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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