History of Rubber Research

2000 ◽  
Vol 73 (3) ◽  
pp. 405-426 ◽  
Author(s):  
Herbert Morawetz
Keyword(s):  
Elemental Composition ◽  
Chemical Structure ◽  
Biosynthetic Pathway ◽  
Low Molecular Weight ◽  
Covalent Bonds ◽  
Chain Molecules ◽  
X Ray ◽  
Covalently Bonded ◽  
History Of

Abstract After the discovery of the tapping of Hevea rubber trees in the middle of the eighteenth century and early technological applications of Hevea rubber, efforts to discover the chemical nature of rubber started with the determination of its elemental composition in 1826. Later it was shown that rubber pyrolysis yields low molecular weight chemicals with the identical elemental composition. It was long believed that these add to each other by “secondary valence bonds.” However Staudinger's work starting in 1920 proved that Hevea (H.) rubber consists of chains linked by covalent bonds. The utility of rubber increased dramatically with the discovery of vulcanization by Goodyear in 1844. However the nature of this process remained for many years controversial due to the influence of the “colloid school” of chemistry. The first observations on the nature of rubber elasticity date back to 1805, but more than a century passed before it was shown that the retractive force of stretched rubber is entropic. X-ray crystallographic studies not only provided the ultimate proof that natural rubber consists of covalently bonded chain molecules, but also gave evidence for its chemical structure. A century ago it was found that polymeric products other than H. rubber exhibited similar elastic properties. The race to produce synthetic rubbers was largely stimulated by the two World Wars. The availability of 14C labeled precursors led to the detailed description of the biosynthetic pathway by which rubber is produced in the Hevea plant.

A Two-step Electrodeposition of Pd-Cu/Cu2O Nanocomposite on FTO Substrate for Non-enzymatic Hydrogen Peroxide Sensor

2021 ◽  
Vol 17 ◽  
Author(s):  
Ke Huan ◽  
Li Tang ◽  
Dongmei Deng ◽  
Huan Wang ◽  
Xiaojing Si ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Cyclic Voltammetry ◽  
Photoelectron Spectroscopy ◽  
Chemical Structure ◽  
Pd Nanoparticles ◽  
Optimal Conditions ◽  
Potential Oscillation ◽  
X Ray Diffraction ◽  
X Ray

Background: Hydrogen peroxide (H2O2) is a common reagent in the production and living, but excessive H2O2 may enhance the danger to the human body. Consequently, it is very important to develop economical, fast and accurate techniques for detecting H2O2. Methods: A simple two-step electrodeposition process was applied to synthesize Pd-Cu/Cu2O nanocomposite for non-enzymatic H2O2 sensor. Cu/Cu2O nanomaterial was firstly electrodeposited on FTO by potential oscillation technique, and then Pd nanoparticles were electrodeposited on Cu/Cu2O nanomaterial by cyclic voltammetry. The chemical structure, component, and morphology of the synthesized Pd-Cu/Cu2O nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties of Pd-Cu/Cu2O nanocomposite were studied by cyclic voltammetry and amperometry. Results: Under optimal conditions, the as-fabricated sensor displayed a broad linear range (5-4000 µM) and low detection limit (1.8 µM) for the determination of H2O2. The proposed sensor showed good selectivity and reproducibility. Meanwhile, the proposed sensor has been successfully applied to detect H2O2 in milk. Conclusion: The Pd-Cu/Cu2O/FTO biosensor exhibits excellent electrochemical activity for H2O2 reduction, which has great potential application in the field of food safety.

scholarly journals DETERMINATION OF TYPE AND MARK OF PROJECTILES BY METHOD OF X-RAY FLUORESCENCE SPECTRAL ANALYSIS IN THE STUDY OF PNEUMATICALLY SHOT INJURIOUS TO SOME CLOTHING MATERIALS

2016 ◽  
Vol 16 ◽  
pp. 391-398
Author(s):  
I. M. Kozachenko
Keyword(s):  
Spectral Analysis ◽  
Small Group ◽  
Elemental Composition ◽  
Medical Examination ◽  
X Ray ◽  
Qualitative And Quantitative ◽  
Foreign Production ◽  
Quantitative Analyses

The X-ray fluorescence spectral qualitative and quantitative analyses were performed for the elemental composition of 4 marks of bullets for pneumatic weapon of home and foreign production, and also for imitators of common clothing materials camouflage fabric and cotton knitwear. It is determined that lead bullets for pneumatic weapons are capable to introduce some elements of their composition, which are inherent in one or another mark of bullets, to the area of damage on certain clothing materials, in particular, camouflage fabric and cotton knitwear. This expands the possibilities of forensic medical examination when dealing with a problem of determining the type and mark of a bullet or of a small group of bullets similar in their elemental composition, due to which the pneumatical shot injuries of examined objects took place.

