Nuclear spin resonance line width measurements of polyethylene

0022-3832

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Physics

The proton spin resonance spectrum of polyethylene consists of two superimposed lines. The narrow line is attributed to the amorphous phase, and the broad line to the crystalline phase. The width of the narrow line was measured at various temperatures from 25-130°C. for Alathon 10, Alathon 14, DYNH, and Marlex 50 polyethylene and it was found to vary with temperature. The results have been interpreted using the theory of motional narrowing, which indicates that the product of temperature and line width is proportional to the viscosity. A plot of log of line width times temperature versus reciprocal temperature is linear for Marlex 50 polyethylene, and is curved for the other three. The linearity is believed due to the simple structure of the material, and the slope yields an activation energy of 8200 cal./mole. The curvature of the other data is believed due to extensive branching which causes a change of composition of the amorphous phase upon cooling, and the apparent activation energy varies from 11,800 cal./mole at 130°C. to 4900 cal./mole at 25°C.

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