Crystallization and the Relaxation of Stress in Stretched Unvulcanized Natural Rubber

1956 ◽  
Vol 29 (4) ◽  
pp. 1195-1198
Author(s):  
A. V. Tobolsky ◽  
G. M. Brown
Keyword(s):  
Natural Rubber ◽  
Temperature Region ◽  
Effect Of Temperature ◽  
Careful Study ◽  
Rubber Vulcanizate ◽  
Crystallization Region ◽  
Different Temperatures ◽  
Made In

Abstract The first observation made in this laboratory in 1946 on the effect of crystallization on stress decay at constant extension was made on a vulcanized Neoprene GN gum stock. It was found that this rubber showed only slight stress decay after 100 hours at 35° C and 50 per cent extension. However, a complete decay of stress to zero stress was observed after only 50 hours at 0° C and 50 per cent extension. Furthermore, the sample after reaching zero stress began to increase in length (spontaneous elongation). This phenomenon was attributed to crystallization. Observations of spontaneous elongation, but no stress decay measurements, were previously reported for vulcanized and unvulcanized natural rubber and for vulcanized and unvulcanized ether polysulfide rubber. It was decided to make a careful study of the effect of temperature and elongation on the stress-decay curves of unvulcanized rubber (cast latex sheet) in the temperature region of crystallization. Some time after these studies were completed, two papers have appeared in which stress decay to zero stress in rubber vulcanizates due to crystallization were reported. In one of these a rather thorough study was made of the decay of stress and change in volume of a natural rubber vulcanizate at −26° C and maintained at four different extension ratios. Our own work on unvulcanized natural rubber was carried out at seven different temperatures in the crystallization region, and were made at five different extension ratios. Quite surprisingly, four of these are the same as were used by Gent. There are interesting differences as well as similarities between our work and the results reported for vulcanized natural rubber.

The Attack of Ozone on Stretched Rubber Vulcanizates. II. Conditions for Cut Growth

1960 ◽  
Vol 33 (4) ◽  
pp. 1156-1165
Author(s):  
M. Braden ◽  
A. N. Gent
Keyword(s):  
Experimental Study ◽  
Tensile Stress ◽  
Natural Rubber ◽  
Critical Value ◽  
Rubber Sheet ◽  
Test Pieces ◽  
Rubber Vulcanizate ◽  
Present Part ◽  
Applied Tensile Stress ◽  
Made In

Abstract In Part I an experimental study was reported of the factors determining the rate of propagation of a cut through a stretched rubber sheet under the action of an atmosphere containing ozone. It was remarked that no growth took place from a small razor cut made in one edge of the test pieces unless a critical value of the applied tensile stress was exceeded. The value was quite small, of the order of 100 g/cm2 for a soft natural rubber vulcanizate. In the present part an examination is reported of the conditions necessary for a crack to form or, being present, to grow.

scholarly journals Aging of Natural Rubber in Air and Seawater

2001 ◽  
Vol 74 (1) ◽  
pp. 79-88 ◽  
Author(s):  
P. H. Mott ◽  
C. M. Roland
Keyword(s):  
Natural Rubber ◽  
Oxygen Concentration ◽  
Failure Strain ◽  
Accelerated Aging ◽  
Activation Energies ◽  
Effect Of Temperature ◽  
Arrhenius Law ◽  
Fatigue Lifetime ◽  
Rubber Vulcanizate ◽  
The Difference

Abstract Accelerated aging experiments were carried out on a natural rubber vulcanizate exposed to air and to seawater. Failure strain, shown to correlate well with the fatigue lifetime, was used to monitor the extent of degradation. The effect of temperature on the rate of aging followed an Arrhenius law, with activation energies equal to 90 ± 4 and 63 ± 3 kJ/mol for air and seawater aging, respectively. The difference can be accounted for by the difference in oxygen concentration for the two environments.

Influence of temperature on microbial colonisation of clayey schist as a support media of a submerged filter for groundwater denitrification

2007 ◽  
Vol 55 (8-9) ◽  
pp. 165-172 ◽  
Author(s):  
A. De la Rúa ◽  
B. Rodelas ◽  
J. González-López ◽  
M.A. Gómez
Keyword(s):  
Biofilm Formation ◽  
Effect Of Temperature ◽  
Cold Environments ◽  
Pseudomonas Mandelii ◽  
Different Temperatures ◽  
Influence Of Temperature On ◽  
Denitrification Activity ◽  
Natural Microbiota ◽  
Denitrification Process ◽  
Made In

