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Grafting Reaction (grafting + reaction)
Selected AbstractsSynthesis of star poly(1,3-cyclohexadiene): Grafting reaction of poly(1,3-cyclohexadienyl)lithium onto C60JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2008Itaru Natori Abstract The grafting reaction of poly(1,3-cyclohexadienyl)lithium onto fullerene-C60 (C60) was strongly affected by the nucleophilicity of poly(1,3-cyclohexadiene) (PCHD) carbanions and the polymer chain microstructure, and progressed via step-by-step reactions. A star-shaped PCHD, having a maximum of four arms, was obtained from poly(1,3-cyclohexadienyl)lithium composed of all 1,4-cyclohexadiene (1,4-CHD) units. The rate of the grafting reaction was accelerated by the addition of amine. The grafting density of PCHD arms onto C60 decreased with an increase in the molar ratio of 1,2-cyclohexadiene (1,2-CHD) units. The electron-transfer reaction from PCHD carbanions to C60 did not occur in either a nonpolar solvent or a polar solvent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3282,3293, 2008. [source] Styrene grafting onto a polyolefin in an internal mixer and a twin-screw extruder: Experiment and kinetic modelPOLYMER ENGINEERING & SCIENCE, Issue 7 2001Jaehyug Cha There has been relatively little effort to quantitatively understand graft copolymerizaution in either batch mixers or twin-screw extruders. Most efforts have concentrated on grafting maleic anhydride, which does not homopolymerize. In this paper we consider grafting with styrene, which may homopolymerize as well as graft. The influence of residence time on degree of grafting in an internal mixer and a twin-screw extruder were studied by measuring reaction yields with respect to reaction time in a mixer and along the screw axis in a twin-screw extruder. The degree of grafting increased with initial monomer and peroxide concentration. Grafting reactions with three different peroxides were also investigated. The degree of styrene grafting in an internal mixer is slightly higher than that in a twin-screw extruder. The rate of reaction along the screw axis in terms of residence time seems higher than for the batch mixer. The melt viscosity dropped dramatically with addition of peroxide. A kinetic scheme is proposed and the experimental results are critically compared with it. [source] Incorporation of a (Cyclopentadienyl)molybdenum Oxo Complex in MCM-41 and Its Use as a Catalyst for Olefin EpoxidationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Marta Abrantes Abstract The tricarbonyl complex [(,5 -C5H4 -COOMe)Mo(CO)3Cl] was prepared from the reaction of sodium (methoxycarbonyl)cyclopentadienide, (C5H4 -CO2Me)Na, with (Bu4N)[Mo(CO)5I]. Heating the ester with 3-(triethoxysilyl)propylamine gave the amide derivative {[,5 -C5H4 -CONH-C3H6Si(OEt)3]Mo(CO)3Cl}. The functionalised tricarbonyl complex was immobilised in the ordered mesoporous silica MCM-41 with a loading of 13 wt.-% Mo (1.4 mmol·g,1) by carrying out a grafting reaction in dichloromethane. Powder X-ray diffraction and nitrogen adsorption,desorption analysis indicated that the structural integrity of the support was preserved during the grafting and that the channels remained accessible, despite significant reductions in surface area, pore volume and pore size. The success of the coupling reaction was confirmed by 29Si and 13C (CP) MAS NMR spectroscopy. A supported dioxo complex of the type [(,5 -C5H4R)MoO2Cl] was subsequently prepared by oxidative decarbonylation of the tethered tricarbonyl complex using tert -butyl hydroperoxide (TBHP). The oxidised material is an active catalyst for the liquid phase epoxidation of cyclooctene with TBHP as the oxygen source. Similar catalytic results were obtained using the tethered tricarbonyl complex directly as a pre-catalyst since fast oxidative decarbonylation occurs under the reaction conditions used. For both systems, the desired epoxide was the only product and the initial activities were about 13 mol·molMo,1·h,1. The solid catalysts were recycled several times. Some activity was lost between the first and second runs but thereafter tended to stabilise. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Rheology and thermal properties of polypropylene modified by reactive extrusion with dicumyl peroxide and trimethylol propane triacrylateADVANCES IN POLYMER TECHNOLOGY, Issue 1 2009Feng-Hua Su Abstract Trimethylol propane triacrylate (TMPTA) and dicumyl peroxide (DCP) were used to modify polypropylene (PP) by reactive extrusion in a twin-screw extruder. The effects of TMPTA concentration on oscillatory shear rheology, melt elongational rheology, and thermal properties were comparatively evaluated. Fourier transform infrared spectroscopy indicated that the grafting reaction took place and TMPTA had been grafted onto the PP backbone. Differential scanning calorimetric results showed that the crystallization temperatures of modified PPs were higher than those of the initial and degraded PPs. The rheological characteristics such as higher storage modulus (G,) at low frequency, increased degree of shear thinning, a plateau in tan ,,, plot, and upturning at high viscosity in the Cole,Cole plots proved that the long-chain branches have been added to the linear PP molecule. The melt elongational rheology showed that the modified PPs exhibit improved melt strength and increased elongational viscosity in the presence of TMPTA and DCP, which further confirmed the existence of long-chain branching (LCB) in their backbone. According to the analytical results from oscillatory shear rheology and elongational rheology, it can be inferred that the LCB level in modified samples increases with an increase in TMPTA concentration. