Mechanochemical Reactions in Black-Filled SBR Vulcanizates under Large Deformation

2007 ◽  
Vol 80 (2) ◽  
pp. 265-278 ◽  
Author(s):  
Asahiro Ahagon ◽  
Yoshiaki Kirino
Keyword(s):  
Large Deformation ◽  
Crosslink Density ◽  
Roll Mill ◽  
Bond Scission ◽  
Wide Range ◽  
Short Time ◽  
Worn Surface ◽  
Number Of Passes ◽  
Mechanochemical Reactions ◽  
Mechanochemical Degradation

Abstract Mechanochemical degradation of black-filled SBR's at large deformation was studied in relation to abrasion. Deformation of rubbers caused bond scission and reduced the crosslink density; however, subsequent free radical reactions reconstructed the network structure in a short time to some extents depending on the strain. The extent of crosslink recovery was larger with larger strains. As a consequence, the loss in crosslink density showed a peak when plotted against the strain. When rubber was deformed by repeatedly passing through a narrow gap of a two-roll mill, the crosslink density was raised appreciably above the original level after a small number of passes. Surprisingly, the rubber could become plastic-like while the crosslink density was maintained high. All of these results matched well with the characteristic phenomena observed in abrasion of rubbers, e.g., the varying appearance of wear with severity, the worn surface and debris prone to be oxidized, and the bimodal size distribution of debris. It was strongly suggested that mechanochemical degradation participated in abrasion in a wide range of severity.

scholarly journals Effects of local isolates of Beauveria bassiana (Balsamo) Vuillemin on the two-spotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae)

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Cenk Yucel
Keyword(s):  
Tetranychus Urticae ◽  
Beauveria Bassiana ◽  
Spider Mite ◽  
Lethal Effect ◽  
Probit Analysis ◽  
Plant Feeding ◽  
Wide Range ◽  
Two Spotted Spider Mite ◽  
Short Time ◽  
Tetranychus Urticae Koch

Abstract Background The two-spotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae), is a widely distributed plant-feeding pest that causes significant yield losses in a wide range of crops. Newly developed or improved environmentally friendly biocontrol agents serve as an alternative to traditional pest control tools. Experiment of the effects of 2 local fungal isolates of Beauveria bassiana (BGF14 and BCA32) was carried out against T. urticae under laboratory conditions. Results Both tested isolates had lethal effect in a short time after application, and this effect increased as time progressed. BGF14 and BCA32 isolates caused T. urticae mortality rates ranging from 25.88 to 61.92 and 32.36 to 62.03% when applied at the concentrations between 1×105 and 1×108 conidia/ml, respectively. According to the Probit analysis performed on the effect of fungi on T. urticae adults, the LC50 values of BGF14 and BCA32 isolates on the 7th day after inoculation were 2.6×106 and 6.3×104 conidia/ml, respectively, and the LT50 values for both fungi applied at a concentration of 108 conidia/ml were 2.14 and 2.23 days, respectively. Conclusions The 2 isolates of B. bassiana (BGF14 and BCA32) had the potentials to suppress T. urticae population and can be recommended as promising biocontrol agent candidates for control of T. urticae.

scholarly journals Breeding Strategies to Improve Miscanthus as a Sustainable Source of Biomass for Bioenergy and Biorenewable Products

Agronomy ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 673 ◽  
Author(s):  
John Clifton-Brown ◽  
Kai-Uwe Schwarz ◽  
Danny Awty-Carroll ◽  
Antonella Iurato ◽  
Heike Meyer ◽  
...  
Keyword(s):  
Significant Contribution ◽  
Perennial Grass ◽  
Time Frame ◽  
Eastern Asia ◽  
Germplasm Collections ◽  
Naturally Occurring ◽  
Wide Range ◽  
Yield Quality ◽  
Short Time ◽  
Commercial Expansion

Miscanthus, a C4 perennial grass native to Eastern Asia, is being bred to provide biomass for bioenergy and biorenewable products. Commercial expansion with the clonal hybrid M. × giganteus is limited by low multiplication rates, high establishment costs and drought sensitivity. These limitations can be overcome by breeding more resilient Miscanthus hybrids propagated by seed. Naturally occurring fast growing indigenous Miscanthus species are found in diverse environments across Eastern Asia. The natural diversity provides for plant breeders, the genetic resources to improve yield, quality, and resilience for a wide range of climates and adverse abiotic stresses. The challenge for Miscanthus breeding is to harness the diversity through selections of outstanding wild types, parents, and progenies over a short time frame to deploy hybrids that make a significant contribution to a world less dependent on fossil resources. Here are described the strategies taken by the Miscanthus breeding programme at Aberystwyth, UK and its partners. The programme built up one of the largest Miscanthus germplasm collections outside Asia. We describe the initial strategies to exploit the available genetic diversity to develop varieties. We illustrate the success of combining diverse Miscanthus germplasm and the selection criteria applied across different environments to identify promising hybrids and to develop these into commercial varieties. We discuss the potential for molecular selections to streamline the breeding process.

