vapor followed by quaternization with 1-bromopropane. The transference number of divalent cation (Fe2+) through the membrane, tFe, decreased with increasing thickness of the plasma polymer layer at the expense of enhanced membrane resistance. A large interfacial resistance was observed between Nafion and the plasma polymer layer which was ascribed to the implantation of cationic species containing nitrogen. To avoid the formation of an interfacial layer, a novel method of plasma-induced surface modification was devised. After a Nafion 117 sheet was placed on an RF (radio-frequency) electrode and sputtered with an oxygen or argon plasma in order to produce active sites on the Nafion, 4-vinylpyridine or 3-(2-aminoethyl)aminopropyltrimethoxysilane vapor was introduced into the reactor to react with radical sites. tFe decreased with increasing RF power. tFe through Nafion modified with 3-(2-aminoethyl)aminopropyltrimethoxysilane was lower than that for Nafion modified with 4-vinylpyridine, probably due to its weak Si-C bond. Nafion treated by the plasma surface modification method exhibited a very high monovalent cation perm-selectivity compared with Nafion treated by the plasma polymerization method.

Fourier transform infrared analysis of hexamethyldisiloxane layers obtained in low‐frequency glow discharge

AbstractPolymer layers from hexamethyldisiloxane (HMDSO) up to 1 μm were produced by glow discharge at 50 Hz under different polymerization conditions. The Fourier transform infrared (FTIR) spectra of such layers were obtained at different current densities of the glow discharge (0.53 to 3.10 mA/cm2), substrate temperatures from 35 to 125°C; gaseous phase pressures from 13.3 to 266 Pa, and layer thicknesses from 0.2 to 0.6 μm. The FTIR spectra of polyhexamethyldisiloxane (PHMDSO) layers modified after treatment in ammoniacal plasma were studied. The spectra of layers obtained in plasma containing both monomer and ammonia vapors were also analyzed. © 1993 John Wiley & Sons, Inc.

The Initiation and the Morphology of Chloroprene Popcorn

The formation of polychloroprene popcorn nuclei has been observed on steel and glass surfaces, where the nuclei appear after a film of polymer has first been formed, as well as within and upon films of the polymer itself that were bathed in the monomer vapor. The nodules appear on steel in contact with wet and with dry monomer, in the latter case after periods longer than 40 days. In the presence of water and monomer stainless steel corrodes and the popcorn nuclei develop at the sites of the corrosion pits, becoming visible to the eye after about 12 days. From a study of the size distribution of nodules it was concluded that after about 6 days nucleation on the steel was sporadic, but after 5 more days it took place regularly, as corrosion developed and provided a rapid flow of initiating species. The morphology of growing nodules was observed. Initially they grew in a nearly spherical shape, but above a certain size the shape became irregular. When cut open they showed signs of internal stress. Despite the nodules having so dense a network that they did not swell in solvents for polychloroprene, at 20°C the nodules developed visible splits once they reached the critical size, and became convoluted on a macroscopic scale because of anisotropic growth. This suggests that the mechanism of growth itself involves scission of the network on a molecular scale, producing new radical centers within the material, to enhance growth and so further distort and strain the network.

The use and handling of acrylic bone cement in Danish orthopaedic departments.

In order to evaluate the use and handling of acrylic bone cement, questionnaire were presented to all Danish orthopaedic departments in 1987 and again in 1992. Marked improvements in the environmental safety precautions for handling of bone cement had taken place during the 5-year period. In 1992, the intraoperative handling and use of bone cement is thus generally considered safe. Further improvements are still to be advocated in some departments. The exposure to methylmethacrylate monomer (MMA) vapour during the cementation procedures should be eliminated by local punctual field suction or change to a bone cement with a lower content of monomer (MMA/n-decylmethacrylate/isobornylmethylacrylate bone cement). Unnecessary manual contact with the cement should be avoided, and if contact is necessary, special protective gloves (butyl rubber gloves or 4H-gloves) should be used in addition to ordinary surgical gloves.

Microlenses in PMMA with high relative aperture: a parameter study

Microlenses with high relative apertures can be fabricated in polymethyl methacrylate by irradiation with a high energy proton beam and diffusion of monomer vapour into the irradiated domains. The most important process parameters are characterized and their effect on the shape of the lenses is discussed.

Surface modification of polymers by photoinitiated graft polymerization

AbstractTwo methods for modification of polymer surfaces by photoinitiated grafting have been developed and applied to films and fibers of synthetic polymers, e.g. polyethylene and polypropylene with acrylic monomers. In the batch process the substrate is enclosed in a cell containing initiator and monomer vapor. UV light through a quartz window initiates the grafting reaction by exciting the initiator (e.g. benzophenone). The grafting reaction is slow (1 to 3 min) due to the inefficient transfer of initiator and monomer through vapor phase. In the continuous process the substrate is presoaked in a solution of initiator and monomer and then drawn into a reactor “on line” where the substrate is irradiated by UV light through a quartz window. The grafting takes place in the very thin surface layer of solution on the substrate. The grafting efficiency is high (70–80% of the polymer formed is grafted) and the process is rapid (5–15 s due to the efficient transfer of initiator and monomer through the liquid phase. The continuous surface grafting process is promising for industrial applications.

Thermodynamic Quantities for Reactions of Alkali Metaborate Monomer and Dimer Vapors.

