Studies of the Conditions Affecting the Vulcanization of Rubber. V. The Effect of Accelerators on the Heat of Vulcanization

1931 ◽  
Vol 4 (2) ◽  
pp. 190-190
Author(s):  
Y. Toyabe
Keyword(s):  
Total Sulfur ◽  
Micellar Structure ◽  
Rubber Compounds ◽  
Chemical Combination ◽  
Differential Thermocouple ◽  
The Times

Abstract The heat of vulcanization of rubber compounds containing various quantities of sulfur and several organic vulcanization accelerators were traced by means of a differential thermocouple during the vulcanization. The profiles of the heating curves were similar to those obtained in the case of unaccelerated compounds, but the temperature maxima appeared sooner with accelerated than with unaccelerated compounds. The vulcanizates corresponding to the temperature-maxima were analyzed chemically by ordinary methods and the ratios of the free to total sulfur were calculated. They vary a little from 50 per cent, and show that the extent of sulfur combination is not much different from that with unaccelerated compounds. The accelerators tested were hexamethylenetetramine, aldehyde-ammonia diphenylguanidine, di-o-tolylguanidine, p-nitrosodimethylaniline, thiocarbanilide, “Vulkacit P”, “Vulkacit PX”, “Vulkacit M”, and tetramethylthiuramdisulfide The results of the experiments show that these accelerators promote the disaggregation of the micellar structure of rubber (as shown in reports II and III 0. this work) before chemical combination of rubber and sulfur occurs. By thus making the single micelle of rubber smaller, they increase the number of chemical units of rubber coming into reaction with sulfur; i. e., the probability of combination of rubber and sulfur becomes greater. The times for the temperature maxima to appear in the experiments above, which are shortened by accelerators, show that this theory holds good, when it is considered that the temperature maxima correspond to the disaggregation maxima of the rubber hydrocarbon under consideration.

Nonlinearity in the Dynamic Properties of Vulcanized Rubber Compounds

1954 ◽  
Vol 27 (1) ◽  
pp. 209-222 ◽  
Author(s):  
W. P. Fletcher ◽  
A. N. Gent
Keyword(s):  
Simple Shear ◽  
Dynamic Modulus ◽  
Dynamic Properties ◽  
Mechanical Vibration ◽  
Frequency Range ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Chemical Combination ◽  
Wide Range ◽  
Static Shear

Abstract Measurements are described of the dynamic properties of rubber, loaded with various amounts and types of filler, when subjected to mechanical vibration in simple shear at amplitudes from 0 to 3 per cent shear in the frequency range 20 to 120 c.p.s. The decrease of dynamic modulus with increasing amplitude is shown, for a wide range of filler types and concentrations, to be determined by the amount of stiffening produced by the filler. This relationship is not influenced by variations in the vulcanizing ingredients, reasonable variations in state of vulcanization, addition of softener, or imposition of static shear strain. Rubber compounds stiffened by mixture with, or chemical combination of, other polymers exhibit a smaller order of nonlinearity than that described above and also exhibit much lower hysteresis values within the amplitude range 0 to 3 per cent shear.

Studies of Hard Rubber Reactions

1937 ◽  
Vol 10 (4) ◽  
pp. 792-797 ◽  
Author(s):  
Seiiti Numajiri
Keyword(s):  
Tensile Strength ◽  
Polymerization Reaction ◽  
Total Sulfur ◽  
Soft Or ◽  
Maximum Loss ◽  
Rubber Compounds ◽  
Initial Stage ◽  
Gradual Loss ◽  
The Relationship ◽  
Rubber Product

Abstract As shown in Fig. 1, all the compounds containing 5 to 150 per cent of sulfur (based on the rubber) indicated a gradual loss of total sulfur, with a relatively rapid loss after about 90 minutes, which corresponds to the period of the hard rubber reaction. Some investigators hold the view that the loss of total sulfur is the result of liberation of hydrogen sulfide by the interaction of sulfur with rubber, resins, and proteins, and sublimation of sulfur. In the present experiments, the cause of the comparatively marked loss of total sulfur seems to be related to the hardening or polymerization reaction in hard rubber. No good mixture could be obtained from which the maximum loss of total sulfur was reached, with reference to the content of rubber, i. e., rubber resins, proteins, and that of sulfur. The loss of sulfur by sublimation was restricted as far as possible by enveloping the samples with cellophane. It appears from these facts that the depolymerization phenomena of soft or semi-hard rubber products may occur during the initial stage of vulcanization and those of the hard rubber after 90 minutes. Considering again the vulcanization curves in the previous report (Part IV), there is no loss of sulfur in the initial stage of vulcanization but considerable losses of sulfur are seen in the present curves of total sulfur; in other words, during the whole course of vulcanization the combined sulfur increases to a certain extent, accompanying the loss of sulfur on one side. In Fig. 2, the relationship between the loss of total sulfur and the tensile strength of the hard rubber product is shown. Of all the hard rubber compounds, the samples containing 70–80 per cent of sulfur showed the maximum loss of sulfur, coinciding with the maximum tensile strength after vulcanization for 90 minutes. It may be assumed that the polymerization and the depolymerization reactions occur simultaneously and are closely related.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

