Advances in Cottonseed-Guayule Resin Research as a Bio-Based Adhesive for Hardwood Plywood

Abstract

This research focuses on the production of wood adhesives from upland cotton (Gossypium hirsutum L.) and guayule (Parthenium argentatum A. Gray) plants. Literature indicates that the cottonseed protein meal can be used as an environmentally safe and friendly, bio-based, formaldehyde-free wood-based adhesive. Harvested guayule woody biomass is ground into bagasse (a fine fibrous wood pulp byproduct) from which solid latex rubber is chemically extracted, leaving a guayule resin byproduct. Research shows that guayule resin has the potential as low-toxicity components of coatings, tackifiers, adhesives, emulsifiers, bio-control agents, insecticides, antimicrobials, and antifungals. Guayule has demonstrated performance as a natural biocide (termiticide and fungicide). This research focused on adding a guayule resin-acetone solution to a cottonseed meal adhesive formulation to produce three-ply yellow poplar (Liriodendron tulipifera L.) plywood. Three adhesives (53% protein cottonseed meal, cottonseed-guayule-acetone adhesive, and 49% protein in-house soybean meal) were prepared and evaluated. Commercially manufactured soybean adhesive bonded yellow poplar plywood panels were also purchased and tested for comparison. Each protein meal was mixed with deionized water, sodium metabisulfite (Na2S2O5), and a polyamido-amine-epichlorohydrin (PAE). The plywood panels were hot pressed for 6 minutes at 135°C at a constant pressure of 1.24 MPa. Then each panel was processed into four different test specimen regimes to conduct mechanical shear strength, water resistance, decay resistance, and termite resistance as per national and international standards. Preliminary results show similar water resistance and mechanical shear strength among the cottonseed, cottonseed-guayule resin, and in-house soybean adhesive bonded plywood panels. The commercial soybean-based adhesive resulted in a lower mechanical shear strength. The cottonseed and cottonseed-guayule adhesives show promise as formaldehyde-free bio-based hardwood-plywood adhesives for interior applications. This research is ongoing with decay and termite resistance testing.

Full text

PROCEEDINGS
One Hundred Eighteenth Annual Meeting
of the
AMERICAN
WOOD PROTECTION
ASSOCIATION
The Francis Marion Hotel
Charleston, South Carolina
May 15-17, 2022
VOLUME 118
AMERICAN WOOD PROTECTION ASSOCIATION
P.O. BOX 361784 • BIRMINGHAM, ALABAMA 35236-1784 • USA

COPYRIGHT, 2022
BY
AMERICAN WOOD PROTECTION ASSOCIATION
P.O. BOX 361784
BIRMINGHAM, ALABAMA 35236-1784
USA
Rights to republish papers and reports published herein, in whole or in part, or by
reference are granted to all persons, provided that reference to the authors and to the
AWPA Proceedings are made.
Statements made or opinions expressed in this publication shall not be the responsibility of
the American Wood Protection Association.
ISBN (Casebound/Hardcover Edition): 979-8-9868619-8-2
ISBN (Perfect Bound/Paperback Edition): 979-8-9868619-9-9
ISSN: 0066-1198
Colin McCown, Editor
Je Schoeld, Assistant Editor

Table of Contents
Proceedings of the 118th Annual Meeting of the
American Wood Protection Association
Monday, May 16, 2022
OPENING SESSION
Welcome – Patrick Stark ............................................................................................................................................................. 3
Invocation – Norman Sedillo ....................................................................................................................................................... 3
Member Recognition – Patrick Stark ........................................................................................................................................... 3
Organizational Sponsor Recognition – Patrick Stark ................................................................................................................... 3
Protectant/Preservative General Committee Report – Grant Kirker ............................................................................................ 5
Treatments General Committee Report – Bill Buczek ................................................................................................................ 6
Vice President’s Remarks – Kevin Archer .................................................................................................................................. 7
President’s Remarks – Patrick Stark ............................................................................................................................................ 9
BUSINESS SESSION
Call to Order, Approval of Minutes – Patrick Stark .................................................................................................................. 11
Antitrust Reminder – Colin McCown ........................................................................................................................................ 11
Treasurer’s Report – Ken Laughlin ........................................................................................................................................... 12
Membership Report – Jay Hilsenbeck ....................................................................................................................................... 12
Resolutions Committee Report – Norm Sedillo ........................................................................................................................ 12
General Election Results – Patrick Stark ................................................................................................................................... 13
TECHNICAL SESSION 1
Keynote Session
Trends Impacting the North American Forest Economy (Abstract) – Pete Coutu ..................................................................... 16
A Lumberman’s Perspective on the Wood Preserving Industry (Title Only) – Furman Brodie ................................................ 18

