Slotevent 'Verbinden van ongelijksoortige materialen' - Lijmen, verbindingstechniek voor nieuwe materialen - P. Coudeville, KU Leuven

1. Ing Coudeville Pol
Lijmen:
verbindingstechniek
voor nieuwe materialen

2. Yes we can…

3. 2/34

4. De nieuwe materialen
Boeing 787 Dreamliner
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5. • Metallic
-(Fe)n-
• Natural • Ceramic
The build up of Materials
-(CaCO3)n-
5/34

6. Links between
chemistry &
physics &
technolgy
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7. Chemistry & physics links between structure & properties (*)
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8. What is in dust?
( * )
8/34

9. Removal of impurities (dirt - vuil): ( * ) residues of combustion
What is dirt?
9/34

10. 10/34
Gas Liquid Diamond
decreasing
chainlength
increasing
crosslinking
Polymer fundamentals: increasing crosslinking–changing properties
Link to & Tm
viscosity – malleability – elasticity – stiffness – ductility – strength – brittleness - ntching
-CH2-CH2-
solids

11. 11/34
Interaction in POLYMERS – an overview
Wettability

12. Link: Feica: educational materials
12/34

13. Basiskennis verbindingstechnieken wenselijk?
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14. ADHESIVES
Physical hardening
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15. hotmelt Water-
oplosbare
lijmen
Struc-
Tu-
rele
lijm
Oplosmiddel
lijm
contactlijm
Pressure
sensitive
adhesive
PSA
Tapes
emulsielijm
2K
adhesive
Secondenlijm
Epoxy lijm
UV-
hardende
lijm
2K PUR
lijm
Anaerobe
lijm
Plastisol
1 K PUR
lijm
Siliconen
kit

16. Removal of
impurities
1
Roughening of the
substrate surface
2
Physical and chemical activation of
the surface
3
Surface activation
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17. WATER
Water prevents adhesion
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1. The removal of impurities ( water, oil, soot, dust, oxides… )
condense!

18. Removal of water, oil, soot, dust, oxides, organic residues…
Drying
Soap, detergent, solvent, base
Acid
Mechanical
Solvent, plasma
Flame,
15/34

19. 19/34
2. Activation by Surface roughening & Mechanical interlocking
diffusive adhesion - entanglement
Tack!!!
Stringing
entanglement
Sticking
PSA

20. tri ethoxy vinyl silane
Primers - Silaneren – Chemical activation of a substrate
Y = vinyl of –CH=CH2
+ polyvinylbenzene (PS)
20/34
3. Physical and chemical activation of the surface
eerst hydrolyse dan
binding op oppervlak
+ H2O
+ ROH
+ H2O
+ H2O

21. Physical activation of a surface by means of Plasma – flame – ai rplasma = corona
hoogspanning
electrode
Procesgas (lucht)
plasma
Surface-activation
21/34
Distribution OH radicals in a turbulent
methane/air flame
=min

22. Activation of a surface by Surface cleaning
22/34
Phosphatation (PO4)3-
Chromatation (CrO4)2-
Anodisation of a metalsurface (oxides)
Activation of a surface by the application of a conversion coating

23. Measuring Surface tension
Water:
* surface energy density of 0.073 J/m2 and
* surface tension of 0.073 N/m.
23/34
H-OH 72,75 mN/m
CH3-OH 22,60 mN/m
CH3-CH2-OH 22,65 mN/m
HOCH2-CH2OH 47,20 mN/m
HOCH2CHOHCH2OH 63,00 mN/m
Glass 250 – 550 mJ/m2
Metals 200 – 1100 mJ/m2

24. Measuring
liquids - surface tension - mN/m
solids - surface energy density - mJ/m2
24/34

25. METALS
-(Fe)n-
22/34

26. 26/20
oil
Water , metals, glass, ceramics and wood are polar and Polyethylene & Polypropylene are oily!!!
-CH2- moistens everything!!!
Hydrophylic - hydrophobic
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POLYMERS
Water on an oily substrate
i.e. PE or PP

27. Compatibilty/Wettability
Liquids:
Surface Tension
1mN/m = 1 dyne/cm
De oppervlakte energie van het substraat moet hoger zijn dan de oppervlakte-energie van de lijm.
↑ 40 mN/m
27/34
Solids:
Surface energy
1mJ/m2
mN/m
mJ/m2mJ/m2
mJ/m2 mJ/m2

