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A ligand free method has been developed for the amidation of benzylic hydrocarbons. A range of benzylic amides has been prepared with the use of dicumyl peroxide and a copper catalyst in good to excellent yields.

A copper-catalyzed radical silylarylation of ynones with commercially available silanes using DCP(dicumyl peroxide) as an efficient oxidant has been developed.This approach represents an efficient route to silyl-functionalized indenone derivatives in moderate to good yield. The resulting silyl-functionalized structures hold potential for further post-modification to construct complex target molecules. This protocol is distinguished by its excellent selectivity, gram scale-up ability and broad scope as well as readily available starting materials.

The effect of dicumyl peroxide (DCPO) concentration on the polymerization kinetics of a polysilazane system has been investigated through DSC analyses. DCPO acts as polymerization initiator by activating the polyaddition of vinyl groups. The overall heat of reaction is found to be a linear function of the DCPO concentration above 1.5 wt%, due to the addition of the heat of fully initiated polymerization and the heat of DCPO decomposition. Below 1.5 wt% of DCPO, the polymerisation of polysilazane is not fully initiated and only part of the reaction occurs. The resulting overall heat of reaction is therefore lower than that provided by the linear law valid for higher concentrations. A two-reaction kinetic model built on this interpretation leads to a satisfactory representation of the DSC analyses performed for each DCPO concentration between 0.1 and 20 wt%. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

Maleated polyethylene (MAPE) and dicumyl peroxide (DCP) are both popularly used in polyethylene-based composites combining with organic fillers such as natural fibers and inorganic fillers such as nanoclay. Systematic studies were undertaken to investigate the influences of MAPE and DCP on the mechanical properties and plasticity of PE composites with or without natural fibers. In addition, the effect of the fiber adding sequence was examined to obtain superior mechanical properties. POLYM. COMPOS., 36:287–293, 2015. © 2014 Society of Plastics Engineers

A Monte Carlo (MC) simulation is performed on peroxide induced branching reactions in a linear low density polyethylene (LLDPE) melt processed with different dicumyl peroxide (DCP) concentrations at various processing times and temperatures. The MC simulation can successfully monitor the microstructural changes due to the induced long chain branching (LCB), decreased terminal double bonds, and increased trans vinyl bonds in LLDPE during peroxide modification. The induced structural changes are in good agreement with the experimental results obtained by rheometery and SEC analysis. The changes in the gel content, M‾w, and MWD as a result of the peroxide modification are also determined. The simulation results also reveal that the chemical mechanism by which the modification proceeded is closely related to the changes in concentrations of reactive vinyl species of the PE molecules. Moreover, the results indicate that the degree of induced LCB increases almost linearly with the DCP concentrations. The findings of this paper indicate that the MC simulation method is able to predict the suitable processing conditions needed for inducing desirable structural changes in a LLDPE.

The article investigates the possibility of obtaining reliable information on the adiabatic behavior of thermally unstable substances based on the thermokinetic data collected by differential scanning calorimetric experiments. In particular, it is developed a novel numerical algorithm which allows the estimation of the adiabatic onset temperature. Theoretical results are verified considering the thermal decomposition of dicumyl peroxide carried out under different calorimetric conditions. Encouraging results point out that the procedures developed allow the assessment of adiabatic critical parameters that are very close to the values determined during the experiments. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3806–3815, 2013

To extend the applications of wood–plastic composites (WPCs), soft WPCs were prepared with ethylene vinyl acetate (EVA) and wood flour (WF) as major components via a two-step process involving two-roll mixing and compression molding. The effect of the various factors, such as WF, unsaturated fatty acid (UFA), and dicumyl peroxide contents, on the mechanical properties, processability, and morphology of the WPCs was investigated in detail. The addition of UFA could effectively improve the processability and flexibility of the composites. The in situ grafting reaction between UFA and EVA considerably improved the adhesion of the WF and resin matrix. Consequently, soft WPCs with good performances in flexibility and processability were successfully obtained. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The first cobalt-catalyzed direct methylation of a C(sp(2) )-H bond using dicumyl peroxide (DCP) as both the methylating reagent and hydrogen acceptor has been established. The reaction proceeded without the use of any additives, and was proven to be applicable to various amides bearing a 2-pyridinylisopropyl (PIP) directing group, providing an efficient access to o-methyl aryl amides with high functional-group tolerance. Preliminary mechanistic studies suggest a radical process would be involved in the catalytic process.

