Simultaneous Measurements of Stress and Infrared Dichroism on Polymers I. Stress Relaxation of Vulcanized Natural Rubber

1967 ◽  
Vol 40 (2) ◽  
pp. 663-672
Author(s):  
Rempei Gotoh ◽  
Tohru Takenaka ◽  
Naomi Hayama
Keyword(s):  
Stress Relaxation ◽  
Absorption Band ◽  
Natural Rubber ◽  
Reference Beam ◽  
Simple Relationship ◽  
Absorption Bands ◽  
Simultaneous Measurements ◽  
Double Beam ◽  
The Difference ◽  
Infrared Dichroism

Abstract A method for simultaneous measurements of stress and infrared dichroism as time-dependent behavior of polymer films was devised using a double beam infrared spectrometer. The film sample held between clamps of a stretching device was placed just in front of the entrance slit of the spectrometer where the sample and reference beams came alternately. Two polarizers were used, one in the sample beam and the other in the reference beam. Thus the sample and reference beams were polarized to have the electric vectors parallel and perpendicular to the stretching direction of the sample, respectively. With this arrangement the spectrometer responded only to the difference in the transmittance of the two beams. Setting the spectrometer at one of the wavenumbers of the absorption band maxima, we could record continuously the change in its dichroism during mechanical treatments which gave rise to molecular orientation in the sample. The stress was recorded automatically by means of a pair of strain gauges pasted on the cantilever beam of the stretching device. By theoretical considerations, a simple relationship was found to exist between the quantity recorded on the spectrometer by this method and the orientation function of transition moment of a vibrational absorption band with respect to the stretching direction. The method was applied to the stress relaxation experiments of vulcanized natural rubber carried out at different elongations less than 600 per cent and at room temperature. Changes of infrared dichroism were measured for five absorption bands at 1664, 1380, 1361, 1129, and 844 cm−1, of which the last one is a crystalline band. From the results of this study, the stress relaxation observed was ascribed mainly to the amorphous orientation rather than to the crystalline orientation, which was completed almost immediately after elongation.

The Determination of Network Chain Density and the Chemical Stress Relaxation of Crosslinked Polymers

1973 ◽  
Vol 46 (2) ◽  
pp. 477-482
Author(s):  
Saburo Tamura ◽  
Kenkichi Murakami
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Main Chain ◽  
Chemical Stress ◽  
Dicumyl Peroxide ◽  
Constant Independent ◽  
Crosslinked Polymers ◽  
Network Chain ◽  
The Difference ◽  
Entanglement Network

Abstract Both initial network chain densities nM(0) and nS(0) of dicumyl peroxide- cured natural rubbers were determined from the tensile stress and swelling method, respectively. The difference between nM(0) and nS(0) was usually constant, independent of the magnitude of network chain density. That is, it was found that the number of entanglement network chains in the crosslinked natural rubber was usually constant, independent of network chain density. The entanglement network chain density nII(0) was 0.7×10−4 mole/cc. This led to the supposition that the molecular weight between entanglement points Me would be about 9000. Although this value is far from exact, it does not differ too greatly from the value found for noncrosslinked natural rubber. Next, in order to calculate the number of main-chain scissions of crosslinked polymers from their chemical stress relaxation, we proposed our modification of Tobolsky's equation. Using our equation, it was found that the scission of dicumyl peroxide-cured natural rubber occurred in the main chain only. Furthermore, this value agreed with the one obtained from the oxidation of toluene solution of noncrosslinked rubber under the same conditions.

Thermomechanical Effects Associated With Crystallization of Rubber Under Stretch and During Slow Extension

1997 ◽  
Vol 119 (3) ◽  
pp. 298-304 ◽  
Author(s):  
Mehrdad Negahban
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Thermodynamic Model ◽  
The Other ◽  
Equilibrium Stress ◽  
Rubber Sample ◽  
Other Hand ◽  
The Difference ◽  
Thermomechanical Effects

A natural rubber sample which crystallizes after stretching normally shows stress relaxation associated with this crystallization and normally ends up at a stress lower than that of the fully amorphous rubber before crystallization. On the other hand, a natural rubber sample which crystallizes during stretching becomes more rigid as a result of the crystallization and the stress required to extend it to a given stretch increases substantially above the stress needed to extend the fully amorphous rubber to the same elongation. Even though the former effect has been modeled and studied by the likes of Flory (1947), the latter effect has not yet been properly modeled or studied. The difference between crystallization during or after stretching will be studied in this article based on a thermodynamic model developed by the author to capture the thermomechanical effects of crystallization in natural rubber. The two limit cases of very rapid and very slow extension to a given stretch are singled out for comparison of the equilibrium stress.

