A Positron Annihilation Lifetime Study of Poly(Bisphenol-a Carbonate)

1986 ◽  
Vol 82 ◽  
Author(s):  
P. L. Jones ◽  
A. J. Hill ◽  
G. W. Pearsall ◽  
J. H. Lind
Keyword(s):  
Bisphenol A ◽  
Positron Annihilation ◽  
Thermal History ◽  
Thermal Response ◽  
Semicrystalline Polymers ◽  
Glass Transitions ◽  
Thermal Dependence ◽  
Positron Annihilation Lifetime ◽  
Ductile To Brittle Transition ◽  
Increasing Temperature

ABSTRACTPositron annihilation lifetime spectroscopy has proven to be sensitive to glass transitions and other free volume dependent phase transitions in amorphous and semicrystalline polymers. The thermal dependence of the lifetime spectra of positrons in compression-molded poly(bisphenol-A carbonate) has been measured from 253K to 323K, then modelled using a three component fit. The longest-lived component lifetime τ3 was found to vary linearly with increasing temperature independent of thermal history. The corresponding component intensity I3 was found to vary in a non-linear fashion with increasing temperature, exhibiting a significant dependence on thermal history. The observed thermal response of τ3 and I3 is discussed in terms of both molecular relaxation and the ductile-to-brittle transition behavior of poly(bisphenol-A carbonate).

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.

Seeking the Good Fitting Procedure of PALS Polymer Spectra

2008 ◽  
Vol 607 ◽  
pp. 64-66
Author(s):  
Nicolas Laforest ◽  
Jérémie De Baerdemaeker ◽  
Corine Bas ◽  
Charles Dauwe
Keyword(s):  
Experimental Data ◽  
Low Temperature ◽  
Positron Annihilation ◽  
Physical Meaning ◽  
Lifetime Measurements ◽  
Positron Annihilation Lifetime ◽  
Fitting Procedure ◽  
Fitting Procedures ◽  
Blob Model

Positron annihilation lifetime measurements on polymethylmethacrylate (PMMA) at low temperature were performed. Different discrete fitting procedures have been used to analyze the experimental data. It shows that the extracted parameters depend strongly on the fitting procedure. The physical meaning of the results is discussed. The blob model seems to give the best annihilation parameters.

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