Peroxide Curing System Research Articles

Sulfur and Peroxide Vulcanization of the Blends Based on Styrene-Butadiene Rubber, Ethylene-Propylene-Diene Monomer Rubber and Their Combinations.

Rubber blends based on styrene-butadiene rubber, ethylene-propylene-diene monomer rubber and a combination of both rubbers were cured with different sulfur and peroxide curing systems. In sulfur curing systems, two type of accelerators, namely tetramethylthiuram disulfide, N-cyclohexyl-2-benzothiazole sulfenamide, and combinations of both accelerators were used. In peroxide curing systems, dicumyl peroxide, and a combination of dicumyl peroxide with zinc diacrylate or zinc dimethacrylate, respectively, were applied. The work was aimed at investigating the effect of curing systems composition as well as the type of rubber or rubber combinations on the curing process, cross-link density and physical-mechanical properties of vulcanizates. The dynamic mechanical properties of the selected vulcanizates were examined too. The results revealed a correlation between the cross-link density and physical-mechanical properties. Similarly, there was a certain correlation between the cross-linking degree and glass transition temperature. The tensile strength of vulcanizates based on rubber combinations was higher when compared to that based on pure rubbers, which points out the fact that in rubber combinations, not only are the features of both elastomers combined, but improvement in the tensile characteristics can also be achieved. When compared to vulcanizates cured with dicumyl peroxide, materials cured with a sulfur system exhibited higher tensile strength. With the application of co-agents in peroxide vulcanization, the tensile strength overcame the tensile behavior of sulfur-cured vulcanizates.

Effects of Peroxide and Sulfur Curing Systems on Physical and Mechanical Properties of Nitrile Rubber Composites: A Comparative Study.

This study compares the effect of sulfur and dicumyl peroxide (DCP) vulcanizing systems on the physical and mechanical properties of rubber compounds based on acrylonitrile butadiene rubber (NBR). NBR compounds cured by different amounts of DCP and NBR vulcanizates filled with various concentrations of carbon black (CB) and a constant amount of sulfur or DCP were prepared. The vulcanizates were characterized by tensile testing, dynamic mechanical thermal analysis (DMTA), and cross-link density determination. The tensile strength and Young's modulus were found to increase with the rising amount of DCP and CB, while elongation at break decreased. The samples vulcanized by the sulfur system and filled with CB show a substantial increase in tensile strength from 13.1 to 21.2 MPa. Higher storage modulus and glass transition temperature were observed with the increase in the amount of peroxide and filler, and consequently, the increase in cross-link density, indicating rigidity increase and lower molecular mobility. The changes in the physical and mechanical properties of the NBR vulcanizates were in correlation with the changes in solvent uptake and cross-link density.

Combined Sulfur and Peroxide Vulcanization of Filled and Unfilled EPDM-Based Rubber Compounds.

The sulfur curing system, peroxide curing system and their combinations were applied for the cross-linking of unfilled and carbon black-filled rubber formulations based on ethylene-propylenediene-monomer rubber. The results demonstrated that the type of curing system influenced the course and shape of curing isotherms. This resulted in the change of curing kinetics of rubber compounds. The cross-link density of materials cured with combined vulcanization systems was lower than that for vulcanizates cured with the peroxide or sulfur system. Good correlation between the cross-link density as well as the structure of the formed cross-links and physical-mechanical characteristics of the cured materials was established. Both filled and unfilled vulcanizates cured with combined vulcanization systems exhibited a higher tensile strength and elongation at break when compared to their equivalents vulcanized in the presence of the peroxide or sulfur curing system. It can be stated that by proper combination of vulcanization systems, it is possible to modify the tensile behavior of vulcanizates in a targeted manner. On the other side, dynamical-mechanical properties were found not be significantly influenced by the curing system composition.

SYNERGIZED THERMAL STABILIZATION EFFECT OF ACID ACCEPTORS ON PEROXIDE CROSSLINKED CHLOROPRENE RUBBER

ABSTRACT Chloroprene rubber (CR) vulcanizates have been widely used in various industrial applications due to their excellent mechanical properties such as elasticity, elongation at break, and superior resistance to chemicals, flame, atmospheric conditions, aging, oil, and ozone. Because of the specific microstructures of CR, it is mainly vulcanized by metal oxide vulcanizing systems. However, CR undergoes rapid thermal degradation when it is crosslinked by peroxide curing systems at high temperatures. Although peroxide curing systems such as dicumyl peroxide (DCP) have attracted tremendous attention in the vulcanization of various saturated and unsaturated elastomers to achieve high-performance engineering properties, it is avoided for CR due to the occurrence of thermal decomposition, which is catalyzed by hydrochloric acid (HCl) vapors released during crosslinking. In the present work, by exploiting different acid acceptors, attempts have been made to design a vulcanizing system composed of inorganic–organic materials as acid acceptors to increase the potential of hindering the thermal decomposition in the CR phase. The designed system provides an accelerated system with a high crosslink density and mechanical properties comparable to metal oxide cured CR with elongation at break of ∼1000% and tensile strength of 10.3 MPa. The extent of thermal stabilization in the CR phase provided by the designed acid acceptor system was studied with thermogravimetric analysis.

