EFFECT OF BENZOTHIAZOLOYLTHIAZOLES AS SECONDARY ACCELERATORS IN THE SULFUR VULCANIZATION OF NATURAL RUBBER

2011 ◽  
Vol 84 (1) ◽  
pp. 88-100 ◽  
Author(s):  
R. Reshmy ◽  
R. Nirmal ◽  
S. Prasanthkumar ◽  
K. Kurien Thomas ◽  
Molice Thomas ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Chemical Method ◽  
Binary Systems ◽  
Minimal Amount ◽  
Tetramethylthiuram Disulfide ◽  
Solvent Free Conditions ◽  
Sulfur Vulcanization ◽  
Cure Time

Abstract The vulcanization of natural rubber and a blend of natural rubber and reclaimed rubber by using binary accelerator systems containing a novel series of benzothiazoloylthiazole as secondary accelerator (SA) has been studied. These secondary accelerators were synthesized by a green chemical method under solvent-free conditions, by the irradiation of microwaves (180 W). The synergistic effect of the SA with N-Cyclohexyl-2-benzothiazolsulfenamide as primary accelerator was studied at 150 °C. These binary systems were effective in reducing the cure time and improving the rheometric and mechanical properties. These SAs were found to be effective in reducing the cure time with a minimal amount of 0.5 phr, but commercially available SAs such as thioureas and tetramethylthiuram disulfide were reported to show reduction in cure time only by increasing the amount of SA. Mechanical properties such as hardness, abrasion loss, tensile strength, percentage strain at break, and modulus at different elongations 100, 200, and 300% were evaluated and found to be immensely improved. The improved mechanical properties were also shown to be at par with crosslink densities (1/2Mc) of different mixes.

EFFECT OF ZINC DITHIOCARBAMATES AND THIAZOLE-BASED ACCELERATORS ON THE VULCANIZATION OF NATURAL RUBBER

2012 ◽  
Vol 85 (1) ◽  
pp. 120-131 ◽  
Author(s):  
Md. Najib Alam ◽  
Swapan Kumar Mandal ◽  
Subhas Chandra Debnath
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Reaction Mechanism ◽  
Natural Rubber ◽  
High Performance ◽  
Binary Systems ◽  
Synergistic Activity ◽  
Tetramethylthiuram Disulfide

Abstract Several zinc dithiocarbamates (ZDCs) as accelerator derived from safe amine has been exclusively studied in the presence of thiazole-based accelerators to introduce safe dithiocarbamate in the vulcanization of natural rubber. Comparison has been made between conventional unsafe zinc dimethyldithiocarbamate (ZDMC) with safe novel ZDC combined with thizole-based accelerators in the light of mechanical properties. The study reveals that thiuram disulfide and 2-mercaptobenzothiazole (MBT) are always formed from the reaction either between ZDC and dibenzothiazyledisulfide (MBTS) or between ZDC and N-cyclohexyl-2-benzothiazole sulfenamide (CBS). It has been conclusively proved that MBT generated from MBTS or CBS reacts with ZDC and produces tetramethylthiuram disulfide. The observed synergistic activity has been discussed based on the cure and physical data and explained through the results based on high-performance liquid chromatography and a reaction mechanism. Synergistic activity is observed in all binary systems studied. The highest tensile strength is observed in the zinc (N-benzyl piperazino) dithiocarbamate-accelerated system at 3:6 mM ratios. In respect of tensile strength and modulus value, unsafe ZDMC can be successfully replaced by safe ZDCs in combination with thiazole group containing accelerator.

Mechanochemical Devulcanization of Vulcanized Gum Natural Rubber

2005 ◽  
Vol 21 (3) ◽  
pp. 183-199
Author(s):  
G.K. Jana ◽  
C.K. Das
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Three Dimensional ◽  
Elongation At Break ◽  
Tear Strength ◽  
Vulcanized Rubber ◽  
Dimensional Network ◽  
Polymeric Chains ◽  
Cure Time

