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Monomer Content (monomer + content)
Selected AbstractsHow to optimize patch testing with diphenylmethane diisocyanateCONTACT DERMATITIS, Issue 3 2007Malin Frick-Engfeldt We have previously shown that patch test preparations of polymeric diphenylmethane diisocyanate (PMDI) are more stable than preparations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI). This study was conducted to (i) investigate whether PMDIs yield as many positive reactions as 4,4'-MDI, (ii) study concurrent reactions to 4,4'-MDI and 4,4'-diaminodiphenylmethane (4,4'-MDA), and (iii) follow the course of positive reactions during 4 weeks. It was shown that PMDIs detect as many positive reactions as 4,4'-MDI. Thus, they are better patch test agents being more stable than preparations of 4,4'-MDI. We recommend that PMDIs with a monomer content of at least 35% is used in 2.0% petrolatum (pet.) (i.e. monomer patch test concentration approximately 0.7%). It was shown that reactions to 4,4'-MDI and PMDIs appear late and we recommend readings on both day (D) 3/4 and D7. 4,4'-MDA was shown to be a good marker for 4,4'-MDI and patch testing with 4,4'-MDA in 0.25% pet. can be used instead of PMDI. Concomitant reactions to 4,4'-MDI and 4,4'-MDA are probably not caused by conversion of 4,4'-MDI into 4,4'-MDA by reaction with water. Another explanation is a path of reactions leading to ureas and MDI conjugates with skin constituents, which are hydrolysed into 4,4'-MDA. This complex process depends upon several factors and might explain why positive MDI reactions appear after D7. [source] Lower critical solution temperature determination of smart, thermosensitive N -isopropylacrylamide- alt -2-hydroxyethyl methacrylate copolymers: Kinetics and physical propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Mohammad M. Fares Abstract The lower critical solution temperatures (LCSTs) were verified and determined for different molar feed ratios of N -isopropylacrylamide (NIPAAm) and 2-hydroxyethyl methacrylate (HEMA) monomers with ultraviolet spectroscopy and differential scanning calorimetry techniques. Increases in the NIPAAm monomer content played a crucial role in the LCST, which increased up to 36.7°C at 50 mol %. However, a further increase in the NIPAAm monomer content steadily reduced the LCST, which decreased to 33°C at 100 mol % NIPAAm [i.e., pure poly(N -isopropylacrylamide)]. The rate of copolymerization, assessed by the conventional conversion (%),time method, and the apparent activation energies were determined. The reactivity ratios of the monomers, determined by the Kelen,Tudos and Fineman,Ross techniques, together with the results of an equation, showed that the copolymer which formed was an alternating copolymer. The Q,e values for the NIPAAm monomer were determined. The equation showed the linear Arrhenius behavior of ln(r1r2) versus the reciprocal of the temperature (where r1 and r2 are the reactivity ratios of NIPAAm and HEMA, respectively): the activation energy difference [i.e., (E12 + E21) , (E11 + E22), where E12, E21, E11, and E22 are various activation energies] was found to be ,109 kJ/mol. The copolymers were characterized with 1H-NMR, 13C-NMR, Fourier transform infrared, ultraviolet,visible, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Lidia Hernández Abstract For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (Tmax), a setting time (tset) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, Tmax, tset, complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 ,m) to the small ones (of mean diameter 69.7 ,m) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Injectable acrylic bone cements for vertebroplasty with improved propertiesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2004Raúl García Carrodeguas Abstract Currently commercially available acrylic bone cements lack adequate radiopacity and viscosity when they are used in percutaneous vertebroplasty (PVP). In this work improved formulations of radiopaque and injectable poly(methyl methacrylate) bone cements were prepared with different amounts (10,50 wt.