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Date of Award


Access Type

Open Access Dissertation

Document type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering


The dynamic birefringence technique has been used to study the total orientation of low density polyethylene, and the dynamic x-ray diffraction technique is augmented to single out and evaluate the crystalline orientation. Svrelling studios on the same type of samples were made using the dynamic birefringence apparatus to assess the form contribution duy to orientation of boundaries betvreen two regions of different refractive index. Samples having different internal structure were obtained by ijnposing different static strain on the samples, and their morphology was varied by the processes of quenching and annealing. The dynamic birefringence results are explained in terms of molecular mechanisms and. the crystalline orientation is explained with respect to the orientation of the a, b and c axes of the unit cell of polyethylene.

It has been found that at low elongations of about 10%, for quenched sample the amorphous and the crystalline contributions to the total dynamic birefringence are comparable and amount to about 40% each. With annealing, the amorphous contribution increases with lower crystalline contribution. At high elongations beyond 50%. the crystalline contribution has been found to be 70-80% of the total in both types of samples. Form contribution is about 5-15% in both cases depending on the static strain of the sample.

Additional dynamic birefringence results are reported on the quenched sample of substituted polyethylnes and the substituent effects on the dynamic mechanical and optical quantities are assessed and discussed.