The effect of temperature on biofilm formation and denitrification activity was evaluated. Assays were made in a lab-scale submerged filter for the denitrification of polluted groundwater, with and without a previous inoculation. The inoculation was carried out with a selected strain of Pseudomonas mandelii. Different temperatures were tested: 5, 10, 20 and 30 °C. Biofilm observations were made, and monitoring of the denitrification capacity of the system was maintained during the experiment. Our results showed that both colonisation of the support material of the filter and biofilm maturity have a dependency with temperature, with an optimum temperature of 20 °C if the system was previously inoculated with the Pseudomonas mandelii strain. For a correct achievement of the denitrification process, a previous inoculation of the system is essential. Although the development of a biofilm from the natural microbiota present in the groundwater is possible, it is not capable to adequately denitrify polluted groundwater. In terms of the correct achievement of the denitrification process, temperature affects the operation of the system at cold environments, although the use of Pseudomonas mandelii strain A103 allows denitrification at 10–30 °C with very good results (above 90% removal), affecting only to the time needed for the stabilisation of the system.

scholarly journals Temperature Dependency of Wing-Beat Frequency in Intact and Deafferented Locusts

1992 ◽  
Vol 162 (1) ◽  
pp. 295-312
Author(s):  
JANE A. FOSTER ◽  
R. MELDRUM ROBERTSON
Keyword(s):  
Ambient Temperature ◽  
Locusta Migratoria ◽  
Beat Frequency ◽  
Effect Of Temperature ◽  
Wing Beat ◽  
Neural Basis ◽  
Wing Beat Frequency ◽  
Thoracic Temperature ◽  
Different Temperatures ◽  
Made In

Locusts do not regulate thoracic temperature during flight and as a result the thoracic temperature of a flying locust generally exceeds ambient temperature by 5–8 °C. Elevated thoracic temperatures were shown to affect wing-beat frequency in intact and deafferented Locusta migratoria. Tethered locusts were flown in a wind tunnel. Temperature was elevated by increasing the ambient temperature of the apparatus and by exposing flying animals to heat pulses. Electromyographic (EMG) recordings were made in deafferented locusts perfused with salines at different temperatures. Wing-beat frequency was shown to vary with thoracic temperature in both the intact and the deafferented situation. The slope of the rise in wing-beat frequency with experimental increases in thoracic temperature was similar in intact and deafferented animals. These experiments demonstrate an effect of temperature on the central flight circuitry. Further intracellular investigationsare needed to determine the neural basis of these effects.

scholarly journals The Respiration of some Planktonic copepods II. The Effect Of Temperature

1953 ◽  
Vol 31 (3) ◽  
pp. 447-460 ◽  
Author(s):  
D. T. Gauld ◽  
J. E. G. Raymont
Keyword(s):  
Respiratory Rate ◽  
The Body ◽  
The Other ◽  
Effect Of Temperature ◽  
Acartia Clausi ◽  
Temora Longicornis ◽  
Different Temperatures ◽  
Planktonic Copepods ◽  
The Difference ◽  
The Relationship

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.The application of these measurements to estimates of the food requirements of the copepods is discussed.

scholarly journals Effect of temperature, CO2 and O2 on motility and mobility of Anisakidae larvae

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aiyan Guan ◽  
Inge Van Damme ◽  
Frank Devlieghere ◽  
Sarah Gabriël
Keyword(s):  
Enzymatic Digestion ◽  
Infected Fish ◽  
Effect Of Temperature ◽  
Video Recordings ◽  
Different Temperatures ◽  
Semi Solid ◽  
Zoonotic Parasites ◽  
The Impact ◽  
Phosphate Buffered Saline

AbstractAnisakidae, marine nematodes, are underrecognized fish-borne zoonotic parasites. Studies on factors that could trigger parasites to actively migrate out of the fish are very limited. The objective of this study was to assess the impact of different environmental conditions (temperature, CO2 and O2) on larval motility (in situ movement) and mobility (migration) in vitro. Larvae were collected by candling or enzymatic digestion from infected fish, identified morphologically and confirmed molecularly. Individual larvae were transferred to a semi-solid Phosphate Buffered Saline agar, and subjected to different temperatures (6 ℃, 12 ℃, 22 ℃, 37 ℃) at air conditions. Moreover, different combinations of CO2 and O2 with N2 as filler were tested, at both 6 °C and 12 °C. Video recordings of larvae were translated into scores for larval motility and mobility. Results showed that temperature had significant influence on larval movements, with the highest motility and mobility observed at 22 ℃ for Anisakis spp. larvae and 37 ℃ for Pseudoterranova spp. larvae. During the first 10 min, the median migration of Anisakis spp. larvae was 10 cm at 22 ℃, and the median migration of Pseudoterranova spp. larvae was 3 cm at 37 ℃. Larval mobility was not significantly different under the different CO2 or O2 conditions at 6 °C and 12 ℃. It was concluded that temperature significantly facilitated larval movement with the optimum temperature being different for Anisakis spp. and Pseudoterranova spp., while CO2 and O2 did not on the short term. This should be further validated in parasite-infected/spiked fish fillets.

scholarly journals Effect of Temperature during Drying and Storage of Dried Figs on Growth, Gene Expression and Aflatoxin Production

