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Dicumyl Peroxide (dicumyl + peroxide)
Selected AbstractsEffect of different types of peroxides on properties of vulcanized EPDM + PP blendsPOLYMER COMPOSITES, Issue 10 2010Witold Brostow Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [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] Preparation and properties of heat-shrinkable cross-linked low-density polyethyleneADVANCES IN POLYMER TECHNOLOGY, Issue 2 2003J. Morshedian Abstract In this work, heat-shrinkable characteristics of a polyethylene compound were obtained by blending mixtures of low-density polyethylene with varying amount of peroxide. These were then extruded and molded to the required shape and then cross-linked by chemical means, followed by heating and stretching and then cooled to "freeze-in" the oriented polymer structure (elastic memory). A decrease in the melting point and heat of fusion (,Hf), as determined from the DSC melting enthalpies, was observed with an increase in the dicumyl peroxide (DCP) concentration. Tests on the heat shrinkablity of the samples showed that the stretching temperature has a large effect on the shrinkage temperature. The results showed that by increasing the peroxide content, the shrinkage temperature was decreased. The elongation at break decreased with an increase in the DCP concentration. Increasing the temperature in lightly cross-linked samples (low percent DCP) resulted in a reduction in the elongation at break. Increasing the cross-linking density (DCP content) gave an opposite effect. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 112,119, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10041 [source] Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium-ion batteryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Xiaoyuan Yu Abstract The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium-ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the Tg and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10,3 S cm,1 at room temperature and 1.42 × 10,2 S cm,1 at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3O2 cell were evaluated at a current rate of 0.1C and in voltage range of 2.8,4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3 O2 cell is 115.3 mAh g,1. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Structure modification of isotactic polypropylene through chemical crosslinking: Toughening mechanismJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007S. Bouhelal Abstract Reversibly crosslinked isotactic polypropylene (iPP) was prepared in the presence of dicumyl peroxide. The effects of the peroxide oxy-radicals in the melt were investigated in relation to the modification of the polymer. The dynamic rheology analysis of the crosslinking process was carried out by using a plastograph. The crosslinking reaction was evaluated by the Monsanto method. The resulting structure of the modified samples was studied by means of differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), microhardness, and mechanical properties. The degree of crystallinity of the modified iPP, derived from DSC and WAXS, remains almost unchanged, i.e., the crystalline structure is unaffected, though the lamellar thickness slightly decreases. The impact strength of the crosslinked iPP is greatly improved with reference to that of the unmodified material. A transition from brittle to ductile behavior appears in the modified iPP for all the crosslinking agents studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2968,2976, 2007 [source] Synthesis of a [60] fullerene,Functionalized isotactic polypropylene derivativeJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Gerardo Martínez Abstract The covalent attachment of [60] fullerene (C60) to isotactic polypropylene (i-PP) is achieved by direct reaction in 1,2,4-trichlorobenzene (TCB) solution in the presence of dicumyl peroxide (DCP). The chemically modified pendant C60/i-PP polymers are soluble in chlorinated solvents and have been characterized by ultraviolet,visible and fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, cyclic voltametry, and thermogravimetric analysis. From the results it can be concluded that the modification of i-PP by grafting via a free-radical reaction competes with the possibility of chain scission of i-PP due to the presence of DCP. The functionalized polymers crystallize in the monoclinic crystal modification, and have high crystallinity. The incorporation of C60 significantly enhances the thermal stability of the i-PP. Electrochemical measurements demonstrate good electron acceptor properties of the fullerenated i-PP samples. