Presence Of Coagent Research Articles

Enhancement of the properties of carbon-black-filled natural rubber compounds containing soybean oil cured with peroxide through the addition of coagents

Due to the hazard of the commercial rubber processing oil such as distillate aromatic extract (DAE), many rubber researchers play attention to find the green alternatives. Vegetable oils seem to gain a lot of attraction for this. It is not just only due to their environmentally friendly nature but also their abundance and affordable cost. The use of soybean oil (SBO) for the carbon black-filled rubber compounds was focused here and comparatively discussed with the use of DAE. Furthermore, this work also proposed the way to improve the mechanical properties and environmental endurance of the rubber compounds containing SBO by adding coagents. There were two types of coagent including trimethylolpropane trimethacrylate (TMPTMA) and triallyl isocyanurate (TAIC) used here. It was found that the cure time, cure rate index, and cure reaction rate constant of SBO-added rubber compounds with and without coagents were higher than those of DAE-added rubber compounds, whereas the activation energy of SBO-added rubber compounds was lower than the one with DAE. Without coagent, the mechanical properties of rubber compounds with DAE and SBO are equal. However, the addition of coagents improved the mechanical properties of rubber compounds containing SBO. The modulus at 100% strain, modulus at 200% strain, and tensile strength of TMPTMA-added rubber compounds increased by 41%, 48%, and 15%, respectively, whereas the rubber compounds with TAIC increased by 7%, 8%, and 20%, respectively, when compared to the one with SBO alone. Interesting, the SBO-added rubber compounds with and without coagents showed better thermal aging and ozone resistances than the DAE-added rubber compounds. All results showed that the presence of coagents especially TMPTMA gave the SBO-added rubber compound with the superior performance to the DAE-added rubber compound and the SBO-added rubber compound without coagent.

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.

Peroxide Curable Elastomer Processing of Brominated Isobutylene-co-p-Methylstyrene in the Presence of a Coagent

In the present study, the curing of brominated polyisobutylene-co-p-methylstyrene (BIMS) using OO-tert-Butyl O-2-(ethylhexyl) monoperoxycarbonate (TBEC) was prepared for low gas permeability applications, and were evaluated in the presence of various coagents. The amount of the coagent used in curing the butyl rubber directly affected rheometric and mechanical properties of the final product. BIMS was found curable by TBEC in the presence of N,N’-m-phenylenedimaleimide (MP) and the crosslinking density (v) were positively correlated to MP content. The mechanical strength and gas barrier properties were also improved upon the increased crosslinking density in BIMS. The peroxide based cured BIMS materials were demonstrated as improved gas barrier properties than the sulfur cured one. Hence, the development of peroxide based vulcanisation may offer an alternative method for the processing of low gas permeability of BIMS.

Curing kinetics of styrene-(ethylene-butylene)-styrene (SEBS) copolymer by peroxides in the presence of co-agents

Abstract In this study, styrene-(ethylene-butylene)-styrene (SEBS) samples with different viscosities were cured using 2,5-dimethyl-2,5-di(t-butylperoxy) hexane (DBPH) and dicumyl peroxide (DCP) separately in the presence of co-agents 2,4,6-tris-2-propenyloxy-1,3,5-triazin (TAC) or 1,3,5-trially-s-triazine-2,4,6,(1H,3H,5H)-trione (TAIC). Curing was carried out by means of a moving die rheometer device (MDR). Curing rate constants and energy of activation were obtained. Swelling and percent gelation values were evaluated by Sol-Gel analysis. Optimal curing conditions were determined to shed light on the curing characteristics of SEBS. It was shown that the rate of curing reaction of SEBS depended on the type of peroxides, co-agents and the viscosity of SEBS. Also it was shown that increased temperature enhanced the rate of curing.

Protective effects in radiation modification of elastomers

Saturated character of ethylene/octene thermoplastic elastomers demands an application of nonconventional methods of crosslinking connections between chains of molecules. These are organic peroxides, usually in the presence of coagents or an application of ionizing radiation. Several approaches (radiation, peroxide, peroxide/plus radiation and radiation/plus peroxide) were applied in crosslinking of elastomere Engage 8200. Attention was directed to the protection effects by aromatic peroxides and by photo- and thermostabilizers on radiolysis of elastomers. Role of dose of radiation, dose rate of radiation as well as the role of composition of elastomere on the radiation yield of hydrogen and absorbtion of oxygen was investigated. DRS method was used to follow postirradiation degradation. Influence of crosslinking methods on properties of elastomers is described. Results were interpreted from the point of view of protective actions of aromatic compounds.