Toxins ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 134
Author(s):  
Ana Isabel Galván ◽  
Alicia Rodríguez ◽  
Alberto Martín ◽  
Manuel Joaquín Serradilla ◽  
Ana Martínez-Dorado ◽  
...  
Keyword(s):  
Gene Expression ◽  
Aflatoxin Production ◽  
Effect Of Temperature ◽  
Mycotoxin Production ◽  
Industrial Processing ◽  
Factors Associated ◽  
Different Temperatures ◽  
Major Producer ◽  
Main Factors ◽  
And Storage

Dried fig is susceptible to infection by Aspergillus flavus, the major producer of the carcinogenic mycotoxins. This fruit may be contaminated by the fungus throughout the entire chain production, especially during natural sun-drying, post-harvest, industrial processing, storage, and fruit retailing. Correct management of such critical stages is necessary to prevent mould growth and mycotoxin accumulation, with temperature being one of the main factors associated with these problems. The effect of different temperatures (5, 16, 25, 30, and 37 °C) related to dried-fig processing on growth, one of the regulatory genes of aflatoxin pathway (aflR) and mycotoxin production by A. flavus, was assessed. Firstly, growth and aflatoxin production of 11 A. flavus strains were checked before selecting two strains (M30 and M144) for in-depth studies. Findings showed that there were enormous differences in aflatoxin amounts and related-gene expression between the two selected strains. Based on the results, mild temperatures, and changes in temperature during drying and storage of dried figs should be avoided. Drying should be conducted at temperatures >30 °C and close to 37 °C, while industry processing, storage, and retailing of dried figs are advisable to perform at refrigeration temperatures (<10 °C) to avoid mycotoxin production.

Mechanochemical devulcanization of natural rubber vulcanizate by dual function disulfide chemicals

2016 ◽  
Vol 129 ◽  
pp. 34-46 ◽  
Author(s):  
Soumyajit Ghorai ◽  
Satyaban Bhunia ◽  
Madhusudan Roy ◽  
Debapriya De
Keyword(s):  
Natural Rubber ◽  
Dual Function ◽  
Rubber Vulcanizate

scholarly journals Corrosion Behaviour of 316L Stainless Steel in CNTs–Water Nanofluid: Effect of Temperature

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 119
Author(s):  
Dana H. Abdeen ◽  
Muataz A. Atieh ◽  
Belabbes Merzougui
Keyword(s):  
Stainless Steel ◽  
316L Stainless Steel ◽  
Corrosion Behaviour ◽  
Gum Arabic ◽  
Steel Sample ◽  
Open Circuit ◽  
Deionized Water ◽  
Effect Of Temperature ◽  
Different Temperatures ◽  
In Series

The inhibition behavior of carbon nanotubes (CNTs) and Gum Arabic (GA) on the corrosion of 316L stainless steel in CNTs–water nanofluid under the effect of different temperatures was investigated by electrochemical methods and surface analysis techniques. Thereby, 316L stainless steel samples were exposed to CNTs–water nanofluid under temperatures of 22, 40, 60 and 80 °C. Two concentrations of the CNTs (0.1 and 1.0 wt.% CNTs) were homogenously dispersed in deionized water using the surfactant GA and tested using three corrosion tests conducted in series: open circuit test, polarization resistance test, and potentiodynamic scans. These tests were also conducted on the same steel but in solutions of GA-deionized water only. Tests revealed that corrosion increases with temperature and concentration of the CNTs–water nanofluids, having the highest corrosion rate of 32.66 milli-mpy (milli-mil per year) for the 1.0 wt.% CNT nanofluid at 80 °C. In addition, SEM observations showed pits formation around areas of accumulated CNTs that added extra roughness to the steel sample. The activation energy analysis and optical surface observations have revealed that CNTs can desorb at higher temperatures, which makes the surface more vulnerable to corrosion attack.

Effect of temperature on composite films made with activated carbon, graphite, or graphene oxide (GO) in a gelatin matrix

BioResources ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 77-95
Author(s):  
Siqiao Yang ◽  
Haichao Li
Keyword(s):  
Contact Angle ◽  
Activated Carbon ◽  
Water Absorption ◽  
Composite Films ◽  
Effect Of Temperature ◽  
Gelatin Matrix ◽  
Vapour Permeability ◽  
Blending Method ◽  
The Matrix ◽  
Different Temperatures

Activated carbon, graphite, and GO/gelatin composite films were prepared by the blending method. The properties of composites were characterized by tensile strength (TS), elongation at break (EB), water vapour permeability (WVP), water-absorption ability, contact angle, scanning electron microscopy (SEM), and moisture at different temperatures. The properties of GO/gelatin composite films were better when each of three kinds of carbon materials were used as reinforcement phases and added into the matrix gelatin. The results showed that EB and TS of GO/gelatin composite films were both excellent. The moisture of GO/gelatin composite films was greater than the others. SEM micrographs showed that GO had better compatibility and dispersibility with gelatin than activated carbon and graphite. The water absorption of GO/gelatin composite films were low, at 15 °C and 25 °C, and the WVP was low at 35 °C. The WVP of GO/gelatin composite films was lower than the others at different temperatures. The contact angle of GO/gelatin composite films was larger than the others.

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