Mechanical Properties of Polymers in the Range of Their Softening. Elongation Diagrams of Raw and Vulcanized Rubber

1956 ◽  
Vol 29 (3) ◽  
pp. 718-724
Author(s):  
N. A. Yuzefovich ◽  
E. V. Kuvshinskiĭ
Keyword(s):  
Mechanical Properties ◽  
Low Temperatures ◽  
Relative Elongation ◽  
The Other ◽  
Butadiene Rubber ◽  
Vulcanized Rubber ◽  
Before And After ◽  
Temperature Controlled ◽  
The One ◽  
Direct Investigation

Abstract A study of the mechanical properties of polymers through the softening range is interesting for two reasons: on the one hand, it throws light on the process of vitrification, and, on the other, a study of reactions at low temperatures can give at least qualitative indications of the behavior of a material at high temperatures and during rapid dynamic processes, i.e., under conditions where direct investigation involves considerable difficulties in the experimental method. The following substances were studied: unloaded butadiene rubber before and after vulcanization, and vulcanized natural rubber. The temperature range studied was ™100° to 20° C. The elongation diagrams were obtained by means of a mechanism constructed in our laboratory. The specimens were stretched in a temperature-controlled chamber. Variations of temperature below 0° C did not exceed 0.5° C, and above 0° C did not exceed 0.2° C. The deforming force F was measured with a spring ring dynamometer. The opening of the clamps was calibrated with respect to the relative elongation λ. A correction was introduced here for deformation of samples in the clamps. The use of a reducing mechanism made it possible to vary the rate of deformation within the limits v=0.0016 and 0.08 cm. per sec., corresponding to rates of deformation from 0.05 to 2.5 per cent per second.

scholarly journals On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

1925 ◽  
Vol 107 (743) ◽  
pp. 510-543 ◽  
Keyword(s):  
Systematic Error ◽  
Low Temperatures ◽  
Room Temperature ◽  
Expansion Chamber ◽  
Small Vessels ◽  
Specific Heats ◽  
Large Expansion ◽  
Before And After ◽  
The One ◽  
Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

scholarly journals Enzymes for Leather Processing: Effect on Pickling and Chroming

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1480
Author(s):  
Renata Biškauskaitė ◽  
Violeta Valeikienė ◽  
Virgilijus Valeika
Keyword(s):  
Mechanical Properties ◽  
Acidic Medium ◽  
Proteolytic Enzymes ◽  
Relative Elongation ◽  
The Other ◽  
Shrinkage Temperature ◽  
Processing Effect ◽  
Leather Processing ◽  
Production Processes ◽  
Pickling Process

Recently, increasing attention has been paid to the application of enzymes in a wide variety of leather production processes. The aim of the present study was to investigate the action of enzymatic pickling on derma’s collagen and the influence of this action on subsequent processes and properties of chromed and finished leather. The application of active in acidic medium proteolytic enzymes in the pickling process led to an additional impact on derma structure: collagen was more strongly affected and the porosity of the pelt dermis was reduced, but the hide became more thermally stable. The enzymatically pickled pelt bonded more chromium and reached higher shrinkage temperature while chroming; dyes penetrated deeper; such leather bonded more fatliquors. On the other hand, the action of enzymes worsened the physical–mechanical properties of the leather, as the experimental leather was weaker than the conventional one. The first was characterised by weaker grain layer and had significantly higher relative elongation. Therefore, as some properties improve and others worsen during such a process, the application of every enzyme should be carefully investigated and optimized to produce a leather with defined properties.

scholarly journals The principal magnetic susceptibilities of neodymium sulphate octahydrate at low temperatures

1939 ◽  
Vol 170 (941) ◽  
pp. 266-271 ◽  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Energy Levels ◽  
Constant Factor ◽  
The Other ◽  
Crystalline Field ◽  
Cubic Symmetry ◽  
The Subject ◽  
The Difference ◽  
The One

The magnetic and other related properties of neodymium sulphate have been the subject of numerous investigations in recent years, but there is still a remarkable conflict of evidence on all the essential points. The two available determinations of the susceptibility of the powdered salt at low temperatures, those of Gorter and de Haas (1931) from 290 to 14° K and of Selwood (1933) from 343 to 83° K both fit the expression X ( T + 45) = constant over the range of temperature common to both, but the constants are not the same and the susceptibilities at room temperature differ by 11%. The fact that the two sets of results can be converted the one into the other by multiplying throughout by a constant factor suggested that the difference in the observed susceptibilities was due to some error of calibration. It could, however, also be due to the different purity of the samples examined though the explanation of the occurrence of the constant factor is then by no means obvious. From their analysis of the absorption spectrum of crystals of neodymium sulphate octahydrate Spedding and others (1937) conclude that the crystalline field around the Nd+++ ion is predominantly cubic in character since they find three energy levels at 0, 77 and 260 cm. -1 .* Calculations of the susceptibility from these levels reproduce Selwood’s value at room temperature but give no agreement with the observations-at other temperatures. On the other hand, Penney and Schlapp (1932) have shown that Gorter and de Haas’s results fit well on the curve calculated for a crystalline field of cubic symmetry and such a strength that the resultant three levels lie at 0, 238 and 834 cm. -1 , an overall spacing almost three times as great as Spedding’s.