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:16,25, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20146 [source] Optimized conditions for the grafting reaction of poly(methyl methacrylate) onto oil-palm empty fruit bunch fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Aznizam Abu Bakar Abstract This article describes the graft copolymerization of poly(methyl methacrylate) (PMMA) onto oil-palm empty fruit bunches (OPEFBs) with a fiber length of less than 75 ,m. The graft copolymerization was carried out under a nitrogen atmosphere by a free-radical initiation technique in an aqueous medium. Hydrogen peroxide and ferrous ions were used as a redox initiator/cocatalyst system. The PMMA homopolymer that formed during the reaction was removed from the grafted copolymers by Soxhlet extraction. Determining the effects of the reaction period, reaction temperature, and monomer concentration on the grafting percentage was the main objective, and they were investigated systematically. The optimum reaction period, reaction temperature, monomer concentration, and initiator concentration were 60 min, 50°C, 47.15 × 10,3 mol, and 3.92 × 10,3 mol, respectively. The maximum percentage of grafting achieved under these optimum conditions was 173%. The presence of PMMA functional groups on OPEFB and the enormous reduction of the hydroxyl-group absorption band in PMMA- g -OPEFB spectra provided evidence of the successful grafting reaction. The improvement of the thermal stability of PMMA- g -OPEFB also showed the optimal achievement of the grafting reaction of PMMA onto OPEFB. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effects of screw configurations on the grafting of maleic anhydride grafted low-density polyethylene in reactive extrusionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Hui Fang Abstract The effects of screw configurations, that is, the staggering angles and disc widths of the kneading blocks, on grafting reactive extrusion for maleic anhydride grafted low-density polyethylene were investigated in a corotating twin-screw extruder. Samples were collected from three positions along the screw and the die exit. The grafting degree (GD) of the specimens was evaluated by titration. It was found that the kneading block configurations had a significant influence on the grafting reactive extrusion. In addition, another three groups of extrusion experiments were performed to explore the intrinsic relationship between the GD, the degree of fill in the screw channel, the residence time distribution (RTD), and the mixing intensity in various screw configurations. The experimental results indicated that the location of the melting endpoint significantly affected the position at which the reaction began; the degree of fill, RTD, and mixing performance of the screw played important roles in the grafting reaction. The reverse kneading blocks with a narrow disc width, which had a high degree of fill and good mixing capacity, enhanced the increase in GD along the screw during the reactive extrusion. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Grafting of poly(N -isopropylacrylamide) onto nylon and polystyrene surfaces by atmospheric plasma treatment followed with free radical graft copolymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Xiaoling Wang Abstract Stimuli-responsive polymer materials (SRPs) have potential uses in drug delivery, tissue engineering, bioreactors, and cell-surface adhesion control. Temperature-responsive surfaces were fabricated by grafting poly(N -isopropylacrylamide) (PNIPAM) onto nylon and polystyrene surfaces via a new procedure, i.e., He atmospheric plasma treatment followed by free radical graft copolymerization. The atmospheric plasma exhibits the activation capability to initiate graft copolymerization. The procedure is suitable for integration into a continuous manufacturing process. To reduce homopolymerization and enhance graft yield, Mohr's salt was added. The graft of PNIPAM was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy. Dramatic water contact angle increase was found for PNIPAM-grafted polymers at about 32°C, indicating the temperature sensitivity of the grafted surface, i.e., the change of surface from hydrophilic to hydrophobic when temperature increases above the