Ultrahigh molecular weight polyethylene free volume hole structure studied by positron annihilation lifetime technique

2000 ◽  
Vol 201 (17) ◽  
pp. 2348-2353 ◽  
Author(s):  
Maria Misheva ◽  
Nikolay Djourelov ◽  
Antoaneta Dimitrova ◽  
Galina Zamfirova
Keyword(s):  
Molecular Weight ◽  
Positron Annihilation ◽  
Free Volume ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Positron Annihilation Lifetime ◽  
Ultrahigh Molecular Weight ◽  
Free Volume Hole ◽  
Hole Structure

A Positron-Annihilation-Lifetime study of Polymer Blends

1993 ◽  
Vol 321 ◽  
Author(s):  
J. Liu ◽  
Y. C. Jean ◽  
H. Yang
Keyword(s):  
Bisphenol A ◽  
Polymer Blends ◽  
Positron Annihilation ◽  
Free Volume ◽  
Weight Fraction ◽  
Bisphenol A Polycarbonate ◽  
Positron Annihilation Lifetime ◽  
Miscible Blend ◽  
Immiscible Blend ◽  
Free Volume Hole

ABSTRACTPositron-annihilation-lifetime (PAL) spectroscopy has been utilized to investigate the free-volume properties of two types of polymer blends, a miscible blend of bisphenol-A polycarbonate (PC) and tetramethyl bisphenol-A polycarbonate (TMPC), and an immiscible blend of PC and polystyrene (PS). In the miscible blend, the free-volume hole size and its fraction follow a linear relationship with respect to the weight fraction while in the immiscible blend, the relationship is not linearly additive. The free-volume hole distributions in the immiscible blend are found to be significantly broader than those in the pure polymers. The difference is thought to be a result of the free volume formed and associated with the conformation and interchain packing between the dissimilar chains in incompatible polymers.

Molecular Packing of Carbohydrate Oligomer Encapsulants - A Free Volume Perspective

2012 ◽  
Vol 733 ◽  
pp. 96-99 ◽  
Author(s):  
Mina Roussenova ◽  
Sam Townrow ◽  
Mathieu Murith ◽  
Job Ubbink ◽  
M. Ashraf Alam
Keyword(s):  
Molecular Weight ◽  
Positron Annihilation ◽  
Free Volume ◽  
Glassy State ◽  
Low Molecular Weight ◽  
Hole Size ◽  
Positron Annihilation Lifetime ◽  
Food Industries ◽  
Molecular Organisation ◽  
Complex Manner

Positron annihilation lifetime spectroscopy (PALS) is used in conjunction with dilatometry to analyse the effects of water and low molecular weight diluents (maltose and glycerol) on the molecular organisation and density of carbohydrate oligomers commonly used in the pharmaceutical and food industries for the formulation of encapsulation matrices. In the glassy state, both maltose and glycerol act as packing enhancers, causing a non-linear decrease in the average molecular hole size of the carbohydrate matrices. Water exists in a highly non-ideal state in these systems and it alters the molecular organisation of the matrices in a complex manner, whereby it can act either as an anti-plasticiser or a plasticiser, depending on the level of hydration.

Studying the Effect of Low α-Radiation Doses on CR-39 Polymers Using Positron Annihilation Lifetime and Mechanical Properties

2012 ◽  
Vol 332 ◽  
pp. 77-83
Author(s):  
M.F. Eissa ◽  
E.M. Hassan ◽  
Emad A. Badawi
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Alpha Particles ◽  
Polymer Materials ◽  
Fractional Free Volume ◽  
Positron Annihilation Lifetime ◽  
Microhardness Test ◽  
Solid Media ◽  
Free Volume Hole ◽  
Different Doses

Positron annihilation lifetime spectroscopy (PALS) is one of the unique tools for studying free-volume defects in solid media. The microhardness test offers a simple and nondestructive tool for investigating the mechanical behavior of polymer materials. Polyallyl diglycol carbonate (CR-39) track detectors have a variety of applications in science and technology. PALS measurements and microhardness tests were verified for CR-39 irradiated with different doses of alpha particles (0 - 69.20 mGy). The variations in free volume hole size and fractional free volume were obtained by using the PALS method. The small free volume hole sizes were found at doses 27.68 and 44.98 mGy. The microhardness test for the two doses yielded medium values.

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