Stearic Acid in Litharge-Cured Rubber Compounds

1929 ◽  
Vol 2 (4) ◽  
pp. 638-655
Author(s):  
J. R. Sheppard
Keyword(s):  
Zinc Oxide ◽  
Stearic Acid ◽  
Organic Acid ◽  
Marked Effect ◽  
The Other ◽  
Low Grade ◽  
Rubber Compounds ◽  
Wide Range ◽  
High Zinc ◽  
Full Activation

Abstract Although an organic acid is essential to vulcanization with litharge, smoked sheet usually has enough natural acid for full activation. For example, when 5 per cent stearic acid (or similar softeners) was added to a standard smoked sheet in a high zinc oxide stock the properties were lowered. On the other hand, a “low-grade” rubber, Lapori, was greatly improved in a high zinc oxide formula by stearic and by other acids. Acidic softeners in a high zinc oxide stock increased set, even when they promoted vulcanization. In a pure gum litharge formula with smoked sheet, 1 per cent stearic had but little effect, while in a high gas black formula, 4 per cent stearic raised the tensile (probably due to improved dispersion) but had no marked effect on rate of cure. When litharge was used as the activator for mercaptobenzothiazole, stearic acid had but little effect either in pure gum or high gas black stocks. On the contrary, when zinc oxide was used proper curing was highly dependent on stearic, especially with gas black. The litharge-mercaptobenzothiazole compounds with gas black in tread stock proportions, either with or without stearic, yielded a high tensile over a wide range of cures.

Behavior of Antioxidants in Rubber Stocks Containing Copper

1931 ◽  
Vol 4 (1) ◽  
pp. 108-115
Author(s):  
Paul C. Jones ◽  
David Craig
Keyword(s):  
Zinc Oxide ◽  
Aromatic Amines ◽  
Practical Importance ◽  
Low Grade ◽  
High Grade ◽  
Degree Of Protection ◽  
Rubber Compounds ◽  
High Zinc

Abstract (1) Deterioration accelerated by copper in a high-grade tread stock, a low-grade tread stock, a high zinc oxide bus-tube stock, and a pure-gum stock has been found to be effectively retarded by the use of suitable antioxidants. (2) Secondary aromatic amines have been found to be much more effective than other antioxidants, in tread stocks, for retarding deterioration due to copper. (3) The degree of protection afforded to rubber compounds containing copper by the use of certain antioxidants, notably secondary aromatic amines, is sufficiently high to make their addition of practical importance.

Thiuram Disulfides in Compounding

1947 ◽  
Vol 20 (3) ◽  
pp. 803-807
Author(s):  
G. D. Morrison ◽  
T. Shepherd
Keyword(s):  
Zinc Oxide ◽  
Stearic Acid ◽  
Room Temperature ◽  
Milling Time ◽  
Steam Pressure ◽  
Base Stock ◽  
Large Batch ◽  
Percentage Recovery ◽  
Test Pieces ◽  
Rubber Compounds

Abstract Perhaps the chief drawback to the greater employment of thiuram disulfides has been the fear, often groundless, of scorching during processing, and for this reason the work detailed in this paper is devoted entirely to this aspect of their use. The scorching tendency, taken as the commencement of cure, and the rate of vulcanization were studied by means of a modified Goodrich type of plastometer, and the results are expressed as the percentage recovery against time in minutes at 120° C. This temperature (equivalent to 15 lbs. per sq. in. steam pressure) was chosen as being the highest likely to be reached in normal mixing, calendering and extrusion. The rubber compounds tested were prepared from one large batch of base stock comprising: smoked sheet rubber, 100 parts; zinc oxide, 5 parts; and stearic acid, 2 parts. After mixing, the stock was divided into the required number of portions and to these were added the various ingredients detailed later; in all cases the same milling time and temperatures were adhered to so that results would be comparable, especially plasticity. An interval of 24 hours at room temperature was allowed in each case before cutting plastometer test-pieces to dissipate strains imposed in the stock during mixing and sheeting. The test-pieces were then placed in an oven at 120° C, and percentage recovery determinations were made at 5-minute intervals over a range of 5 to 60 minutes.

