Peroxide crosslinking reactions of polymers

Loan, L. D.

doi:10.1351/pac197230010173

Cited by 34 publications

(24 citation statements)

References 14 publications

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“…The large decrease in crosslinking efficiency upon dilution is in contrast to the behavior reported for natural rubber and cispolybutadiene.1.2 The much smaller reduction in crosslinking efficiency found for these polymers is probably connected with the different nature of the crosslinking process in cis-polybutadiene and with the stability of the ally1 radicals involved in crosslinking of natural rubber. 15 The results of the gas chromatographic analysis of the decomposition products of the peroxide are in line with the suggestion that crosslinking of polyethylene in solution proceeds by essentially the same mechanism as in the undiluted state. This is due to the fact that the solvent is relatively inert: first, because the quantitative yield of acetophenone, 2-phenyl-2-propano1, and a-methylstyrene shows that grosso mod0 the same reactions take place;lg and second, because the very high ketone to alcohol ratio (2 to 5, as compared with 0.8 for undecane, a model substance for p~lyethylenel~) indicates that 1,2,4-trichlorobenzene is far more inert towards hydrogen abstraction than polyethylene.…”

Section: Crosslinking Reactionsupporting

confidence: 75%

Polyethylene networks crosslinked in solution: Preparation, elastic behavior, and oriented crystallization. I. Crosslinking in solution

Boer

Pennings

1976

J. Polym. Sci. Polym. Phys. Ed.

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A study has been made of the crosslinking of linear polyethylene in solution. Networks containing a low number of trapped entanglements and elastically ineffective chain ends were prepared by crosslinking high molecular weight linear polyethylene in 1,2,4‐trichlorobenzene solutions with dicumyl peroxide at 120°C. No syneresis was observed during crosslinking except at high peroxide concentrations. The networks were characterized by swelling measurements, infrared spectroscopy, and differential scanning calorimetry. The crosslinking efficiency, calculated from swelling, was found to be proportional to the square of the polymer volume fraction. The proportionality constant was 0.8, indicating close to unit efficiency for undiluted polymer. Chemical modification of the polyethylene chains by attachment of peroxide and solvent fragments was of the order of one foreign unit per elastically active network chain, depending on peroxide and polymer concentration. Sol–gel analysis indicated that no chain scission occurred. These results are shown to be consistent with a “cage” mechanism for crosslinking. The possible topological consequence of this mechanism, preferential crosslinking of entanglements, is discussed. The concentration of trapped entanglements was also found to be proportional to the square of the polymer volume fraction. The proportionality constant corresponds to a molecular weight between entanglements of 4000 for the undiluted polymer, which is close to the value of 4200 found for networks prepared from the undiluted polymer. Since the results obtained are based mainly on the use of the swelling equation, different aspects of the applicability of this equation for the evaluation of the crosslinking process are discussed. As regards the reference dimensions, which should be known for a quantitative application of the elastic theory, the results strongly support the use of the dimensions of the network chains after completion of crosslinking.

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Section: Crosslinking Reactionsupporting

confidence: 75%

Polyethylene networks crosslinked in solution: Preparation, elastic behavior, and oriented crystallization. I. Crosslinking in solution

Boer

Pennings

1976

J. Polym. Sci. Polym. Phys. Ed.

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“…Polymer radicals and inactive polymer molecules can be of any size, thus making the number of reactions a very large number. The reaction mechanism shown in Figure 1 can be summarized into Equation (1) to (4).…”

Section: Model Developmentmentioning

confidence: 99%

“…[1][2][3] The chemistry of sulphur vulcanization has been studied extensively. [4] A great number of studies on the crosslinking of natural, isoprene, polybutadiene and styrene-butadiene rubbers with organic peroxides (such as dicumyl, benzoyl and tert-butyl peroxides) were carried out during the twentieth century. The reaction mechanisms proposed and the kinetic studies carried out to validate them led to the conclusion that crosslinking of rubbers takes place by the attack of a proton in an allylic position, with respect to the rubber double bond, by a free radical.…”

Section: Introductionmentioning

confidence: 99%

“…Direct attack to double bonds was considered to be negligible. [1,2,[4][5][6][7][8][9][10][11][12][13][14] Summary: A kinetic model for the thermal crosslinking of rubbery polymers is presented. The reaction mechanism used to develop the model includes thermal radical generation producing a polymeric radical and a primary radical, crosslinking from attack of a polymer radical to any inactive polymer molecule, bimolecular radical termination among chains of any degree of branching, and radical termination between a polymer radical and a primary radical from the thermal radical generation.…”

Section: Introductionmentioning

confidence: 99%

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Development of a Kinetic Model for Thermal Crosslinking of Rubbery Polymers

