Paper

A Formaldehyde-Free, Technical Sustainable Alternative for the Engineered Wood Industry

By Dr. Gregory J. Tudryn ngineered woods, such as particle come under substantial scrutiny due board and medium density to rising costs (now accounting for Ecovative is a recipient of RadTech’s fiberboard (MDF), are common upward of 30% of the product cost) 2014 Emerging Technology Award. Ewithin the furniture industry as each and detrimental human health effects. provides an inexpensive alternative to State regulations on the emission of solid wood construction. Although the formaldehyde from composite wood physical performance of particle board products (such particle board, MDF and MDF is adequate for furniture and hardwood plywood) and federal applications, there are significant amendments to the Toxic Substances legislative drivers for safer structural Control Act set formaldehyde emission core materials to limit the emission limits for composite wood products of volatile organic compounds. The sold in the United States. The National most common resins are urea Toxicology Program most recently formaldehyde (UF) or methylene added formaldehyde, a precursor to diphenyl diisocyanate (MDI), typically engineered woods, to the federal list constituting between 7% and 10% of of carcinogens. the final product’s total mass, which Ecovative has begun to develop a emit toxic volatiles either during or drop-in replacement for engineered post production. wood products (Myco Board™) which These resins instituted in the is economically competitive and production of traditional engineered intrinsically safe. This mycological wood products (UF, MDI) have recently biocomposite is comprised of biobased Figure 1 Mycelium, agricultural waste and grown biomaterial

(Left) 140x magnification of mycelium; (Middle) agricultural waste from the cotton industry; (Right) grown biomaterial that serves as protective packaging, the mycelium is white.

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Table 1

Physical performance metrics for flat engineered wood products at0.50 ” thickness

Metric Myco Board™ Myco Board™ Laminate MDF Technical Density (lbs/ft3) 30 37 53 Modulus of Rupture (psi) 820 1,700 1,595 Modulus of Elasticity (psi) 120,400 336,100 217,500 Screw Hold Strength (lbf) 110 110 132 Internal Bond Strength (lbf) 55 55 44 Energy to Produce (MJ/ft3) 79.5 98.1 234.9 Formaldehyde Emission (ppm) <0.001 <0.001 5

materials (ASTM D6866), which grown using biological resins, and is resources to manufacture materials, is unachievable with conventional comprised of lignocellulosic agricultural this material takes advantage of engineered wood products that rely byproducts bound cohesively into regionally sourced agricultural waste on synthetic resins. This product is designed shapes by filamentous to grow the biological resin, which literally grown, and is composed of fungal tissue (mycelium), analogous binds the desired product in a self- regionally sourced agricultural waste to traditional composite fillers and assembling process. Fungal vegetative that is bound with mycelium. resins, respectively (Figure 1). tissue (mycelium) propagates and The uniting of this biological The UV surface coating, developed binds to the agricultural fillers as it composite with UV-curable natural by Dr. James Crivello (Rensselaer grows apically into an interconnected resins enables this biotechnology as Polytechnic Institute), is comprised of fibrous network, analogous to addition- a finished boardstock, molded stock epoxidized vegetable oils and onium reaction synthetic resins forming in and paneling for a broad range of salt photoinitiators. situ within a composite material. demanding engineered wood markets The core material (mycological The mycelium derives its network with both structural and non-structural biocomposite) challenges the current strength from chitinous cell walls, product offerings. UV curing of natural paradigm of synthetic materials imparting high flame retardance and elastic modulus, and low thermal resins on mycological biocomposites and resins. Rather than using high- embodied energy processes and finite conductivity to the composite through enables the tailoring of surface features such as gloss, texture, coloration and embedding of antimicrobial agents Figure 2 while adding to overall mechanical Molded mycological composite engineered performance, all with minimal wood material additive and process time. This value-add is important to markets such as engineered woods, and is also applicable to coatings in Ecovative’s core technology of protective packaging using a sustainable, rapid, cost-effective UV process. This investigation highlights the use of two biologically inspired Features molded in place without subtractive processing resins—a self-propagating core bioresin and labor such as milling or cutting in replacement of formaldehyde, and a naturally derived UV-crosslinked surface coating. The core material is