28. 28/34
HO
OH
tack - “glueing” – sticking – hardening
Toughness elastomer
thermoplast
thermoset
OH HO O
Heat
Tack!!!
ADHESION

29. Hybride verbindingen
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31. 31/34
The build up of POLYETHYLENE - PE
Molecular movement on a macromolecular scale
Entanglement
Pe is lighter than water
Pe is less dense than water
Polymers

32. 28/34

33. https://www.techsil.co.uk/media/wysiwyg/pdf/Adhesive_Bonding_of_Polyolefin.pdf
https://www.google.com/patents/EP0476203A1?cl=en
“Thermosetting acrylic adhesives have been introduced that can bond
directly to many low surface energy plastics, including many grades of
polypropylene, polyethylene, and other polyolefin, without special surface
preparation.
This characteristic is believed to be due to diffusion of the acrylic
monomer into the substrate before cure.
It seems that the bonds formed on low density polyethylene result in substrate
failure and that an interphase of mixed adhesive and polyethylene is formed
up to 1.5 mm thick.”
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Joining of polyolefins by means of adhesives is not the most appropriate
way of joining. Polyolefins can best be joined through entanglement-
welding,

34. Cyanoacrylate adhesives do not wet or adhere well to polyolefins. The surface
tension of the adhesive is much higher than that of the substrate.
However, polyolefins can be primed for adhesion to cyanoacrylates by certain chemical compounds normally
considered to be activators for cyanoacrylate polymerization.
Materials such as long chain amines, quaternary ammonium salts and phosphine can be applied in either pure
form or in solution to the surface of the polyolefin.
It appears that one of the main reasons for improved adhesion by primers with
cyanoacrylate adhesives is that the solvents wet-out and swell the polyolefin. This
then facilitates interpenetration of the low viscosity cyanoacrylate resin.
These primers are simply sprayed or brushed onto the substrate. After drying of the primer, the cyanoacrylate
adhesive is conventionally applied and bonds extremely well to the substrate.
Triphenylphosphine or cobalt acetylacetonate primers used with cyanoacrylate adhesives produce adhesive
bonds with polypropylene and low density polyethylene that are sufficiently strong to exceed the bulk shear
strength of the substrate. They are also sufficiently durable as to withstand immersion in boiling water for long
periods of time.
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35. Primer [1]
Acrylate [3]
PE or PP
Acrylate adhesive
polymerized adhesive physically
bonded to (PE or PP) [4]
31/34
swollen PE or PP [2]

36. Hechting op een substraat met een lage oppervlakte-energie [1] is eigenlijk een contradictio in
terminis. Hechting (moleculaire interactie) ontstaat als gevolg van de energietransfer van het
substraat naar de lijmmolecules.
Een hechting wordt dan ook bespoedigd door technieken toe te passen die de oppervlakte-energie
van een grondig gereinigd substraat verhogen (oppervlakte-activatie behandeling met plasma, vlam,
primers, sterke zuren etc…)
Anderzijds kan men er ook zorgen dat er zich vlot een intermolecuaire vernesteling voordoet tussen
met primer “ijler” gemaakte PE/EE-substraatmoleculen [2] en de geappliceerde polymeriserende
lijm-monomeermolecules (vloeibare acrylaten [3]). De groeiende lijmmolecules omkapselen hierbij
de olefinemolecules en verzekeren op die manier de hechting [4].
Maar eigenlijk is het evidenter om niet te verlijmen maar de tot smelten opgewarmde substraat-
staafjes, tegen elkaar te drukken. Tijdens het samendrukken van beide uiteinden zal er zich een
fysische cohesieve vernesteling voordoen van de molecules in de smeltzone. Dit leidt tot een intense
vernesteling of een aanzienlijke interactie/binding/adhesie over de contactzone (spiegel-, plasma-,
ultrasoon-, smelt- en hete lucht lassen). Bij deze alternatieve verbindingstechniek is de sterkte van
de verbindingszone gewoonlijk zelfs groter dan de treksterkte van het basismateriaal.
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37. De meest logische manieren van verbinden
van PE en PP
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38. pol.coudeville@kuleuven.be
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