Energy Dispersive X-Ray Spectrometry of Gold-Silver-Copper Standards for Comparison with Historic Gold Objects

1990 ◽  
Vol 185 ◽  
Author(s):  
S.M. White ◽  
R.J. Koestler ◽  
C. Blair ◽  
N. Indictor
Keyword(s):  
Elemental Composition ◽  
Ternary Mixtures ◽  
Energy Dispersive ◽  
X Ray ◽  
Silver Copper ◽  
Gold Silver

AbstractSeven ternary mixtures of gold(80-95%)-silver(4-15%)-copper(1-15%) were prepared as standards for the determination of elemental composition by energy dispersive X-ray spectrometry (EDS). Two geometric forms (flat and oblate) of the standards were prepared for comparison to the analyses of historic gold objects. Surface analyses were performed. Polished sections of the standards were also analysed Comparison between two methods for collecting EDS data is reported. The analyses are discussed in terms of developing a generalized methodology for estimating elemental composition of museum artifacts.

An X-ray Diffraction Method for the Determination of Temperatures in Coke Reactions

1984 ◽  
Vol 28 ◽  
pp. 383-388 ◽  
Author(s):  
Jack L. Johnson ◽  
Seymour Katz
Keyword(s):  
Diffraction Method ◽  
Temperature History ◽  
Maximum Temperature ◽  
Slag Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Potential Source ◽  
History Of ◽  
Extract Information

Information about the conditions and reactions in a foundry cupola is essential to understand the thermochemistry of a cupola and thus improve its efficiency. A potential source of such information is coke taken from inside an operating cupola. In the region of the cupola that extends from the melt zone to the taphole, coke is directly involved in important chemical processes such as combustion, gasification, slag formation, iron sulfurization, carbon pickup, and oxide reduction. Coke is also suspected of being involved in the transport of silicon to the liquid iron. Each of these processes produces characteristic physical and/or chemical changes in the coke, making it possible to extract information about the processes from an examination of coke pieces taken from within an operating cupola. A program to study such coke samples is in progress. To effectively interpret these data it is necessary to know the temperature history of the coke being examined, especially the maximum temperature attained by the coke piece in the cupola.

The determination of composition and thermal history of plagioclase by the X-ray powder method

1955 ◽  
Vol 30 (229) ◽  
pp. 648-656 ◽  
Author(s):  
J. Goodyear ◽  
W. J. Duffin
Keyword(s):  
Chemical Composition ◽  
Low Temperature ◽  
Similar Composition ◽  
X Ray ◽  
Naturally Occurring ◽  
Cell Dimensions ◽  
History Of ◽  
Unit Cell Dimensions ◽  
Ray Patterns

In a recent paper (hereafter referred to as GD) Goodyear and Dufiln (1954) described X-ray powder data for a number of synthetic and chemically analysed plagioclases of composition An0Abl00-Anl00Ab0. Important aspects of this work were a correlation of the X-ray patterns with chemical composition, and a distinction between the pattern of a naturally occurring material of low-temperature origin and that of a synthetic of similar composition. The investigation showed quite clearly that the unit-cell dimensions of a synthetic plagioelase depend but little on composition from An0Abl00 to An70Ab30, whilst they differ from those of the low-temperature modification greatly for albite, to a lessening degree as the composition approaches An70Ab30, and practically not at all in the range An70Ab30-Anl00Ab0.

scholarly journals Comparative analysis of X-ray fluorescence methods for elemental composition determination of the archaeological ceramics from low sample quantity

2021 ◽  
Vol 25 (1) ◽  
pp. 20-33
Author(s):  
G. V. Pashkova ◽  
◽  
M. M. Mukhamedova ◽  
V. M. Chubarov ◽  
A. S. Maltsev ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Inductively Coupled Plasma ◽  
Bulk Composition ◽  
Fluorescence Analysis ◽  
Total Reflection ◽  
Late Neolithic ◽  
Burial Site ◽  
Archaeological Ceramics ◽  
X Ray

Wavelength-dispersive X-ray fluorescence analysis (WDXRF) and total-reflection X-ray fluorescence (TXRF) analysis were applied to study the elemental composition of the Late Neolithic ancient ceramics collected at the Popovsky Lug burial site (Kachug, Upper Lena river, Russia). Semi-quantitative non-destructive analysis of ceramic pieces showed that measurements of the upper and lower sides of the ceramic are less informative than the measurement of its cut. Various sample preparation techniques for the low quantity of crushed ceramics such as fusion, pressing and preparation of suspensions were compared to preserve the material. Samples were prepared as 150 mg fused beads and 250 mg pressed pellets for WDXRF, and as suspensions of 20 mg sample based on the aqueous solution of the Triton X-100 surfactant for TXRF. Certified methods were used to validate the obtained contents of rock-forming oxides and inductively coupled plasma mass spectrometry was used to confirm the results of trace elements determination. Based on the carried-out studies, a combination of the wavelength-dispersive X-ray fluorescence analysis (glass) and total-reflection X-ray fluorescence analysis (suspension) methods was chosen to obtain the data on the elemental bulk composition of archaeological ceramics. The proposed combination allowed the quantitative determination of Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, V, Cr, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Pb, and Ba from the sample of crushed ceramics weighing only about 170 mg.

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