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method (convective or conductive). Figure 3 Thermally activated surface coatings are prepared from epoxidized linseed Mechanical testing fixtures oil, applied manually (≤8g/ft2) and Technical cured at a temperature of 180°F for a duration of 10 minutes. UV-activated surface coatings are prepared from epoxidized linseed oil and applied manually (≤8g/ft2), using a 2 x 30 watt UV-C lamp (λ=254 nm) to cure at room temperature at a target distance of 48 inches for a duration of 10 minutes to ensure completion. Mechanical testing fixtures used for testing mycological Mechanical Testing composites to provide (a) Testing was performed in replicates of modulus of elasticity, modulus 12 on Instron testing machines 3345 of rupture, and (b) screw and 4411, using ASTM D1037 for Elastic withdraw strength following modulus, modulus of rupture and ASTM D1037. screw withdraw strength, ASTM C303 (EIN323) for density and externally for formaldehyde content using ASTM E1333 (EIN 120) (Figure 3). Alongside the sustainable and clean this high-Tg biopolymer. The ability content in excess of 10% [m:m], which to auto-generate tissue passively is comparable to the current state- solution to engineered wood arises the throughout the composite offers a of-the-art. Post processing of core desire to have an equally eco-conscious substantial reduction in resin cost and board material is denoted by drying coating. Applications of external processing energy—while remaining renewable, as well as cost- and Figure 4 performance-competitive (Table 1). Additionally, this self-assembling Modulus of elasticity for mycological composites process offers the ability to grow using convective processing precision features into the final product without further subtractive downstream processing or wasted material (Figure 2).

Materials Preparation Corn stover agricultural waste is industrially sourced, profiled for nutrition and sorted using market grade mesh sizing (fine to coarse). Sorted materials are grown separately, intermixed or layered to observe the effect of particle size on material packing and surface features. All Front axis denotes corn stover filler particle subtype, right material is autoclaved prior to axis denotes product treatment (foam referring to low density mycological composite analogs). inoculation (120°C, 15 psi, one hour), and incubated passively in warehouse conditions to achieve internal resin

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surface coating properties. At Figure 5 relatively higher contact temperature, conductively dried samples have Modulus of elasticity for mycological composites efficient heat transfer to the mycelium

using conductive processing resin, promoting a uniform distribution Technical of fused structural β-glucans (predominantly bound to the structural chitin layer of the mycelial cell wall). This resin sets on the product surface, preventing excess penetration of linseed oil, thus improving the UV exposure during the crosslinking of triglycerides by minimizing inaccessible reactive sites beneath the surface, and as such is reflected in the higher relative mechanical performance. Mycological composites prepared using fine particles offer good overall Front axis denotes corn stover filler particle subtype, right space filling and packing, resulting axis denotes product treatment (foam referring to low density in the highest density (43.6lb/ft3) mycological composite analogs). and well-resolved features. However, these composites are susceptible to fracture due to a relatively low aspect coatings each offer unique drawbacks. pinene, limonene and others. New ratio of fine particles. Coarse particles Liquid paint requires extensive photoinitiators demonstrate rapid provide less packing ability under preparation and often has relatively a curing of readily prepared unsaturated the same conditions as fine particles, high installation cost and low drying oils or commercially available but provide more desirable flexural throughput. Laminate materials have epoxidized vegetable oils, facilitating performance due to higher aspect ratios the ability to be grown into the core a rapid processing route that remains of lignocellulosic filler reinforcement 3 material without additional resin; sustainable and cost-effective, as well at lower density (21.9lb/ft ). The however, the necessity for edge as impart desirable surface coverage open-cell structure of uniform coarse banding or T-molding remains. and finish characteristics. particle results in a rougher surface Vinyl wrapping offers better and higher compressibility than the conformance than laminate; however, Results and Conclusions densely packed fine particles. Mixed drawbacks include a significant Figures 4 and 5 show the modulus of particle composites (33.3lb/ft3) offer amount of waste foil material and often elasticity of mycological composites higher elastic modulus relative to poorer visual aesthetics. Universally, determined from ASTM D1037, with coarse materials due to the interstitial traditional synthetic coatings often variation in filler particle size—fine, site-occupying nature of fine particles reinstate the selected drawbacks of coarse, mixed and layered (fine in a blend. This holds true in either petroleum-derived resins mentioned particles on the exterior)—in addition drying process method. This composite earlier. Naturally derived resins to coating type. Figure 4 provides blend provides uniform distribution of historically encounter a slow curing results from the convective drying applied stress, and a facile path for the process (e.g., autooxidation of diene process of mycological composites. mycelium to use turgor pressure and, bonds), thus limiting throughput. Figure 5 summarizes results from the subsequently, propagate and respire as However, photoinitiators (such as conductive drying process. The added a uniform bioresin. onium salts developed by Dr. Crivello’s mechanical strength of thermally cured Finally, layered materials (38.6lb/ft3) team at RPI) enable the consideration linseed oil and UV-cured linseed oil is perform similarly to coarse materials of sustainable epoxy monomer sources, more pronounced in samples subjected when untreated; however, with an including epoxidized vegetable oil to the conductive drying processing. applied linseed coating, they display triglycerides such as linseed, soybean, This is due to resultant consistent a marked increase in modulus if

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lignocellulosic core filler in corn Figure 6 stover; however, stover was selected for the specific nutrition profile for Mycological biocomposite material grown with the mycelium selected in this study.

