Dicumyl Peroxide System Research Articles

Different Organic Peroxides that Cure Low‐k 1,2‐PB/SBS/EPDM Composites for High‐Frequency Substrate

AbstractSince the advent of 5G network, polymeric low dielectric constant (low‐k) materials have been indispensable for high speed and stable signal transmission at microwave frequency. Herein, the low‐k composites of 1,2‐polybutadiene/styrene‐butadiene‐styrene triblock copolymer/ethylene‐propylene‐dicyclopentadiene (1,2‐PB/SBS/EPDM) were prepared with cured organic peroxide. Two structurally different organic peroxides, namely dicumyl peroxide (DCP) and bis(1‐(tert‐butylperoxy)‐1‐methylethyl)‐benzene (BIPB), were used as free‐radical initiators. The composites with highly efficient initiator—BIPB exhibited considerably enhanced conversion rate, thermal stability, and cross‐link density compared with the DCP system. Furthermore, the increased cross‐link density contributed to dielectric stability over a broad range of frequency (3‐15 GHz) and superior mechanical properties. The cross‐linked composites possessed the typical low polarity group of C─C single bond with suppressed dielectric constant (Dk) and loss (Df). Especially, the average Dk of 2.36 and average Df of 0.0054 were obtained for the composite containing 4 part‐by‐weight (pbw) BIPB. This work demonstrated that the 1,2‐PB/SBS/EPDM composite with 4 pbw BIPB is a good candidate for high‐frequency substrate materials.

Effect of different curing systems on cell structure, mechanical properties and aging resistance of nitrile butadiene rubber foam coating with liquid compounds

Gaskets made of acrylonitrile butadiene rubber (NBR) coating and metal plate were one of the classified seals used in automotive engine. In the present study, NBR foam–metal composite gaskets were prepared by liquid NBR overlain metal plate. The foam coating was thinner and more uniform compared with solid rubber forms usually used. Two different curing systems of dicumyl peroxide (DCP) system and a combined system of sulphur with DCP (S/DCP system) were investigated for curing NBR foam coating. The effects of curing system and agent content on cell structure, mechanical properties and resistance to fluid and heat of NBR foam, and the interfacial adhesion between NBR foam coating and metal plate, were examined. It was found that the S/DCP system gave NBR foam coating with bigger cell size, higher porosity and cross-link density compared with the DCP system. Furthermore, the S/DCP system had better tensile property and played a better role in the protection of the gasket seals against fuel B and hot air.

Influence of stearic acid treated nano-CaCO3 on the properties of silicone nanocomposites

The aim of the work reported here was to study the influence of treated nano-CaCO3 on the silicone:dicumyl peroxide system. Thermal degradation was studied using TGA of treated and untreated nano- and commercial CaCO3:silicone rubber composites. Thermal stability as well as % char yield increased with increasing content of treated nano-CaCO3 as compared to untreated and commercial CaCO3. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed to study the degree of dispersion of treated and untreated nano-CaCO3 and commercial CaCO3 in silicone rubber composites. Moreover, the nanocomposites were subjected to various tests, such as those for tensile strength, % elongation at break, flammability and abrasion resistance. The tensile strength (8.5 kg/cm2) and elongation at break (780%) showed their greatest improvements at 10 wt% loading with treated nano-CaCO3 in comparison to the untreated nano- and commercial CaCO3:silicone rubber composites. The improvements in the properties of treated CaCO3:silicone composites compared to the untreated nano- and commercial CaCO3 silicone rubber composites were due to the uniform dispersion of nanoparticles in the treated composites and their good compatibility with the rubber chains, as shown by AFM and SEM studies.