De-vulcanization of vulcanized elastomers represents a great challenge because of their three-dimensional network structure. Sulfur-cured gum natural rubbers containing three different sulfur/accelerator ratios were de-vulcanized by thio-acids. The process was carried out at 90 °C for 10 minutes in an open two-roll cracker-cum-mixing mill. Two concentrations of de-vulcanizing agent were tried in order to study the cleavage of the sulfidic bonds. The mechanical properties of the re-vulcanized rubber (like tensile strength, modulus, tear strength and elongation at break) were improved with increasing concentrations of de-vulcanizing agent, because the crosslink density increased. A decrease in scorch time and in optimum cure time and an increase in the state of cure were observed when vulcanized rubber was treated with high amounts of de-vulcanizing agent. The temperature of onset of degradation was also increased with increasing concentration of thio-acid. DMA analysis revealed that the storage modulus increased on re-vulcanization. From IR spectroscopy it was observed that oxidation of the main polymeric chains did not occur at the time of high temperature milling. Over 80% retention of the original mechanical properties (like tensile strength, modulus, tear strength and elongation at break) of the vulcanized natural rubber was achieved by this mechanochemical process.

Effect of Ashes as Biomass in Silica Filled Natural Rubber

2017 ◽  
Vol 735 ◽  
pp. 153-157
Author(s):  
Wasinee Pinpat ◽  
Wirunya Keawwattana ◽  
Siree Tangbunsuk
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Rice Husk Ash ◽  
Silica Content ◽  
Elongation At Break ◽  
Compression Set ◽  
Cure Time ◽  
Oil Palm Ash ◽  
Reinforcing Filler

Silica has been used as reinforcing filler in natural rubber for a period of time as it results in excellent properties for NR vulcanizes. Rice husk ash (RHA), bagasse ash (BA), and oil palm ash (OPA) obtained from agricultural wastes are mainly composed of silica in the percentage of 80.00%, 57.33%, and 40.20% by weight, respectively. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at fixed silica content at 35 parts per hundred of rubber (phr) were investigated. The results indicated that ashes showed greater cure time compared to that of the silica. The incorporation of ashes into natural rubber gradually improved compression set but significantly decreased tensile strength, elongation at break, and resilience. Moreover, young's modulus increased, while hardness showed no significant change with the addition of ashes. Overall results indicated that ashes could be used as cheaper fillers for natural rubber materials where improved mechanical properties were not critical.

Preparation and Properties of Sponge Rubber Based on Natural Rubber and Cassava Starch

2014 ◽  
Vol 931-932 ◽  
pp. 68-72
Author(s):  
Komsun Temna ◽  
Nitinart Saetung ◽  
Anuwat Saetung
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Cassava Starch ◽  
Interfacial Interaction ◽  
Morphological Properties ◽  
Elongation At Break ◽  
Cure Time ◽  
The Difference ◽  
Cure Characteristic

In this work, the sponge rubbers based on cassava starch masterbatch in latex phase with the difference technique (non-gelatinized and gelatinized cassava starch) were preformed. The cassava starch contents from 0 to 70 phr were also studied. The cure characteristic, mechanical and morphological properties were investigated. It was found that the scorch time and cure time were increased with an increasing of cassava starch contents in both techniques. The mechanical properties i.e., tensile strength, elongation at break and tear strength were decreased with an increasing of cassava starch contents, except 500% modulus. However, the sponge based on gelatinized technique gave the better mechanical properties than that of non-gelatinized cassava starch. The SEM micrographs of sponge NR from gelatinized technique were also able to confirm a good interfacial interaction between hydrophilic cassava starch and hydrophobic NR.

Cure and Mechanical Properties of Natural Rubber Filled Bacterial Cellulose

2016 ◽  
Vol 705 ◽  
pp. 40-44
Author(s):  
Chaiwute Vudjung
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Bacterial Cellulose ◽  
Elongation At Break ◽  
Roll Mill ◽  
Cure Time ◽  
Mooney Viscosity

Natural rubber (NR) containing the nata de coco fiber or Bacterial cellulose (BC) was prepared by co-coagulation of BC and concentrated NR latex with CaCl2 and compounded by two roll mill. The effect of BC content was the important factor in this study. It was that found tensile strength and elongation at break of NR filled BC (NR/BC) decreased with increasing BC content. The addition of BC into NR affect Mooney viscosity of NR/BC masterbatch, with increasing BC content, scorch time and cure time of their compound decreased.