lower critical solution temperature (LCST). The addition of Mohr's salt enhances the grafting reaction and the magnitude of temperature sensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3614,3621, 2007 [source] Surface modification of nylon-6 fibers for medical applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007S. E. Shalaby Abstract Hydroxyethylmethacrylate (HEMA) is considered to be one of the important vinyl monomers. The ability of polyhydroxyethyl-methacylate (PHEMA) graft sites to consecutive chemical modification makes the use of nylon-6 fibers grafted with PHEMA a feasible bed for immobilization of a wide range of biologically active reagents, specially enzymes, drugs, cells, and immunadsorbents. Stemming from the above discussions, in this article, the graft copolymerization of HEMA onto modified nylon-6 fibers containing Polydiallyldimethylammonium chloride (PDADMAC) in the presence of Cu2+,K2S2O8 as a redox initiating system was carried out, with very high rate and almost without homopolymer formation. The factors affecting the grafting reaction (monomer, K2S2O8 and cupric ion concentrations, the amount of PDADMAC as well as the reaction temperature) were studied. Kinetic investigation revealed that the rate of grafting (Rp) of HEMA onto modified nylon-6 fibers is proportional to [HEMA]1, [CuSO4.5H2O] 0.7, [PDADMAC]0.4, and [K2S2O8]1.4. The overall activation energy was calculated (71 KJ/mol). The fine structure, surface topography, thermal and electrical properties of parent and grafted nylon-6 fibers were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3788,3796, 2007 [source] Photografting of unable-to-be-irradiated surfaces.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Abstract In this article, a batch liquid-phase process was reported, by which the photo-initiated grafting polymerization could be carried out on the dark surfaces that were not directly irradiated by UV light. In the reaction system, an aluminum foil was placed horizontally to reflect UV light back and form a dark area underneath where the grafting polymerization took place. The occurrence of the polymerization was demonstrated by gravitational analyses and XPS spectra. The factors affecting the grafting reaction have been studied and the results showed that increasing irradiation time, reaction temperature, and benzophenone concentration and decreasing distance (D) between the light area and the place where grafting reaction took place were beneficial to the grafting reaction. The highest grafting density was obtained at a acrylic acid concentration of 15 vol %. Moreover, some further investigations were also made. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 118,124, 2007 [source] Synthesis of star poly(1,3-cyclohexadiene): Grafting reaction of poly(1,3-cyclohexadienyl)lithium onto C60JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2008Itaru Natori Abstract The grafting reaction of poly(1,3-cyclohexadienyl)lithium onto fullerene-C60 (C60) was strongly affected by the nucleophilicity of poly(1,3-cyclohexadiene) (PCHD) carbanions and the polymer chain microstructure, and progressed via step-by-step reactions. A star-shaped PCHD, having a maximum of four arms, was obtained from poly(1,3-cyclohexadienyl)lithium composed of all 1,4-cyclohexadiene (1,4-CHD) units. The rate of the grafting reaction was accelerated by the addition of amine. The grafting density of PCHD arms onto C60 decreased with an increase in the molar ratio of 1,2-cyclohexadiene (1,2-CHD) units. The electron-transfer reaction from PCHD carbanions to C60 did not occur in either a nonpolar solvent or a polar solvent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3282,3293, 2008. [source] Simulations of grafting monomers and associated degradation of polypropylene in a modular co-rotating twin screw extruderJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2005Jongmin Keum Kinetic models of grafting maleic anhydride (MAH) and methyl methacrylate (MMA) on polypropylene (PP) were developed for screw extrusion. However, the kinetic models were insufficient to explain the grafting reactions along the length of modular co-rotating twin screw extruders because the rheological properties and the residence time of PP changed owing to degradation of PP during the grafting reaction. In order to model this system for a modular co-rotating twin screw extruder, the kinetic model of grafting reaction and models for degradation of PP were combined with fluid mechanics and heat transfer. Given the geometrical configurations of the screw, the operating conditions, and the physical properties of the polypropylene, the simulations predicted variation of molecular weight and mean residence time due to degradation of PP. The weight percent of grafted MAH or MMA on PP profiles along the screw axis was also calculated in the simulation. These predictions were compared with experimental data for various operating conditions. J. VINYL. ADDIT. TECHNOL. 