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6722,6733, 2008 [source] Cp2TiCl-catalyzed living radical polymerization of styrene initiated from peroxidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2006Alexandru D. Asandei Abstract The effects of the reaction conditions and nature of the initiator were investigated in the Cp2Ti(III)Cl-catalyzed living radical polymerization of styrene initiated by benzoyl peroxide (BPO), tert -butyl peroxide (TBPO), tert -butyl peroxybenzoate (TBPOB), dicumyl peroxide (CPO), and tert -butylperoxy 2-ethylhexyl carbonate (TBPOEHC). The reversible termination of the growing chains with Cp2Ti(III)Cl affords a linear dependence of molecular weight on conversion over a wide range of temperatures (60,120 °C) with an optimum in polydispersity (Mw/Mn < 1.2) for St/BPO/Cp2TiCl2/Zn = 100/1/3/6 at 60,90 °C. The similarity of the kinetic parameters from polymerizations initiated by peroxides with vastly different half-life times (t = 1 h, t = 543 h) and the minimum peroxide/Ti = 1/2 ratio required for a living process indicate that initiation occurs primarily by the redox reaction of the peroxide with Cp2Ti(III)Cl rather than peroxide thermal decomposition. This is consistent with one Ti equivalent consumed in the redox initiation and the second one utilized in the reversible termination of the growing chains. Qualitatively, based on the livingness of the process, these initiators ranked as BPO > TBPOB , TBPO > CPO > TBPOEHC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1106,1116, 2006 [source] Grafting of maleic anhydride onto linear polyethylene: A Monte Carlo studyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004Yutian Zhu Abstract Monte Carlo simulation was used to study the graft of maleic anhydride (MAH) onto linear polyethylene (PE-g-MAH) initiated by dicumyl peroxide (DCP). Simulation results revealed that major MAH monomers attached onto PE chains as branched graft at higher MAH content. However, at extremely low MAH content, the fraction of bridged graft was very close to that of branched graft. This conclusion was somewhat different from the conventional viewpoint, namely, the fraction of bridged graft was always much lower than that of branched graft under any condition. Moreover, the results indicated that the grafting degree increased almost linearly to MAH and DCP concentrations. On the other hand, it was found that the amount of grafted MAH dropped sharply with increasing the length of grafted MAH, indicating that MAH monomers were mainly attached onto the PE chain as single MAH groups or very short oligomers. With respect to the crosslink of PE, the results showed that the fraction of PE-(MAH)n -PE crosslink structure increased continuously, and hence the fraction of PE-PE crosslink decreased with increasing MAH concentration. Finally, quantitative relationship among number average molecular weight of the PE, MAH, and DCP contents was given. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5714,5724, 2004 [source] Role of minority structures and mechanism of peroxide crosslinking of polyethyleneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2004Milan Lazár Abstract Minority structures are considered to be defect structures that are formed during polyethylene (PE) preparation and during the crosslinking process in PE. The minority structures that play the predominant role in PE crosslinking are vinyl double bonds. Moreover, the decomposition of dicumyl peroxide in PE does not proceed according to first-order kinetics, but induced peroxide decomposition also takes part. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 675,688, 2004 [source] Microwave-Assisted Free Radical Copolymerizations of Styrene and Methyl MethacrylateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2007Heiner Stange Abstract Free radical copolymerizations of styrene and MMA were performed in toluene and DMF as solvents using different peroxide initiators with and without microwave irradiation. A general trend showed significant solvent dependence of monomer conversion rate only for copolymerizations initiated by tert -butyl perbenzoate in DMF compared to toluene but nearly no impact for copolymerizations initiated by dicumyl peroxide and dibenzoyl peroxide. Significant variations in copolymer composition were not observed for reactions under conventional heating compared to microwave irradiation. It was concluded that enhanced initiator decomposition under microwave irradiation in DMF accelerate polymerization of styrene and MMA by formation of larger amount of initiator radicals. [source] Thermal and mechanical properties of dough modeling compound reinforced ethylene propylene diene monomer/silicon rubber compositesPOLYMER COMPOSITES, Issue 6 2006Weili Wu Ethylene propylene diene monomer (EPDM)/silicon rubber composite was prepared by adding dough-modeling compound (DMC). EPDM/silicon rubber is the matrix of the composite, and DMC is a disperse phase (reinforced phase). The morphology of the composite was studied by scanning electron microscopy, and it was found that the compatibility of DMC/EPDM/silicon rubber composite was good. The influence of the DMC and peroxide curing agents on the mechanical and thermal properties were studied. The results showed that the mechanical and thermal properties of the composite were best, when DMC/EPDM/silicon rubber was 80/25/75. The thermal properties of the composite prepared with added equivalent dicumyl peroxide was better than those with added benzoperoxide, but Shore A hardness and elongation at break are unchangeable. The integral properties of DMC reinforced EPDM/silicon rubber composite was much better than three raw materials. POLYM. COMPOS. 