EFFECT OF SULFUR TO ACCELERATOR RATIO ON CROSSLINK STRUCTURE, REVERSION, AND STRENGTH IN NATURAL RUBBER

2016 ◽  
Vol 89 (3) ◽  
pp. 450-464 ◽  
Author(s):  
Kanoktip Boonkerd ◽  
Chudej Deeprasertkul ◽  
Kanyarat Boonsomwong
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Thermal And Mechanical Properties ◽  
High Concentration ◽  
Cure Time ◽  
Pass Through

ABSTRACT A new relationship among the sulfur to accelerator (S/A) ratio, the degree of reversion or the net loss of crosslinks at the prolonged cure time, and the tensile strength and crosslink structure of gum natural rubber (NR) vulcanizates is described here. To study this, N,N-dicyclohexyl-2-benzothiazole sulfenamide (DCBS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), 2,2′-dithiobisbenzothiazole (MBTS), and tetrabenzylthiuram disulfide (TBzTD) were used as accelerators. The results showed that for all four tested accelerators, the degree of reversion and tensile strength of the vulcanizates did not simply increase with increasing S/A ratios within the range of 0.26–6.67 by weight. This was because the proportion of polysulfidic linkages playing an important role on these properties was not simply proportional to the S/A ratios but turned out to pass through a maximum and then decline with further increasing S/A ratios for the DCBS, CBS, and MBTS cure systems. Nevertheless, when considering the effect of crosslink structure on the thermal and mechanical properties, it was observed that for all four tested accelerators, the increase in the extent of polysulfidic linkages gave the vulcanizate with the lower reversion resistance but the higher tensile strength. Therefore, the generalization that it is the high concentration of polysulfidic linkages in the network that causes a decrease in the reversion resistance but an increase in the tensile strength is seemingly still applicable.

Structural Characterization of Vulcan-Izates. XII. Efficient Vulcanization Using a Sulfenamide-Thiuram Disulfide Accelerator System

1972 ◽  
Vol 45 (5) ◽  
pp. 1366-1371 ◽  
Author(s):  
D. S. Campbell
Keyword(s):  
Natural Rubber ◽  
Structural Characterization ◽  
High Ratio ◽  
Mixed System ◽  
Tetramethylthiuram Disulfide ◽  
Sulfur Vulcanization ◽  
Cure Time ◽  
Accelerator System ◽  
Cyclic Sulfide

Abstract Vulcanizates obtained from the sulfur vulcanization of natural rubber using a combination of the accelerators N-cyclohexyl-2-benzothiazole sulfenamide (CBS) and tetramethylthiuram disulfide (TMTD) have been analyzed in terms of the numbers of poly-, di-, and monosulfide crosslinks, network-bound accelerator residues, and cyclic sulfide chain modifications as a function of cure time. The vulcanization system produced mainly monosulfide crosslinks at optimum cure, although there were differences in detail between this mixed system and a previously reported efficient sulfur vulcanization (EV) system using a high ratio of CBS to sulfur.

Mechanical Properties, Morphological Properties, and Cure Characteristics of Sisal Fiber/Natural Rubber Composites: Effects of Fiber and Compatibilizer Content

2010 ◽  
Vol 123-125 ◽  
pp. 1171-1174 ◽  
Author(s):  
Wittawat Wongsorat ◽  
Nitinat Suppakarn ◽  
Kasama Jarukumjorn
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
Positive Impact ◽  
Morphological Properties ◽  
Sisal Fiber ◽  
Maximum Torque ◽  
Cure Characteristics ◽  
Roll Mill ◽  
Cure Time

Sisal fiber/natural rubber (NR) composites were prepared by the incorporation of sisal fiber into NR at various content (10, 20, 30 phr) using a two-roll mill. Natural rubber grafted with maleic anhydride (NR-g-MA) prepared in house was used to improve interfacial adhesion between sisal fiber and NR matrix. NR-g-MA contents were varied. Mechanical properties, morphologies, and cure characteristics of the composites were studied. Maximum torque, modulus at 100% strain (M100), modulus at 300% strain (M300), and hardness of the composites increased with increasing fiber content while scorch time, cure time, tensile strength, and elongation at break decreased. The addition of NR-g-MA into the composites gave a positive impact on M100, M300, tensile strength, and hardness. Moreover, increasing NR-g-MA content resulted in increased scorch time, cure time, maximum torque, M100, M300, tensile strength, and hardness of the composites. SEM micrographs of the composites revealed that the addition of NR-g-MA into the composites improved the interfacial interaction between sisal fiber and NR matrix. In addition, the compatibilized NR composites exhibited higher specific tensile strength and modulus than the carbon black/NR composites.