Rolling/Sliding Wear Behavior of High Carbon Steel Wire Rod (HSWR) of Traction Machine

2008 ◽  
Author(s):  
Beom-Taek Jang ◽  
Seock-Sam Kim
Keyword(s):  
Wear Behavior ◽  
Steel Wire ◽  
High Carbon Steel ◽  
Wire Rope ◽  
Wear Volume ◽  
Steel Wires ◽  
Volume Curve ◽  
Wide Range ◽  
Lubrication Condition ◽  
Worn Surface

Steel wires are critical load-bearing components in a wide range of applications such as elevator, cranes, mine haulage etc. The traction machine of elevator which transmits power to wire rope causes micro-slip between wire rope and sheave during reciprocating action. The lubrication condition of wire rope is also changed due to the lack of grease. This study focuses on the wear behavior of steel wire and effect of both dry and grease conditions by using the rolling/sliding contact wear tester done under various slip ratios and rolling speeds. The experimental results of the wear volume curve against the number of revolutions under the grease condition are compared with the results under dry condition. The worn surface of steel wire and the size of wear particles were observed by SEM. In order to quantify the wear amount of steel wire we established an equation and finally obtained the wear coefficient.

A Novel Versatile Process for the Production of Polymer Foams

1998 ◽  
Vol 550 ◽  
Author(s):  
V.P. Shastri ◽  
I. Martin ◽  
R. Langer
Keyword(s):  
Water Soluble ◽  
Wound Dressings ◽  
High Porosity ◽  
Polymer Foams ◽  
Polymer Foam ◽  
Water Soluble Polymers ◽  
Soluble Polymers ◽  
Great Utility ◽  
Wide Range ◽  
Short Time

AbstractPorous polymeric media are used in several applications such as solid supports for separations and catalysis, as well as biomedical applications such as vascular grafts and wound dressings. We have developed a novel versatile process to produce polymeric cellular solids. This process which is based on a phase extraction-co-polymer precipitation is applicable to a wide range of polymer systems including water soluble polymers. It is capable of yielding polymer foams of high porosity (> 90%) and excellent mechanical characteristics in a very short time (less than 2 hours) without limitations in foam thickness. Polymer foam with such characteristics have great utility in tissue engineering applications. We have successfully explored polymer foams of biocompatible polymers produced by the presented approach for bone and cartilage engineering using bone marrow stromal cells.

Mechanochemical Reactions Leading to Reinforcement in Rubbers

1960 ◽  
Vol 33 (4) ◽  
pp. 929-939
Author(s):  
R. J. Ceresa
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Covalent Bond ◽  
Vinyl Monomers ◽  
Research Association ◽  
Block Copolymerization ◽  
Wide Range ◽  
Carbon Gel ◽  
Internal Mixer ◽  
Mechanochemical Reactions

Abstract The development of the single rotor internal mixer (at the British Rubber Producers' Research Association) has facilitated the research into mechanochemical reactions of a wide range of high polymers. The term “mechanochemical” has been applied to reactions such as mastication, the mechanism of which involves the primary step of mechanical scission of a polymer chain into polymeric free radicals at a carbon to carbon or other covalent bond. The processes which have been studied previously include the cold mastication of rubberlike polymers, the formation of carbon gel, the interpolymerization of two elastomers during blending, and block copolymerization by the cold mastication of polymers plasticized by vinyl monomers. The evidence for the polymeric free radical nature of these reactions has recently been reviewed.

