scholarly journals Blooming of Compounding Ingredients in Natural Rubber Compounds under Different Peroxide Loading

2019 ◽  
Vol 8 (4) ◽  
pp. 7027-7031
Keyword(s):  
Natural Rubber ◽  
Paraffin Wax ◽  
Dicumyl Peroxide ◽  
Curing Agent ◽  
Bending Vibration ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Powdery Material ◽  
Zinc Diethyldithiocarbamate ◽  
Processing Aids

Rubber compounds normally shows blooming phenomena whereby a thin layer of powdery material or films and oils formed on the surface. These blooms are usually low molecular weight compounding ingredients such as curing agents, accelerator, processing aids and activators that migrated to the surface. Excessive blooming can degrade the vulcanized rubber and reduced its quality. It is therefore necessary to determine the compounding ingredients that bloomed in an effort to reduce the effect of blooming. This study was aimed at identifying the compounding ingredients that dominate the blooming process. Sulphur, paraffin wax and zinc diethyldithiocarbamate (ZDEC) with specific functions were added as compounding ingredients in natural rubber (SMR L). Dicumyl peroxide were added as the curing agent at several loadings. The rubber compounds were cured at 150oC in the presence of dicumyl peroxide as curing agent at several loadings. They were stored under room temperature for blooming to take place. Blooms were analysed using FTIR and EDX. EDX analysis detected the major element present in the blooms to be carbon at 53.5% abundance. Similarly, FTIR results produced high intensity of C-H band at 2916 cm-1 and 722 cm-1 which are due to stretching and bending vibration of C-H paraffinic. It was concluded that paraffin wax preceded sulphur and ZDEC in blooming of SMR L.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

Processing aids for mixing and extrusion of silica-natural rubber compounds

1992 ◽  
Vol 32 (15) ◽  
pp. 981-988 ◽  
Author(s):  
N. Nakajima ◽  
W. J. Shieh ◽  
Z. G. Wang
Keyword(s):  
Natural Rubber ◽  
Rubber Compounds ◽  
Processing Aids

Preliminary Study on Curing of Thick Rubber Article

2015 ◽  
Vol 1134 ◽  
pp. 23-27
Author(s):  
Siti Zulaikha Ibrahim ◽  
Che Mohd Som Said ◽  
Mohamad Asri Ahmad ◽  
Azemi Samsuri
Keyword(s):  
Tensile Strength ◽  
Temperature Region ◽  
The State ◽  
Curing Temperature ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Cure Time ◽  
Zinc Diethyldithiocarbamate ◽  
Preliminary Study ◽  
Rubber Article

In this study, several batches of natural rubber (SMR L) were compounded with three different types of accelerators, which were N-cyclohexylbenzothiazole-2-sulphenamide (CBS), diphenylguanidine (DPG) and zinc diethyldithiocarbamate (ZDEC). ZDEC is known as an ultrafast accelerator. The rubber compounds were cured at 140°C, 130°C, 120°C, 110°C and 100°C in accordance with the temperature gradients observed within the thick rubber block. The main aim of this study is to cure the rubber at each temperature region to the same cure time as that of the outermost region (20 minutes at 140°C). The amount of sulfur and accelerator were adjusted accordingly at each curing temperature to match the state of cure at 140°C. The state of cure of of the vulcanized rubbers were measured using hardness and tensile strength. The same state of cure is achieved if the hardness and tensile strength value are within ±2 IRHD and ±3 MPa, respectively with that of the control vulcanized rubber (hardness and tensile strength cured at 140°C). The results shows that the hardness and tensile strength of the vulcanized rubber at each temperature region are within the expected margins. The results clearly indicated that the type and amount of accelerators, and the amount of sulfur were correctly chosen at each temperature.

Smearing of Vulcanized Rubber

1955 ◽  
Vol 28 (2) ◽  
pp. 508-518 ◽  
Author(s):  
S. D. Gehman ◽  
C. S. Wilkinson ◽  
R. D. Daniels
Keyword(s):  
Melting Point ◽  
Thermal Degradation ◽  
Natural Rubber ◽  
Sulfur Compound ◽  
Important Variable ◽  
Cross Linking ◽  
Curing Agent ◽  
Point Bar ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanized Rubber

Abstract The surface heating which occurs at the interface of rubber sliding under a load may be part of the mechanism of abrasion, especially under severe conditions. Removal of rubber by thermal degradation and a smearing process occurs if the rubber attains sufficiently high localized temperatures. A procedure, using a melting point bar, was developed for measuring the temperature at which smearing occurred for rubber vulcanizates. Smear points reproducible to about ±2° F were measured. The effect of compounding variables on the smear point was investigated. The most important variable in this category was the vulcanization system, probably inasmuch as it determined the type of cross-linking. The presence of free sulfur within the rubber also tended to increase the smear temperature. Highest smear points were obtained with mercaptobenzothiazole-tetramethylthiuram disulfide mixtures, and for a non-sulfur compound using p-quinone-dioxime as the curing agent. The highest smear point observed for natural rubber was 475° F, obtained with this system. GR-S tread compounds showed no smearing even at 560° F, which was as high as could be obtained with the apparatus used. The resistance to smearing of GR-S may be an important factor in explaining its superiority in road wear under severe conditions. Laboratory abrasion experiments were performed to illustrate the effect of smearing on the relative abrasion loss of GR-S and natural-rubber tread compounds.

Simple Method for Determining the Dynamic Coefficient of Friction of Vulcanized Rubber

1951 ◽  
Vol 24 (2) ◽  
pp. 374-380
Author(s):  
B. B. S. T. Boonstra
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Coefficient Of Friction ◽  
Simple Method ◽  
Rubber Powder ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
The Coefficient Of Friction ◽  
Rubber Concrete ◽  
Better Than

Abstract A method for measuring the coefficient of friction at low speeds by means of a normal dynamometer for rubber testing is described. To this end a couple of molded rubber wheels are pulled over a piece of roadlike surface. At the same time the wheels are forced to rotate with a speed nonconcordant with the linear speed on the surface, so that a certain amount of friction occurs. The force necessary to turn the wheels over the surface is recorded on the dynamometer; the average is proportional to the average coefficient of friction. Preliminary experiments were carried out to prove the usefulness of the apparatus. A number of compounds of natural rubber, GR-S, and “cold” rubber were tested on four surfaces: asphalt, asphalt with rubber, concrete, and ground glass. Although the apparatus allows variation of load and of speed, the experiments were carried out at a speed of 100 cm. per minute and only with a load of 4 kilograms. On dry surfaces, the highest coefficient of friction was found with a natural-rubber compound on an asphalt material in which rubber powder had been dispersed. With most rubbers this surface showed a somewhat higher coefficient of friction than did the asphalt without rubber-powder, which in turn was better than the other two surfaces. On the average there was little difference between the various rubber compounds, though natural rubber seemed to yield the highest values. Natural-rubber pure gum compound did not show higher values than the carbon black mixes, but a vulcanizate with cyclorubber instead of carbon black was definitely better.

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