Influence of Mixed Sulfur and Peroxide Curing Systems on Cross‐Linking and Properties of Rubber Compounds Based on EPDM

AbstractIn this work, sulfur vulcanization system, peroxide vulcanization system, and combined sulfur and peroxide curing systems are applied for cross‐linking of rubber compounds based on ethylene propylene diene monomer rubber. The goal is to investigate the influence of curing system composition on cross‐linking and properties of rubber formulations. The combination of both vulcanization systems in cross‐linking of rubbers combines the pattern of carbon–carbon linkages and sulfidic bridges, which gives the real presumption to modify physical–mechanical properties of final vulcanizates. The results reveal that the combination of vulcanization systems affects the curing characteristics, cross‐link density as well as physical–mechanical properties of tested materials. In comparison with vulcanizates cured only with sulfur or peroxide system, rubber compounds cross‐linked with mixed sulfur and peroxide curing systems exhibite higher tensile strength and elongation at break.

Influence of curing system composition and aging on the performance of rubber magnets based on NBR and EPDM

ABSTRACT Rubber magnetic composites were fabricated by incorporation of strontium ferrite in constant loading level in ethylene propylene diene monomer rubber and acrylonitrile butadiene rubber. Different curing additives based on peroxide, sulfur and combined sulfur/peroxide systems were introduced for cross-linking of rubber matrices. Both sulfur and peroxide curing systems lead to the formation of cross-links with different length and structure, which subsequently results in different properties of rubber products. Moreover, due to various bonding energies of the formed cross-links, rubber articles exhibit different propensity to degradation factors as to thermo-oxidative aging. Therefore, the work was aimed at the investigation of curing system composition and aging on cross-link density and properties of rubber magnetic composites. The achieved results point out to close correlation between cross-link density and physical-mechanical characteristics with exception of tensile strength, which showed increasing tendency with increasing amount of peroxide in combined vulcanization systems. It can be stated that no significant changes in physical-mechanical and magnetic properties were recorded during aging.

Unfilled Natural Rubber Compounds Containing Bio-Oil Cured with Different Curing Systems: A Comparative Study

This study focuses on the properties of unfilled natural rubber compounds containing bio-oils cured with a peroxide curing system and then discusses the comparisons to those cured using the sulfur system from our previous work. Two types of bio-oils, i.e., palm oil and soybean oil, were used, and distillate aromatic extract (DAE)-based petroleum oil was employed as a reference. The bio-oils caused no significant change in the vulcanization of rubber compounds cured using peroxide. However, the compounds containing bio-oils and cured with sulfur showed a faster vulcanization than the ones with DAE. The bio-oils strongly affected the crosslink density of rubber compounds in both curing systems. The use of bio-oils caused a low crosslink density due to the possible implication of curing agents to bio-oil molecules. The properties of rubber compounds dependent on the different levels of crosslink density were also investigated. The results revealed that when the crosslink density increased, the modulus, tensile strength, and hardness of the rubber compounds increased and the elongation at break and compression set decreased. The use of bio-oils in the rubber compounds cured with different curing systems gave low modulus at 300% strain, tensile strength, and hardness but high elongation at break and compression set when compared to the ones with DAE. However, no significant change was observed for the compression set of the rubber compounds cured using sulfur. With the presence of bio-oils, the properties of rubber compounds cured with sulfur system deteriorated less than those of the ones cured with peroxide.

Application of Sulfur and Peroxide Curing Systems for Cross-Linking of Rubber Composites Filled with Calcium Lignosulfonate.

