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chapter 4 - Chapter4 Polymer Structures C h a p t e r 4...

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C h a p t e r 4 / Polymer Structures C h a p t e r 4 Polymer Structures T ransmission electron micrograph showing the spherulite structure in a natural rubber specimen. Chain-folded lamellar crystallites approximately 10 nm thick extend in radial directions from the center; they appear as white lines in the micrograph. 30,000 × .
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C h a p t e r 4 / Polymer Structures Why Study Polymer Structures? Chemical and structural characteristics affect the properties and behaviors of polymeric materials. 2. Degree of crosslinking—on the stiffness of rubber- like materials 1. Degree of crystallinity of semicrystalline polymers — on density, stiffness, strength, and ductility. 密密密密密密密密密密密 密密
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C h a p t e r 4 / Polymer Structures 4.1 INTRODUCTION Natural polymers plants animals wood, rubber, cotton, wool, leather, silk. proteins, enzymes, starches, and cellulose Other natural polymers biological and physiological Many of our useful plastics, rubbers, and fiber materials are synthetic polymers. This chapter explores molecular and crystal structures of polymers; 密密密密密密密密密密密密
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C h a p t e r 4 / Polymer Structures 4.2 Hydrocarbon Molecules Hydrocarbons :many organic materials are hydrocarbons; that is, they are composed of hydrogen and carbon . methane (CH 4 ). 甲甲 Ethylene C 2 H 4 甲甲 H | H— C —H | H acetylene, C 2 H 2 甲甲 H - C C - H H H | | C = C | | H H
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C h a p t e r 4 / Polymer Structures Unsaturated A term describing carbon atoms that participate in double or triple covalent bonds and, therefore, do not bond to a maximum of four other atoms. Saturated 密 A term describing a carbon atom that participates in only single covalent bonds with four other atoms. Some of the simple hydrocarbons belong to the paraffin family; the chainlike paraffin molecules include methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 ), and butane (C 4 H 10 ). 密密 The covalent bonds in each molecule are strong, but only weak hydrogen and van der Waals bonds exist between molecules, 密密密密 密密密 密密密密密密密密
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C h a p t e r 4 / Polymer Structures
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C h a p t e r 4 / Polymer Structures Isomerism 甲 The phenomenon where by two or more polymer molecules or mer units have the same composition but different structural arrangements and properties. 密密密密 For examples: butane isobutane 密密密 密密 normal butane -0.5 o C isobutane -12.3 o C the boiling temperatures 密密
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C h a p t e r 4 / Polymer Structures where R and R’ represent organic radicals 密密 密密 密密 密密密 密密 密密 密密 密密 密密
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C h a p t e r 4 / Polymer Structures 4.3 Polymer Molecules Macromolecule : A huge molecule made up of thousands of atoms. Within each molecule, the atoms are bound together by covalent interatomic bonds.
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