Chemical Compatibility as a Factor in the Dispersion of Fillers in Rubber

1962 ◽  
Vol 35 (4) ◽  
pp. 881-888 ◽  
Author(s):  
C. A. Carlton
Keyword(s):  
Zinc Oxide ◽  
Organic Acid ◽  
Resin Acids ◽  
Chemical Analyses ◽  
White Pigment ◽  
Inorganic Oxides ◽  
Vulcanized Rubber ◽  
Synthetic Rubber ◽  
Rubber Compounds ◽  
Time Dispersion

Abstract Poor dispersion of fillers in rubber compounds has been a troublesome problem since the beginning of the rubber industry. An example of this kind of difficulty is the presence of white pigment lumps in black or dark-colored compounds that are surface buffed, such as some types of shoe soling. Chemical analyses of filler agglomerates removed from a large number of unvulcanized and vulcanized rubber compounds revealed the fact that in practically every instance a substantial amount of zinc oxide was present. This is of major importance since good dispersion of zinc oxide is necessary for the proper vulcanization of a rubber compound. It is quite difficult to identify positively the specific variable or variables in any one given formulation which may cause filler agglomerates. They may be due to the composition of one or more of the ingredients present in the mix, the order in which the ingredients are added, or to the mixing procedure. However, a series of tests indicated one major cause, the addition of acidic materials such as fatty acids, organic acid vulcanization retarders, or acidic accelerators to natural rubber or some synthetic rubbers simultaneously with basic activators such as lime, litharge, magnesia, and zinc oxide, or with some basic fillers such as finely divided calcium and magnesium carbonates. High-temperature mixing (about 325° F) gave better dispersion than low-temperature mixing (about 220° F) when acidic or basic materials were added simultaneously, but in some instances poor dispersion resulted even at temperatures up to 325° F. This was particularly true of litharge and magnesia. It was also found that when zinc oxide and stearic acid were added to synthetic rubber at the same time, dispersion was better in some types of rubber than in others. The stiffer mixes of NBR (nitrile) and cold, unfilled SBR gave better dispersions than those of the softer IIR (butyl) and oil-extended SBR. Regardless of the type of rubber being used, the safest procedure to insure satisfactory dispersion of inorganic oxides is to add any acidic materials separately during the mixing procedure. This approach is particularly necessary if the mix contains resin acids and/or organic acid vulcanization retarders such as benzoic or salicylic acids. If it is not feasible to add the acidic and basic compounding materials separately to the rubber, then the inorganic oxides should be added to the mix in the form of masterbatches.

Investigation on the Influence of Various Kinds of Soaps on the Mechanical Properties of Silica Filled Composites Based on Natural Rubber

2018 ◽  
Vol 26 (4) ◽  
pp. 325-334
Author(s):  
Omar A. Al-Hartomy ◽  
Ahmed A. Al-Ghamdi ◽  
Said A. Fahra Al-Said ◽  
Nikolay Dishovsky ◽  
Mihail Mihaylov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Zinc Oxide ◽  
Fatty Acid ◽  
Stearic Acid ◽  
Natural Rubber ◽  
Rubber Compounds ◽  
Zinc Salts

The aim of this study was to investigate the influence that different fatty acid zinc salts had on the rheological, curing and mechanical properties of natural rubber based composites filled with silica and containing bi-functional organosilanes in the presence or absence of zinc oxide. The results demonstrated that the combination of zinc oxide and zinc soaps had a strongly pronounced anti-reversion effect. The absence of reversion in the cure curves of the rubber compounds comprising a combination of zinc oxide, stearic acid and zinc soaps, results in retention of their mechanical properties, even after overcure.

scholarly journals The effect of the compositional curing activator formation on the properties of elastomers

2020 ◽  
Vol 81 (4) ◽  
pp. 178-183
Author(s):  
O. V. Karmanova ◽  
A. Y. Fatneva ◽  
S. G. Tikhomirov ◽  
L. V. Popova
Keyword(s):  
Mechanical Properties ◽  
Fatty Acids ◽  
Zinc Oxide ◽  
Stearic Acid ◽  
Silicon Dioxide ◽  
Physical And Mechanical Properties ◽  
Rubber Compound ◽  
Regulatory Requirements ◽  
Rubber Compounds ◽  
Positive Effect

