Effects of Pressure on Amorphous Polymers. III. Thermodynamic Properties of Densified Polymethyl Methacrylate

1971 ◽  
Vol 42 (12) ◽  
pp. 4917-4925 ◽  
Author(s):  
R. M. Kimmel ◽  
D. R. Uhlmann
Keyword(s):  
Thermodynamic Properties ◽  
Polymethyl Methacrylate ◽  
Amorphous Polymers

Thermoelasticity and Stress Induced Crystallization of EPDM Elastomers

1971 ◽  
Vol 44 (4) ◽  
pp. 1093-1108 ◽  
Author(s):  
U. Flisi ◽  
A. Valvassori ◽  
G. Novajra
Keyword(s):  
Thermodynamic Properties ◽  
Composition Range ◽  
Amorphous Polymers ◽  
Microstructural Parameter ◽  
Sequence Distribution ◽  
Monomer Sequence ◽  
Stretching Ratio ◽  
Narrow Composition Range ◽  
Stress Induced Crystallization ◽  
Induced Crystallization

Abstract The thermoelastic behavior of various EPDM rubbers has been investigated by performing stress-temperature measurements at different stretching ratios in order to determine their thermodynamic properties and the occurrence of stress induced crystallization. A broad range of terpolymer compositions was investigated and the regularity of monomer sequence distribution was also taken into account. It has been found that statistical terpolymers, like the commercial ones, are generally amorphous and hardly crystallize under stretching for propylene contents higher than 40% by weight. Below this level it is possible to obtain, in a narrow composition range, amorphous polymers that can crystallize under stretching, provided that their monomer sequence distribution is regular enough. The influence of this microstructural parameter has been studied by testing a 3/1 ethylene/propylene model copolymer, obtained by hydrogenation of a sample of poly-3-methyloctenamer. Studying the influence of stretching ratio on crystallization temperature of standard EPDM rubbers, it has been noticed that crystallization occurs at low elongation, which might be related to the presence of “nuclei” in the undeformed state.

Morphology of Amorphous Polymers

1968 ◽  
Vol 26 ◽  
pp. 414-415
Author(s):  
S.L. Lambert ◽  
G.S.Y. Yeh
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Polymethyl Methacrylate ◽  
Size Variation ◽  
Unknown Origin ◽  
Amorphous Polymers ◽  
General Concept ◽  
Polymer Molecules ◽  
Polyphenylene Oxide ◽  
Preparation Conditions

Our general concept of the amorphous morphology of polymers is that of a structureless mass of coiled and intercoiled molecules. However, replica studies of freeze-fractured rubbers, amorphous polystyrene and polymethyl methacrylate and ion-etched glassy polycarbonate often suggest the presence of nodular structures (100-1000 Å) of unknown origin. Recently a nodular ball-like structure of the order of 100 Å was also observed in thin films of amorphous polyethylene terephthalate, its appearance being due to polymer molecules tending to back fold and arranging themselves more or less parallel to one another.We have extended these studies to several other polymers including amorphous and crystallizable polystyrene and polymethyl metha-crylate, trans- and cis-polyisoprene, polyphenylene oxide, etc. and have observed similar ball-like structures (Figs. 1 and 2). The size of these structures may vary from polymer to polymer (30-100 Å), however for a given polymer no substantial size variation has been observed with respect to preparation conditions, e.g., temperature, solvent and molecular weight.

Models of Thermodynamic Properties of Prominences

1979 ◽  
Vol 44 ◽  
pp. 349-355
Author(s):  
R.W. Milkey
Keyword(s):  
Thermodynamic Properties ◽  
Mass Transport ◽  
Emission Spectrum ◽  
Thermodynamic Parameters ◽  
Working Group ◽  
Physical Processes ◽  
Theoretical Concepts ◽  
Group 3 ◽  
Observational Techniques

The focus of discussion in Working Group 3 was on the Thermodynamic Properties as determined spectroscopically, including the observational techniques and the theoretical modeling of physical processes responsible for the emission spectrum. Recent advances in observational techniques and theoretical concepts make this discussion particularly timely. It is wise to remember that the determination of thermodynamic parameters is not an end in itself and that these are interesting chiefly for what they can tell us about the energetics and mass transport in prominences.

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