%) of BaTiO3 or SrTiO3 particles as the radiopaque agent. Two sets of cements were prepared by using untreated or silanated radiopaque particles, respectively. The influence of the content and nature of the radiopaque agent as well as its silanation with 3-(trimethoxysilyl) propyl methacrylate (,-MPS), on the curing parameters, residual monomer content, radiopacity, mechanical properties, and injectability of the resulting materials, was examined. Doughing and setting times, maximum temperature, and compressive strength of all formulations fulfilled the requirements of standard specifications, with values of peak temperature in the range 57,72 °C and those of compressive strength between 114 and 135 MPa. Formulations containing at least 20 wt.% BaTiO3 or SrTiO3 had radiopacities equal to or greater than that corresponding to 2 mm of Al as required for surgical plastics. Injectability of any of the formulations provided 75,80 wt.% of the total mass manually injected through a conventional biopsy needle 4 min after mixing. Silanation of the BaTiO3 or SrTiO3 particles led to formulations with improved mechanical properties and injectability compared to those obtained with the untreated fillers. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 94,104, 2004 [source] Synthesis of oily core-hybrid shell nanocapsules through interfacial free radical copolymerization in miniemulsion: Droplet formation and nucleationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Z. H. Cao Abstract Nanocapsules with an oily core and an organic/inorganic hybrid shell were elaborated by miniemulsion (co)polymerization of styrene, divinylbenzene, ,-methacryloyloxy propyl trimethoxysilane, and N -isopropyl acrylamide. The hybrid copolymer shell membrane was formed by polymerization-induced phase separation at the interface of the oily nanodroplets with water. It was shown that the size, size distribution, and colloidal stability of the miniemulsion droplets were extremely dependent on the nature of the oil phase, the monomer content and the surfactant concentration. The less water-soluble the hydrocarbon template and the higher the monomer content, the better the droplet stability. The successful formation of nanocapsules with the targeted core-shell morphology (i.e., a liquid core surrounded by a solid shell) was evidenced by cryogenic transmission electron microscopy. Both nanocapsules and nanoparticles were produced by polymerization of the miniemulsion droplets. The proportion of nanoparticles increased with increasing monomer concentration in the oil phase. These undesirable nanoparticles were presumably formed by homogeneous nucleation as we showed that micellar nucleation could be neglected under our experimental conditions even for high surfactant concentrations. The introduction of ,-methacryloyloxy propyl trimethoxysilane was considered to be the main reason for homogeneous nucleation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 593,603, 2010 [source] Performance evaluation of synthesized acrylic acid grafted polypropylene within CaCO3/polypropylene compositesPOLYMER COMPOSITES, Issue 2 2000F. Rahma A polymeric coupling agent acrylic acid grafted polypropylene (AAgPP) was synthesized and its efficiency in CaCO3/PP composite was investigated. The grafting of acrylic acid monomer (AA) onto polypropylene was performed using an internal mixer. The effect of peroxyde, acrylic acid monomer content, temperature and RPM was studied. A grafting reaction between the polypropylene and the acrylic acid was evidenced through FTIR, UV, DSC and MFI testing. The highest grafting yield was obtained at 0.85 phr peroxide and 5 phr acrylic acid. The selected mixing temperature was 200°C, the rotor speed 150 rpm and the residence time 5 min. The obtained coupling agent (AAgPP) was used with 30 wt% CaCO3 filled polypropylene. Strong interactions with the composite were observed. The effect of increasing the coupling agent content on Izod impact and tensile properties was investigated. A maximum in the above properties is attained at 15 wt% AAgPP. The most important effect is clearly shown in the Izod test. In fact, a threefold increase has been observed for either notched and untoched specimen. The 15 wt% AAgPP is considered to be a critical concentration for the composite considered. This corresonds to maximum interactions occurring between the matrix and the filler. SEM analysis clearly shows strong interactions between the filler and the matrix in the presence of acrylic acid grafted polypropylene. This is another proof of the efficiency of the synthesized AAgPP as a potential coupling agent for CaCO3 filled PP. [source] Kinetics of acrylate emulsion polymerization containing hydrophilic hydroxyl