Vivaldo‐Lima

Roa‐Luna

Saldívar‐Guerra

2005

Macro Theory & Simulations

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Summary: A kinetic model for the thermal crosslinking of rubbery polymers is presented. The reaction mechanism used to develop the model includes thermal radical generation producing a polymeric radical and a primary radical, crosslinking from attack of a polymer radical to any inactive polymer molecule, bimolecular radical termination among chains of any degree of branching, and radical termination between a polymer radical and a primary radical from the thermal radical generation. The overall polymer population is divided into “generations”, which are defined in terms of the number of primary (linear) chains of original rubbery polymer attached to the polymer molecule. Mass balances for each generation are written down, and expressions to calculate fraction of branched molecules, gel fraction, and number and weight average chain lengths are derived. Model simulations, parameter sensitivity analyses and preliminary parameter estimation studies are presented, taking the thermal crosslinking of linear polybutadiene as a case study.Development of a kinetic model for thermal crosslinking of rubbery polymers: reaction mechanism, model equations and parameter sensitivity analyses.magnified imageDevelopment of a kinetic model for thermal crosslinking of rubbery polymers: reaction mechanism, model equations and parameter sensitivity analyses.

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“…This method also can make it possible to decrease the rate of poly mer aging during membrane operation. As an effective cross linking additive, 5 ethylidene 2 norbornene can be used, which is widely applied in industry for synthesis and crosslinking of the ethylene propylene, and ethylidenenorbornene terpolymer [3]. The crosslinking occurs via the radical mechanism, and peroxide initiation or irradiation (fast electrons, UV light) is mostly used for this purpose [4].…”

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confidence: 99%

Copolymerization of 5-(trimethylsilyl)norbornene and 5-ethylidene-2-norbornene

et al. 2012

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It is known that polymerization of 5 (trimethylsi lyl)norbornene proceeds according to two different schemes, additiion and metathesis (Scheme 1) [1, 2]:Both polymers have promising gas transport prop erties and addition poly 5 (trimethylsilyl)norbornene belongs to a group of highly permeable polymers [1]. However, insufficiently high mechanical properties of addition poly 5 (trimethylsilyl)norbornene impede its application. The problem can be solved by con trolled crosslinking of polymeric chains. This method also can make it possible to decrease the rate of poly mer aging during membrane operation. As an effective cross linking additive, 5 ethylidene 2 norbornene can be used, which is widely applied in industry for synthesis and crosslinking of the ethylene propylene, and ethylidenenorbornene terpolymer [3]. The crosslinking occurs via the radical mechanism, and peroxide initiation or irradiation (fast electrons, UV light) is mostly used for this purpose [4].Metathesis polymerization of silicon substituted norbornenes is a well known process. In particular, 5 (trimethylsilyl)norbornene polymerizes via the met[Ni], [Pd] Scheme 1. Polymerization of 5 (trimethyl silyl)nobornene. athesis route in the presence of different catalytic sys tems on the basis of tungsten, rhenium, or ruthenium [1,5]. The most convenient catalyst for metathesis polymerization of 5 (trimethylsilyl)norbornene is the first generation Ru carbene Grubbs' complex, which makes it possible to obtain polymers with high yields and easily controlled molecular weight. Catalytic sys tems on the basis of metal halides and oxides (WCl 6 , RuCl 3 , Re 2 O 7 ) are less active and require a presence of an activator in the mixture. Therefore, the copolymer ization of 5 (trimethylsilyl)norbornene and 5 eth ylidene 2 norbornene was carried out in the presence of the first generation Grubbs' catalyst.The number of works devoted to the addition poly merization of silicon containing norbornenes is rather limited. The addition polymerization of 5 (trimethyl silyl)norbornene in the presence of Ni and Pd con taining systems was studied in more detail [6]. It was found that the binary system based on nickel naphthenate and MAO was the most active. Namely, this system was chosen for investigation of the addition copolymerization of 5 (trimethylsilyl)norbornene and 5 ethylidene 2 norbornene.In this work, we performed copolymerization of 5 (trimethylsilyl)norbornene (TMSNB) and 5 eth ylidene 2 norbornene (ENB) according to the both of the schemes mentioned above. EXPERIMENTALThe 1 H NMR spectra were recorded on a Bruker Avancer™ 600 NMR spectrometer operating at a fre quency of 600.22 MHz. Proton NMR signals were attributed with reference to residual CDCl 3 protons (7.24 ppm).Abstract-Addition and metathesis copolymerization of 5 (trimethylsilyl)norbornene (TMSNB) and 5 eth ylidene 2 norbornene (ENB) has been studied. High molecular weight metathesis copolymers have been obtained on the first generation Grubbs catalyst based on the Ru carbene complex Cl 2 Ru(=CHPh)(...

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Peroxide crosslinking reactions of polymers

Abstract: Abstract

Cited by 34 publications

References 14 publications

Polyethylene networks crosslinked in solution: Preparation, elastic behavior, and oriented crystallization. I. Crosslinking in solution

Polyethylene networks crosslinked in solution: Preparation, elastic behavior, and oriented crystallization. I. Crosslinking in solution

Development of a Kinetic Model for Thermal Crosslinking of Rubbery Polymers

Copolymerization of 5-(trimethylsilyl)norbornene and 5-ethylidene-2-norbornene

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