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.

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.

scholarly journals Composites from Thermoplastic Natural Rubber Reinforced Rubberwood Sawdust: Effects of Sawdust Size and Content on Thermal, Physical, and Mechanical Properties

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Chatree Homkhiew ◽  
Surasit Rawangwong ◽  
Worapong Boonchouytan ◽  
Wiriya Thongruang ◽  
Thanate Ratanawilai
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Natural Rubber ◽  
High Density Polyethylene ◽  
High Performance ◽  
Physical And Mechanical Properties ◽  
Modulus Of Rupture ◽  
Shore Hardness ◽  
Thermoplastic Natural Rubber ◽  
Plastic Content

The aim of this work is to investigate the effects of rubberwood sawdust (RWS) size and content as well as the ratio of natural rubber (NR)/high-density polyethylene (HDPE) blend on properties of RWS reinforced thermoplastic natural rubber (TPNR) composites. The addition of RWS about 30–50 wt% improved the modulus of the rupture and tensile strength of TPNR composites blending with NR/HDPE ratios of 60/40 and 50/50. TPNR composites reinforced with RWS 80 mesh yielded better tensile strength and modulus of rupture than the composites with RWS 40 mesh. The TPNR/RWS composites with larger HDPE content gave higher tensile, flexural, and Shore hardness properties and thermal stability as well as lower water absorption. The TPNR/RWS composites with larger plastic content were therefore suggested for applications requiring high performance of thermal, physical, and mechanical properties.

The Effects of Heat Treatment on the Chemical Alterations of Oak Wood

2016 ◽  
Vol 688 ◽  
pp. 44-49 ◽  
Author(s):  
Iveta Čabalová ◽  
František Kačík ◽  
Tereza Tribulová
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
High Performance Liquid Chromatography ◽  
Renewable Energy ◽  
Liquid Chromatography ◽  
Thermal Treatment ◽  
High Performance ◽  
Treated Wood ◽  
National Renewable Energy Laboratory ◽  
Oak Wood

Samples prepared from oak (Quercusrobur L.) wood were exposed to heat treatment at temperatures of 160, 180, 200 and 220 oC for 3, 6, 9 and 12 hours. In both untreated and thermally treated wood there were determined extractives and lignin by National Renewable Energy Laboratory (NREL) procedures, cellulose by Seifert's method, holocellulose according to Wise, hemicelluloses as difference between holocellulose and cellulose. Monosaccharides were determined by high performance liquid chromatography (NREL).The results show that hemicelluloses are less stable at thermal treatment than cellulose. The amounts of lignin and extractives rose by increasing both temperature and time of the treatment while the amounts of hemicelluloses decreased. Thermal treatment also resulted in significant decreases of the yields of non-glucosic saccharides. Degradation of carbohydrates can cause the deterioration of mechanical properties of wood.

Reinforcement of Natural Rubber with Silanized Precipitated Silica Nanofiller

2005 ◽  
Vol 78 (5) ◽  
pp. 793-805 ◽  
Author(s):  
A. Ansarifar ◽  
N. Ibrahim ◽  
M. Bennett
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Zinc Oxide ◽  
Reaction Mechanism ◽  
Energy Density ◽  
Natural Rubber ◽  
Elemental Sulfur ◽  
Stored Energy ◽  
Tear Strength ◽  
Precipitated Silica

Abstract The effect of a large amount of precipitated amorphous white silica nanofiller, pre-treated with bis[3-triethoxysilylpropyl-)tetrasulfide (TESPT), on the mechanical properties of a sulfur-cured natural rubber (NR) was studied. TESPT chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur-cure. The silica particles were fully dispersed in the rubber, which was cured primarily by using sulfur in TESPT, or, by adding a small amount of elemental sulfur to the cure system. The cure was also optimized by incorporating sulphenamide accelerator and zinc oxide into the rubber. The hardness, tear strength, tensile strength, and stored energy density at break of the vulcanizate were substantially improved when the filler was added. Interestingly, these properties were also enhanced when the rubber was cured primarily by using sulfur in TESPT.