27:621,626, 2006. © 2006 Society of Plastics Engineers [source] Tailoring viscoelastic and mechanical properties of the foamed blends of EVA and various ethylene-styrene interpolymersPOLYMER COMPOSITES, Issue 3 2003I-Chun Liu Foamed materials (EVA/ESI) have been prepared from blends of ethylene-vinyl acetate copolymer (EVA) and ethylene-styrene interpolymers (ESI) in the presence of various amounts of dicumyl peroxide (DCP). Four ESIs of different compositions were employed in this study; their styrene contents ranged from 30 to 73 wt% and their Tg ranged from ,2 to 33°C. It has been found that microcellular morphology, degree of crosslinking and expansion ratio were strongly affected by the DCP concentration and the type of ESI employed. A minimum degree of crosslinking was required for making good foams and the same degree of crosslinking could be achieved by employing a smaller amount of DCP for an EVA/ESI blend having a higher styrene content. In contrast to other EVA blends, such as EVA/LDPE, these EVA/ESI blends exhibited no existence of any optimum DCP concentration, and the , glass transition temperatures of the foams varied with the ESI type, covering a wide span from 0°C to 37°C. Therefore, it was possible to tailor the Tg of an EVA/ESI blend by choosing an appropriate type of ESI. Furthermore, by correctly tailoring the Tg, the EVA/ESI foam could be made into a rubbery material with a custom-designed damping factor. Tensile strength and modulus of the EVA/ESI foams increased generally with an increase in the styrene content, with the exception that ESIs with very low styrene content will confer on the blend a high modulus at small strain and a large elongation at break. [source] Compatibilization of starch,polyester blends using reactive extrusionPOLYMER ENGINEERING & SCIENCE, Issue 3 2006R.B. Maliger Maleic anhydride (MA) and dicumyl peroxide (DCP) were used as crosslinking agent and initiator respectively for blending starch and a biodegradable synthetic aliphatic polyester using reactive extrusion. Blends were characterized using dynamic mechanical and thermal analysis (DMTA). Optical micrographs of the blends revealed that in the optimized blend, starch was evenly dispersed in the polymer matrix. Optimized blends exhibited better tensile properties than the uncompatibilized blends. X-ray photoelectron spectroscopy supported the proposed structure for the starch,polyester complex. Variation in the compositions of crosslinking agent and initiator had an impact on the properties and color of the blends. POLYM. ENG. SCI. 46:248,263, 2006. © 2006 Society of Plastics Engineers [source] An investigation of the effect of silane water-crosslinking on the properties of poly(L-lactide)POLYMER INTERNATIONAL, Issue 5 2010Changyu Han Abstract A silane-grafting water-crosslinking approach was developed to crosslink poly(L -lactide) (PLLA) by grafting vinylalkoxysilane onto PLLA using dicumyl peroxide, followed by silane hydrolysis to form siloxane linkages between PLLA chains. The degree of silane grafting onto PLLA was qualitatively characterized using Fourier transform infrared spectroscopy and quantitatively determined using inductively coupled plasma mass spectrometry. Crosslinked PLLA films were obtained by curing of silane-grafted PLLA in hot water. Gel fractions were evaluated in order to calculate the crosslinking reaction kinetics and crosslinking density. Various techniques were used to investigate the effect of silane water-crosslinking on the thermomechanical properties, hydrolysis resistance and biodegradation of PLLA. In addition to an improvement in thermal stability and mechanical properties, hydrolysis resistance was significantly enhanced as a result of silane water-crosslinking of PLLA. Moreover, the biodegradation of silane water-crosslinked PLLA was retarded compared with neat PLLA. Copyright © 2010 Society of Chemical Industry [source] Crosslinking of elastomers upon ageing: a kinetic approach based on crystallinity changes followed by DSCPOLYMER INTERNATIONAL, Issue 6 2003Mohamed Baba Abstract It was observed that crosslinking reactions resulting both from peroxide decomposition or photoageing at wavelengths longer than 300,nm involve a drastic decrease of the crystallinity of some dienic elastomers, such as polybutadienes (rich in cis 1,4 and 1,2 microstructures) and polycyclo-octene. By comparing precisely the rate of decomposition of dicumyl peroxide and that of the crystallinity decrease, it was possible to show that the kinetics of crystallinity loss observed upon ageing can be identified with that of the crosslinking of elastomers. The results indicate that the crosslinking process can be followed directly by DSC measurement of the crystallization/melting cycle. © 2003 Society of Chemical Industry [source] Hazard ratings for organic peroxidesPROCESS SAFETY PROGRESS, Issue 2 2008Yih-Shing Duh Abstract Nine of commercially available organic peroxides were assessed with differential scanning calorimeter (DSC) and adiabatic calorimeters. These organic peroxides are cumene hydroperoxide (CHP), di- tert -butyl peroxide (DTBP), methyl-ethyl-ketone peroxide (MEKPO), tert -butyl hydroperoxide (TBHP), benzoyl peroxide (BPO), hydrogen peroxide, lauroyl peroxide (LPO), tert -butyl peroxybenzoate (TBPBZ), and dicumyl peroxide (DCPO). Exothermic onset temperatures, self-heat temperature and pressure rates, and heats of decomposition were measured and assessed. Adiabatic runaway reaction characteristics were determined by using ARC (accelerating rate calorimeter) and VSP2 (vent sizing package). Incompatibility, tests with several potential contaminants, was made using DSC, VSP2, and microcalorimeter. An incompatibility rating was developed using onset temperature, lowering of the onset temperature, heat of decomposition, maximum self-heat rate, adiabatic temperature rise, maximum pressure of decomposition, and maximum pressure rising rate, etc. © 2008 American Institute of Chemical Engineers Process Saf Prog 2008 [source] | |||||||||||||