Calcium lignosulfonate in different loadings was applied to the rubber matrix based on EPDM. A sulfur curing system, organic peroxide, and a combination of organic peroxide with two coagent types were used for cross-linking of rubber compounds. The work was focused on the investigation of filler content and curing system composition in the curing process, cross-link density, morphology, and physical–mechanical properties of composites. The achieved results demonstrated that the curing parameters of rubber compounds cured with the sulfur system were significantly different from those cured with peroxide systems. There was also an observed different influence of curing systems composition on cross link density, though in all cases, the degree of cross-linking showed a decreasing trend with increasing content of lignosulfonate. The tensile strength of the composites cured with sulfur system and organic peroxide was comparable, regardless of lignosulfonate loading. This points to the application of both curing systems in cross-linking of rubber compounds with biopolymer filler. However, the introduction of coagents in peroxide vulcanization led to the improvement of adhesion and compatibility between the rubber and the filler on the filler–rubber interface. This subsequently resulted in the improvement of the tensile characteristics of composites. The introduction of organic peroxide in combination with coagent seems to be a very simple and efficient way for the preparation of biopolymer-filled composites with applicable physical–mechanical properties.

Influence of the curing system on the physical-mechanical, dynamic properties, and aging resistance of ethylene–propylene–diene monomer formulations for applications at high temperatures

The effects of three curing systems on rheometric, morphological, physical-mechanical, thermal, and dynamic properties of ethylene–propylene–diene monomer (EPDM) composites was investigated. The influence of thermo-oxidative aging on crosslink density and physical-mechanical properties was studied. Based on a standard composition for application at high temperatures, EPDM formulations with semi-efficient vulcanization systems (ES), efficient vulcanization systems (ED), and peroxide curing systems (EP) were prepared. Experimental results indicated that EPDM compounds cured with efficient vulcanization systems exhibit the highest scorch time with an intermediate maximum torque value at 150°C. The filler dispersion in the elastomeric matrix was greater than 94%; however, the ED formulation showed a more pronounced decrease, with the increase in deformation indicating a greater filler–filler interaction. In comparison with those cured with peroxide and semi-efficient systems, EPDM formulations cured with an efficient system presented better thermal resistance and the crosslink density was sufficient to maintain the mechanical integrity, leading to an intermediate hardness value, tensile strength, modulus, and greater elongation at breaking. In summary, the results indicated that the efficient curing system was the most appropriate to be used in the envelope’s manufacture, due to the better performance of the mechanical properties associated with the better resistance to thermal aging.

Influence of Combined Sulfur and Peroxide Curing Systems and Ageing on the Properties of Rubber Magnets

AbstractStrontium ferrite in constant loading is incorporated into acrylonitrile butadiene rubber in order to prepare rubber magnetic composites. Sulfur, peroxide and combined sulfur/peroxide curing systems are applied for cross‐linking of rubber composites. The work is focused on the investigation of curing system composition and thermo‐oxidative ageing on cross‐link density, physical‐mechanical and magnetic properties of rubber magnets. The results revealed that the cross‐link density and the structure of the formed cross‐links within the rubber matrices affect the property spectrum of vulcanizates.

Effect of crosslinked structure on the chemical degradation of EPDM rubber in an acidic environment

The degradation of peroxide-cured EPDM and sulfur-cured EPDM in an acid solution (12.5 ppm H2SO4+1.8 ppm HF) was investigated, and it was found that the degradation of the two in an acid solution was different. The degradation degree of the sulfur curing system is lower than that of the peroxide curing system. During the aging process, the molecular main chain of the peroxide-cured EPDM was broken, resulting in a double bond and C=O structure. When there is a coagent TAIC in the peroxide curing system, the presence of TAIC delays the degradation time of the EPDM molecular backbone, and the hydrolysis reaction of the TAIC crosslinking point occurs preferentially, which makes the stability of EPDM improved. In addition, regardless of the presence or absence of TAIC, the peroxide-cured EPDM undergoes a crosslinking reaction in the later stage of aging, resulting in an ether-crosslinked structure, thereby improving the damaged crosslinking network. Unlike the degradation of the peroxide curing system, the breakage of the molecular backbone does not occur in the sulfur-cured EPDM, but only an internal crosslinking reaction of the curing precursor occurs, resulting in a crosslinked network dominated by polysulfide bonds, thereby increasing the crosslinking density of the EPDM during the aging process.

Combined sulfur and peroxide curing systems applied in cross-linking of rubber magnets

In the present work, barium ferrite in constant loading was dosed to the rubber matrices based on NR, SBR and NBR. Sulfur, peroxide and mixed sulfur and peroxide curing systems were applied for cross-linking of rubber magnetic composites. The application of sulfur or peroxide curing system leads to the formation of different types of linkages between rubber chain segments. As the structure of the formed cross-links plays a significant role in determining the final properties of rubber articles, the main aim of the work was to use the combination of curing systems in order to suppress the disadvantages of both systems and possibly to highlight their benefits. The results showed that composition of curing system has considerable influence on cross-link density of composites, which was subsequently reflected in typical change of physical-mechanical properties and glass transition temperature. The tensile strength was improved with increasing amount of peroxide curing system. The reason can be attributed to the presence of co-agent zinc methacrylate, which exhibits strong adhesion to magnetic filler and thus it contributes to the improvement of compatibility and homogeneity on the interphase filler–rubber. On the hand, there was observed no influence of curing system composition or type of rubber matrix on magnetic characteristics of composites.