The direct methylation of ortho C–H bonds in aromatic amides with dicumyl peroxide (DCP) using a nickel complex as the catalyst is reported. The reaction shows a high functional group tolerance and is inhibited by radical scavengers. In reactions of meta-substituted aromatic amides, the reaction proceeds in a highly selective manner at the less hindered C–H bonds.

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low-density polyethylene (LLDPE)/ethylene-co-methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (

The mechanical and damping properties of blends of ethylene-vinyl acetate rubber(VA content >40 wt %) (EVM)/nitrile butadiene rubber (NBR) and EVM/ethylene-propylene-diene copolymer (EPDM), both with 1.4 phr BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by DMA. The effect of polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and dicumyl peroxide (DCP) on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range from 41.1°C for EVM/NBR to 62.4°C, while CPVC mixed EVM/NBR blends had an expanded effective damping temperature range of 63.5°C with only one damping peak. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its effective damping temperature range to 64.9°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The nature of the chemiluminescence phenomenon generally observed during oxidation of organic substances at elevated temperatures, was studied on the system dicumyl peroxide-polypropylene. Arguments are put forward in favour of the assumption that the luminescence observed during decomposition of dicumyl peroxide, should be interpreted as phosphorescence of the reaction product acetophenone.

N2-filled hollow glass beads (HGB) were first used as novel gas carriers to prepare microcellular polymers by compression molding. Dicumyl peroxide was acted as crosslink agent to control the produced microcellular structure of low density polyethylene (LDPE)/HGB. The effect of temperature, pressure and the content of gel on the embryo-foaming, and final-foaming structure are investigated. Scanning electronic microscopy shows that the average cell size of microcellular LDPE ranges from 0.1 to 10 μm, and the foam density is about 109–1011 cells/cm3. A clear correlation is established between preserving desirable micromorphologies of microcellular LDPE in different processing stage and tuning processing factors. The pertinent foaming mechanism of microcellular materials foamed with HGB is proposed. Because of the good mechanical strength, low density, weak water-absorption, and excellent heat insulate ability, microcellular LDPE has great potential application in energy building materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Electron spin resonance (ESR) measurements under the tensile deformation of cross-linked polyisoprene were examined by the combination of home-built stretching machine with commercially available ESR spectrometer. The changes of radical concentration during tensile deformation were successfully determined by this technique. It was found that the number of radicals produced by the stretching process decreased during the retraction of stretched sample. In addition, at a given strain, the decrease of radical concentration with time was accompanied by the increase of stress. Such changes were more prominent in the cross-linked sample by sulfur PS sample (PS) than by dicumyl peroxide (PCP), PD sample (PD). The tensile modulus of the samples after the one cyclic deformation increased with increasing the keeping time at room temperature after the cyclic deformation. The increase was larger for the PS than for the PD. These results suggest that the broken cross-linking structure induced by the stretching process was partly reconstructed during and after the retraction with this tendency more prominent in the PS than in the PD. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The technique of grafting silane by in-situ extrusion to improve the compatibility between wood flour and high density polyethylene (HDPE) composites was studied. It was found that the silane grafted composites showed enhanced mechanical properties compared to both the coupled and non-coupled PE-g-MAH composites. The effects of silane contents and dicumyl peroxide (DCP) concentrations on the mechanical properties of the composites were investigated in detail. Moreover, the water absorption, morphology and thermal stability of the composites were also investigated. Copyright © 2008 John Wiley & Sons, Ltd.