Spectroscopic Studies on Reaction between Squalene and Vulcanizing Agents in the Presence and Absence of Zinc-2-Mercaptopyridine-N-Oxide

2004 ◽  
Vol 77 (2) ◽  
pp. 201-213
Author(s):  
C. C. Pierre ◽  
R. N. Datta
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Nmr Spectroscopy ◽  
Carbon Black ◽  
Natural Rubber ◽  
High Performance ◽  
Model Compound ◽  
Spectroscopic Studies ◽  
Reversed Phase ◽  
Zinc Stearate

Abstract Model compound vulcanization in combination with reversed-phase high-performance liquid chromatography and NMR spectroscopy was used to elucidate the reactions of accelerator, sulfur, zinc stearate and zinc-2-mercaptopyridine-N-oxide (ZPNO) in natural rubber vulcanization. Studies of different curing ingredient formulations in squalene have been done to determine the influence of each component during the vulcanization. It was found that 2-mercaptopyridine-N-oxide bridged adducts (R-Sx-Pyr(O)) were formed when squalene was heated in the presence of sulfur, curing ingredients and 2,2′-dithiobis(pyridine-N-oxide) (PyrO-S2-PyrO). Possible interactions of R-Sx-Pyr(O) with carbon black have been proposed.

scholarly journals Quality Assessment of Artemether-Lumefantrine Samples and Artemether Injections Sold in the Cape Coast Metropolis

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
James Prah ◽  
Elvis Ofori Ameyaw ◽  
Richmond Afoakwah ◽  
Patrick Fiawoyife ◽  
Ernest Oppong-Danquah ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Side Effects ◽  
Quality Assessment ◽  
Uncomplicated Malaria ◽  
High Performance ◽  
Cape Coast ◽  
Regulatory Bodies ◽  
Wavelength Detector

Most prescribers and patients in Ghana now opt for the relatively expensive artemether/lumefantrine rather than artesunate-amodiaquine due to undesirable side effects in the treatment of uncomplicated malaria. The study sought to determine the existence of substandard and/or counterfeit artemether-lumefantrine tablets and suspension as well as artemether injection on the market in Cape Coast. Six brands of artemether-lumefantrine tablets, two brands of artemether-lumefantrine suspensions, and two brands of artemether injections were purchased from pharmacies in Cape Coast for the study. The mechanical properties of the tablets were evaluated. The samples were then analyzed for the content of active ingredients using High Performance Liquid Chromatography with a variable wavelength detector. None of the samples was found to be counterfeit. However, the artemether content of the samples was variable (93.22%−104.70% of stated content by manufacturer). The lumefantrine content of the artemether/lumefantrine samples was also variable (98.70%–111.87%). Seven of the artemether-lumefantrine brands passed whilst one failed the International Pharmacopoeia content requirements. All brands of artemether injections sampled met the International Pharmacopoeia content requirement. The presence of a substandard artemether-lumefantrine suspension in the market should alert regulatory bodies to be more vigilant and totally flush out counterfeit and substandard drugs from the Ghanaian market.

Model Compound Studies on the Devulcanization of Natural Rubber Using 2,3-Dimethyl-2-Butene

2005 ◽  
Vol 78 (4) ◽  
pp. 572-587 ◽  
Author(s):  
V. V. Rajan ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer ◽  
R. Joseph
Keyword(s):  
Molecular Weight ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Natural Rubber ◽  
High Performance ◽  
Model Compound ◽  
Zinc Stearate ◽  
Low Molecular Weight ◽  
Second Stage ◽  
Weight Model

Abstract The mechanism of devulcanization of sulfur-vulcanized natural rubber with aromatic disulfides and aliphatic amines has been studied using 2,3-dimethyl-2-butene (C6H12) as a low-molecular weight model compound. First C6H12 was vulcanized with a mixture of sulfur, zinc stearate and N-cyclohexyl-2-benzothiazylsulfenamide (CBS) as accelerator at 140 °C, resulting in a mixture of addition products (C6H11−Sx−C6H11). The compounds were isolated and identified by High Performance Liquid Chromatography (HPLC) with respect to their various sulfur ranks. In a second stage, the vulcanized products were devulcanized using the agents mentioned above at 200 °C. The kinetics and chemistry of the breakdown of the sulfur-bridges were monitored. Both devulcanization agents decompose sulfidic vulcanization products with sulfur ranks equal or higher than 3 quite effectively and with comparable speed. Diphenyldisulfide as devulcanization agent gives rise to a high amount of mono- and disulfidic compounds formed during the devulcanization, hexadecylamine, as devulcanization agent, prevents these lower sulfur ranks from being formed.

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