Low frequency electromagnetic shielding efficiency of composites based on ethylene propylene diene monomer and multi‐walled carbon nanotubes

Ethylene propylene diene monomer rubber was filled with multi‐walled carbon nanotubes to prepare composite materials with the effect of electromagnetic radiation (EMR) shielding. Sulfur‐based curing system as well as peroxide curing system were used for vulcanization of rubber compounds. The main goal of the work was the investigation of curing system composition and filler content on curing process, physical‐mechanical properties, cross‐link density, and shielding efficiency of the prepared composites. The results showed that curing characteristics and cross‐link density of composites were dependent on both, amount of carbon nanotubes and curing system composition. The incorporation of filler resulted in the enhancement of physical‐mechanical properties of composites. Higher values of tensile strength were found to have composites cured with organic peroxide in combination with co‐agent. The achieved results also demonstrated that carbon nanotubes filled rubber composites are suitable candidates for applications, in which shielding of EMR at low frequencies is based on reflection.

Peroxide curing systems applied for cross-linking of rubber compounds based on SBR

Abstract The work was aimed at the investigation of influence of peroxide curing system on cross-linking and properties of rubber compounds based on SBR. First, the temperature of vulcanization and the amount of dicumyl peroxide on curing process and physical-mechanical properties were investigated. Then, co-agents Type I and Type II were added to the rubber formulations cured with peroxide. The results revealed that the increase in temperature leads to the acceleration of curing process while both, curing kinetics and physical-mechanical properties were influenced by the amount of peroxide. The application of Type I co-agents resulted in the acceleration of curing process and increase in cross-link density of vulcanizates, which was reflected in the increase of hardness and decrease of elongation at break. The influence of Type II co-agents on curing kinetics was negligible, while most of them caused the reduction in cross-linking degree of vulcanizates. Type I co-agents contributed to the improvement of tensile strength of vulcanizates, while the influence of Type II co-agents on tensile strength was of minor importance.

Rubber magnets based on NBR and lithium ferrite with the ability to absorb electromagnetic radiation

Rubber magnetic composites were prepared through the incorporation of magnetic soft lithium ferrite into acrylonitrile butadiene rubber. Standard sulfur‐based curing and peroxide curing systems were used for cross‐linking of rubber matrices. The experimental part was focused on the investigation of ferrite content and curing system composition on cross‐link density, physical‐mechanical, magnetic and shielding characteristics of composites. The results demonstrated that cross‐link density and physical‐mechanical properties of composites can be modified by both the amount of ferrite and composition of the curing system. The influence of curing systems on magnetic properties was negligible. It can be stated that the application of lithium ferrite to rubber matrix leads to the preparation of rubber composites with the ability to efficiently absorb harmful electromagnetic radiation in the tested frequency range. The shielding efficiency of composites increased with increasing content of magnetic filler.

Effect of gamma irradiation and lead content on the physical and shielding properties of PVC/NBR polymer blends

In the present work, polyvinylchloride/acrylonitrile butadiene rubber PVC/NBR was blended on a Brabender mixer. The blends obtained were cured with peroxide curing systems and loaded with different concentrations of lead monoxide (PbO) for increasing shielding properties of the investigated blends. The physicomechanical and the shielding properties of the prepared blends were evaluated. The surface morphology and structure of the blends were studied by SEM, XRD and FTIR spectroscopy. The morphological analysis of the blends shows that PbO material exhibited homogeneous dispersion in polymer matrix. The gamma attenuation performance of the composites was evaluated by 232Th gamma radiation source. Mass attenuation coefficients of the blends were found to be increased with the increase in PbO content. The tensile strength was found to be enhanced in the presence of the lead oxide filler till 60 phr. The investigated blends were irradiated by 60Co gamma radiation source. The dielectric properties of the prepared blends were evaluated by broadband dielectric spectroscopy. The physicomechanical and dielectric properties of the irradiated blends were investigated. Based on the present obtained results, PVC/NBR/PbO blends are promising materials for low gamma radiation doses.

