Nanoparticle Deposition on Packaging Materials by the Liquid Flame Spray Hannu Teisala a, Mikko Tuominen a, Mikko Aromaa b, Jyrki M. Mäkelä b, Milena Stepien c, Jarkko J. Saarinen c, Martti Toivakka c and Jurkka Kuusipalo a a Paper Converting and Packaging Technology, Tampere University of Technology,P.O.Box 541, FI-33101 Tampere, Finland b Aerosol Physics Laboratory, Tampere University of Technology,PO.Box 692, FI-33101 Tampere, Finland c Laboratory of Paper Coating and Converting, Center for Functional Mateials, Åbo Akademi University, FI- 20500 Turku, Finland Email: hannu.teisala@tut.fi Metal oxide nanoparticles were successfully deposited on-line at atmospheric conditions on packaging materials using a thermal liquid flame spray (LFS) method. LFS is a novel method for producing nanoparticle coatings on paper, paperboard and low density polyethylene (LDPE) laminates. Most of the present surface treatment/deposition methods are batch processes and require special conditions, e.g. low pressure atmosphere, which increase the operation costs and set limits for industrial applications. The LFS coating process is demonstrated in Figure 1a and the influences of process parameters on coating quality are presented. Physical and chemical properties of nanocoatings were investigated using scanning electron microscopy (SEM), water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Droplet behaviour on the nanocoated surfaces was illustrated by high speed video system images. a) b) Figure 1. a) The LFS coating process (on-line) and b) SEM images of the pigment coated paperboard surface before (above) and after (below) TiO 2 nanocoating. Titanium dioxide (TiO 2 ), silicon dioxide (SiO 2 ), aluminium oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) nanoparticle coatings were generated on packaging material surfaces. Such coatings possess high surface roughness in both micro- and nanoscale, and hence the hydrophobicity or hydrophilicity of the surfaces is increased. Figure 1b shows the specific hierarchical roughness of the TiO 2 coating that increases the hydrophobicity of the surface. Falling water droplets were able to bounce off from the nanocoated surface (Fig. 2a), on which the highest measured water
contact angle was over 160. Regardless of the high hydrophobicity, the coating showed sticky nature, creating a high adhesion to water droplets immediately as the motion of the droplets stopped. Because of the adhesive forces, water droplets are able to remain on the surface even though it is flipped upside down (Fig. 2b). Opposite to TiO 2 coating, on SiO 2 nanocoating the surface roughness benefits the wetting of the surface, and therefore the water contact angles even below 10 were obtained. Figure 2. a) Dynamics of the falling water droplet on the paperboard (rows a and c) and on the nanocoated paperboard (rows b and d). The droplet is able to bounce off the nanocoated surface. b) A set of images from the CA measurement illustrates the high adhesion between the water droplet and the nanocoating surface (left). 5 µl droplet is able to remain on the flipped surface (right). The composition and thickness of the nanocoating, and thus surface properties can be tailored with the coating parameters, i.e., with the concentration and the feed rate of the precursor solution, the burner distance and the line speed. Depending on the type of the substrate, different kinds of coating parameters are also needed in order to obtain superhydrophobicity or superhydrophilicity. The LFS coating process is a relatively simple, inexpensive and continuous method for the production of surfaces with nanoparticles of variable sizes from various materials. The method can be up-scaled straightforwardly for the industrial applications.
