8 th June 2015, Valencia, Spain. INNOVHUB-SSI, Paper Division, Milano, Italy

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1 8 th June 2015, Valencia, Spain INNOVHUB-SSI, Paper Division, Milano, Italy

2 Outline Studies on the antibacterial effect of TiO 2 NPs coated paper Influence of the storage conditions Hydrophilic vs. Hydrophobic paper Development of photo-active TiO 2 /NFC coating formulations Direct Mixture vs. LbL approach Antibacterial activity Industrial Pilot trial at Multipackaging Solutions (UK) Development of an active overprint varnish formulation Antibacterial assessment of paper-based packaging with ZnO active nanoparticles Considerations on the impact on End of Life options Biodegradability Recyclability 2

3 TiO 2 NPs Mechanism Typical semiconductor, creates holes and electrons by light irradiation with higher energy than TiO 2 's band gap energy (wave length < 380nm). Solar radiation: only 5% radiation in the UV range. Ngo et al, Interface Science 163 (2011) Advantages Decomposition and elimination of organic compounds (e.g. NOx, ethylene) Possible inactivation of bacteria and moulds. Disadvantage Potencial oxidative degradation of cellulose and subsequent cleavage of polymer chain. 3

4 Methodology Functionalization of the paper surface with TiO 2 NPs Dip-coating: physical adsorption of inorganic nanoparticles Rod-coating: previous inclusion of nanoparticles in the NFC Sample Grammage (g.m -2 ) Cobb60 (H 2 O.m -2 ) BK BPK Paper TiO 2 photoactivation sample Dip-coated paper TiO 2 Water suspension TiO 2 Water suspension 4 h of exposition: - solar lamp (GE ARC70/UVC/ lux) Antibacterial activity Based on AATCC Test Method

5 log CFU T24 Studies on the antibacterial effect of TiO 2 NPs coated paper Bleached Kraft paper - BK S. aureus log T o = 5.6 Sample R BK1 4.1 Reference - BK BK TiO 2 retained on paper, g/m 2 log CFU T 0 5

6 log CFU T24 Antibacterial activity: Influence of the storage conditions Influence of the storage conditions over time: Indoor-light vs. dark 1 week Bactericidal effect for both indoor-light and dark conditions. 3 weeks: The bactericidal effect continues and is independently of the storage conditions log CFU T 0 1 week indoor-light 1 week dark 3 weeks indoor-light 3 weeks dark Reference 0.2g TiO2 0.8g TiO2 6

7 log CFU T24 Antibacterial activity: Hydrophilic vs. Hydrophobic paper Bleached Kraft paper (BK) versus Bleached pre-coated Kraft paper (BPK) S. aureus log T o = 5.6 Sample R BK BPK BK1 4.1 BK2 5.5 BPK1 0 BPK2 0 % TiO 2 BPK - Drawbacks Lower Cobb 60 hydrophobic paper Non-homogenous coating 7

8 Zeta potential (mv) Development of photo active TiO 2 /NFC coatings Advances in the use of NFC as a binder for rod-coating formulations NFC nanofibrillated cellulose Negatively charged surface NPs suspension Initial conditions: 6%TiO 2, ph = 1 Positively charged Electrostatic behaviour of the NPs suspension ph(i) ph TiO 2 NPs suspension is stable only at positive charge. 8

9 Direct mixture TiO 2 /NFC coating formulations Deposition of inorganic nanoparticles onto the NFC fibres surface IDEA: Increase the retention of NPs on NFC Layer-by-layer assembly - LbL approach By modification of NFC: 1. Polycation solution (PDDA) 2. Polyanion solution (PSS) Increasing the negative charge of NFC 9

10 TiO 2 added onto NFC (g/100g) Direct Mixture vs. LbL approach: retention efficiency Relation on the %TiO 2 retention by NFC DM formulations PE formulations PE - 2 layers P1 PE - 3 layers NFC DM TiO 2 retained on NFC (g/100g) DM formulations: just 25% of retention efficiency; PE type formulations presents a better efficiency for higher quantities of TiO 2 added to NFC; PE-3 layers shows the highest electrostatic interaction with a maximum of 90% of NPs grafted onto NFC. 10

11 Antibacterial activity BPK paper samples rod-coated with TiO 2 /NFC coating formulations S. aureus log T o = 5.6 Sample R Bacteriostatic effect 0.7 g TiO g TiO Inhibition to bacterial growth ( 2 log bacterial reduction) is verified on paper surfaces with 0.7 g of TiO 2 NPs per square meter; Antibacterial effect increases for higher concentrated samples. Possibility to develop contact active surfaces 11

