1. PECVD in ORGANOSILICON FED PLASMAS

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1 F. FRACASSI Department of Chemistry, University of Bari (Italy) Plasma Solution srl SURFACE MODIFICATION OF POLYMERS AND METALS WITH LOW TEMPERATURE PLASMA OUTLINE METAL TREATMENTS 1 low pressure PECVD with organosilicons Surface protection of metals 3. Rubber-metal adhesion reduction PLASTIC TREATMENTS. high pressure plasma: dielectric barrier discharge (DBD) 5. surface fluorination of PET and PP 6. fluoropolymer deposition 1

2 1. PECVD in ORGANOSILICON FED PLASMAS OCH CH3 CH3CH O-Si-OCH CH3 CH3CH O CH3 CH3 CH3-Si-O-Si-CH3 CH3 CH3 OCH3 CH3O-Si-OCH3 OCH3 CH3 CH3-Si-CH3 CH3 TEOS HMDSO TMOS TMS organosilicon monomer plasma activation fragments homogeneus reactions and oxidation precursors powders coating eterogeneous oxidation CH 3 CH 3 CH 3 -Si-O-Si-CH 3 Inorganic coating O CH 3 CH 3 HMDSO Inert (Ar, He) inorganic glassy, SiO x (SiO -like) organic, SiO x C y H z

3 COATING STABILITY Si-OSi Si-OSi NO SYLANOL Si-OH after 70 h in NaCl 0,1 M after h in NaCl 0,1 M as deposited SYLANOLS ARE REACTIVE HOW TO REDUCE SiOH SiO-H CH x 100W 00W 300W Si(CH 3 ) x Si-O-Si Si-OH wavenumber (cm -1 ) wavenumber (cm -1 ) HIGH INPUT POWER LOW Si-OH 3

4 . SURFACE PROTECTION: - CORROSION PROTECTION Magnesium alloys: WE3 (Mg 9%, Y 3%, Nd 3%) AM 60B (Mg 9 %, Al 5.5%,.) EVALUATION OF CORROSION PROTECTION EIS (Electrochemical Impedance Spectroscopy) High Rct High corrosion resistance Salt spray fog test RESULTS 8 8 Mg best corrosion resistance vs monomer 7 Log Rct (Ω cm ) HMDSO TEOS 3 HMDSN OEt EtO-Si-OEt EtO TEOS O- -O-Si-O- -O SiO

5 EFFECT OF O ADDITION ON CORROSION RESISTANCE 10 5 log R ct (Ω cm ) organic inorganic O / TEOS 10 3 Inorganic coatings have a better protection capability Mg: the corrosion resistance decreases with surface roughness log R ct (Ω cm ) roughness (nm) 1 3 5

6 Optimization of the deposition process on rough Mg substrates multilayer coating SiOx (TEOS-O -Ar) inorganic SiOC (TEOS-Ar) organic Mg THE CONFORMALITY OF COVERAGE DOES APPRECIABLY WITH FEED COMPOSITION NOT CHANGE 1.0 side top R= side / top O /TEOS The better performance is not due an improved coverage of the rough surface But probably to the better adhesion of the organic layer 6

7 TARNISHING PROTECTION OF SILVER ALLOYS PECVD SiOx (inorganic) can be utilized for tarnishing protection of silver alloys Tarnishing test Intermittent exposures (,( 8 and 7 hours) ) to air and sulph phide solution 0.1 M (Na S) aerated solution at room temperature Visual evaluation of tarnishing and comparation with uncoated samples. Silver (Ag90Cu10) after the tarnishing test uncoated Silver After 1 min in Na S solution Silver coated with 900 nm SiO x (H pretreatment) after h in Na S Silver coated with 100 nm SiO x (H pretreatment) after 8 h in Na S 7

8 3. RUBBER-METAL ADHESION REDUCTION AND REDUCTION OF RUBBER RESIDUES SUBSTRATES: STEEL AND ALLUMINUM NATURAL AND SYNTHETIC RUBBER ADHESION EVALUATION EVALUATION OF THE STRENGHT NECESSARY TO SEPARATE THE RUBBER TO THE METAL SUBSTRATE AT 180 C COATING EXPLORED -TEFLON-LIKE deposited at 150 C - inorganic SiOx deposited at 5 C - inorganic SiOx deposited at 50 C - organic polysiloxane deposited at 5 C 8