EFFECT OF DEVULCANIZATION ON CROSSLINK DENSITY AND CROSSLINK DISTRIBUTION OF CARBON BLACK FILLED NATURAL RUBBER VULCANIZATES

2016 ◽  
Vol 89 (4) ◽  
pp. 653-670 ◽  
Author(s):  
Anu Mary Joseph ◽  
Benny George ◽  
Madhusoodanan K. N. ◽  
Rosamma Alex
Keyword(s):  
Carbon Black ◽  
Natural Rubber ◽  
Crosslink Density ◽  
Morphological Properties ◽  
Original Sample ◽  
Ambient Conditions ◽  
Absolute Value ◽  
Roll Mill ◽  
Percentage Retention ◽  
The Absolute

ABSTRACTCarbon black filled natural rubber (NR) vulcanizates were devulcanized at ambient temperature in a two roll mill. The effect of cure system, that is, conventional vulcanization (CV), semiefficient vulcanization (semi EV), and efficient vulcanization (EV) systems, used for vulcanization of the original sample, on the efficiency of devulcanization was studied. The efficiency of devulcanization expressed as percentage devulcanization of the samples calculated from residual crosslink density measurements was correlated with the sol fraction of the devulcanized samples based on Horikx analysis. Using chemical probe analysis, we determined (i) the crosslink distribution pattern of the original sample, (ii) the extent to which the different types of crosslinks—that is, polysulfidic, disulfidic, and monosulfidic crosslinks—have been debonded or broken during the shearing process in the two roll mill, and (iii) the pattern of bond formation during revulcanization. Mechanical shearing predominantly breaks the majority crosslink type (polysulfidic crosslinks in CV and semi EV cure systems and disulfidic crosslinks in EV samples). Irrespective of the significant reduction in total crosslink density in all three sets of samples, chain shortening reactions similar to the post-crosslinking chemical reactions at curing temperatures also occur during mechanical shear at ambient conditions, which increased the absolute value of monosulfidic links in CV and semi EV systems. However, in the devulcanized EV system, the absolute value of polysulfidic crosslinks increased, which might be due to the re-crosslinking of the cleaved bonds. All the devulcanized samples were revulcanized, and the mechanical and morphological properties were analyzed. The percentage retention of the vulcanizate properties after revulcanization of the devulcanized samples correlated very well with efficiency of devulcanization.

scholarly journals Curing and mechanical properties of chlorosulphonated polyethylene rubber blends

2011 ◽  
Vol 17 (3) ◽  
pp. 315-321 ◽  
Author(s):  
Gordana Markovic ◽  
Vojislav Jovanovic ◽  
Suzana Samarzija-Jovanovic ◽  
Milena Marinovic-Cincovic ◽  
Jaroslava Budinski-Simendic
Keyword(s):  
Mechanical Properties ◽  
Crosslink Density ◽  
Hydraulic Press ◽  
Elongation At Break ◽  
Rubber Blends ◽  
Tensile Tester ◽  
Roll Mill ◽  
Cure Time ◽  
Chlorosulphonated Polyethylene ◽  
Scanning Electron

In this paper the curing and mechanical properties of two series of prepared blends, i.e., chlorosulphonated polyethylene (CSM)/isobutylene-co-isoprene (IIR) rubber blends and chlorosulphonated polyethylene (CSM)/chlorinated isobutylene-co-isoprene (CIIR) rubber blends were carried out. Blends were prepared using a two roll-mill at a temperature of 40-50?C. The curing was assessed by using a Monsanto Oscillating Disc Rheometer R-100. The process of vulcanization accelerated sulfur of pure rubbers and their blends was carried out in an electrically heated laboratory hydraulic press under a pressure of about 4 MPa and 160?. The stress-strain experiments were performed using tensile tester machine (Zwick 1425). Results indicate that the scorch time, ts2 and optimum cure time, tc90 increase with increasing CSM content in both blends. The values of modulus at 100% and at 300% elongation and tensile strength increases with increasing CSM content, whereas elongation at break shows a decreasing trend. The enhancement in mechanical properties was supported by data of crosslink density in these samples obtained from swelling measurement and scanning electron microscopy studies of the rubber blends fractured surfaces.

HIGHWAY IMPACT STUDY OF THE EFFICIENCY OF COATING AND BASE COMPACTION WITH THREE-ROLLER TANDEM COMPACTORS

2021 ◽  
pp. 114-122
Author(s):  
Владимир Александрович Нилов ◽  
Владимир Алексееич Жулай ◽  
Виталий Леонидович Тюнин ◽  
Алексей Николаевич Щиенко
Keyword(s):  
Impact Study ◽  
Economic Calculation ◽  
Vertical Loading ◽  
Wide Range ◽  
Increase In Productivity ◽  
Number Of Passes