Alkali metaborate monomer and dimer vapors have been studied thermodynamically, and these results have been compared with those for alkali halides. The ratios of mean dissociation energies for one M-BO2 bond in the M2(BO2)2(g) dimers to dissociation energies for one M-BO2 bond in the MBO2(g) monomers are almost constant for all the alkali metals (M) and an average value is 0.63±0.01. This value is just equal to the corresponding ratios for halides. For the dimerization reactions of MBO2(g), both free energies and enthalpies decrease in going from M=Li to M=Cs, while entropies are almost constant. A similar tendency can be seen in chlorides. For the alkali-alkali exchange reactions in the dimers, free energies, enthalpies, and entropies are very small for both metaborates and chlorides. Excess stabilities in the alkali-alkali mixed-dimer formations are explained from the correlation with the increases in the alkali cation-cation repulsion energies.

Acrylonitrile-smectite complexes

AbstractThe adsorption of acrylonitrile (AN) monomer vapour in the interlamellar space of smectites exchanged with different cations (Na or Y or hexylammonium) was monitored and used to yield macromolecular layers. Polymerization in the presence or absence of a free-radical initiator was obtained by heating at 100°C for 72 h. Cyclization can already be obtained at this stage, and is completed by heating the polyacrylonitrile (PAN)-complexes at 220°C for 48 h.

Modification of an Ion-Exchange Membrane Surface by Plasma Process Part 3: Interfacial Resistance of Monovalent Cation Perm-Selective Membrane from Nafion®

Abstract The monovalent cation perm-selectivity of Nafion® 117, perfluoro-sulfonate cation-exchange membrane, was enhanced by depositing on its surface an ultrathin anion-exchange layer prepared by plasma polymerization. The anion exchanger was deposited from a 4-vinylpyridine monomer vapor followed by quaternarization with 1-bromopropane. The resulting anion-exchange layers were found to be pinhole-free and of uniform thickness. The monovalent cation perm-selectivity of the plasmamodified Nafion membrane was determined by measuring the Fe 2+ ion transference number, tFe in a Li+–Fe2+ system. The influence of the thickness of the plasma layers on the tFe and the membrane resistance was investigated. The tFe decreased with increasing thickness of the plasma polymer layer, but at the cost of enhanced membrane resistance. The resistance of treated Nafion was separated into bulk resistance and interfacial resistance. A large interfacial resistance was observed between Nafion and the plasma polymer layer, and was ascribed to the implantation of cation species.

Modification of Ion Exchange Membrane Surface by Plasma Process: I . H+ Ion Perm‐Selective Membrane from Nafion for Redox‐Flow Battery

The proton perm‐selectivity of a perfluorosulfonate cation exchange membrane, Nafion 117, was enhanced by depositing on its surface an ultra‐thin anionic exchange layer containing fixed pyridine rings. The thin layer was deposited from 4‐vinylpyridine monomer vapor using a glow‐discharge (plasma) polymerization technique. The resulting plasma polymer layers were found to be pinhole‐free and of uniform thickness (∼0.2 μm). The influence of the plasma parameters (monomer flow rate, applied power) on the plasma polymer deposition rate was investigated. The IR spectra of the plasma polymers showed the preservation of pyridine rings in the polymers; the lower the applied RF power, the greater the retention of pyridine rings. The proton perm‐selectivity of plasma‐modified Nafion membrane was determined by using it as the separator in a typical two‐compartment cell and measuring , the transference number of the Fe++ ion through the membrane. Pretreatment of the Nafion membrane by oxygen sputtering increased its proton perm‐selectivity and enhanced the adhesion of plasma polymer onto its surface. Plasma‐modified Nafion membranes exhibited very high proton perm‐selectivities, but at the cost of high membrane resistances. For example, membranes having values of 0.00034 and 0.012 had corresponding resistances of 40 and 4.1 Ω‐cm2, respectively.

Equilibrium character of postradiational grafting of MMA to a tetrafluoroethylene-vinylidenefluoride copolymer

The kinetics and mechanism of postradiational graft polymerization of MMA to a copolymer of tetrafluoroethylene and vinylidene fluoride were investigated. The phenomenon of the “limitation” of polymer yield was observed at a constant concentration of monomer in the gas phase and a constant concentration of active centres as determined by the methods of EPR spectroscopy; an increase in monomer vapour pressure leads to resumption of polymerization and to the establishment of a new, higher limiting yield of polymer. By EPR spectroscopic methods with deuterium labelled MMA, the reversible character of monomer addition to the macroradicals was established under the conditions of polymer yield limitation. The specific growth rates of kinetic chains and the rate constant of depolymerization were determined from the kinetics of equilibrium establishment. The possible causes of the observed effects are discussed.

In vitro blood compatibility of glow discharge‐grafted silicone rubber tubings

AbstractSmall diameter silicone rubber tubings were grafted with vinyl methyl acetamide using a glow discharge treatment. Discharge conditions were chosen which allowed grafting exclusively on the inner surface of the tubings. Increasing the voltage as well as a posttreatment at increased monomer vapor pressures leads to higher conversions as a posttreatment at increased monomer vapor pressures leads to higher conversions as determined by contact angle measurement and gravimetry; no influence of the discharge pressure could be observed. Human blood plasma exposed to the grafted tubings showed some alterations in comparison to blood plasma exposed to ungrafted tubings. A prolongation of the activated partial thromboplastin time and lower levels of factor V and platelet factor 4 were measured, while almost no differences in the generation of fibrinopeptide A could be noticed. Platelet adhesion on grafted tubings was less than on unmodified tubings.