Applied Surface Science 266 (2013) 319–325 Contents lists available at SciVerse ScienceDirect Applied Surface Science j our nal ho me p age: www.elsevier.com/loc ate/apsusc Lotus-like paper/paperboard packaging prepared with nano-modified overprint varnish Wenting Chen a , Xinling Wang a,∗ , Qingsheng Tao b , Jinfang Wang b , Zhen Zheng a , Xiaoliang Wang b a School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang District, Shanghai 200240, PR China b Unilever R&D Shanghai, 66 Lin Xin Road, Shanghai 200335, PR China a r t i c l e i n f o Article history: Received 10 September 2012 Received in revised form 14 November 2012 Accepted 5 December 2012 Available online 16 December 2012 Keywords: Paper and paperboard Packaging Varnish coating Nano-structured Water resistance Anti-frost a b s t r a c t Paper/paperboard has great advantages over plastics as packaging material in terms of cost and sustaina- bility. However, the application of paper/paperboard packaging is limited due to their inferior water resistance performance. Here we report a functional overprint varnish prepared with the aim to signif- icantly abate the wettability of the printed packaging. The prominent water repellency of the varnish is rendered by its unique nano-structured morphology, a technology bio-mimicking lotus surface. The frost formation on the applied packaging is also inhibited. Moreover, the transparency and the applica- tion process of the varnish are retained. We expect such varnish has high potential for expanding the application field of paper/paperboard packaging, especially for uses requiring a strict standard of water resistance. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Papers and paperboards are extensively used in various indus- tries. The primary consumption of this kind of material is for producing various types of flexible, semi-rigid, or rigid packaging [1]. In addition to its effective cost and high application flexibility, paper/paperboard is also considered as the most environmentally friendly material for packaging, in view of its natural sourcing and easy recyclability. As a result, paper and paperboard are the largest- used packaging material throughout the world, by weight. The global paper packaging market in 2011 is reported to be worth 236 billion US dollar [2]. Paper and paperboard are sheet materials comprising an inter- laced network of cellulose fibers, which is intensely vulnerable to water or moisture owing to its hydrophilic nature. In many cases, an additional barrier material such as aluminum or plastic [3–5] is incorporated to improve their performance and function. How- ever, this laminated paper/paperboard packaging is not only more expensive but also less recyclable than those made only by paper [1]. Besides the metallic or plastic film, over-print varnish is another widely used protection technology, which is very cost-effective and very easy to apply. However, varnish does not have as good water ∗ Corresponding author. Tel.: +86 21 5474 5817; fax: +86 21 5474 1297. E-mail address: xlwang@sjtu.edu.cn (X. Wang). repellency as film. In an effort to enhance the water-resistance, hydrophobic polymer has been utilized to produce the over-print varnish, or wax/silicone additive has been incorporated. Although the performance of such varnish is good, neither of the methods is able to render the printed paper packaging completely waterproof like a lotus leaf. The mechanism underlying the super-hydrophobic properties of the lotus leafs was unveiled more than two decades ago [6]. Since then, mimicking such natural phenomenon to prepare the lotus- like surface has aroused intense interest both in academia and in industry, as the surface has demonstrated self-cleaning [7], water repellency [8], stain repellency [9], anti-bacteria [10], and many other superior benefits [11,12]. However, most of the reported technologies of preparing such surfaces are highly complicated and very difficult to be applied in industrial scale. That is proba- bly why only rarely have packaging materials, to the best of our knowledge, been reported to be modified to have the lotus-like surface. Nevertheless, if lotus-like superhydrophobic modification can be further applied to paper or paperboard packaging, to utilize its unique lotus-like properties, such as water and moisture-repellent, anti-frost formation, it will provide better packaging appearance benefits with less water/moisture/frost damage. In addition, it could also eliminate the usage of plastic coating on paper package and thus reduce environmental impact by yielding fully recyclable paper packages. 0169-4332/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2012.12.018