Type Of Curing System Research Articles

The effect of apparent density of sulfidic crosslink and their chemical nature on self-heat build-up in carbon black filled Natural Rubber under cyclic mechanical loading

Natural rubber is a widely used elastomer for the preparation of cyclically mechanically loaded products such as tires, where it reduces self-heating behavior. From a material point of view, the degree of self-heating depends on the composition of the rubber compound. One of the parameters influencing the self-heating of rubber is the type of curing system, which leads to different crosslinking density. The crosslinking density value for carbon black filled rubbers is only apparent due to the its physical interactions present and is referred to as the apparent crosslinking density (aCLD).Therefore, this work focuses on investigating the effect of sulfur intermolecular network formation by conventional (CV), semi-efficient (SEV) and efficient (EV) curing systems on the temperature development of cyclically loaded rubber using an advanced test method to in-situ determine the heat build-up. Rubber samples based on different curing systems were prepared by varying the concentration of the accelerator N-Tertiarybutyl-2-benzothiazole sulfenamide (TBBS) at a constant concentration of sulfur (2.5 phr). Using basic mechanical tests, it was found that the stiffness and hardness of the rubber increased with increasing aCLD and decreasing proportion of poly-sulfide bonds, respectively. Furthermore, cyclic mechanical analysis showed that with increasing aCLD and parallel decrease in the proportion of poly-sulfide bonds, both the loss modulus (G'') and dissipated strain energy increased, which was also reflected in the values of the mechanical stress-induced self-heating gradient. From the values of maximum developed temperatures, it was evident that the group of material with CV curing system showed the lowest self-heat build-up.

Investigating the Impact of Curing System on Structure-Property Relationship of Natural Rubber Modified with Brewery By-Product and Ground Tire Rubber.

The application of wastes as a filler/reinforcement phase in polymers is a new strategy to modify the performance properties and reduce the price of biocomposites. The use of these fillers, coming from agricultural waste (cellulose/lignocellulose-based fillers) and waste rubbers, constitutes a method for the management of post-consumer waste. In this paper, highly-filled biocomposites based on natural rubber (NR) and ground tire rubber (GTR)/brewers’ spent grain (BSG) hybrid reinforcements, were prepared using two different curing systems: (i) sulfur-based and (ii) dicumyl peroxide (DCP). The influence of the amount of fillers (in 100/0, 50/50, and 0/100 ratios in parts per hundred of rubber) and type of curing system on the final properties of biocomposites was evaluated by the oscillating disc rheometer, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, swelling behavior, tensile testing, and impedance tube measurements. The results show, that the scorch time and the optimum curing time values of sulfur cured biocomposites are affected by the change of the hybrid filler ratio while using the DCP curing system, and the obtained values do not show significant variations. The results conclude that the biocomposites cured with sulfur have better physico-mechanical and acoustic absorption, and that the type of curing system does not influence their thermal stability. The overall analysis indicates that the difference in final properties of highly filled biocomposites cured with two different systems is mainly affected by the: (i) cross-linking efficiency, (ii) partial absorption and reactions between fillers and used additives, and (iii) affinity of additives to applied fillers.

Relationship between the cross-link structure and properties of peroxide and sulfur-cured magnetic composites based on NR and NBR

In the present work, rubber magnetic composites were prepared by incorporation of strontium ferrite into rubber matrices based on natural rubber (NR) and acrylonitrile butadiene rubber (NBR). The sulfur and peroxide curing systems were introduced in cross-linking of rubber matrices. The research was aimed at the evaluation of magnetic filler content and type of curing system on the cross-link density, physical–mechanical and magnetic properties of prepared composites. The relationship between the composition of elastomers and cross-link structure within the rubber matrices, formed by applying different curing systems, was under investigation through strain–stress behavior of tested materials. The achieved results showed that ferrite behaves as a reinforcing filler in peroxide-cured composites based on NR, and in both, sulfur as well as peroxide-cured composites based on NBR. The results also demonstrated that the cross-linking degree and the type of cross-link structure as well as the composition of rubber matrices, to a large extent, influence the property spectrum of tested composite systems.

