1Direct bonding mechanism of plastic
materials to metals using C=O bond2

CFRP: Carbon Fiber Reinforced Plastic
Matrix; ❶Thermosetting resin, ❷Thermoplastic resin*Thermoplastic is much cost-effective in mass-production.
e.g., high productivity, recycle of defective products

3

4(a) Melting of PA66(a)(b) Dissolution (PA66)(b)

Typical thermal decomposition behaviorof thermoplastic resin used in this study

5❶Shear & tensile stress❷TEM-EDS analysis on interface

Shear stresstest specimen❸Thermal & structural analysis
 DTA (Differential thermal analysis)
 FT-IR (Fourier transform infrared
Tensile stresstest specimenspectroscopy)
 XPS (X-ray photoelectron spec.) Raman spectroscopy etc.

6Metal sheets with mirror-polished surface（Ra:0.01~0.05μm）;
pure Cu, Al, Ti and Mg plates
CFRP
plate

All metals chemicallybonded to CFRPs

CFRP compositions
Matrix; Polyamide66 (PA66), Reinforcements; Carbon fiber

PA66
Cu

PA66‐Cu

7

Bonding pure Ti plate to PA66, PET and PS plastics by hot press

Metal; pure Ti➡ C=O/C-O bond in PA66 & PETis effective for direct bonding ofplastic to Ti plate by hot pressing.

8Bonding pure Ti plate to PA66, PET and PS plastics by hot press

Metal; pure Ti

9Mechanical bonding – Locking (anchoring) effectBonding strength –Chemical bonding –Metal oxides formation
Metal complex formation

Load transfer at bonding interface by formation of oxides,
H-C-M complex and nitrides at interference during HPing

PA66 ⇨ C=O(C-O) & NH2
C=O;
Oxygen atoms separation anddiffusion to metal during H.P➡ Solution into metal and/orOxides formation at interface

NH2;
Hydrogen & nitrogen separation➡ C-H ⇒ H-C-M [complex]➡ N-M [nitrides] formation

10

FT-IR analysis on Ti-PA66 bonded specimen (T=260C×8s)

11 In Carbonyl group, A is major, but resonance structure with A and B➡ C=O (A) > C-O (B) in commercial PA66
Ratio of A ⇧ ➡ strong bonding➡ k value ⇧ ➡ κ ; wavenumber ⇧C=O bond more dominant atbonding interface to Ti
Oxygen atoms from PA66
concentrated at interface➡Solution & Oxides formation

12

Original oxide layer; 1~2 nm

13

TEM-EDS analysis on Ti-PA66 bonded specimen (260C×8s)

14

PA66
Ti
②③
❶

15

Oxygen content (at.%)Ti content (at.%)

16

17

XPS analysis on Ti-PA66 bonded specimen (T=256C)
3000

C-H
Intensity (cps)

2500
2000
1500

C-O
Interface of PA66
bonded to pure Ti

1000
500

PA66 matrix
0277

279

281

283

285

287

289

291

Binding Energy (eV)

293

295

297

18

Original PA66

[H-C-M complex]

19

Sputtered Ti film

PA66

Au

After H.T at 234C-1min.

20

Mechanical bonding – Locking (anchoring) effectBonding strength –Chemical bonding –Metal oxides formation
Metal complex formation

21

Mechanical bonding – Locking (anchoring) effectBonding strength –Chemical bonding –Metal oxides formation
Metal complex formation

PS (polystyrene) without C=O;
No ability in chemical bonding
Mechanical bonding behavior
evaluation using PS material➡ Effect of surface roughness ofmetal plates on bonding strength22

Mirror-polishing

23

In larger roughness, “limited” mechanical locking effect by gaps at interface
CuCu

PA66

5 μm

5 μm

CO

5 μm

5 μm

24

Specimens
Temperature
Applied loadPure Ti plate (18×18×1mm) and PA66 columnar
400℃ (pure Ti) in argon gas atmosphere
195g weight (for 30 sec)

25

ACCBAFlat topB

Round-edge(R=3mm)

26

Glassplate

PA66
VideoMirror

Set-up specimens

VideoMirror

Bubble formation from PA66 in melt
➡ Removing bonded area at interface

27

Key factors of metals for bonding Thermal stability of metal oxides
 Oxygen solubility in metals

28

FeCuMgAl

29

1. C=O bond was necessary for chemical bonding between
plastic and metal materials, where oxygen, hydrogen,carbon and nitrogen elements have roles in load transfer
at bonding interface by oxides, H-C-M complex andnitrides formation.
2. Chemical reaction was active when temperature of plastic
was over its melting point.
3. Mechanical locking effect due to metal surface roughness
was obviously effective to improve shear bonding strength
in using PS materials without C=O/C-O bond.
4. In-situ observation on direct bonding behavior indicatedbubble formation in plastic material at interface resulting
in removing bonded area.