ISSN:
0098-1273
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
X-ray line broadening measurements were used to determine the apparent “mosaic block” sizes of randomly oriented polyethylene and polyoxymethylene single crystals. Both dried-down and uncollapsed crystals were examined. PE lamellae were grown at 80, 85, and 90°C by isothermal crystallization from a 0.1% solution in xylene. POM crystals were grown at 125°C by self seeding from an 0.05% solution of the polymer in o-dichlorobenzene. A given preparation was split into two parts. One part was dried down in the usual manner, the other was exchanged to paraffin oil and the crystals never permitted to dry down. Previously reported studies used dried-down crystals and gave crystallite sizes of approximately 300 Å. More recently, using electron microscopy, it has been postulated that PE single crystals are free of “mosaic block” over regions of several thousand angstroms. It is evident from this present study that crystallite sizes in uncollapsed lamellae are significantly larger than those observed for the same crystals dried down. In the case of uncollapsed lamellae, one can explain the observed crystallite sizes solely on the basis of chain obliquity rather than by invoking the “mosaic block” model. It has also been determined that there is an upper limit to the crystallite sizes that can be observed in PE and POM crystals using wide-angle x-ray techniques. This limit may account for discrepancies between x-ray and electron diffraction.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1976.180140211
