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Surface-modified wood based on silicone nanofilaments for improved liquid repellence

Time: Wed 2020-12-09 10.00

Location: Via Zoom:, Du som saknar dator/datorvana kan kontakta Tom Thöyrä / Use the e-mail address if you need technical assistance, Stockholm (English), (English)

Subject area: Civil and Architectural Engineering, Building Materials

Doctoral student: Haiyan Yin , Byggnadsmaterial, RISE Research Institutes of Sweden

Opponent: Professor Lars Wadsö, Lunds Tekniska Högskola

Supervisor: Professor Magnus Wålinder, Byggnadsmaterial; Professor Agne Swerin, Yt- och korrosionsvetenskap; Researcher Andra Dédinaité, Ingenjörspedagogik

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The increasing awareness of sustainability motivates the development of building materials from renewable resources. The requirements of wood-based products with improved durability, for example, an enhanced liquid repellence, is still a challenge. The aim of this thesis is to develop and study concepts to functionalize wood surfaces to obtain superhydrophobicity or superamphiphobicity, i.e. extreme liquid repellence of both water and oils.

Birch and acetylated birch veneer samples were surface-modified by hydrophobized silicone nanofilaments. Specifically, birch samples surface-modified by fluorinated silicone nanofilaments (F-SMB) showed superamphiphobicity, which repelled water, ethylene glycol and hexadecane with static contact angles greater than 150° and roll-off angles lower than 10°. Birch and acetylated birch samples surface-modified by non-fluorinated silicone nanofilaments (SMB and SMAB) showed superhydrophobicity with static contact angles greater than 160° towards water, even for samples prepared using the shortest silicone nanofilaments reaction time of 1 h.

In liquid uptake measurements submerging the F-SMB in water, ethylene glycol and hexadecane, a superamphiphobic plastron effect was observed which indicates that the wood surface was in Cassie-Baxter state. The plastron reduced the liquid uptake rate and extent depending on the interactions (diffusion and solubility) between the liquid and the silicone nanofilaments. The F-SMB showed good self-cleaning properties towards water and hexadecane.

In multicycle Wilhelmy plate measurements, the SMB showed a lower water uptake than that of the acetylated samples, while the SMAB showed the lowest water uptake, i.e. a pronounced increased water resistance, due to a combined effect of acetylation and surface modification.

In addition, the SMB exhibited more color change than the SMAB, which was caused by the release of hydrochloric acid during the surface modification process.