12 Industrial Pilot trial at Multipackaging Solutions Development of an active overprint varnish formulation based on ZnO nanoparticles flexography printing Target Medical packaging to prevent cross contamination in hospitals 12

13 Viscosity (mpa) Development of the overprint varnish Industrial trial considerations Inorganic nanoparticles were chosen due to their commercial availability and good compatibility with industrial needs (e.g. absence of odour); TiO 2 was not compatible with the commercial varnish used at the industrial installation; ZnO was found compatible with the commercial varnish and had the advantage of being less sensitive to photo activation (dual antibacterial mechanism) Strain Rate (s -1 ) C1 C2 ZnO formulation C3 C4 Relatively good viscosity behaviour when up to 10% of the varnish was replaced by ZnO formulation. 13

14 log CFU T24 Antibacterial activity Paper-based medical packaging with ZnO active nanoparticles - MPK On the other hand! Poor bacteriostatic effect (R<1) S. aureus log T o = Sample R ZnO on paper, mg/m mg mg mg mg 3.8 Promising results for packaging with higher amounts of ZnO NPs Bactericidal effect 14

15 Considerations on the impact on End of Life options Biodegradability Recyclability 15

16 Biodegradability (%) Biodegradability (%) Biodegradability Tested Does the according nanoparticles to EN13432 affects standard the Biodegradability?? Time (days) Time (days) Paper ReferencePaper Reference MPK MPK+ZnO NPs MPK+ZnO NPs NO SIGNIFICANT DIFFERENCES between treated papers and reference! 16

17 Biodegradability (%) Does the nanoparticles affects the Biodegradability?? 100 Biodegradability days Time (days) Reference 1% TiO2 (w/w) 10% ZnO (w/w) Slightly delay for ZnO paper samples, maybe function of: Concentration of NPs Type of NPs Very likely both samples will reach the required 90% pass-level in the end of the experiment. 17

18 Recyclability of active packaging material Test carried out on kraft paper functionalized with TiO 2 NPs based on Aticelca method MC To understand where the nanoparticles goes! To the water stream, or Retained in the fibres? > 99% of TiO 2 NPs retention on the fibres, after one cycle. 18

19 Conclusions Photoactive TiO 2 nanoparticles can be directly deposited on hydrophilic bleached Kraft paper achieving strong antibacterial contact active surfaces; The bactericidal effect last several weeks after activation, under light or dark conditions; TiO 2 /NFC based coatings formulations can be used for hydrophobic paper samples. They can be developed by direct mixing, however polyelectrolyte-assisted deposition by LBL assembly is a good option to increase retention (90% retention efficiency against 25%); The industrial trial performed with an active overprint varnish formulation based on ZnO nanoparticles showed a relatively poor inhibitory effect; Future work will focus on finding suitable varnish components thus increasing ZnO concentration. Packaging End of Life options Laboratory tests showed only marginal effect of active ingredients on biodegradability performance. Recyclability tests proves a very good retention of TiO 2 nanoparticles in the fibres; After one recyclability cycle there is not migration of the NPs to the water stream; 19

20 Oral presentations: Outreach activities European Paper Week 2013, Brussels, Belgium, November 26-28, 2013, Antibacterial photo-active TiO 2 dip-coated paper. ICNF2015, 2 nd International Conference on Natural Fibers, Azores, Portugal, April 27-29, 2015, Antibacterial coating formulations based on NFC and photo-active TiO 2 nanoparticles. Aticelca, 46 th Annual Congress of the Italian Paper Industry, Sestri Levante, Italy, May 28-29, 2015, Development of Antibacterial Papers by Incorporation of Active Nanoparticles. Poster Presentations: NanotechItaly 2013 International Conference, Venice, Italy, November 27-29, 2013, Photoactive titanium dioxide for paper based packaging applications. Joint Conference PTS/COST FP 1003 On Innovative Packaging, Munich, Germany, May 20-21, 2014, Contact active materials for developing innovative antimicrobial paper based packaging. IFIB rd Italian Forum on Industrial Biotechnology and Bioeconomy, Naples, Italy, October 22-23, 2013, Antibacterial activity of TiO 2 on dip-coated papers for food contact packaging applications. Secondments: CBIMO, West Pomeranian University of Technology, Szczecin, Poland, July 2013; Encapsulation techniques suitable for paper based coatings applications; CICECO, University of Aveiro, Aveiro, Portugal, November, 2014, Development of suitable coating formulations by Layer by Layer Assembly for functionalize paper surfaces. 20

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