Приведено технико-экономическое обоснование повышения эффективности уплотнения покрытий и оснований за счет использования трехвальцевых дорожных катков тандемного типа. Выполнены расчеты, показывающие возможность последовательного увеличения вертикального нагружения вальцев катка по мере возрастания прочности уплотняемой поверхности в широких пределах (до 1,1 веса серийного катка) за счет применения дополнительной управляемой секции. Установлена возможность уменьшения числа проходов катка за счет увеличения количества его вальцев. Проведен технико-экономический расчет, подтверждающий целесообразность применения таких дорожных катков, выполненных на базе серийных двухвальцевых машин, которая обусловлена увеличением производительности в 1,27…1,5 раза. We present a highway impact study for increasing efficiency of compaction of coatings and bases through the use of three-roller tandem compactors. Calculations have been performed showing the possibility of a sequential increase in the vertical loading of the rollers of a compactor as the strength of the compacted surface increases over a wide range (up to 1.1 of the weight of a serial compactor) due to the use of an additional controlled section. The possibility of reducing the number of passes of the compactor by increasing the number of its rollers has been established. A technical and economic calculation was carried out confirming the feasibility of using such road compactors made on the basis of serial two- roller tandem compactors, which is due to an increase in productivity by 1,27…1,5 times.

scholarly journals An Efficient Time Reversal Method for Lamb Wave-Based Baseline-Free Damage Detection in Composite Laminates

2018 ◽  
Vol 9 (1) ◽  
pp. 11 ◽  
Author(s):  
Liping Huang ◽  
Junmin Du ◽  
Feiyu Chen ◽  
Liang Zeng
Keyword(s):  
Damage Detection ◽  
Time Reversal ◽  
Lamb Wave ◽  
Composite Laminates ◽  
Narrow Band ◽  
Great Influence ◽  
Time Intervals ◽  
Wide Range ◽  
Reconstructed Signal ◽  
Short Time

Time reversal (TR) concept is widely used for Lamb wave-based damage detection. However, the time reversal process (TRP) faces the challenge that it requires two actuating-sensing steps and requires the extraction of re-emitted and reconstructed waveforms. In this study, the effects of the two extracted components on the performance of TRP are studied experimentally. The results show that the two time intervals, in which the waveforms are extracted, have great influence on the accuracy of damage detection of the time reversal method (TRM). What is more, it requires a large number of experiments to determine these two time intervals. Therefore, this paper proposed an efficient time reversal method (ETRM). Firstly, a broadband excitation is applied to obtain response at a wide range of frequencies, and ridge reconstruction based on inverse short-time Fourier transform is applied to extract desired mode components from the broadband response. Subsequently, deconvolution is used to extract narrow-band reconstructed signal. In this method, the reconstructed signal can be easily obtained without determining the two time intervals. Besides, the reconstructed signals related to a series of different excitations could be obtained through only one actuating-sensing step. Finally, the effectiveness of the ETRM for damage detection in composite laminates is verified through experiments.

The Creep of Natural and Snythetic Rubber Compounds in Shear

1941 ◽  
Vol 14 (2) ◽  
pp. 433-443 ◽  
Author(s):  
Stuart H. Hahn ◽  
Ivan Gazdik
Keyword(s):  
Processing Technique ◽  
Creep Tests ◽  
Time Service ◽  
Wide Range ◽  
Recent Developments ◽  
Long Time ◽  
The Many ◽  
Short Time ◽  
Relative Creep ◽  
Rubberlike Materials

Abstract Creep tests, extending in some cases as long as 900 days, indicate that both natural and synthetic rubbers such as Neoprene and butadiene copolymer can be compounded to give satisfactory service in shear mountings. At 140° F, creep is from two to nine times greater than at 80° F, depending on the compound. Tests at room temperature do not indicate either the amount of creep or the life to be expected at higher temperatures. Actual creep (measured in inches) increases with stress, but when expressed at percentage of initial deflection, it may be independent of stress. Creep curves are linear over a considerable range of time when plotted on log-log scales. However, extrapolation of such curves to predict results after very long times is not justified, because the curves may not continue to be linear, or failure of the mountings may occur, particularly at high temperatures. Short time tests of any sort are not necessarily indicative of the relative creep or life of compounds in long-time service. The tests reported here are a small portion of a large number which is being continued and augmented. It is hoped that these and other investigations now under way may contribute to clearing the picture of the complex interrelations between the many physical properties of compounds of rubberlike materials. The rubber technologist uses his specialized knowledge to develop a wide variety of compounds, making use of several types of basic rubberlike materials. He chooses whichever fits service requirements best from performance and economic viewpoints. Modern materials and recent developments in processing technique have made possible compounds suitable for a wide range of service conditions.

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