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Tài liệu Ktf_2_polymerchemie und bindungskräfte_final stbo

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Adhesive Bonding Technologies Chapter 2: Polymer Chemistry and Bonding Mechanism‘s Univ.-Prof. Dr.-Ing. Prof. h.c. Stefan Böhm Source: Wikipedia Agenda  Basic Concepts of Chemistry  Introduction to Polymers  Classifications of Plastics  Formation Reactions  Adhesion and Cohesion 2 Basic Concepts in Chemistry & Bonding Forces  All known materials, whether hard, fluid or gaseous, are made of atoms.  An atom is the smallest piece in the material that can be presented as a purely chemical element.  Subdivision: Atomic nucleus (Nucleus) and electron shell Particles Where? Charge Electron, e Shell -1 Proton, p Nucleus +1 Neutron, n Nucleus 0 3 Atomic Structure  The number of protons and electrons within an atom is always the same  The electrons are on orbits or shells that are positioned around the nucleus or Orbits Shells 4 Atomic Structure  Criteria for the structure The 1st orbit only has room for 2 electrons !! Hydrogen Helium The others offer room for 8 e !!! Lithium Sodium Lithium Beryllium Neon 5 Classification of Atoms – The Periodic Table Periode Hauptgruppe 1 2 1 1 2,1 H Wasserstoff 3 2 1,0 0,9 0,8 5 12 20 1,0 Ca 38 55 1,6 Caesium 0,9 Ga Gallium Barium 1,8 8 9 In 33 1,8 Ge 2,0 Germanium 1,8 Indium Sn Thallium 1,9 Zinn 1,8 As Pb Blei 1,9 Bi Bismut 2,5 - 18 Cl Polonium - Chlor Br - Kr Krypton 54 I - Iod - Ar Argon 36 85 Po Ne Neon Brom Tellur 84 - Fluor 53 Te 2,1 Antimon 83 2,8 Selen 52 Sb F 35 Se 2,4 Arsen 10 17 34 51 82 Tl 16 He Helium Si 2,1 P 2,5 S 3,0 Silizium Phosphor Schwefel 50 81 Ba - Symbol Name 15 32 49 56 Cs U 7 14 8 2 2,5 C 3,0 N 3,5 O 4,0 Bor Kohlenstoff Stickstoff Sauerstoff 31 Calcium 7 B 13 0,8 Rb 1,0 Sr 1,7 Rubidium Strontium 0,7 6 Na 1,2 Mg 1,5 Al 1,8 Natrium Magnesium Aluminium 37 6 1,4 6 Uran Kalium 5 Electro negativity 1,5 Be 2,0 Lithium Beryllium K 5 92 Li 19 4 4 Number of order 4 11 3 3 Xe Xenon 86 At Astat - Rn Radon 6 Types of Bonds – Chemical bonds  When using adhesive bonding, three types of chemical bonds mainly occur. Chemical Bonds Primary Valence Bonds Covalent Bond Homopolar Bond Ionic Bond Heteropolar Bond Metallic Bond 7 Covalent Bonds  All atoms strive to fill their outer orbits/shell with electrons  Therefor, only the outer electrons (valence electrones) are important when forming bonds Carbon Phosphorus 8 Covalent Bonds  An atom shares an electron with its bonding partner so that both profit from the other H-Atom H-Atom H-Molecule H2 9 Covalente Bonds  Also called homopolar bond because the bonding electrons equally belong to both bonding partners  Bond occurs between non-metals – Range of the bonding force: 0.1 – 0.2 nm – Bonding energy: 60 – 1100 kJ/mol Bonding energy: 413 kJ/mol Bonding length: 0,108 nm Bonding energy: 614 kJ/mol Bonding length: 0,134nm Bonding energy: 811 kJ/mol Bonding length: 0,12 nm 10 Ionic Bonds  Often between metals and non-metals  Example: Sodium and Chlorine Sodium-Atom 1 Valence-Electron Chlorine-Atom 7 Valence-Electrons Sodium-Ion, Na+ Chlorine-Ion, Cl8 Valence-Electrons 8 Valence-Electronen 11 Ionic Bonds  Electrostatic interaction leads to a three dimensional formation of a cristal lattice, ions are organised evenly 12 Ionic Bonds  Also called heteropolar bonds as bonding elements are not distributed evenly.  Based on electrostatic attraction between negatively and positively charged ions ● Range of the forces: 0.1 – 0.2 nm ● Bonding energy: 600 – 4000 kJ/mol ● Plays a tangential role as regards the bonding forces 13 Metallic Bonds  Based on the electrostatic attraction between the positively charged metal ions and electrons (negatively charged)  The valence-electrons can move freely within the lattice of the positively charged metal ions + Lithium Lithium-Ion Li+ Electron e14 Types of bonds – Intermolecular Forces  The intermolecular bonds that occur when bonding can be classified as follows: Intermolecular Bonds Secondary Valence Bond Hydrogen Bond Van-der-Waals-Bonds Dipole Forces Induction forces Dispersion forces 15 Electronegativity  Electronegativity EN measures how strongly the electrons of a bond are attracted to one of the atoms  The higher the EN is, the more the atom attracts the electrons of the bond Periode Hauptgruppe 1 2 1 1 2,1 H Wasserstoff 3 2 1,0 11 3 0,9 3 4 5 Number of Order 92 Electronegativity 1,4 6 5 Li 1,5 Be 2,0 Lithium Beryllium 12 13 6 U 7 - Symbol Name 8 9 2,5 C 3,0 N 3,5 O 4,0 Bor Kohlenstoff Stickstoff Sauerstoff 14 15 16 He Helium B Na 1,2 Mg 1,5 Al 1,8 Natrium Magnesium Aluminium 8 2 Uran 4 7 10 F Fluor 17 Si 2,1 P 2,5 S 3,0 Silizium Phosphor Schwefel - Ne Neon 18 Cl Chlor - Ar Argon 16 Electronegativity & Polar Bonds  EN-Difference (DEN) DEN Type of Bond 0 to 0,5 Covalent Bond > 1,7 Ionic Bond 0,5 to 1,7 polar covalent Bond (dipole-molecule) 3,5 2,1 2,1 17 Visualisation of the EN-Difference  Electron density distribution: the different colours in the „Shell“ where the electron density is high and where it is low within the molecule O H O O H H H 3C O H 3C CH3 18 Types of Bonds – Intermolecular Bonds Intermolecular Bonds Secondary Valenz Bonds Hydrogen Bonds Van der Waals Bonds Dipole Forces Induction Forces Dispersion Forces 19 Types of Bonds – Intermolecular Bonds  Hydrogen Bonds  Especially for bonds with OH-groups or NH-groups  Is based on the strong polar character of the bonding molecules  Bonding energy up to 50 kJ/mol  Is based on electrostatic attraction 20
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