Ozonation of bromide-containing drinking waters:a delicate balance between disinfection and bromate formation

2000 ◽  
Vol 41 (7) ◽  
pp. 53-59 ◽  
Author(s):  
U. von Gunten ◽  
U. Pinkernell
Keyword(s):  
Temperature Dependence ◽  
Low Temperatures ◽  
The Other ◽  
Ozone Exposure ◽  
Oh Radicals ◽  
Strong Temperature Dependence ◽  
Control Options ◽  
The One ◽  
Kinetics Of ◽  
Ozonation Process

The occurrence of Cryptosporidium in raw waters and bromate formation during ozonation of bromide-containing waters leads to a difficult optimisation of ozonation processes. On the one hand inactivation of Cryptosporidium requires high ozone exposures, on the other hand under these conditions bromate formation is favored. In order to overcome this problem we need information about (i) the oxidant concentrations (ozone and OH radicals) during an ozonation process, (ii) kinetics of the inactivation of Cryptosporidium, (iii) kinetics and mechanism of bromate formation, and (iv) the reactor hydraulics. The strong temperature dependence of the inactivation of Cryptosporidium which results in a higher ozone exposure (time-integrated action of ozone) at low temperatures makes it more difficult to fulfil disinfection and bromate standards at low temperatures. Underthese conditions control options for bromate formation can be applied. Depressionof pH and addition of ammonia have been selected to be the best options. For a given ozone exposure both measures lead to a reduction of bromate formation in the order of 50%.

Study on Flexible Fatigue Properties of Nature Rubber with Different Styrene-Butadiene Rubber

2016 ◽  
Vol 717 ◽  
pp. 57-61
Author(s):  
Wei Liu ◽  
Zhong Cun Bao ◽  
Cheng Zhong Zong
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Service Life ◽  
Special Structure ◽  
Fatigue Properties ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Vulcanized Rubber ◽  
Different Types ◽  
Styrene Butadiene

Flexible fatigue properties is an important property of rubber, it can reflect the service life of rubber products. Different types of SSBR were used in the vulcanized rubber with NR contributed different to the flexible fatigue properties. In this paper, 5 different types of SSBR with special structure were used to study the mechanical properties, thermal properties and the flexible fatigue properties. In a result, with different types SSBR, the vulcanized rubber show different basic mechanical properties and flexible fatigue properties, but little effect to the hardness and stretching stress. Above all these SSBR, RC2564S is the best which contribute to flexible fatigue properties.

Dependence of stress-optical coefficients on the mechanical and optical properties of polymers

1973 ◽  
Vol 8 (4) ◽  
pp. 267-276 ◽  
Author(s):  
P S Theocaris
Keyword(s):  
Mechanical Properties ◽  
Refractive Index ◽  
Optical Properties ◽  
Internal Structure ◽  
The Other ◽  
Linear Region ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Behaviour ◽  
The One

The internal structure of the stress-optical coefficients, as they are related to various direct interferometric methods, has been analysed and the nature of their components studied. It is shown that the stress-optical coefficients are composed of two parts. The one part depends on the variation of the mechanical properties; the other is related to the variation of the refractive index of the polymer. The influence of the mechanical properties is considerable and comparable to the influence of the optical properties. The study of the mechanical and optical contributions to the values of the stress-optical coefficients included not only the linear, but also the non-linear viscoelastic behaviour of the polymers. It is concluded that the corresponding limits of linearity of these coefficients do not coincide. Furthermore, the influence of the mechanical properties on the stress-optical coefficients is increasing relatively to the influence of the optical properties in the non-linear region.

A Novel Method to Recycle Scrap Tires: High-Pressure High-Temperature Sintering

2002 ◽  
Vol 75 (5) ◽  
pp. 955-968 ◽  
Author(s):  
Jeremy E. Morin ◽  
Drew E. Williams ◽  
Richard J. Farris
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
High Temperature ◽  
Rubber Particle ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Scrap Tires ◽  
Vulcanized Rubber ◽  
High Pressure High Temperature ◽  
Styrene Butadiene