Rubber Magnetic Composites Cross-Linked with Peroxide Curing Systems

Styrene–butadiene rubber and acrylonitrile–butadiene rubber as elastomer matrices were filled with barium ferrite in order to prepare rubber magnetic composites. For cross-linking of rubber compounds, peroxide curing systems consisting of dicumyl peroxide as curing agent and four types of low molecular weight organic compounds as co-agents were used. The work was focused on the investigation of different types of co-agents on the cross-linking, physical-mechanical and magnetic properties of the prepared composites. The results revealed that the type and amount of co-agent has no influence on magnetic characteristics of composites. On the other hand, cross-link density and physical-mechanical properties were significantly dependent on the composition of curing system. Co-agents contribute to the improvement of adhesion on the interphase filler-rubber. Considering the type of rubber matrix, higher values of tensile strength exhibited composites based on acrylonitrile–butadiene rubber. As magnetic filler and co-agents are polar materials, their compatibility with polar elastomers like acrylonitrile-butadiene rubber is much higher when compared to no-polar elastomers like styrene–butadiene rubber.

Preparation of natural rubber elastomeric bridge bearing pad compound formula on various curing systems

Commercial elastomeric bridge bearing (EBB) pad is dominated by the laminated type. Laminated EBB pad comprises of rubber composite layers which are arranged intermittently among the thin steel plates. The rubber composite uses natural rubber or chloroprene synthetic rubber as the base elastomer. Local EBB pad industries mostly produce natural rubber bridge bearing pad type due to the enormous availability of natural rubber in Indonesia. However, the quality of natural rubber bridge bearing pad product often cannot fulfil the standard requirement in compression set and accelerated aging parameters. The research studied the design of EBB pad compound formula based on natural rubber type. The EBB compound formulas were prepared by varring the curing system such as sulphur (efficient and semi-efficient) and peroxide curing system. Designing the compound formula was in accordance to the methods required in improving the compression set and accelerating aging quality of natural rubber bridge bearing pad. The result of curing characteristic of the natural rubber bridge bearing pad compound showed that peroxide curing system gave the longest optimum curing time. Further, sulphur curing system produced high crosslink density followed with good mechanical properties of natural rubber bridge bearing pad vulcanizate. The compression set value of natural rubber bridge bearing pad vulcanizates which were obtained by efficient and semi-efficient curing systems as 14.09% and 24.81%, respectively were regarded to be below the maximum requirement (25%). The peroxide curing system was not recommended due to the high compression set value of 40.68%. Meanwhile, maximum percent changes of tensile properties and retention values which indicated accelerated aging parameter of natural rubber bridge bearing pads were formed either by sulphur and peroxide curing system could fulfilled the standard requirement of EBB Duro 70 refered to SNI 3967:2013.

Rubber magnets cured with peroxide and coagents

Barium ferrite in constant amount (50 phr) was incorporated into styrene-butadiene rubber to prepare rubber magnetic composites. Dicumyl peroxide was used as a curing agent for cross-linking of the prepared composites. Four different types of low-molecular-weight organic compounds were applied as coagents to enhance the efficiency of cross-linking process and to improve the compatibility between the rubber and the filler on the interphase. The main goal of this work was to investigate the influence of the composition of peroxide curing system on cross-link density, physical–mechanical and magnetic properties of the composites. The results revealed that the type and amount of coagents have no influence on magnetic properties of the rubber magnets. On the other hand, cross-link density and physical–mechanical properties were significantly dependent on the composition of curing system. The increase of tensile strength can be attributed to the improvement of adhesion on the interphase filler–rubber due to the presence of coagents.

Effect of Long-Chain Branch of Poly(methyl acrylate-co-1-octene) on the Vulcanization and Mechanical Properties

The unsaturated linear (UL) copolymer of methyl acrylate (MA), 1-octene, and allyl glycidyl ether (AGE) and the long-chain branch (LCB) copolymer of MA, 1-octene, and 1,7-octadiene were synthesized, respectively, via AlCl3-catalyzed radical copolymerization, and then both UL and LCB copolymers were vulcanized using dicumyl peroxide (DCP) curing system. For UL copolymer, cross-linking heat first increases with DCP dosages and then decreases when DCP dosages increases further to 2.5, that is quite reasonable to relate with cross-link and degradation reactions during vulcanization. However, the reaction heat flow curves of DCP-LCB curing system with DCP dosages ranging from 1.5 phr to 3.5 phr exhibit a bimodal-like “crosslinking” endotherm, suggesting a two-stage reaction of intramolecular cross-linking and intermolecular cross-linking. Results from dynamic mechanical analysis and tensile tests confirm that LCB copolymers are propitious to form effective networks at low DCP dosages and to keep the vulcanized...