The properties of rubber compounds and vulcanizates made using a compositional curing activator with a low content of zinc oxide were studied in this work. Technological modes of obtaining new curing activator activators in the form of an alloy of zinc oxide with a mixture of fatty acids have been developed. To give a convenient outlet shape, finely dispersed fillers of various types were introduced into the experimental products: silicon dioxide, carbon black, microcellulose, bentonite, shungite. The physicochemical properties of compositional curing activator were studied and it was established that, according to the values of acid and iodine numbers, the experimental products satisfy the regulatory requirements for stearic acid. A comparative analysis of the properties of elastomers of experimental products with widely used as curing activator activators of zinc oxide and stearic acid is carried out. It was found that the use of experimental products improves the processability of the compositions due to their better dispersion in an elastomeric medium. The ratios of the compositional curing activator components are determined, which ensure the optimal complex of vulcanization and physical and mechanical properties of elastomers made on their basis. The effectiveness of the action of composite vulcanization activator in the manufacture of elastomeric products is shown - a reduction in the mixing cycle of experimental compositions by an average of 10% is noted compared to the standard rubber compound. The analysis of the research results confirmed the improvement of technological and vulcanization properties of rubber compounds, resistance to scorching. It is shown that the use of compositional curing activators provides the required level of physical and mechanical properties of rubbers even with a decrease in the content of zinc oxide in the experimental product to 20 wt%, and also improves the dispersion of the components of the rubber compound, having a positive effect on the technological and vulcanization properties of rubber compounds.

2D Color-Intensity Representation of Ultrasonic Thickness Gauge Measurements

2020 ◽  
pp. 1192-1198
Author(s):  
M.S. Mohammad ◽  
Tibebe Tesfaye ◽  
Kim Ki-Seong
Keyword(s):  
Cost Effective ◽  
The Other ◽  
Thickness Gauge ◽  
Color Intensity ◽  
Digital Readout ◽  
Flat Surfaces ◽  
Video Cameras ◽  
Wide Range ◽  
Cost Effective Alternative ◽  
Ultrasonic Thickness

Ultrasonic thickness gauges are easy to operate and reliable, and can be used to measure a wide range of thicknesses and inspect all engineering materials. Supplementing the simple ultrasonic thickness gauges that present results in either a digital readout or as an A-scan with systems that enable correlating the measured values to their positions on the inspected surface to produce a two-dimensional (2D) thickness representation can extend their benefits and provide a cost-effective alternative to expensive advanced C-scan machines. In previous work, the authors introduced a system for the positioning and mapping of the values measured by the ultrasonic thickness gauges and flaw detectors (Tesfaye et al. 2019). The system is an alternative to the systems that use mechanical scanners, encoders, and sophisticated UT machines. It used a camera to record the probe’s movement and a projected laser grid obtained by a laser pattern generator to locate the probe on the inspected surface. In this paper, a novel system is proposed to be applied to flat surfaces, in addition to overcoming the other limitations posed due to the use of the laser projection. The proposed system uses two video cameras, one to monitor the probe’s movement on the inspected surface and the other to capture the corresponding digital readout of the thickness gauge. The acquired images of the probe’s position and thickness gauge readout are processed to plot the measured data in a 2D color-coded map. The system is meant to be simpler and more effective than the previous development.

p-Sulfonic acid calix[n]arene catalyzed synthesis of bioactive heterocycles: A review

2020 ◽  
Vol 24 ◽  
Author(s):  
Bubun Banerjee ◽  
Gurpreet Kaur ◽  
Navdeep Kaur
Keyword(s):  
Supramolecular Chemistry ◽  
Sulfonic Acid ◽  
Catalytic Efficiency ◽  
The Other ◽  
Reaction Conditions ◽  
Metal Free ◽  
Bioactive Scaffolds ◽  
Wide Range ◽  
Efficient Alternative ◽  
Bioactive Heterocycles

: Metal-free organocatalysts are becoming an important tool for the sustainable developments of various bioactive heterocycles. On the other hand, during last two decades, calix[n]arenes have been gaining considerable attention due to their wide range of applicability in the field of supramolecular chemistry. Recently, sulfonic acid functionalized calix[n] arenes are being employed as an efficient alternative catalyst for the synthesis of various bioactive scaffolds. In this review we have summarized the catalytic efficiency of p-sulfonic acid calix[n]arenes for the synthesis of diverse biologically promising scaffolds under various reaction conditions. There is no such review available in the literature showing the catalytic applicability of p-sulfonic acid calix[n]arenes. Therefore, we strongly believe that this review will surely attract those researchers who are interested about this fascinating organocatalyst.

