Abstract
A process is described for developing bio-based foam board using state of the art freeze-casting technology. The bio-based thermal insulation foam board was produced starting from wood-based cellulose nanomaterials (CNs) water suspensions. Its performance properties were compared to the current products on the market: Foamular® 150 (F150), Styrofoam™ brand square edge insulation (SF), and GreenGuard® XPS (GG). The bio-based foam board’s density was 0.1 g/cm3 with an 8.16% coefficient of variation (CV), which was higher than F150’s density (0.03 g/cm3 with 0.35% CV), SF’s density (0.04 g/cm3 with 3.79% CV), and GG’s density (0.04 g/cm3 with 0.03% CV). The insulation value (R-value) was determined as 3.14 (1.47% CV) for bio-based thermal insulation foam board, 4.37 (0.39%) for F150, 4.43 (0.39%) for GG, and 5.59 (1.55%) for SF. The mechanical performance of the bio-based thermal insulation foam board was lower than those of the current products on the market, so that it requires further enhancement before potential commercialization. However, being among the first nanocellulose thermal insulation foam boards currently available, it still has great potential for use in building systems.
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Performance Comparison of Bio-based Thermal Insulation Foam Board with Petroleum-based Foam Boards on the Market
Nadir Yildirim *
A process is described for developing bio-based foam board using state of the art freeze-casting technology. The bio-based thermal insulation foam board was produced starting from wood-based cellulose nanomaterials (CNs) water suspensions. Its performance properties were compared to the current products on the market: Foamular® 150 (F150), Styrofoam™ brand square edge insulation (SF), and GreenGuard® XPS (GG). The bio-based foam board’s density was 0.1 g/cm3 with an 8.16% coefficient of variation (CV), which was higher than F150’s density (0.03 g/cm3 with 0.35% CV), SF’s density (0.04 g/cm3 with 3.79% CV), and GG’s density (0.04 g/cm3 with 0.03% CV). The insulation value (R-value) was determined as 3.14 (1.47% CV) for bio-based thermal insulation foam board, 4.37 (0.39%) for F150, 4.43 (0.39%) for GG, and 5.59 (1.55%) for SF. The mechanical performance of the bio-based thermal insulation foam board was lower than those of the current products on the market, so that it requires further enhancement before potential commercialization. However, being among the first nanocellulose thermal insulation foam boards currently available, it still has great potential for use in building systems.
Keywords: Building material; Nanocellulose; Bio-based; Foam board; Thermal insulation; Mechanical performance
Contact information: Assistant Research Professor, Bursa Technical University, Bursa, Turkey;
* Corresponding author: nadir.yildirim@btu.edu.tr
INTRODUCTION
The environmental, economic, and political impacts of energy production and use are an area of great concern. One of the most prominent uses of energy is the heating and cooling of buildings. Thus, construction companies are continually searching for ways to improve the insulation performance of the building envelope. However, the rigid foam board insulation products in widespread use today are produced from petroleum-based chemicals (Cervin et al.2013) that emit high levels of carbon during production. The materials also cannot be reused or recycled.
From 2008 to 2013 there was a significant increase in the insulation market, and global demand for insulation is projected to be nearly 26 billion square meters of R-1 (thermal resistivity) value in 2020 (The World Insulation Market 2016). This mirrors impressive growth in building construction activity. In North American residential construction applications alone, demand is projected to grow over 5% annually (The Smart Market Report, World Green Building Trends 2016).
Polystyrene represents approximately 8% of the global insulation market (The World Insulation Market 2016). The insulation market is well-established and has been home to much innovation during the past 50 years as new materials have been developed. Improvements have ranged from the development of improved paper insulation products to the invention of new foam boards. The bio-based thermal insulation foam board developed in this study offers a direct replacement for the petroleum-based rigid thermal insulation products that currently constitute the largest portion of the rigid insulation board market. The U.S. Department of Energy (DOE; US DOE 2017) data on the primary competitive products are shown in Table 1.
Table 1. Primary Competitive Products on Market
In addition to these petroleum-based products (Table 1), there have been many studies focusing on developing rigid and flexible green insulation products. Researchers have focused on design of flexible polyurethane foams using lignin-like waste residue obtained from Arundo donax L. (Bernardini et al. 2017). They successfully produced A. donax residue-based open-cell foams. Also, cork based insulation products exist on the market. Researchers compared the prices and the performances of the cork based products (Corecork NL10, Corecork NL20, Divinycell H60) and showed that the Divinycell H60 foam, which is the least expensive, also has the lowest mechanical performance properties (Urbaniak et al. 2017). Tondi et al. (2016) manufactured lignin foams in different densities as an alternative for traditional insulation materials (Tondi et al. 2016). These studies reveal strong interest in green thermal insulation products for use in building systems.
In this research, a bio-based foam board for thermal insulation was developed, characterized, evaluated, and compared to current commercially available thermal insulation foam boards.
The bio-based foam boards were developed using mechanically produced nanocelluloses. The first successful mechanical production of nanometer scale cellulose was in the 1980’s when a research group passed a wood pulp suspension through a homogenizer several times, resulting in a gel-like suspension of highly fibrillated cellulose that was named microfibrillated cellulose (MFC) (Turbak et al. 1983). This process involved forcing the material through a small capillary to break fibers apart. This requires high pressure to allow the wood fibers to break down from 30 µm to a size of 20 nm to 50 nm in diameter. Other mechanical methods have been reported, such as microfluidization, micro-grinding, refiners, and cryocrushing. Today, the nanoscale material generated through the mechanical process is often called nanofibrillated cellulose (NFC) or cellulose nanofibrils (CNF) (Turbak et al. 1983; Revol et al. 1992). The advantages of mechanical methods are high yield and the absence of chemical costs and chemical disposal costs.
This study concentrated on creating a novel bio-based foam board for use in the construction industry and comparing its performance properties with the current petroleum based products on the market.
EXPERIMENTAL
Materials
In this study, a bio-based foam board for thermal insulation purposes was created using biodegradable polymers that have low thermal conductivities and satisfactory mechanical properties. Then, the developed novel bio-based foam board was evaluated and compared with the current products on the market. Three commercialized products: Foamular® 150 (F150) (Owen’s Corning, Toledo, OH, USA), GreenGuard® (GG) (Lowes, Mooresville, NC, USA), and Styrofoam™ brand square edge insulation (SF) (Dow, Midland, MI, USA), were tested, evaluated, and compared with the bio-based foam board developed in this study.
The manufacturing process began with a nanocellulose, obtained from the University of Maine (Orono, ME, USA) and water suspension that was placed in trays. An industrial corn starch was added to the suspension after being cooked for 1 h at 90 °C to provide crosslinking (Yildirim et al. 2014). The obtained gel-like suspension was then placed into a freeze-dryer (SPScientific 25ES; SPScientific, Warminster, PA, USA). Next, thermocouples were placed in the material to monitor the temperature during the freeze-drying process (Fig. 1).