bioresources. com
PEER-REVIEWED ARTICLE
Currently, engineered wood products use petroleum-based thermosetting resins such as urea formaldehyde, phenol formaldehyde, melamine fortified urea formaldehyde, or polymeric diphenylmethane diisocyanate (Hemmilä HWDO . 2017). Using these resins to create engineered wood products has adverse environmental and health consequences because of the emission of volatile organic compounds (VOCs) such as formaldehyde (Hemmilä HWDO . 2017). New engineered wood products often employ isocyanate resins since they do not contain formaldehyde and are considered non-volatile when cured. In addition, other additives are incorporated into the FB such as borate compounds (to prevent termites, wood boring beetles, molds, and fungi) and waxes (to increase hydrophobicity) (Hemmilä HWDO . 2017). Engineered wood products are a major source of formaldehyde off-gassing in US homes and present a serious health problem (CPSC 2013). Formaldehyde is classified as a carcinogen, and its exposure levels are regulated in the USA to avoid health problems (CEPA-ARB 1997; EPA 2010; CPSC 2013; ClassAction.org 2015; Hemmilä HWDO . 2017). However, wood composite flooring made in China and exported to the US have formaldehyde emission levels that exceed current US safety emission standards, in some cases by as much as 350% (ClassAction.org 2015). Soy protein-based adhesives derived from soya bean meal (SBM) have been employed to some extent over the last 80 years (Zhong HWDO . 2001). Soybean proteins are an alternative to petroleum polymers because of their abundance, renewability, biodegradability, and feasibility (Mo HWDO 2001, 2003; Mohanty HWDO . 2002; Lodha and Netravali 2005a, 2005b; Liu and Li 2007; Frihart HWDO . 2014; Nasir HWDO 2014; Xu HWDO 2014). Soybean meal is inexpensive, abundant, and easy to handle because it can be cold or hot pressed (Zhong HWDO . 2001; Amaral-Labat HWDO . 2008; Jeon HWDO . 2011; Reddy and Yang, 2011; Gu HWDO . 2013; Xu HWDO 2014). However, SBM was essentially replaced in the 1960s by less-expensive synthetic adhesives. In recent years, interest in their use as adhesives was renewed because they are biodegradable and free of VOCs. For example, Uniboard (Laval, Quebec, Canada) markets a “Nu Green SOYA” particle board uti lizing a soy based adhesive (Uniboard Canada Inc. 2016). Soya protein isolate (SPI) has high adhesion strength but costs more than PF and UF (Mo HWDO . 2001; Zhong HWDO . 2001; Kumar HWDO . 2002; Lodha and Netravali 2005a; 2005b; Liu and Li 2007; Vnučec HWDO 2015). Commercial products such as SPI (Pro-Fam 970) (ADM, Decatur, IL) containing 90% protein (dry basis) and defatted SBM such as Prolia (PRO) (Cargill, Cedar Rapids, IA) containing ≥ 50% protein are available. SBM currently sells for | $0.45 to $0.50/lb ($0.99 to $1.10/kg) (Alibaba.com 2016). Other sources of bio-based adhesives have also been developed (Shukla and Cheryan 2001; Beg HW DO . 2005; Norström HW DO 2014). Of particular interest is the employment of zein, which is derived from corn gluten meal and is highly effective as a resin/adhesive (Shukla and Cheryan 2001). Zein is a prominent storage protein (a prolamine protein) in corn and comprises | 35 to 40% of the corn protein. It is extracted from corn gluten meal, which is obtained from the wet milling processing of corn seeds. Unfortunately, the cost of zein is prohibitive to most commercial enterprises such as bio- plastics and bio-composites. Zein sells for | $4.54 to $18.20/lb ($10 to $40/kg) (Shukla and Cheryan, 2001). Corn gluten meal itself contains 55 to 70% protein and is considerably less expensive, selling for | $0.36 to $0.45/lb ($0.79 to $0.90/kg) (Alibaba, 2016). Corn gluten meal has been employed in a myriad of products including livestock feed, plastic fillers, coatings, and bio-plastics (Beg HWDO 2005; Samarasinghe HWDO 2007).
2679
Tisserat et al . (2018). “DDGS - PW fiberboards” B io R esources 13(2), 2678-2701.
Made with FlippingBook Ebook Creator