Abstract High-pressure high-temperature sintering (HPHTS) is a novel recycling technique that makes it possible to recycle vulcanized rubber powders made from waste rubber (namely scrap tires) through only the application of heat and pressure. A brief look into the mechanism of sintering will be presented along with information about the influence of molding variables, such as time, temperature, pressure and rubber particle size on the mechanical properties of the produced parts. One of the most interesting observations is that powders of every crosslinked elastomer attempted sintered together via this technique, including silicone rubber (SI), sulfur cured [natural rubber (NR), ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR)], peroxide cured butadiene rubber (BR), and fluoroelastomers (FKM). Early work on sintered rubber made from commercially available rubber powder had a modulus of 1 to 2 MPa, strength of 4 to 7 MPa and an elongation at break of 150–250%. Recently, in-house ground samples of SBR have had sintered values over 9.5 MPa strength and 275% elongation, or greater than 60% retention of the original properties. Many of these mechanical properties are comparable with industrially manufactured rubbers, and it is believed that recycled rubbers produced via HPHTS offer the potential to replace virgin rubber in numerous applications.

scholarly journals Effects of Dyeing Process on the Change in Color, Microstructural Characteristics and Physico-Mechanical Properties of Hoa Ca Crocodile Skin 

2021 ◽  
Vol 31 (1) ◽  
pp. 91-97
Keyword(s):  
Mechanical Properties ◽  
The Other ◽  
Microstructural Characteristics ◽  
Commercial Products ◽  
Unique Structure ◽  
Dyeing Process ◽  
Before And After ◽  
Surface Patterns ◽  
Finishing Processes ◽  
Different Parts

In recent years, the crocodile has been farmed and produced many commercial products, especially in the South of Vietnam. Crocodile skin is one of the highest value skins to compare to other types due to its unique structure and texture in different parts of the skin. Crocodile skin has often been tanned to prevent putrefaction, then dyed and finished to improve the practicability of leather products. In this study, the authors have assessed the change in color, surface patterns, microstructures and physico-mechanical properties of the different parts of the 2 years old Hoa Ca crocodile skin before and after dyeing and finishing processes. This paper could be a valuable scientific document on the dyeing and finishing of crocodile leather for the other leather making workshops applying to the crocodile leather production.

scholarly journals Code-switching as appraisal resource in talking about third parties

2012 ◽  
Vol 51 (1) ◽  
Author(s):  
Nicole Baumgarten ◽  
Inke Du Bois
Keyword(s):  
Third Parties ◽  
Code Switching ◽  
The Other ◽  
German Immigrants ◽  
The Us ◽  
Before And After ◽  
Group Interviews ◽  
The One ◽  
Migration Experiences ◽  
Individual Speaker

This article explores the function of code-switching in talking about absent third parties. The basis for the investigation is a corpus of sociolinguistic individual and group interviews with German immigrants in the US and American immigrants in Germany. In these interviews, the interviewees are asked to recount their migration experiences and their lives before and after migration. For each individual speaker, the interviewer and – in the group interviews – the other participants in the group are, on the one hand, potentially 'sympathetic' fellow migrants. On the other hand, however, they are potentially problematic figures, because talking about absent third parties means that these third parties might share characteristics with the interviewer or the others in the group. Talking about third parties can, thus, be face-threatening for both the interviewer and the interviewees. In the analyses presented in this article, we identify how speakers employ English-to-German code-switching when it comes to verbalizing others – specifically members of home and host cultures – in discourse and how they position themselves and their audience in relation to them.

scholarly journals Graphite Modified Polylactide (PLA) for 3D Printed (FDM/FFF) Sliding Elements

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1250 ◽  
Author(s):  
Robert E. Przekop ◽  
Maciej Kujawa ◽  
Wojciech Pawlak ◽  
Marta Dobrosielska ◽  
Bogna Sztorch ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Stress ◽  
Low Cost ◽  
Chemical Properties ◽  
Spare Parts ◽  
The Other ◽  
Graphite Content ◽  
Before And After ◽  
3D Printed ◽  
And Chemical Properties

With the development of 3D printing technology, there is a need to produce printable materials with improved properties, e.g., sliding properties. In this paper, the authors present the possibilities of producing composites based on biodegradable PLA with the addition of graphite. The team created composites with the following graphite weight contents: 1%, 2.5%, 5%, 7.5%, and 10%. Neat material was also subjected to testing. Tribological, mechanical, and chemical properties of the mentioned materials were examined. Measurements were also made after keeping the samples in ageing and climatic ovens. Furthermore, SEM observations of samples before and after friction tests were carried out. It was demonstrated that increasing graphite content caused a significant decrease in wear (PLA + 10% graphite had a wear rate three times lower than for a neat material). The addition of graphite did not adversely affect most of the other properties, but it ought to be noted that mechanical properties changed significantly. After conditioning in a climatic oven PLA + 10% graphite has (in comparison with neat material) 11% lower fracture stress, 47% lower impact strength, and 21% higher Young’s modulus. It can be certainly stated that the addition of graphite to PLA is a step towards obtaining a material that is low-cost and suitable for printing sliding spare parts.

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