The dielectric properties of natural rubber, synthetic polyisoprene, andpolybutadiene samples crosslinked with sulfur and of natural rubber samplescrosslinked simultaneously with sulfur and dicumyl peroxide were studied. Inthe investigated systems, the number of polar groups in unit volume and thecrosslink density may be changed independently over relatively wide ranges.The measurements were performed in the frequency range from 101 to 105 Hzat various temperatures, and macroscopic parameters describing the dielectricproperties of the samples were evaluated. The position and intensity of thedielectric dispersion peak in the main transition zone is only slightly dependenton the crosslink density of the samples. These two values are mainly influencedby the amount of combined sulfur, or more generally, by the number and thedipole moments of polar groups in the sample. The influence of crosslink densityon the width of the absorption curve is very strong; the width increases withincreasing crosslink d...

Gravimetric determinations of weight gain were carried out for ethylene-propylene elstomer (EPR) samples crosslinked by dicumyl peroxide and immersed for periods up to IS minutes in various swelling solvents. The weight gain data were analyzed on the assumed existence of a power-law relationship with immersion time as well as the more usual assumption that the swelling rate is diffusion-controlled. The former analysis led to strong correlations between initial swelling rates and the Flory-Huggins interaction parameter of a polymer-solvent pair. The latter analysis correlated initial uptake rates with crosslink densities obtained from equilibrium swelling results. Initial uptake rates were used to estimate the interaction parameter for the system EPR-tetrahydronaphthalene, and to measure the effect of rutile and carbon black filler on the cross-linking process. Rutile behaved as an inert filler, but results for carbon black proved anomalous, indicating need for further study.

A systematic study of the effect of concentration of maleated poly(propylene) (MAPP), dicumyl peroxide (DCP), polyisobutadiene isocyanate (PBNCO) and fiber content on the mechanical properties of aspen-poly(propylene)(PP) composite was undertaken with the objective to maintain or increase the impact strength without losing tensile strength reinforcement. Using STAGRAPHIC Plus it was possible to determine the optimum concentration of additives and to maximize both the impact as well as tensile properties well above that of pure PP. Copyright © 2006 John Wiley & Sons, Ltd.

Anthranilic acid amides are cyclized to the corresponding dihydro-quinazolinones in good yields with dicumyl peroxide as radical methyl donor.

Dicumyl peroxide is an efficient methyl radical donor for the methylation/cyclization reaction of N-arylacrylamides and isocyanides providing oxindoles and phenanthridines in reasonable yields.

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot-pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006

The crosslinking efficiency of various commercially available organic peroxides (dicumyl peroxide, O,O-t-butyl O-2-ethylhexylperoxycarbonate, t-butyl peroxybenzoate, t-butyl 3,5,5-trimethylperoxyhexanoate, and t-butyl 2-ethylperoxyhexanoate) was tested on high-density polyethylene (HDPE) in its molten state. The variations of the concentrations of the peroxides versus the crosslinking extent were plotted for these peroxides, and the values were compared. Dicumyl peroxide was found to be the best crosslinking agent for HDPE. The efficiency of the HDPE crosslinking with each peroxy derivative was analyzed on the basis of the behavior of the radicals generated from it. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 75–81, 2004

The thermal and mechanical properties of different crosslinked and uncross-linked polyethylene/wax blends were investigated over a period of time. This paper summarizes the results and observations. It was found that (i) both LLDPE and LDPE cross-links in the presence of low dicumyl peroxide concentrations, while wax only grafts onto the polyethylene chains, (ii) polyethylene and wax have relatively good miscibility, (iii) both wax content and cross-linking change the mechanical properties of polyethylene in one way or the other, (iv) the route of sample preparation has a marked influence on the thermal and mechanical properties of the blends, and (v) oxygen-containing groups in oxidised wax apparently do not change the way in which the wax interacts with polyethylene.

