ISSN:
0098-1273
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
An anisotropic dispersive continuum model for the collective modes of polyethylene of any degree of crystallinity is suggested. The model successfully explains the experimental results for specific heat of polyethylene of 100%, 84.1%, 74.5%, 45.9%, and 0% crystallinity in the temperature range 2.5-60 K, where the specific heat of amorphous polyethylene is markedly different from that of crystalline polyethylene. The variation of specific heat with degree of crystallinity can be obtained by varying only one parameter θ1 (characterizing the low energy cubic modes), keeping the other two parameters (characterizing the transverse and longitudinal chain modes) constant. Thus, in going from the crystalline to the amorphous state, it is essentially the interchain binding which is affected, the chain modes being left undisturbed. Using the calculated values of specific heat for varying degrees of crystallinity, the variation of θ1 with the crystallinity is reported. Observed high-temperature specific heats for crystalline and amorphous polyethylene up to 300 K are also explained using additional optical modes. The anisotropic Mössbauer elastic scattering fraction (MESF) for polyethylene of different degrees of crystallinity in the temperature range 0-425 K is obtained. For a given degree of crystallinity there is marked anisotropy in MESF which increases with increase in temperature. For a given direction, longitudinal or transverse, there is a large difference between the MESF of 0% and 100% crystalline polyethylene, which also increases with the increase in temperature. It is quite possible that the MESF experiment may prove to be more sensitive than the usual method for the determination of degree of crystallinity.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1980.180180804
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