Frequency dependence of the Kerr constant

1962 ◽  
Vol 267 (1329) ◽  
pp. 271-282 ◽  
Keyword(s):  
Frequency Dependence ◽  
Excited States ◽  
Strong Electric Field ◽  
Dipole Moments ◽  
Rate Of Change ◽  
Kerr Constant ◽  
Absorption Bands ◽  
Double Beam ◽  
Solutions Of Electrolytes ◽  
The Difference

The theory of the Kerr effect is developed for wavelengths close to those corresponding to absorption bands. Unlike the transparent regions, where orientation of anisotropic molecules is the major contributor to the Kerr constant, in absorption bands distortion of the molecular structure by the strong electric field is apparently the dominant effect. For molecules with dipole moments in either the ground or the relevant excited states, the sign of the rate of change of the Kerr constant with frequency is determined by the direction of the transition moment with respect to molecular axes, and its magnitude is proportional to the square of the difference between the dipole moments of the ground and excited states. Anomalous dispersion should also occur at frequencies corresponding to forbidden transitions from the ground state, provided there is a third state with dipole transition moments with the ground and excited states. The quantum theory of the Kerr constant of gases is developed and applied to the vibration-rotation spectral region of diatomic and symmetric top molecules. A brief discussion of the potentialities of the effect is presented; since orientation is unimportant, aqueous solutions of electrolytes could presumably be studied after freezing to reduce their conductivity. An experimental method of measuring the frequency dependence of the Kerr constant, using a double beam spectrometer, is proposed.

Excimer Laser Induced 5.8 eV Absorption and 1.9 eV Emission Bands in Fused Silicas

1991 ◽  
Vol 244 ◽  
Author(s):  
Nobu Kuzuu ◽  
Yasutaka Matsumoto ◽  
Masataka Murahara
Keyword(s):  
Absorption Band ◽  
Excimer Laser ◽  
Fused Silica ◽  
Absorption Bands ◽  
Type Iii ◽  
Arf Excimer Laser ◽  
The Creation ◽  
The Difference ◽  
Order Structures ◽  
Reducing Condition

ABSTRACTCharacteristics of ArF excimer laser induced 1.9 eV emission and 5.8 eV absorption bands in type III and soot remelted silicas were investigated. In a type III silica synthesized in a reducing condition, an absorption band at 5.8 eV band is induced. The creation of this band can be prevented by annealing in an atmosphere of He. In the soot remelted silicas with and without OH, the creation of the 5.8 eV band is strongly promoted by annealing in H2. An emission band at 1.9 eV is induced in a type III fused silica synthesized in an oxydizing condition and soot remelted silica containing OH. When annealing in He, creation of the 1.9 eV band is strongly promoted in the former but suppressed in the latter sample. This difference is derived from the difference of higher order structures between the type III and the soot remelted silicas.

Crosslink Formation during Aging of Natural Rubber Vulcanizates

1965 ◽  
Vol 38 (2) ◽  
pp. 374-378
Author(s):  
L. J. Maisey ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Cross Linking ◽  
Crosslinking Reaction ◽  
Oxidative Reactions ◽  
Relaxation Measurements ◽  
Equilibrium Swelling ◽  
Form Part ◽  
The Difference ◽  
Natural Rubber Vulcanizates

Abstract The effect of antioxidant on the crosslinking reaction occurring during the oxidation of sulphur vulcanizates of natural rubber was investigated by using both continuous and intermittent stress relaxation measurements. Similarly, by means of continuous stress relaxation and equilibrium swelling measurements the cross-linking reaction in vacuum was followed. The presence of antioxidant or removal of air reduced considerably both continuous and intermittent relaxation and also the difference between them, which measures the crosslinking. The crosslink formation must therefore form part of the sequence of oxidative reactions.