11:143,149, 2005. © 2005 Society of Plastics Engineers. [source] Ultrasonically Initiated Grafting of Maleic Anhydride onto Poly(propylene)MACROMOLECULAR REACTION ENGINEERING, Issue 1 2007Xiumin Tan Abstract This paper presents the studies on the grafting of MAH onto PP performed in solution by means of ultrasonic initiation. The effect of sonic intensity and monomer concentration on the amount of grafted MAH was investigated. It was found that grafting reaction could be initiated by ultrasound at ambient temperatures in the absence of an initiator. The quantity of product grafted was found to be 1.35%. It has been shown that optimum conditions for grafting are reached at an ultrasonic intensity of 300 W and a MAH concentration of 30%. PP- g -MAH is characterized by FTIR and XRD. DSC shows that the crystallinity of PP- g -MAH is lower than that of pure PP. [source] Preparation, characterization, and thermal stability of novel PMMA/expandable graphite halogen-free flame retardant compositesPOLYMER COMPOSITES, Issue 1 2010Chia-Hsun Chen In this investigation, expandable graphite was functionalized using a coupling agent to produce covalent bonds between the organic and inorganic phases, enhancing the thermal stability of the composites. The modified expandable graphite had an OEt function group that reacted with methyl methacrylate- co -3-(trimethoxysilyl)propyl methacrylate. Fourier transform-infrared spectrometry and X-ray photoelectron spectra were adopted to characterize the grafting reaction between vinyltriethoxysilane and expandable graphite. It is affirmed that VTES has reacted with expandable graphite. The results of thermogravimetric analysis and thermogravimetric difference (TG,) reveal that functionalized expandable graphite can improve the thermal stability of composites. Scanning electron microscope was utilized to observe the morphology of the composites, and the behavior of expansion was discussed after the materials were burned. These results of X-ray photoelectron spectra for char confirm that expandable graphite improves the degree of accumulation of char and that of the antioxidation of the composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [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] Rheology and melt strength of long chain branching polypropylene prepared by reactive extrusion with various peroxidesPOLYMER ENGINEERING & SCIENCE, Issue 2 2010Feng-Hua Su Long Chain Branching Polypropylenes were prepared in an extruder by a melt grafting reaction in the presence of various peroxides and a polyfunctional monomer of 1,6-hexanediol diarylate. Fourier Transformed Infrared spectra and the rheological characteristics indicated that the grafting reaction added long branched chains to linear polypropylene (PP). In comparison to the initial PP, the branched samples exhibited higher melt strength, lower melt flow index, and enhancement of crystallization temperature. The branching number of the modified samples agreed well with their melt viscoelasticity and the improved degree of their melt strength. The branching level in modified PPs could be controlled by the property and structure of the peroxide used. Peroxides with lower decomposition temperature and more stable radicals after decomposition promoted the branching reaction, leading to the modified PPs with higher branching level and melt strength. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Functionalization of high density polyethylene with maleic anhydride in the melt state through ultrasonic initiationPOLYMER ENGINEERING & SCIENCE, Issue 4 2003Yuncan Zhang Grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE) performed in the melt state through ultrasonic initiation by a laboratory-scale ultrasonic extrusion reactor was studied in this paper. The effect of sonic intesity on the amount of grafted MAH, viscosity-average molecular weight and melt flow index of the grafted product was investigated. The results show that the ultrasonic waves can obviously decrease the molecular weight of the grafted product and cause the increase of the amount of grated MAH, implying that the grafting reaction consists of the chain scission and the grafting reaction of the produced macroradicals with MAH. The percentage of grafting of the product amounts to 0.6%; its melt-flow index is between 0.5 and 2.0 g/10 min, depending upon ultrasonic intensity, MAH content and grafting temperature. Compared with the method of peroxide initiation, in this method the crosslinking reaction can be prevented easily through the allocation of ultrasonic intensity. The mechanical properties of the improved HDPE/GF composite produced by ultrasonic initiatives are higher than in those produced by peroxide initiatives. [source] Modification of polystyrene properties through grafting with N -vinylcarboxamido-2-methylpropane sulfonic acid monomerPOLYMER INTERNATIONAL, Issue 12 2004A Aggour Abstract Polystyrene (PS) possesses good mechanical properties, but its surface is relatively inert and hydrophobic. Grafting of N -vinylcarboxamido-2-methylpropane sulfonic acid (VCMP) is useful to hydrophilize the PS surface. Grafting was performed using benzoyl peroxide (BPO) as an initiator in toluene:methanol solvent mixture (3:1 volume ratio). The influence of the main factors on grafting, such as temperature, time, concentrations of initiator, PS and VCMP, has been studied. The results show that the initial rate of polymerization and percentage of grafting are enhanced by increased temperature. Furthermore, the specific rate constants of the first order reaction/are determined, and the activation energy of the grafting reaction is estimated. The grafting parameters are established and a suitable mechanism of the reaction is proposed. The grafted PS is to characterized through infrared spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential gravimetric analysis (DTG). The kinetics of thermal degradation and the order of the thermal stabilities are given. Also the decomposition activation energies of the thermal degradation are determined, and confirm the thermal stabilities of the polymers used. © 2004 Society of Chemical Industry [source] Reaction kinetics of graft copolymerization and thermochemical studies of the degradation of poly(vinyl alcohol) graft copolymerPOLYMER INTERNATIONAL, Issue 3 2001Yassin A Aggour Abstract Poly(vinyl alcohol) (PVA) is a water-soluble and biomedical polymer. 2-Acrylamido-2-methyl-1-propanesulfonic acid was grafted onto PVA using ammonium persulfate as radical initiator. The influences of synthesis conditions such as temperature, concentrations of initiator, PVA and monomer were investigated. Both the initial rate of grafting and the final percentage of grafting were increased by an increase in reaction temperature. The reaction kinetics were studied to determine the rate constants of the first-order reactions. An activation energy of 16.3,kJ,mol,1 was found for the grafting reaction. The graft copolymers were characterized by IR and intrinsic viscosity measurements. A proposed mechanism of the grafting reaction is discussed. Kinetics of the thermal degradation were studied using a thermogravimetric method and the order of thermal stabilities are given. The apparent activation thermodynamic parameters, Ea, ,H*, ,S* and ,G* were determined and correlated to the thermal stabilities of the homo- and grafted polymers. © 2001 Society of Chemical Industry [source] Arborescent polymers and other dendrigraft polymers: A journey into structural diversityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007Mario Gauthier Abstract Arborescent polymers are characterized by a dendritic, multilevel branched architecture derived from successive grafting reactions. In spite of their much larger size, these materials display properties analogous to dendrimers and hyperbranched polymers, the two other dendritic polymer families. The distinguishing features of arborescent polymers are their assembly from polymeric building blocks of uniform size and their very high molecular weights attained in few synthetic steps. This article offers an overview of the historical aspects of the development of dendrigraft polymers, starting from our initial efforts on the synthesis of arborescent polystyrenes. Major subsequent developments in the synthetic techniques from our and other research groups allowing the synthesis of dendrigraft copolymers, tailoring of the structural characteristics of the molecules, and further simplifications to their synthesis are also reviewed, with emphasis over the broad range of architectures attainable in these systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3803,3810, 2007 [source] Simulations of grafting monomers and associated degradation of polypropylene in a modular co-rotating twin screw extruderJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2005Jongmin Keum Kinetic models of grafting maleic anhydride (MAH) and methyl methacrylate (MMA) on polypropylene (PP) were developed for screw extrusion. However, the kinetic models were insufficient to explain the grafting reactions along the length of modular co-rotating twin screw extruders because the rheological properties and the residence time of PP changed owing to degradation of PP during the grafting reaction. In order to model this system for a modular co-rotating twin screw extruder, the kinetic model of grafting reaction and models for degradation of PP were combined with fluid mechanics and heat transfer. Given the geometrical configurations of the screw, the operating conditions, and the physical properties of the polypropylene, the simulations predicted variation of molecular weight and mean residence time due to degradation of PP. The weight percent of grafted MAH or MMA on PP profiles along the screw axis was also calculated in the simulation. These predictions were compared with experimental data for various operating conditions. J. VINYL. ADDIT. TECHNOL. 11:143,149, 2005. © 2005 Society of Plastics Engineers. 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