Enhancement of thermal and physical properties of epoxy composite reinforced with basalt fiber

The basalt chopped fiber reinforced epoxy composites using different curing systems were prepared in order to investigate the thermal characteristics of the composites. 2 different curing systems for bisphenol F type epoxy resin — an epoxy-amine curing system and an epoxy-anhydride curing system — were selected and used to investigate the interaction between matrix resin and basalt fiber in the means of thermal properties and physical properties. Through the evaluation of T g and thermal degradation behavior of both systems, it was deduced that the type of curing system as well as basalt fiber reinforcement have a great role in determining thermal properties of the composites. Also, the tensile and flexural properties of the composites were systematically evaluated in order to further understand the effect of curing agents on the interaction with basalt fiber.

UV Curing of Inks and Coatings in Digital Printing Applications

UV curing of inks and coatings is discussed in relation to the type of UV source and curing systems available for use in digital printing applications.Comparison is made between classic arc, microwave powered UV and LED technologies. The advantages and limitations of each are critically reviewed for curing the wide range of materials as used in both the graphic arts and industrial processes.Factors influencing cure are identified by detailed consideration of material and process. Variables include chemistry, substrate types, application requirements and optical design / spectral emission of the curing system. A method of lamphead characterisation is outlined using computer ray trace tools and dosimetry measurement techniques, with view to maximising dose efficiencies and optimising curing performance.Selection of the most appropriate type of curing system is concluded as being based on simple cost to performance ratio for the given application.

Effect of Temperature on the Course of Thiuram-Accelerated Sulfur Vulcanization

Abstract These results confirm the validity of our theory of thiuram-accelerated sulfur vulcanization supposing that ZnDMDC arising from TMTD and zinc oxide is the actual accelerator in this type of curing system. The formation of ZnDMDC from TMTD during the curing process affects particularly the slow crosslinking reaction. Therefore, the activation energy of slow crosslinking is in very good accordance with the activation energy of TMTD decrease, and its value differs significantly from the activation energies of fast crosslinking and degradation. Simultaneously, these facts answer the question why the shape of the cure curves depends strongly on the temperature of cure.

Effect of temperature on the course of thiuram‐accelerated sulfur vulcanization

AbstractTetramethylthiuram disulfide‐accelerated sulfur vulcanization of styrene‐butadiene rubber has been investigated at temperatures from 100°C to 170°C over 0.5 to 600 min. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Apart from the induction period (ti), the kinetic graphs are satisfactory represented by a rate equation assuming three independent first‐order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for ti−1, for fast crosslinking, and for degradation. The activation energy of slow crosslinking only is significantly greater. Due to the presence of Aerosil, the reciprocal values of the induction periods and the values of the ultimate extents of fast crosslinking are increased, and the values of the rate constants of degradation and slow crosslinking are decreased. Simultaneously, the activation energy of slow crosslinking is also significantly decreased. On the basis of these results, the proposed theory of tetramethylthiuram disulfideaccelerated sulfur vulcanization supposing that zinc dimethyldithiocarbamate is the actual accelerator in this type of curing system is discussed.

The determination of zinc oxide in rubber vulcanizates by x-ray diffraction

The important role of zinc oxide in accelerated rubber vulcanization has not been throughly defined. One major void in the investigations reported has been the absence of a suitable analytical method for following the rate of disappearance of zinc oxide. A method based on x-ray diffractometry is here presented for the direct determination of zinc oxide in rubber vulcanizates. The technique employed is rapid and nondestructive and has a relative error less than ±10% of the amount of zinc oxide present. Application to typical accelerated rubber vulcanizates has shown that the rate of zinc oxide disappearance was independent of the amount and type of reinforcing filler. It was found also to be independent of the degree of crosslinking despite the known dependence of high level crosslink formation on the presence of zinc oxide in this type of curing system. The major part of the reacted zinc oxide appeared as zinc sulfide.