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Crosslinked Polymers (crosslinked + polymer)
Selected AbstractsCation exchange finishing of nonwoven polyester with polycarboxylic acids and cyclodextrinsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007L. Ducoroy Abstract We describe a chemical method for the finishing of polyester nonwoven fabrics that aimed to obtain ion exchange textiles. This approach was based on the use of polycarboxylic acids (PCA) and cyclodextrins as carbohydrate compounds and finishing agents, respectively. It was observed that the reaction between these reactants yielded a crosslinked polymer that was physically anchored onto the fibers. This polymer can be considered as a resin issued from the esterification between the COOH groups of the PCA with the OH groups of the carbohydrate. As the esterification reaction was not complete, many free carboxylic groups remained on the surface of the coating polymer. This feature offered the ion exchange properties to the textile support. In this article, we described the pad-dry-cure process and showed the influence of the curing parameters (time and temperature), the nature, and the concentration of the components and the pH of the impregnating bath. The grafting rate (in wt %) and the ion exchange capacity (IEC) were observed in parallel. First, it was observed that the best IEC capacity (that could reach 1 mmol/g) was obtained when an ideal compromise was applied between time and temperature of curing. We also evidenced that IEC depended on the nature and on the concentration of the PCA (chosen among citric acid, 1,2,3,4-butanetetracarboxylic acid, and polyacrylic acid) and on the pH of the impregnating bath. Finally, it was observed that cyclodextrins were more appropriate than starch as finishing coreactants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3730,3738, 2007 [source] Synthesis and characterization of polyelectrolyte hydrogels with controlled swelling behaviourPOLYMER INTERNATIONAL, Issue 12 2001Ayman M Atta Abstract Copolymerization of sulfopropyl methacrylate potassium salt (K-SPMA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) has been studied in the range 10,90% K-SPMA in the feedstock. The reactivity ratios have been determined for K-SPMA/AMPS copolymers. The copolymer compositions, utilized for determining the reactivity ratio, have been determined from nitrogen content. Crosslinked poly(AMPS) and K-SPMA/AMPS copolymers were prepared in water in the presence of potassium persulfate as initiator and N,N -methylene bisacrylamide (MBA) as tetrafunctional crosslinker. Irradiation of K-SPMA and AMPS with an electron-beam was carried out at 50,wt% aqueous solution with low pH and irradiation dose 40,120,kGy. The swelling behaviour of highly crosslinked K-SPMA/AMPS copolymer polyelectrolyte gels in aqueous medium was studied in the presence of different types of salts. The crosslink density, the average molecular weight between the crosslinks and the dissociation constant (pKa) of the crosslinked polymer were determined from stress,strain measurements. © 2001 Society of Chemical Industry [source] Understanding the kinetics and network formation of dimethacrylate dental resinsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 6 2001Lale G. Lovell Abstract Dimethacrylate monomers are commonly used as the organic phase of dental restorative materials but many questions remain about the underlying kinetics and network formation in these highly crosslinked photopolymer systems. Several novel experimental and modeling techniques that have been developed for other multifunctional (meth)acrylates were utilized to gain further insight into these resin systems. Specifically, this work investigates the copolymerization behavior ofbis-GMA (2,2-bis[p-(2-hydroxy-3-methacryloxyprop-1-oxy)-phenyl]propane) and TEGDMA (triethylene glycol dimethacrylate), two monomers typically used for dental resin formulations. Near-infrared spectroscopy, electron paramagnetic resonance spectroscopy, as well as dynamic mechanical and dielectric analysis were used to characterize the kinetics, radical populations, and structural properties of this copolymer system. In addition, a kinetic model is described that provides valuable information about the network evolution during the formation of this crosslinked polymer. The results of these numerous studies illustrate that all of the aforementioned techniques can be readily applied to dental resin systems and consequently can be used to obtain a wealth of information about these systems. The application of these techniques provides insight into the complex polymerization kinetics and corresponding network formation, and as a result, a more complete understanding of the anomolous behaviors exhibited by these systems, such as diffusion controlled kinetics and conversion dependent network formation, is attained. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis and characterization of biodegradable crosslinked polymers from 5-hydroxylevulinic acid and ,,,-diolsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Yan Zhang Abstract Novel biodegradable chemically crosslinked polymers, poly(5-hydroxylevulinic acid- co -,,,-diol)s (PHLA-diols), were synthesized from 5-hydroxylevulinic acid and ,,,-diols and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The gel content, swelling ratio, tensile properties, and hydrolytic degradation behaviors were also measured and assessed. The glass-transition temperature of the PHLA-diols could be adjusted within a wide range (,50 to 30°C) by the type and feed ratio of the diol. Because of the low glass-transition temperature and crosslink structure, they exhibited certain elastic properties. The tensile modulus, strength, and elongation at break measured at 37°C were 1.4,6.3 MPa, 0.8,1.6 MPa, and 10,25%, respectively. These polymers could be hydrolytically degraded. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Crosslinking of a polyacrylate bearing a spiroorthoester pendant group with mixtures of diglycidyl ether of bisphenol A and phosphorus-containing glycidyl derivativesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2007J. Canadell Abstract The cationic crosslinking of a polyacrylate bearing a spiroorthoester pendant group with mixtures of diglycidyl ether of bisphenol A and three phosphorus-containing glycidyl derivatives was carried out with ytterbium triflate as an initiator. The curing process was monitored with Fourier transform infrared spectroscopy. The thermomechanical and thermogravimetric properties were evaluated. The glass transition temperatures of the obtained materials were, in general, above 100 °C. The incorporation of phosphorus into the network increased the limiting oxygen index values, thus improving the flame retardancy of the materials. During crosslinking, all the crosslinked polymers showed slight shrinkage that was much lower than that observed in conventional epoxy resins. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1920,1930, 2007 [source] Kinetic Study and New Applications of UV Radiation CuringMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2002Christian Decker Abstract Highly crosslinked polymers can be readily synthesized by photoinitiated polymerization of multifunctional monomers or functionalized polymers. The reaction can be followed in situ by real-time infrared (RT-IR) spectroscopy, a technique that records conversion versus time curves in photosensitive resins undergoing ultrafast polymerization upon UV exposure. For acrylate-based resins, UV-curing proceeds with long kinetic chains (7700 mol/radical) in spite of the high initiation rate. RT-IR spectroscopy proved very valuable in assessing the influence of various parameters, such as initiation efficiency, chemical structure of the telechelic oligomer, light intensity, inhibitory effect of oxygen, on polymerization kinetics. Interpenetrating polymer networks can be rapidly synthesized by means of UV irradiation of a mixture of difunctional acrylate and epoxy monomers in the presence of both radical and cationic-type photoinitiators. The same UV technology can be applied to crosslink solid polymers at ambient temperature, which bear different types of reactive groups (acrylate and vinyl double bonds, epoxy ring). UV radiation curing has been successfully used to produce within seconds weathering resistant protective coatings, high-resolution relief images, glass laminates and nanocomposites materials. Photoinitiated crosslinking polymerization. [source] Low loss second-order non-linear optical crosslinked polymers based on a phosphorus-containing maleimidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2004Chih-Ping Chen Abstract A series of crossslinked organic and organic/inorganic polymers based on maleimide chemistry have been investigated for second-order non-linear optical (NLO) materials with excellent thermal stability and low optical loss. Two reactive chromophores (maleimide-containing azobenzene dye and alkoxysilane-containing azobenzene dye) were incorporated into a phosphorus-containing maleimide polymer, respectively. The selection of the phosphorus-containing maleimide polymer as the polymeric matrices provides enhanced solubility and thermal stability, and excellent optical quality. Moreover, a full interpenetrating network (IPN) was formed through simultaneous addition reaction of the phosphorus-containing maleimide, and sol-gel process of alkoxysilane dye (ASD). Atomic force microscopy (AFM) results indicate that the inorganic networks are distributed uniformly throughout the polymer matrices on a nano-scale. The silica particle sizes are well under 100,nm. Using in situ contact poling, the r33 coefficients of 2.2,17.0,pm/V have been obtained for the optically clear phosphorus-containing NLO materials. Excellent temporal stability (100°C) and low optical loss (0.99,1.71,dB/cm; 830,nm) were also obtained for these phosphorus-containing materials. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||