Wide range modulation of synaptic weight in thin-film transistors with hafnium oxide gate insulator and indium-zinc oxide channel layer for artificial synapse application

Nanoscale ◽  
2021 ◽  
Author(s):  
Keonwon Beom ◽  
Jimin Han ◽  
Hyun-Mi Kim ◽  
Tae-Sik Yoon
Keyword(s):  
Thin Film ◽  
Zinc Oxide ◽  
Thin Film Transistors ◽  
Hafnium Oxide ◽  
Synaptic Weight ◽  
Drain Current ◽  
Gate Insulator ◽  
Channel Layer ◽  
Indium Zinc Oxide ◽  
Wide Range

Wide range synaptic weight modulation with a tunable drain current was demonstrated in thin-film transistors (TFTs) with a hafnium oxide (HfO2−x) gate insulator and an indium-zinc oxide (IZO) channel layer...

scholarly journals Density Guarantee on Finding Multiple Subgraphs and Subtensors

2021 ◽  
Vol 15 (5) ◽  
pp. 1-32
Author(s):  
Quang-huy Duong ◽  
Heri Ramampiaro ◽  
Kjetil Nørvåg ◽  
Thu-lan Dam
Keyword(s):  
Lower Bound ◽  
State Of The Art ◽  
The State ◽  
The Other ◽  
Exact Methods ◽  
Practical Solution ◽  
Novel Approach ◽  
Wide Range ◽  
Real World Datasets ◽  
Tensor Data

Dense subregion (subgraph & subtensor) detection is a well-studied area, with a wide range of applications, and numerous efficient approaches and algorithms have been proposed. Approximation approaches are commonly used for detecting dense subregions due to the complexity of the exact methods. Existing algorithms are generally efficient for dense subtensor and subgraph detection, and can perform well in many applications. However, most of the existing works utilize the state-or-the-art greedy 2-approximation algorithm to capably provide solutions with a loose theoretical density guarantee. The main drawback of most of these algorithms is that they can estimate only one subtensor, or subgraph, at a time, with a low guarantee on its density. While some methods can, on the other hand, estimate multiple subtensors, they can give a guarantee on the density with respect to the input tensor for the first estimated subsensor only. We address these drawbacks by providing both theoretical and practical solution for estimating multiple dense subtensors in tensor data and giving a higher lower bound of the density. In particular, we guarantee and prove a higher bound of the lower-bound density of the estimated subgraph and subtensors. We also propose a novel approach to show that there are multiple dense subtensors with a guarantee on its density that is greater than the lower bound used in the state-of-the-art algorithms. We evaluate our approach with extensive experiments on several real-world datasets, which demonstrates its efficiency and feasibility.

scholarly journals Grasp to See—Object Classification Using Flexion Glove with Support Vector Machine

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1461
Author(s):  
Shun-Hsin Yu ◽  
Jen-Shuo Chang ◽  
Chia-Hung Dylan Tsai
Keyword(s):  
Support Vector Machine ◽  
Daily Life ◽  
Object Classification ◽  
Target Object ◽  
The Other ◽  
Support Vector ◽  
Wide Range ◽  
Dark Space ◽  
Flex Sensors ◽  
Shape And Size

This paper proposes an object classification method using a flexion glove and machine learning. The classification is performed based on the information obtained from a single grasp on a target object. The flexion glove is developed with five flex sensors mounted on five finger sleeves, and is used for measuring the flexion of individual fingers while grasping an object. Flexion signals are divided into three phases, and they are the phases of picking, holding and releasing, respectively. Grasping features are extracted from the phase of holding for training the support vector machine. Two sets of objects are prepared for the classification test. One is printed-object set and the other is daily-life object set. The printed-object set is for investigating the patterns of grasping with specified shape and size, while the daily-life object set includes nine objects randomly chosen from daily life for demonstrating that the proposed method can be used to identify a wide range of objects. According to the results, the accuracy of the classifications are achieved 95.56% and 88.89% for the sets of printed objects and daily-life objects, respectively. A flexion glove which can perform object classification is successfully developed in this work and is aimed at potential grasp-to-see applications, such as visual impairment aid and recognition in dark space.

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