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Chapter 4 Polymer Structures
Transmission electron micrograph showing the spherulite structure in a natural rubber specimen. Chain-folded lamellar
crystallites approximately 10 nm thick extend in radial directionsfrom the center; they appear as white lines in the micrograph.
30,000×. (Photograph supplied by P. J. Phillips. First published in R. Bartnikas and R. M. Eichhorn,Engineering Dielectrics,
Vol. IIA,Electrical Properties of Solid Insulating Materials: Molecular Structure and Electrical Behavior, 1983. Copyright ASTM,
1916 Race Street, Philadelphia, PA 19103. Reprinted with permission.)WHY STUDYPolymer Structures?
A relatively large number of chemical and structural
characteristics affect the properties and behaviors of
polymeric materials. Some of these influences are as
follows:
1.Degree of crystallinity of semicrystalline polymers—on
density, stiffness, strength, and ductility (Sections 4.11
and 8.18).2.Degree of crosslinking—on the stiffness of rubber-like
materials (Section 8.19).
3.Polymer chemistry—on melting and glass-transition
temperatures (Section 11.17).