Double Beam Spectrophotometer for Simultaneous Measurements of the Upwelling Sea Radiance and the Incident See Irradiance

2019 ◽  
pp. 105-110
Author(s):  
Mikhail Yongon Lee ◽  
Sergei V. Fedorov
Keyword(s):  
Spectral Characteristics ◽  
Sea Surface ◽  
Input Port ◽  
Silicon Photodiode ◽  
New Approach ◽  
Surface Irradiance ◽  
Simultaneous Measurements ◽  
Double Beam

The article describes the structure and the operation principle of the spectrophotometer developed on the basis of a compact rapid monochromator with one input port and two output ports and a radiometric unit where upwelling radiation radiance and sea surface irradiance channels are located. A new approach to measurements of spectral characteristics of upwelling radiation of sea based on combination of advantages of a double beam photometer with a photomultiplier and a directreading photometer with a highstability silicon photodiode for its absolute adjustment in energy units is implemented.

First Nano-Infrared Spectroscopy and Imaging Measurements of Single Phospholipid Bilayers

2018 ◽  
Author(s):  
Adrian Cernescu ◽  
Michał Szuwarzyński ◽  
Urszula Kwolek ◽  
Karol Wolski ◽  
Paweł Wydro ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Ir Spectroscopy ◽  
Absorption Band ◽  
Spectral Region ◽  
Near Field ◽  
Phospholipid Bilayers ◽  
Model Systems ◽  
Absorption Bands ◽  
Protein Complement ◽  
20 Nm

<div><div>Scattering-mode Scanning Near-Field Optical Microscopy (sSNOM) allows one to obtain absorption spectra in the mid-IR region for samples as small as 20 nm in size. This configuration has made it possible to measure FTIR spectra of the protein complement of membranes. (Amenabar 2013) We now show that mid-IR sSNOM has the sensitivity required to measure spectra of phospholipids in individual bilayers in the spectral range 800 cm<sup>-1</sup>–1400 cm<sup>-1</sup>. We have observed the main absorption bands of the dipalmitoylphosphatidylcholine headgroups in this spectral region above noise level. We have also mapped the phosphate absorption band at 1070 cm<sup>-1</sup> simultaneously with the AFM topography. We have shown that we could achieve sufficient contrast to discriminate between single and multiple phospholipid bilayers and other structures, such as liposomes. This work opens the way to further research that uses nano-IR spectroscopy to describe the biochemistry of cell membranes and model systems.</div></div><div></div>

Effects of accelerator type on stress relaxation behavior and network structure of aged natural rubber/chloroprene rubber vulcanizates

2016 ◽  
Vol 49 (5) ◽  
pp. 381-396 ◽  
Author(s):  
Farzad A Nobari Azar ◽  
Murat Şen
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Network Structure ◽  
Structural Changes ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Rubber Blends ◽  
Chloroprene Rubber ◽  
Weather Changes ◽  
Behavior Network

Natural rubber/chloroprene rubber (NR/CR) blends are among the commonly used rubber blends in industry and continuously are exposed to severe weather changes. To investigate the effects of accelerator type on the network structure and stress relaxation of unaged and aged NR/CE vulcanizates, tetramethyl thiuram disulfide, 2-mercaptobenzothiazole, and diphenyl guanidine accelerators have been chosen to represent fast, moderate, and slow accelerator groups, respectively. Three batches have been prepared with exactly the same components and mixing conditions differing only in accelerator type. Temperatures scanning stress relaxation and pulse nuclear magnetic resonance techniques have been used to reveal the structural changes of differently accelerated rubber blends before and after weathering. Nonoxidative thermal decomposition analyses have been carried out using a thermogravimetric analyzer. Results indicate that there is a strong interdependence between accelerator type and stress relaxation behavior, network structure, cross-linking density, and aging behavior of the blends. Accelerator type also affects decomposition energy of the blends.

Aging of Natural Rubber Vulcanizates in the Presence of Dithiocarbamates

1959 ◽  
Vol 32 (3) ◽  
pp. 739-747 ◽  
Author(s):  
J. R. Dunn ◽  
J. Scanlan
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Protective Action ◽  
Dicumyl Peroxide ◽  
Vulcanized Rubber ◽  
Aging Properties ◽  
Photochemical Aging ◽  
Natural Rubber Vulcanizates

Abstract The thermal and photochemical aging of extracted dicumyl peroxide-, TMTD (sulfurless)- and santocure-vulcanized rubber, in presence of a number of metal and alkylammonium dithiocarbamates, has been investigated by measurements of stress relaxation. The dithiocarbamates have a considerable protective action upon the degradation of peroxide- and TMTD-vulcanizates, but they accelerate stress decay in santocure-accelerated vulcanizates. The reasons for this behavior are discussed. It is suggested that the excellent aging properties of unextracted TMTD vulcanizates are due to the presence of zinc dimethyldithiocarbamate formed during vulcanization.

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