The Problem of the Configurations of Hydratropic Acid and Atrolactic Acid. Application of the Method of Melting Point—Composition Diagrams

1952 ◽  
Vol 74 (14) ◽  
pp. 3668-3670 ◽  
Author(s):  
Kurt Mislow ◽  
Milton Heffler
Keyword(s):  
Melting Point ◽  
Point Composition

Preparation and Properties of Condensation Block Copolymers

1957 ◽  
Vol 30 (1) ◽  
pp. 283-295 ◽  
Author(s):  
D. H. Coffey ◽  
T. J. Meyrick
Keyword(s):  
Melting Point ◽  
Block Copolymers ◽  
Impact Strength ◽  
Hexamethylene Diisocyanate ◽  
Random Copolymers ◽  
Copolymer Composition ◽  
Block Copolymerization ◽  
Random Arrangement ◽  
Composition Curve ◽  
Point Composition

Abstract By using diisocyanates to link together two different polyesters having terminal hydroxyl or carboxyl groups, copolymers have been obtained in which the two repeating units occur in blocks and not in the random arrangement obtained by normal methods of preparing copolymers. Melting points have been measured by a penetrometer method and the effects of copolymer composition on melting point determined. In a series of crystalline copolymers made by linking various amounts of polyethylene sebacate and polyethylene adipate with hexamethylene diisocyanate, a step-shaped melting point-composition curve is obtained. Copolymers containing up to about 40 per cent of polyethylene adipate have the same melting point as that of polyethylene sebacate. Further increase in the polyethylene adipate content results in a rapid drop in melting point until the melting point of polyethylene adipate is reached. Thereafter increasing amounts of polyethylene adipate do not alter the melting point. Random copolymers of ethylene adipate and ethylene sebacate give a V-shaped melting point-composition curve. The step-shaped curve of block copolymers is almost identical with the melting point-composition curve of melt blends of the two polymers. Stress-strain characteristics and impact strengths of the block copolymers have been measured. In the polyethylene adipate/polyethylene sebacate/ hexamethylene diisocyanate series no great differences are found between random and block copolymers. If, however, the crystalline polyethylene adipate is replaced by the noncrystalline polypropylene adipate, then block copolymers containing 15–30 per cent of polypropylene adipate have outstanding impact strength. Similar high impact strength is obtained by using a compatible rubbery polymer as an external plasticizer with hexamethylene diisocyanate modified polyethylene sebacate. This method of block copolymerization has an advantage over random copolymerization in that a crystalline copolymer can be modified without reduction of its melting point, and by suitable selection of a second component it affords a means of “building in” a plasticizer.

The Melting Point—Composition Diagram of the Zirconium—Oxygen System1

1951 ◽  
Vol 73 (5) ◽  
pp. 2032-2035 ◽  
Author(s):  
Daniel Cubicciotti
Keyword(s):  
Melting Point ◽  
Composition Diagram ◽  
Point Composition

COMPARISON OF METHOXYMERCURIALS DERIVED FROM CYCLOPENTENE AND CYCLOHEXENE

1953 ◽  
Vol 31 (6) ◽  
pp. 536-542 ◽  
Author(s):  
A. G. Brook ◽  
R. Donovan ◽  
George F Wright
Keyword(s):  
Melting Point ◽  
Dipole Moments ◽  
Thermal Analyses ◽  
X Ray ◽  
Point Composition

The α- and β-2-methoxycyclopentylmercuric chlorides, bromides, and iodides have been prepared. The X-ray powder patterns, dipole moments, and thermal analyses among each series have been compared with the homologous methoxycyclohexyl derivatives. In both of the series the dipole moments of the β-diastereomers are greater than those of the corresponding α -isomers. In both series the α- and β-diastereomers seem to comprise isostructural series among the three halides. This isostructural relationship seems to be reflected in the melting point composition diagrams.

The Heptacarboxylic Porphyrin of Various Types of Porphyria and the Melting-Point Curve of Methyl Esters of the I and III Isomers

1966 ◽  
Vol 12 (10) ◽  
pp. 647-658 ◽  
Author(s):  
T C Chu ◽  
Edith Ju-Hwa Chu
Keyword(s):  
Melting Point ◽  
South African ◽  
Porphyria Cutanea Tarda ◽  
Methyl Esters ◽  
Acute Intermittent Porphyria ◽  
Type I ◽  
X Ray Diffraction ◽  
Different Types ◽  
Composition Curve ◽  
Point Composition

Abstract The heptacarboxylic porphyrin (hepta) isolated from different types of porphyric urine samples contains different proportions of the isomers I and III. These were separated chromatographically. The hepta in congenital porphyria was found to contain 65% of Type I isomer and 35% of Type III; that in acute intermittent porphyria, 70-80% III and 20-30% I; and that in porphyria cutanea tarda, 80-90% III. Several other cases including 1 of coproporphyria, 1 of South African genetic porphyria, 1 of Bantu porphyria, 4 of hexachlorobenzene poisoning in Turkish individuals were also examined. From the X-ray diffraction pattern and long-column chromatography, the Hepta III prepared either from decarboxylation of Uroporphyrin III or by condensation of porphobilinogen revealed a more complex configuration than that isolated from porphyric materials. The natural hepta might be dominated by one of the four possible isomers of the III series. A melting-point composition curve of methyl esters of Hepta I and III was constructed, and its applicability was tested. The identity of the hepta isolated in porphyria cutanea tarda with "208" and "pseudouro" porphyrins is discussed, and the name "cutano-porphyrin" suggested.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

The observation of nano-voids in Au thin films

1987 ◽  
Vol 45 ◽  
pp. 366-367
Author(s):  
William Krakow
Keyword(s):  
Thin Films ◽  
Melting Point ◽  
Present Author ◽  
Stacking Faults ◽  
Damage Threshold ◽  
Ionic Species ◽  
Rare Gases ◽  
Chain Defects ◽  
Vacancy Chains ◽  
Au Thin Films

It has long been known that defects such as stacking faults and voids can be quenched from various alloyed metals heated to near their melting point. Today it is common practice to irradiate samples with various ionic species of rare gases which also form voids containing solidified phases of the same atomic species, e.g. ref. 3. Equivalently, electron irradiation has been used to produce damage events, e.g. ref. 4. Generally all of the above mentioned studies have relied on diffraction contrast to observe the defects produced down to a dimension of perhaps 10 to 20Å. Also all these studies have used ions or electrons which exceeded the damage threshold for knockon events. In the case of higher resolution studies the present author has identified vacancy and interstitial type chain defects in ion irradiated Si and was able to identify both di-interstitial and di-vacancy chains running through the foil.

Higher-melting-point polyolefines as flexible dielectrics

1965 ◽  
Vol 112 (8) ◽  
pp. 1633
Author(s):  
S. Verne
Keyword(s):  
Melting Point

Benzene confined in MCM-41 below its melting point : A proton NMR study

2000 ◽  
Vol 10 (PR7) ◽  
pp. Pr7-99-Pr7-102 ◽  
Author(s):  
G. Dosseh ◽  
D. Morineau ◽  
C. Alba-Simionesco
Keyword(s):  
Melting Point ◽  
Proton Nmr ◽  
Nmr Study ◽  
Mcm 41

ELLIPSOMETRIC STUDY OF THE ICE SURFACE STRUCTURE JUST BELOW THE MELTING POINT

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-495-C1-501 ◽  
Author(s):  
Y. FURUKAWA ◽  
M. YAMAMOTO ◽  
T. KURODA
Keyword(s):  
Melting Point ◽  
Surface Structure ◽  
Ice Surface ◽  
Ellipsometric Study
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