SILICA-RICH FILLER FOR THE REINFORCEMENT IN NATURAL RUBBER

2012 ◽  
Vol 85 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Kanoktip Boonkerd ◽  
Saowaroj Chuayjuljit ◽  
Dalip Abdulraman ◽  
Weerakul Jaranrangsup
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Tensile Strength ◽  
Particle Size Distribution ◽  
Natural Rubber ◽  
The Other ◽  
Particle Sizes ◽  
Reinforcing Efficacy ◽  
Cure Time ◽  
Jet Milling

Abstract The aim of the study was to determine the reinforcing efficacy of a silica-rich filler, pottery stone (PS), in natural rubber (NR). The effects of amount and particle size of PS on curing and mechanical properties of the NR compounds were determined. The PS was first divided into four groups. Two of these were raw PS without grinding, which were sieved to particle sizes of less than 106 μm (PS(<106)) and less than 38 μm (PS(<38)). The other two were ground PS, one by current jet milling to obtain PS(JM), and the other by wet ball milling to obtain PS(BM). The particle size distribution of the four different PS prior to ultrasonication was in the ranked order (largest to smallest size), based upon their d(0.5) and d(0.9), of PS(BM), PS(<106), PS(<38), and PS(JM). However, after ultrasonication for 10 min, PS(BM) had the smallest d(0.5) at less than a micron, while the remaining three PS groups showed nearly the same d(0.5) being within the range of 3–5 μm. The presence of PS shortened the cure time, with PS(BM) inducing the greatest decrease in the cure time, while this was somewhat dose independent for at least PS(JM) and PS(<106). For all four PS groups, when present at 20 phr or more, the delta torque of the PS filled NR was higher than that of the unfilled one. However, the addition of PS had no significant effect on the number of crosslinks. With respect to the mechanical properties of the NR filled with PS, it was generally observed that NR filled with PS(BM) at 20–50 phr gave a higher tear and tensile strength, abrasion resistance, and hardness than both the unfilled NR and also the NR filled with the other three PS groups. The optimum PS(BM) loading was at 30 phr.

Study on sulfur vulcanized natural rubber formulated with nitrosamine safe diisopropyl xanthogen polysulfide/tertiary butyl benzothiazole sulphenamide binary accelerator system

2020 ◽  
pp. 147776062097749
Author(s):  
IHK Samarasinghe ◽  
S Walpalage ◽  
DG Edirisinghe ◽  
SM Egodage
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Strength Properties ◽  
Nitroso Compounds ◽  
Tertiary Butyl ◽  
Study Behavior ◽  
Cure Characteristics ◽  
Sulfur Vulcanization ◽  
Cure Time ◽  
Accelerator System

An outstanding interest on elimination of nitrosamine generation in traditional sulfur vulcanization systems has led to introduce nitrosamine safe accelerator/s to produce safe natural rubber (NR) vulcanizates. It is an effective way to prevent formation of carcinogenic N-nitroso compounds during manufacture of rubber products. In the present study, behavior of nitrosamine safe binary accelerator system consisting of diisopropyl xanthogen polysulfide (DIXP) with commonly used non-regulated accelerator N-tert-butyl-2-benzothiazole sulfenamide (TBBS) was investigated in efficient sulfur vulcanization of NR. Cure characteristics, physico-mechanical properties and crosslink density of vulcanizates prepared with different combinations of the accelerator system were evaluated and compared with those of individual accelerators. The study reveals that moduli and strength properties of the vulcanizate prepared with DIXP accelerator are inferior to those of the vulcanizate prepared with TBBS accelerator. Nevertheless, optimum cure time of the DIXP compounds is lower in comparison to TBBS compounds. Moreover, progressive replacement of DIXP with TBBS in the accelerator system showed a synergistic effect in regard to cure characteristics and physico-mechanical properties.

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