Poly(butylene adipate-co-succinate) (PBAS), a saturated aliphatic polyester cured by dicumyl peroxide (DCP), was prepared and the viscoelastic property was investigated. The viscosity of crosslinked PBAS increased, and it exhibited rubbery behavior as the content of curing agent was increased. The results suggested that the viscosity and elasticity of PBAS could be regulated by adding a small amount of DCP; hence, the processibility could be improved. Prior to foaming, a proper formulation of blowing agent (blowing agent/urea activator = 100:8 phr) was examined to prepare expanded PBAS foam. Low-density PBAS expanded foams were prepared using a chemical blowing agent and DCP. The effect of the foaming temperature, additive content, and curing agent content on the blowing ratio and morphology of expanded PBAS foams was investigated. A closed-cell structure PBAS foam of high blowing ratio (density about 0.05 g/cm3) could be obtained by adding 3 phr DCP. To manufacture expanded PBAS foam under 0.1 g/cm3 using a chemical blowing agent, the storage modulus of the matrix polymer should exceed the loss modulus by enough to stabilize growing bubbles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2443–2454, 2001

In conjunction with previous experiments studying the effect of decomposition products of dicumyl peroxide (DCP) and antioxidants (AOs) in cross-linked polyethylene (XLPE) insulation on electrical tree generation, the authors conducted experiments investigating tree inhibition by phenolic AOs. The experiments were conducted using XLPE slabs containing four different phenolic AOs. Among the specimens containing these AOs, the specimen containing 4,4e-thio-bis(3-methyl-6-tert-butylphenol) was found to show the highest tree inception voltage. To examine the reasons for the significant increase in tree inception voltage in this specimen, further experiments were carried out on XLPE specimens containing both phenolic AO and a sulfur-containing AO. The results demonstrated that the tree inception voltages of specimens containing both phenolic AO and sulfur-containing AO were higher than those of the specimens containing only one of these two types of AOs. The roles of antioxidants in XLPE dielectrics are discussed with reference to the mechanisms of autoxidation of polymeric materials. The great increase in the tree inception voltage of XLPE specimens containing 4,4e-thio-bis(3-methyl-6-tert-butylphenol) appears to be due to a synergistic effect between the phenolic AO and the sulfur-containing AO. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 1–7, 2001

To enhance the thermal properties of ultrahigh molecular weight ( UHMW ) (viscosity-average molecular weight of 6 x 10 6 ) polyethylene (PE) gel film, this was crosslinked by dicumyl peroxide ( DCP ) during a high-temperature zone drawing, which is effective to orient film. Through a series of experiments, it turned out that crosslinking actualized by an optimum amount of DCP and high-temperature zone drawing technique caused significant changes in the structure and properties of UHMW PE gel film. That is, crosslinking increased storage modulus of UHMW PE gel film at 25°C, resulting in improving thermal properties of the film. On the contrary, the crosslinking effect played a hindering role in raising the draw ratio of UHMW PE gel film. Maximum storage modulus of 165 GPa at 25°C could be obtained at the draw ratio of 324 of uncrosslinked homo-PE gel film. In the case of crosslinked PE gel film, the highest storage modulus at 25°C reached 65 GPa at maximum draw ratio of 150. Crosslinked film exhibited high modulus, even at 190°C, to some extent, while uncrosslinked homo-PE gel film was molten completely at 150°C.

Swelling measurements in six organic solvents were carried out on samples of dicumyl peroxide crosslinked ethylene–propylene–diene (EPDM) having various crosslink densities. The Flory–Huggins interaction parameter χ was determined for EPDM vulcanizates 312 and 812 as well as their mixture 312/812 using the Flory–Rehner equation. The results show that the χ parameter for the crosslinked polymer is greater than for the uncrosslinked one and is a linear function of the crosslink density. The swelling behavior of the networks were also interpreted by the Flory–Erman theory using the structural factor F4′ to characterize the network and its behavior during the swelling. The obtained χ values indicate that broadening of the molecular mass distribution, in the Gaussian region of distribution, mixture 312/812, increases interactions with solvents. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:991–999, 1997