Radiation-induced crosslinking of UHMWPE in the presence of co-agents: chemical and mechanical characterisation

Radiation-induced crosslinking has been shown to have a beneficial effect on the wear resistance of ultra high molecular weight polyethylene (UHMWPE). Since we postulate that crosslinking takes place through reactions involving terminal double bonds, unsaturated additives were added to UHMWPE in this study to enhance crosslinking. UHMWPE specimens soaked in 1,7-octadiene, methylacetylene and ethylene, respectively, were irradiated with electron beam to different doses in single or multiple passages. FTIR spectroscopy was used for the chemical characterisation of the crosslinked polymer. Tensile tests were performed with all samples in order to monitor changes in the mechanical properties. Gel fraction measurements proved that crosslinking took place in all the irradiated samples, but 1,7-octadiene turned out to be the most effective additive for the present purpose, exhibiting a good efficiency in enhancing crosslinking. The FTIR analyses showed that consumption of vinyl double bonds is proportional to the irradiation dose, with an efficiency which increases with increasing their initial concentration, confirming the hypothesis of the involvement of these groups in the crosslinking process. In the case of UHMWPE with 1,7-octadiene irradiated to high doses in multiple passages, the results of the tensile tests indicated a significant decrease in both elongation at break (up to 65%) and ultimate stress (up to 25%). A possible explanation of the diminished strength of the crosslinked material has also been proposed.

Adhesion of Modified PE/EPDM Blends to Steel

Crosslinking of low and high density polyethylene blends with ethylene-propylenediene terpolymer (EPDM) involving 10, 20, 30% EPDM with dicumyl peroxide (DCP) in the presence of coagent, Zn diacrylate, was investigated. It was found that such blends exhibit increased adhesion against steel and improved strength-deformation properties in comparison with similar blends crosslinked with DCP alone. The peel strength of about 16 kN/m (in the case of modified LDPE/EPDM blend) and 4 kN/m (in the case of modified HDPE/EPDM blend) was observed. The correlation between peel strength and parameters (oxygen uptake, content of oxygen containing groups, change of weight depending on temperature) which characterize thermooxidative conversations in polymer, was studied. The sol and gel fractions of crosslinked blends were characterized by IR spectroscopy, DSC and TG methods. Based on these results, it was assumed that improved peel strength of modified LDPE/EPDM blend is due to optimal ratio between oxidative crosslinking and oxidative degradation for this blend. Another reason may be the increase of interfacial adhesion caused by possible formation of graft copolymer LDPE-EPDM.

FT-IR Spectroscopy, a Major Tool for the Analysis of Peroxide Vulcanization Processes in the Presence of Coagents. I. Mechanism of EPM Peroxide Vulcanization with Aromatic bis(Allyl)Esters as Coagents

Abstract In this paper the results of investigations on the mechanism of EPM peroxide vulcanizations in the presence of various bis(allyl)esters of aromatic diacids—as coagents—are presented. These coagents are commonly used in the rubber industry to increase the crosslinking efficiency, however, until now the mechanism of this process remained unclear. In our studies it is demonstrated that when using FT-IR spectroscopy in combination with equilibrium swelling techniques and atomic force scanning microscopy, the role of the coagents can be elucidated.

Interactions of various liquids with EPDM peroxide vulcanisates cured in the presence of coagents

EPDM peroxide vulcanisates, cured in the presence of the coagent triallylcyanurate were swollen in various liquids and the Flory-Huggins parameters were determined. It was found that the presence of triallylcyanurate in the network did not influence the value of the X-parameter significantly. This result was explained by the fact that the coagent is not homogeneously distributed in the elastomer matrix. Furthermore, it was demonstrated that crosslink densities with highest accuracy could be calculated from equilibrium swelling data, using swelling agent-vulcanisate systems with low X-values.