材料科学导论(英文课件)--青岛科技大学Polymer structures and properties【荐】.pdf

TEM image of the spherulite structure in a natural rubber specimen. Chain- folded lamellar crystallites approx.10nm thick extend in radical directions from the center. The chain-folded structure for a plate-shaped polymer crystallite. Chapter 4 Polymer Structures, Applications Processing Introduction • Natural polymers: (1) Derived from plants and animals, such as wood, rubber, cotton, wool, leather and silk. (2) proteins, enzymes, starches, and cellulose in biological and physiological process. • Synthetic polymers: plastics, rubbers, and fiber materials. After WWII, the field of materials has been virtually revolutionized by the advent of synthetic polymers. Hydrocarbon molecules Hydrocarbon molecules: hydrogen and carbon. Intramolecular bond: covalent. Saturated and unsaturated molecules: saturated – all the bonds are single ones (CH4); unsaturated – molecules have double and triple covalent bonds (CH =CH , CH≡CH). 2 2 Polymer molecules • Polymers - Macromolecules C-C backbone formed by covalent bonding. • Monomers • Homopolymers and copolymers L = 0.154 nm Molecular configurations Molecular characteristics Chemistry Size Shape structure (mer composition) (molecular weight) (chain twisting, entanglement) linear branched crosslinked network Isomeric states stereoisomers Geometrical isomers isotactic atactic cis trans syndiotactic Isotactic 全同立构 S