ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Studies have been published relating the mechanical properties of ethylene copolymers with short chain branching structures. Other work has emphasized that crystallites in these copolymer systems participate in superstructures and that stress distribution during mechanical testing depends on the arrangement of these structures, the morphology. While developing structure-property correlations, morphologies of some random and non-random olefin copolymers have been examined. Surprising morphological differences were found depending on the length, concentration and degree of randomness of the n-alkyl branch and on vicinal substitution with norbornene derivatives as comonomers. X-ray diffraction yielded unexpected results which can be explained by a change in the direction of chain folding. Linear side chains randomly introduced into an otherwise high density polyethylene result in a two to three fold increase in the 110:200 x-ray intensity ratios, a slight reduction in the 110:020 intensity and a 5 to 10 fold decrease in the 200:02 intensities. These results cannot be explained by orientations introduced in sample preparation. There are associated morphological changes. Vincinal substitution with norbornene comonomers has little effect on crystal habit but does change the morphology, tending to shift superstructures from lamellar to fibrillar in nature.
Additional Material:
13 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760151205