Low-density polyethylene (LDPE) waste was blended with high-density polyethylene (HDPE) waste of different degrees of degradation. Structural, mechanical and rheological properties of these blends were investigated. It was found that 2 wt.-% of dicumyl peroxide improves simultaneously the tensile strength and elongation at break without serious decrease of the melt elasticity of separate PE wastes and their binary blends in comparison with unmodified PE. It was shown by DSC analyses that modification of the blends leads to better compatibility between LDPE and HDPE. Aus Abfallen von Polyethylen niedriger Dichte (LDPE) und Polyethylen hoher Dichte (HDPE) mit unterschiedlichen Abbaugraden wurden Blends hergestelt und deren strukturelle, mechanische und rheologische Eigenschaften untersucht. Durch die Zumischung von 2 Gew.-% Dicumylperoxid konnte sowohl die Zugfestigkeit als auch die Bruchdehnung der Proben verbessert werden, ohne das sich die Schmelzelastizitat der LDPE- bzw. HDPE-Abfalle und deren Blends gegenuber nichtmodifiziertem Material merkbar verringerte. Auserdem wurde durch DSC-Messungen eine verbesserte Kompatibilitat zwischen LDPE und HDPE festgestellt.

The reaction mechanisms of thermal crosslinking of polyethylene with dicumyl peroxide (DCP) at high temperatures were investigated by electron spin resonance (ESR). The crosslinking reactions were induced by the alkyl radicals formed by the thermal decomposition of DCP above 120°C. The kinetics of the free radical reaction were followed during crosslinking reactions at temperatures between 145 and 180°C. © 1997 John Wiley & Sons, Inc.

The title hybrid material for Li ion battery anodes is prepared from a slurry of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, dicumyl peroxide as radical initiator, and TiO2 nanoparticles.

Natural rubber (NR)-poly(ethylene-co-vinyl acetate) (EVA) blends have been studied by incorporation of mercapto-modified EVA (EVASH) combined with dicumyl peroxide (DCP) as a curing agent. The mechanical, thermal, and morphological properties of NR-EVA blends as functions of blend composition and compatibilizer and/or curative additions were investigated. An EVASH-DCP combined system leads to the greatest improvement in tensile strength when EVA is dispersed within the NR matrix. Higher performance on Shore A hardness was also achieved with this combined system. For blends characterized by NR domains dispersed in the EVA matrix, the efficiency of pure DCP in improving the tensile strength is higher. Morphological observations and selective extraction experiments indicate the cross-linking of NR phase in both systems. A cross-linking of the EVA phase is also suggested by DCP or an EVASH-DCP combined system, based on the decreasing degree of crystallinity of this phase. © 1996 John Wiley & Sons, Inc.

Two types of ethylene-vinylacetate copolymers, containing 16% and 9% of vinylacetate, respectively, were crosslinked with dicumyl peroxide in a Brabender plastograf. The time of the torque maximum was proportional to the degree of crosslinking. The degree of crosslinking was determined by extraction and depended on the concentration of the crosslinking agent and of vinylacetate in the copolymer, and on the crosslinking temperature and time. It was found by DSC and by solid-state CP-MAS 13C NMR that with the progress of crosslinking the crystalline phase of the copolymers changed to the amorphous phase. Crosslinking took place mostly on the acetate groups.

Some polyaminedisulphides were studied as thermal stabilizers of polyethylene vulcanized by dicumyl peroxide. The effects of temperature, time, and concentration were investigated. A reaction mechanism is suggested.

A systematic study of the mechanical properties of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) filled with cellulose was conducted. When benzoyl peroxide (BPO) was used and when the components were mixed at 160°, the yield strength of the LLDPE/cellulose composite increased by 70% whereas that of HDPE increased by only 15%. If BPO is replaced by dicumyl peroxide (DCP) the yield strength attains a plateau value at a lower concetration. Yield strength for the cellulose/LLDPE system, where the cellulose had been pretreated with silane, showed a relatively small improvement as compared to the effect of the peroxides addition. The presence of gel in the compound is also discussed.