2010 INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY FOR THE FOREST PRODUCTS INDUSTRY 1 Nanoparticle Deposition on Packaging Materials by the Liquid Flame Spray HANNU TEISALA, M. TUOMINEN, J. KUUSIPALO (1 M. AROMAA, J. M. MÄKELÄ (2 M. STEPIEN, J. J. SAARINEN, M. TOIVAKKA (3 1) Paper Converting and Packaging Technology, Tampere University of Technology, P.O. Box 541, FIN-33101, Tampere, FINLAND 2) Department of Physics, Tampere University of Technology, P.O. Box 692, FIN-33101, Tampere, FINLAND 3) Laboratory of Paper Coating and Converting, Åbo Akademi University, Turku, FINLAND
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4 Content Background Liquid Flame Spray (LFS) process Results Superhydrophobicity and superhydrophilicity Superhydrophobicity vs. adhesion The amount of coating and the line speed Conclusions
5 Background Generate nanoparticles with flame process, i.e. liquid flame spray Particle material: TiO 2, SiO 2, ZrO 2, Al 2 O 3, Ag, Pd, Pt, Au, oxides of Na, Mg, Sr, Si, Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ag, W, Pl, Nd, Pr, Yb, Se and mixtures/composites Nanomaterial feed rate: 0.001-2.0 g/min Particle size range: 2-200 nm Develop thin layer -coatings on fiber based packaging materials: Pigment coated paperboard Paperboard Uncoated paper Paper Low density polyethylene coated paper LDPE
Liquid Flame Spray (LFS) process 6 LFS BURNER PRECURSOR SOLUTION LFS PROCESS LFS COATING PARAMETERS LINE SPEED LEVELS 30 150 m/min HYDROGEN OXYGEN BURNER DISTANCE FEED RATE 4 25 cm 4 32 ml/min DROPLETS CONCENTRATION 10 50 mg (atomic metal)/ml VAPOUR NANOPARTICLES NANOPARTICLE COATING MOVING SUBSTRATE ROLL 1 ROLL 2
7 Superhydrophobicity and superhydrophilicity Paperboard, (ref.), CA=77 SiO 2 coated, CA=12 TiO 2 coated, CA=161 Coated, TiO 2 Coating parameters of SiO 2 and TiO 2 : Fixed parameters: line speed 50 m/min, concentration 50 mg (atomic metal)/ml Variable parameters: 1) feed rate 32 ml/min, distance 15 cm
Superhydrophobicity and superhydrophilicity 8 Uncoated paper, (ref.), CA=120 SiO 2 coated, CA=7 TiO 2 coated, CA=164 1 µm 1 µm 200 nm Coating parameters of SiO 2 : 2) feed rate 12 ml/min, distance 15 cm Coating parameters of TiO 2 : 3) feed rate 12 ml/min, distance 6 cm
Superhydrophobicity and superhydrophilicity 9 TiO 2 coated LDPE, CA=151 LDPE, (ref.), CA=98 SiO 2 coated LDPE, CA=33 30 mg/m 2 10 mg/m 2 Coating parameters of TiO 2 : 1) feed rate 32 ml/min, distance 15 cm Coating parameters of SiO 2 : 2) feed rate 12 ml/min, distance 15 cm
10 Superhydrophobicity vs. adhesion Paper substrate (Bendtsen roughness: ~ 180 ml/min) < 10 > 10 non-adhesive surface Paperboard substrate (Bendtsen roughness: ~ 20 ml/min) 90 90 highly adhesive surface
The amount of coating and the line speed 1 1 Total amount of titania on paperboard ICP-MS Inductively Coupled Plasma Mass Spectrometry Flame temperature at 10 15 cm: 450 2000 C Paperboard temperature: 70 115 C LDPE, (1 parameters = 40 mg/m 2 Paper, (3 parameters = 30 mg/m 2 Paperboard, (3 parameters = 45 mg/m 2
12 The amount of coating and the line speed Paperboard (ref. 77 ) Paper (ref. 120 ) LDPE coating (ref. 98 ) Coating parameters 1-3) were constant at different line speeds TiO 2 The amount of TiO 2 coating on paperboard, (1 parameters: 50 m/min = 47 mg/m 2 100 m/min = 43 mg/m 2 150 m/min = 38 mg/m 2 SiO 2
Surface characteristics 13 XPS, X-ray photoelectron spectroscopy, (ESCA) SiO 2 and TiO 2 coatings on paperboard, coating parameters 1)
14 Conclusions Liquid Flame Spray (LFS) can be used to generate superhydrophobic and superhydrophilic surfaces onto paperboard and paper LFS has great potential for industrial scale method because of its continuous nature, low coating amounts and high line speeds The micro- and nanoroughness of surfaces enable the superhydrophobicity and superhydrophilicity The adhesive forces of superhydrophobic surfaces depend on the contact area between the liquid and the solid larger contact area leads to higher adhesive forces The different amount of carbonaceous material on the TiO 2 and SiO 2 coatings is the main reason for the opposite wetting behaviour of the surfaces
2010 INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY FOR THE FOREST PRODUCTS INDUSTRY 15 Thank you! Acknowledgements Tekes (Finnish Funding Agency for Technology and Innovation) Industrial partners: Stora Enso, UPM, Kemira and Beneq