Effect of different curing systems on heat shrinkability and mechanical properties of ethylene vinyl acetate/epoxidized natural rubber blends

AbstractEthylene vinyl acetate (EVA)/epoxidized natural rubber (ENR) blends containing 10 and 30 wt % ENR were prepared by using an internal mixer. Five different types of curing systems were employed: dicumyl peroxide (DCP), sulfur (S), phenolic resin (Ph), DCP + S, and DCP + Ph. DCP could crosslink with both EVA and ENR while S and Ph were curing agents for ENR. The DCP system provided the lowest tensile properties and tear strength because of low crosslinking in ENR phase. Addition of sulfur or phenolic resin increased the mechanical properties due to a better vulcanization of the rubber phase. The mechanical properties of the blends decreased with increasing ENR content. The rubber particle size in the blends containing 30% ENR played a more important role in the mechanical properties than the blends containing 10% ENR. ENR particle size did not affect heat shrinkability of EVA and a well vulcanized rubber phase was not required for high heat shrinkage. Furthermore, heat shrinkage of the blends slightly changed as the ENR content increased for all curing systems. With regard to the mechanical properties and heat shrinkability, the most appropriate curing system was DCP + Ph and in the case the 10 wt % ENR content produced a more favorable blend. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The β Phase of Isotactic Polypropylene in TPVs Based on PP/EPDM

β‐Nucleating agent was added into maleic anhydride (MAH) compatiblized isotactic polypropylene (iPP)/ethylene‐propylene‐diene monomer (EPDM) blend systems, dynamically vulcanized by dicumyl peroxide (DCP). The β phase of iPP formed in TPVs was investigated by means of WAXD, and the effect of DCP content, MAH content and system viscosity on the β phase of iPP was also studied. With increasing DCP content, the MFR values of blend systems increased a little and then decreased, indicating that the DCP content showed a remarkable effect on the system viscosity. Also, with increasing MFR, the β phase content increased first and then decreased, while with increasing MAH content, the β phase content decreased sharply.

Cure characteristics and mechanical properties of short nylon fiber‐reinforced nitrile rubber composites

AbstractAcrylonitrile butadiene rubber (NBR)‐based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two‐roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle‐type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N‐dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber–fiber interaction in the former. The crosslink densities of various composites were also compared. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1023–1030, 2004

Effects of brominated flame retardants and crosslinking agents on the flame retardancy of rubbers

AbstractTetrabromo‐p‐cresol (TBPC), pentabromophenol (PBP), and their allyl ether derivatives—tetrabromo‐p‐cresol allyl ether (TBPC–AE) and pentabromophenol allyl ether (PBP–AE)—were used in the study of flame retardancy of ethylene–vinyl acetate (EVA) copolymer and styrene–butadiene rubber (SBR), which were cured by dicumyl peroxide (DCP) and sulfur, respectively. The dependence of the flammability of crosslinking polymers on the polymer matrix, its additives, and the degree of crosslinking was investigated. The empirical equations of flame retardancy were established for these rubbers and compared with the measured values. It was found that the oxygen index of SBR–S system was in accordance with the empirical equations, while the EVA–DCP system, affected by the decomposed residue of DCP, showed a slight deviation. The brominated phenolic compounds of allyl ether (BPs–AE) showed a greater deviation than their precursors. This may be due to the fact that allyl group could react with DCP and lose its excellent flame resistance characteristic, which may be caused by the modified Claisen rearrangement produced in the thermal processing or burning. The phenolic brominated compounds containing the allyl group and a higher bromine content showed better flammability.

Structural characterization of vulcanizates. Part IX. Comparison of the vulcanization of natural rubber and cis‐trans‐isomerized natural rubber with sulfenamide‐accelerated sulfur and dicumyl peroxide vulcanization systems

AbstractLarge variations in the microstructure of 1,4‐polyisoprenes, from ca. 100% cis‐trialkylethylene groups, as in natural rubber (NR), to ca. 40% cis‐ and 60% trans‐trialkylethylene groups, as in an equilibrium‐isomerized NR, have little influence on the overall chemistry of vulcanization of the polyisoprenes by a N‐cyclohexylbenzothiazole‐2‐sulfenamide‐accelerated sulfur system or by a dicumyl peroxide system. The peroxide crosslinks the equilibrium‐isomerized NR more efficiently than it crosslinks NR; this is attributed to the sulfur dioxide, which is used to isomerize the NR, scavenging some of the nonrubber constituents in the NR, which are known to compete with the rubber hydrocarbon for reaction with free radicals from the peroxide. By comparison with NR vulcanizates, the corresponding equilibrium‐isomerized NR vulcanizates have higher values of the C2 term of the Mooney‐Rivlin stress–strain equation and higher χ (polymer–swelling liquid interaction parameter) values of the Flory‐Huggins equation.