Chemical Species Identification in an SEM by Changes in Emitted X-Ray Energies

1974 ◽  
Vol 32 ◽  
pp. 570-571
Author(s):  
R. H. Duff
Keyword(s):  
Species Identification ◽  
Valence Electron ◽  
Chemical Species ◽  
X Rays ◽  
Chemical Bonds ◽  
Small Shift ◽  
X Ray ◽  
Electron Transitions ◽  
Peak Energy ◽  
Chemical Combination

A material irradiated with electrons emits x-rays having energies characteristic of the elements present. Chemical combination between elements results in a small shift of the peak energies of these characteristic x-rays because chemical bonds between different elements have different energies. The energy differences of the characteristic x-rays resulting from valence electron transitions can be used to identify the chemical species present and to obtain information about the chemical bond itself. Although these peak-energy shifts have been well known for a number of years, their use for chemical-species identification in small volumes of material was not realized until the development of the electron microprobe.

PERUBAHAN MINDSET MENGAJAR DALAM MENYIAPKAN PENDIDIK YANG PROFESIONAL DALAM PERSAINGAN DI ERA MEA

KEBERLANJUTAN ◽  
2018 ◽  
Vol 3 (2) ◽  
pp. 897
Author(s):  
ROMENAH ROMENAH
Keyword(s):  
Economic Community ◽  
National Education ◽  
Professional Educators ◽  
Free Competition ◽  
National Education System ◽  
Asean Countries ◽  
Asean Economic Community ◽  
The Times ◽  
Agent Of Change

AbstractThe National Education System has grown so rapidly over time. A variety of efforts have been made to build every prosperous, dignified Indonesian human being, so that the quality of Indonesian thinking is progressing. The ASEAN Economic Community which has been launched since 2015 has resulted in free competition, both in trade, employment, and there is free competition for educators in ASEAN countries. Besides that, Indonesian education is faced with challenges and developments in the times, where the culture between ASEAN countries has no limits, this is the challenge faced when implementing the Asean Economic Comunity (ASEAN Economic Community) MEA. Indonesia as a country in the ASEAN region must prepare domestic educators to have professionalism and character so that they can compete with the AEC. Educators must be aware of the essence of the existence of their profession, continue to struggle to make changes in order to realize professionalism with noble character. Efforts made in preparing professional educators to face the challenges of the AEC must touch the most fundamental aspects of changing their competencies, namely the mindset. A student must be more advanced and innovative in developing his learning so that he can change the mindset of students to do agent of change. Through this mindset educators will become professional and characterized so that they can compete and compete in the MEA era. Keywords: MEA, Changes in Mindset, Professional Educators

Tantangan Pondok Pesantren dalam Menghadapi Era Bonus Demografi

2018 ◽  
Vol 10 (2) ◽  
pp. 409-434
Author(s):  
Ibnu Chudzaifah
Keyword(s):  
Human Resources ◽  
Boarding School ◽  
Educational Institutions ◽  
Human Beings ◽  
Current Development ◽  
The Face ◽  
The Times

Pondok Pesantren is one of the Islamic educational institutions that aim to form human beings who have noble character, so that created a human who has a balance between physical and spiritual. Some educational institutions offer various models of learning to balance the current development so that its existence is still recognized by the community. While boarding school in dealing with the development of the times, has a commitment to make new innovations by presenting the pattern of education that can give birth to a reliable Human Resources. Especially pesantren currently has a challenging enough weight in facing the era of "Demographic Bonus". Demographic bonus is a phenomenon in which the structure of the population greatly benefits the community from the side of development in various sectors, because the productive age is more than the non productive age. This means that the dependency burden will decrease with the ratio of 64 percent of the productive age population to bear only 34 percent of the nonproductive age population. With all kinds of scholarships and skills given to students, students are expected to compete in all fields, especially in the face of Indonesia gold in 2020 to 2035.

HUKUM DAN TEKLOGI SUATU KAJIAN TEORITIS TERHADAP PENOMENA LAYANAN TRANSFORTASI ONLINE

2017 ◽  
Vol 6 (1) ◽  
pp. 20
Author(s):  
Aria Dimas Harapan
Keyword(s):  
Economic Growth ◽  
Theoretical Study ◽  
Legal Protection ◽  
Creative Economy ◽  
Legal Certainty ◽  
The People ◽  
The Government ◽  
The Times

ABSTRACTThe essence of this study describes the theoretical study of the phenomenon transfortation services online. Advances in technology have changed the habits of the people to use online transfortation In fact despite legal protection in the service based services transfortation technological sophistication has not been formed and it became warm conversation among jurists. This study uses normative juridical research. This study found that the first, the Government must accommodate transfotation online phenomenon in the form of rules that provide legal certainty; second, transfortation online as part of the demands of the times based on technology; third, transfortation online as part of the creative economy for economic growth . 

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