9 PLANARIZING EFFECT OF PECVD SiOx sandblasted virgin aluminum, AFM inspection UNCOATED COATED RESULTS OF ADHESION TESTS 1 1 Avg. Adhesion Force (N) Untreated Al Teflon-like 150 C Dep Polysiloxane 5 C Dep SiO -like 5 C Dep SiO -like 50 C Dep 9

10 masked zone low T organic SiOx RUBBER masked zone untreated Teflon like high T inorganic SiOx. DIELECTRIC BARRIER DISCHARGES (DBD) Atmospheric pressure non-equilibrium plasma At least one dielectric layer in the current path between the metallic electrodes. HV Generator ~ electrode dielectric electrode The dielectric No arc transition Atmospheric pressure cold plasma Experimental conditions AC Voltage: Amplitude,8 kv rms, frequency = khz Electrode configurations: parallel plate geometry, Interelectrode distance = - 5 mm Dielectric materials: alumina 10

11 Filamentary DBD ~ Glow DBD ~ High number of MICRODISCHARGES randomly and evenly distributed both in time and in space No evidence of microdischarge formation. microdischarge through a transparent electrode U. Kogelschatz, Plasma Chem. Plasma Process., Vol. 3, No. 1, SURFACE FLUORINATION of PET and PP CF He f (khz) V a (kv pk-pk ) P (W cm - ) φ He (slm) φ CF (sccm) [CF ] (%) d = 5 mm Gas Position (mm) HT measurement position Electrode Dielectric Substrate SWCA (degree) untreated PP untreated PET PP PET [CF ] (%) 11

12 EFFECT OF TREATMENT TIME 5 KHz SWCA (degree) PET PP t tr (min) EFFECT OF FREQUENCY HT Electrode Dielectric d = 5 mm Gas Substrate 10 Position (mm) SWCA (degree) PET PP untreated PP PP untreated PET PET Frequency (khz) 1

13 6. FLUOROCARBON DEPOSITION He-C 3 F 8 -H f (khz) V a (kv p-p ) P (W cm - ) φ He (slm) φ C3F8 (sccm) φ H (sccm) [C 3 F 8 ] (%) [H ]/[C 3 F 8 ] ratio (a.u.) EFFECT OF FEED COMPOSITION r d (nm min -1 ) DEPOSITION RATE [H ]/[C 3 F 8 ] ratio (a.u.) Normalized absorbance (a.u.) [H ]/[C 3 F 8 ] ratio FTIR CF C=CF, OH CH CF=CF, C=O CF CF Wavenumber (cm -1 ) XPS C 1s curve fit CF CF 3 C-CF CF (CO) [H ]/[C 3F 8] = 0 F/C = 1.5 C-C [H ]/[C 3F 8] = 0.5 F/C = 1. [H ]/[C 3F 8] = 1.0 F/C = 0.9 [H ]/[C 3F 8] =.0 F/C = Binding Energy (ev) 13

14 XPS Atomic concentration ratio (a. u.) Atomic concentrations F/C O/C [H ]/[C 3 F 8 ] ratio (a. u.) WCA [H ]/[C 3 F 8 ]: 0 SWCA: AWCA: RWCA: [H ] F/C O/C Crosslinking degree H addition increases: - crosslinking, - concentration of dangling bonds in the film - oxygen uptake EFFECT OF FREQUENCY (15-30 KHz) FTIR XPS and WCA Normalized absorbance (a.u.) 30 khz 5 khz 0 khz 15 khz OH C=CF CF=CF C=O CF x Wavenumber (cm -1 ) F/C XPS ratio (a.u.) Frequency (khz) SWCA (degree) rough surface, powders smooth no powder 1

15 CONCLUSIONS - Low pressure PECVD of organosilicon compounds can be utilized to protect metal surfaces and to modify metal-rubber adhesion. - Atmospheric pressure glow dielectric barrier discharges is a suitable way to implant fluorine atoms on PET and PP thin films. - Atmospheric pressure glow dielectric barrier discharges ca also be utilized for fluoropolymer deposition. Hydrogen addition has the same effect than in low pressure plasma. 15