The melt flow index and oxidation induction period of low-density polyethylene crosslinked with dicumyl peroxide (DCP) in the presence of tetrakis (methylene β-3, 5-di-t-butyl-4-hydroxyphenyl)-propionate) methane (Antioxidant 1010) were determined. The results suggest that there is a negative synergism between this crosslinking agent and antioxidant. Part of the antioxidant terminated the chain propagation by trapping radicals, and thus reduced the efficiency of crosslinking. The antioxidant efficiency was also reduced owing to meaningless consumption

Conventional crosslinking of low density polyethylene (LDPE) was carried out using dicumyl peroxide (DCP) as crosslinking agent. DCP in various concentrations was mixed with LDPE chips in an extruder at 135 – 145°C. Monofilaments were drawn on a laboratory drawing machine at 110°C. It was found that tensile properties, percent shrinkage and density were improved with the increase in the concentration of DCP and in the heating period, whereas, however, the percent swelling decreased. Herkommliches Vernetzen von Polyethylen niedriger Dichte (LDPE) wurde mit Dicumylperoxid (DCP) als Vernetzer durchgefuhrt. DCP wurde in verschiedenen Konzentrationen mit LDPE-Schnitzeln in einem Extruder bei 135 – 145°C gemischt. Monofilamentfaden wurden bei 110°C auf einer Laborziehmaschine gezogen. Die Zugdehnungseigenschaften, der prozentuale Schrumpf und die Dichte wurden mit Zunahme der DCP-Konzentration und der Heizdauer verbessert, wahrend jedoch die prozentuale Quellung abnahm.

A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.

Reactions of polyisoprene, polybutadiene and polyoctenamer in o-xylene with dibenzoyl peroxide and dicumyl peroxide were investigated by measuring the apparent viscosity ηa of the solutions with a coaxial cylinder viscometer. As a new effect a ‘pre-maximum’ in the increase of ηa with reaction time was found. Possible reasons for the pre-maximum being due to the measuring device could be excluded. The dependence of the pre-maximum on the reaction conditions was investigated. A probable explanation of the pre-maximum is that the network first formed is destroyed by shear. Die Umsetzungen von Polyisopren, Polybutadien und Polyoctenamer in o-Xylol mit Dibenzoylperoxid und Dicumylperoxid wurden durch Messung der scheinbaren Viskositat ηa der Losungen mit einem Koaxialzylinder-Viskosimeter untersucht. Als ein neuer Effekt wurde ein ‘Vormaximum’ in der Zunahme von ηa mit der Reaktionszeit gefunden. Mogliche Ursachen fur das Vormaximum, die auf die Mesvorrichtung zuruckzufuhren waren, konnten ausgeschlossen werden. Die Abhangigkeit des Vormaximums von den Reaktionsbedingungen wurde untersucht. Eine wahrscheinliche Erklarung fur das Vormaximum ist, das das zunachst gebildete Netzwerk durch die Scherung zerstort wird.

A simple method to determine the chain scission mechanism of the oxidative degradation of rubber vulcanizates is proposed. The method involves the measurement of oxidative stress decay and the change in sol fraction, which allow us to distinguish whether scission occurs randomly along the main chain, near crosslinks or of crosslinks. The applicability of this method was well established using natural rubber vulcanizates as the reference samples. The chain scission of cis-1,4-polyisoprene vulcanizaties was proved to take place randomly along the main chain irrespective of their crosslink structure. On the other hand, the chain scission of dicumyl peroxide cured cis-1,4-polybutadiene takes place selectively near crosslinks. It is suggested that the unusual behavior of cis-1,4-polybutadiene vulcanizates is due to the characteristic structure of the crosslinks.

Methylene groups of 1,4-polybutadiene were partially brominated with N-bromosuccinimide. A subsequent Grignard-Wurtz-reaction with 4-methoxyphenyl-, 3,4-dimethoxyphenyl-, and 2-thienylmagnesium bromide resulted in an exchange of the bromine atoms for 4-methoxyphenyl, 3,4-dimethoxyphenyl and 2-thienyl groups. Another type of modification was the reaction of 1,4-polybutadiene with 4-methoxytoluene and o-resp: p-toluic acid methylester in the presence of dicumyl peroxide. Thereby 4-methoxyphenylmethyl and 2- resp. 4-methoxycarbonylphenylmethyl groups were introduced into the polymer. The modified polymers were investigated by IR-spectroscopy and degraded by olefin metathesis with 4-octene using a WCl6/Sn(CH3)4 catalyst. The degradation products were separated by gas chromatography and identified by mass spectrometry.