monomer in the presence of nano-SiO2 particlesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3 2009Cai-Li Yu Abstract Kinetics of acrylate emulsion polymerization containing hydrophilic hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) in the presence of nano-SiO2 were investigated. The influence of temperature, emulsifier level, hydroxyl monomer content and the level of nano-SiO2 on monomer conversion, polymerization rate (Rp), and the particle size was studied. The results showed that the presence of nano-SiO2 increased the Rp when the level was below 5% but decreased when the level was above 7.5%, the more levels, the more seriously. As the temperature and emulsifier levels increased, and the presence of hydroxyl monomer, the Rp increased. The active energy of the system was 142.01,kJ/mol and the relationship of Rp and the concentration of emulsifier (E) was Rp,,,[E]0.38. The mean particle size increased, particle size distribution became broader as the nano-SiO2 levels increased. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mutations in the cinnamate 4-hydroxylase gene impact metabolism, growth and development in ArabidopsisTHE PLANT JOURNAL, Issue 5 2009Anthony L. Schilmiller Summary The initial reactions of the phenylpropanoid pathway convert phenylalanine to p -coumaroyl CoA, a branch point metabolite from which many phenylpropanoids are made. Although the second enzyme of this pathway, cinnamic acid 4-hydroxylase (C4H), is well characterized, a mutant for the gene encoding this enzyme has not yet, to our knowledge, been identified, presumably because knock-out mutations in this gene would have severe phenotypes. This work describes the characterization of an allelic series of Arabidopsis reduced epidermal fluorescence 3 (ref3) mutants, each of which harbor mis-sense mutations in C4H (At2g30490). Heterologous expression of the mutant proteins in Escherichia coli yields enzymes that exhibit P420 spectra, indicative of mis-folded proteins, or have limited ability to bind substrate, indicating that the mutations we have identified affect protein stability and/or enzyme function. In agreement with the early position of C4H in phenylpropanoid metabolism, ref3 mutant plants accumulate decreased levels of several different classes of phenylpropanoid end-products, and exhibit reduced lignin deposition and altered lignin monomer content. Furthermore, these plants accumulate a novel hydroxycinnamic ester, cinnamoylmalate, which is not found in the wild type. The decreased C4H activity in ref3 also causes pleiotropic phenotypes, including dwarfism, male sterility and the development of swellings at branch junctions. Together, these observations indicate that C4H function is critical to the normal biochemistry and development of Arabidopsis. [source] Stability and optimum polymerized condition of polysiloxane,polyacrylate core/shell polymerADVANCES IN POLYMER TECHNOLOGY, Issue 3 2010Chengyue Ge Abstract The stable emulsion of core/shell latex with little coagulum (no more than 0.5% in quality relative to total monomers) has been prepared at low temperature with potassium-persulfate (KPS), sodium formaldehyde sulfoxylate (SFS), and 2,2,-azobis(2-(2-imidazolin-2-yl)propane)dihydrochloride (VA-044) as composite initiators by staged emulsion polymerization. Reactive surfactants were used to significantly improve the stability of emulsion. More interestingly, reverse core/shell structure was investigated when the organic silicon was added in the late period of polymerization. The effects of the emulsifier, initiators, dosage of organic silicon, and monomer's content on conversion and graft efficiency were studied in detail. Moreover, the stability of emulsion was investigated by the values of zeta potential (,) and coagulum. More importantly, the thermal performance and stability of PSI/PA composite latex was studied by the glass transition temperature (Tg). The results showed that there are appropriate values for all factors to obtain high conversion, graft efficiency, and excellent stability: The dosage of surfactant was about 0.44 g, the dosage of VA-044 was about 1000 mg kg,1, the dosage of organic silicon was about 15%, and the monomer's content was about 30%. In addition, the introduction of organic silicon improved the Tg. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:161,172, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20182 [source] | ||||||||||