Technical surface features and a rounded-edge feature, using Flexural strength (noted in Figure 7) lignocellulosic waste, convection dried and coated is imparted solely by the biological with UV-crosslinked vegetable oil resin and treatment coating, and can be bolstered using high aspect ratio fibers or veneers (Table 1, Figure 8). These experimental sets are beyond the scope of this investigation. It is observed that the thermally cured coat of linseed oil provides an increase in modulus of rupture, relative to non- coated samples. UV-cured coatings do not impart an additional increase in modulus of rupture on these corn particle subtypes. processed with conductive methods. In sets—with the highest modulus in this all scenarios, the linseed coating and study relative to density, and the most Summary UV coating are more amenable toward aesthetic and uniform surface coating A series of mycological biocomposites conductively processed samples, among test samples. were grown, processed, surface and the UV coating yields the most Figure 7 displays modulus of coated and tested for mechanical desirable finish (Figure 6) and strength rupture for corn stover mycological performance. The marriage of two (Figure 7). Overall, the mixed particle composites using conductive drying. bioderived technologies confirm that size composite using conduction The overall values represented here fungal mycelium composites using processing with UV coating offers the are lower than the products presented agricultural waste are enhanced when highest performance among the sample in Table 1 due to lack of fibrous used in conjunction with UV-cured epoxidized vegetable oil coatings. Figure 7 The resultant material demonstrates conductive drying of mycological Modulus of rupture (flexural strength) of composites is desirable to optimize mycological composites using conductive processing coating retention at the surface, maximizing UV exposure to minimize processing time. The use of conductive drying bolsters modulus of elasticity and modulus of rupture, while decreasing overall processing time due to efficient heat transfer and further enhances surface coating uniformity. Mixed filler particle sizes provide an optimal environment for biological resin, which is four-fold: • Improves incubation environment for biological resin formation Front axis denotes corn stover filler particle subtype, right • Provides a flat surface for coating axis denotes product treatment (foam referring to low density application mycological composite analogs). • Improves stress distribution through desired particle-particle interactions

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Figure 8 Mycological biocomposite with veneer laminate

bound to the agricultural waste and mycological Technical composite core

• Maintains relatively low density Acknowledgements with respect to mechanical strength This material is based upon work The verification of a rapidly supported in part by the National cured renewable surface coating on Science Foundation SBIR under mycological biocomposites solidifies Phase II Grant No. IIP-1152476. a cost-effective, environmentally The author thanks Todd Aldrich for safe alternative to engineered wood support in biological preparation and materials. Upcycling agricultural processing, and Dr. James V. Crivello waste using fungal tissue offers green for helpful discussions and coating composites competitive in both formulations. performance and cost to traditional MDF (Table 1). Epoxidized vegetable References oils provide the surface finish aesthetics . 1 “Information on California’s that can be specifically tuned to Formaldehyde Air Toxic Control Measure.” Composite Panel Association incorporate faster cure time, coloration, website. www.carbrule.org/index.htm texture, gloss or antimicrobial activity. (accessed August 10, 2010). These prospects, in combination 2. Long, Gary, Greg Fowler, and Check out with high fiber composites or veneers Simon Castley. “New Law Sets Formaldehyde Emission Standards for RADWIRE (Table 1, Figure 8), facilitate safe Composite Wood Products.” Lexology and sustainable options for the non- website. July 22, 2010. www.lexology. for all the load-bearing and possibly structural com/library/detail.aspx?g=1563f279- d6f4-4ebb-9d63-d31800a814b8 latest UV/EB material markets. This combination (accessed August 10, 2010). industry news of innovative design and processing 3. Crivello, J.V. “The Discovery and will enable sustainable engineered Development of Onium Salt Cationic To submit your latest materials that are lighter and as strong Photoinitiators” Journal of Polymer Science: Part A: Polymer Chemistry, news to both RadTech as selections that we have today. Vol. 37, 4241–4254 (1999) Consequently, transportation cost Report and RADWIRE, is lessened, air quality is improved —Dr. Gregory J. Tudryn is a email RadTech at and the complete product life cycle materials research director [email protected]. at Ecovative Design in improves both health and global Green Island, N.Y. environmental impact. w

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