TECHNICAL SESSION 2
Colley/Hartford Memorial Lecture and Research Symposium
Colley/Hartford Memorial Lecture: Wood Architecture: Current Trends in Mass Timber and Thoughts about
Exposing Wood – Ulrich Dangel ........................................................................................................................................ 20
Plant Polyphenolic Extracts as Natural Pesticides for Wood Protection Treatments – Jean-Paul Joseleau, Katia Ruel,
Daouïa Messaoudi, Florent Chopinet, Jany-Damien Cardia ............................................................................................... 28
Advances in Cottonseed-Guayule Resin Research as a Bio-Based Adhesive for Hardwood Plywood – Edward D.
Entsminger, Dercilio J.V. Lopes, Ramon F. Oliveira, Gabrielly dos Santos Bobadilha, Amy L. Rowlen, Rubin
Shmulsky, Michael K. Dowd .............................................................................................................................................. 34
Durability of 33-Year-Old Preservative Treated Test Structures in Mississippi – Brianna A. Duquette, C. Elizabeth
Stokes ................................................................................................................................................................................. 43
How Industry-University Partnership Drives Innovation (Abstract) – Tâmara França ............................................................. 46
Automated Means for Assessing Wood Failure – Ramon Ferreira Oliveira, Dercilio Junior Verly Lopes, Edward D.
Entsminger .......................................................................................................................................................................... 47
TECHNICAL SESSION 3
Student Presentations
Thermally Modified Wood Particles for Production of Water and Fungi Resistant Wood Plastic Composites –
Edgars Kuka, Bruno Andersons, Dace Cirule, Ingeborga Andersone ................................................................................ 54
Migration Assessment of Creosote Components from Creosote-Treated Posts: Preliminary Results – Skyler Foster,
Matthew Konkler, Gerald Presley ...................................................................................................................................... 69
Switchable Superhydrophobic Titania Coating on Wood Surface by Using Liquid-Precursor Flame Spray Pyrolysis –
Ganesh Sedhain, Shuaib A. Mubarak, Yunsang Kim ......................................................................................................... 82
Selected Physical and Mechanical Properties and Durability of Alder Wood (Alnus glutinosa Gaertn.) Before and
After Thermal Modification and Thermo-Mechanical Densification – Juliusz Formella, Marek Grześkiewicz,
Bogusław Andres ................................................................................................................................................................ 94
Development of Preservative-Treated Cross-Laminated Timber: Effects of Panel Layup and Thickness on Preservative
Penetration and Retention – Samuel Ayanleye, Franklin Quin, Xuefeng Zhang, Darrel Nicholas, Rubin Shmulsky,
Hyungsuk Lim .................................................................................................................................................................. 107
Tuesday, May 17, 2022
TECHNICAL SESSION 4
Preservative Analysis and Performance
Sample Preparation Guidelines for X-Ray Fluorescence Analyzers – Kim Merritt, Vicki Luckie, Robert Bartek ................. 114
Copper Naphthenate - Data and Capability Update – Jae-Woo Kim, Jeff Lloyd .................................................................... 128

Research on Carrier Oils and Their Contribution to Preservative Performance and Depletion of IPBC/Permethrin
Formulation – Min Chen, Geoff Webb ............................................................................................................................. 143
Leaching Study of Coated Wood Pilings in Saltwater (Abstract) – C. Elizabeth Stokes, Emily White, Mike Sanders,
Kevin Ragon, Grady Brafford .......................................................................................................................................... 148
AWPA & Zinc Borate – Mark Manning .................................................................................................................................. 149
Long-term Performance of ACQ and CCA Treated Radiata Pine Heartwood Decking in a Subtropical Above-ground
Exposure – Babar Hassan, Michael Powell, Jeffrey J. Morrell, David Gardner ............................................................... 153
Durability of Pressure Treated Domestic Hardwood Trailer Decking in the Tropical Rainforest (Abstract) – Xinfeng
Xie, Joseph Eskola, Grant Kirker, Xiping Wang, Keith York, Nathan Kamprath, Sebastian Karwaczynski ................... 163
TECHNICAL SESSION 5
Public Utility and Railroad Issues
Assessing Utility Pole Strength with Ultrasonic Stress Waves (Abstract) – Frederico França ............................................... 166
The Role of Wood Utility Poles and Preservatives in Grid Resiliency (Abstract) – Chad Newton, Robert Batchelor ........... 167
Prolonged Performance of Boron Rods as Internal Utility Pole Treatments – Matthew J. Konkler, Jed Cappellazzi,
Gerald Presley, Jeffrey Morrell ........................................................................................................................................ 168
Exterior Fire Retardant Coating for Utility Poles – Min Kuang, Jun Zhang ........................................................................... 173
Degradation of Low Concentrations of DCOI from Soil, Water, and Wood Suggest Low Environmental Persistence
and Reduced Off-target Effects from Treatment Migration – Leon Rogers, Matthew Konkler, Gerald Presley ............. 177
The Railway Tie Association: Past, Present, and Future (Abstract) – Nathan Irby ................................................................. 182
TECHNICAL SESSION 6
Environmental Considerations
Wood Preserving Regulatory Overview (Abstract) – Robert T. Smith ................................................................................... 184
Developing Environmental Benchmarks for New Chemistries: Opportunities for Collaboration – Christine M.
Britton, Dan Skall ............................................................................................................................................................. 186
EPA Regulatory Update on Wood Preservatives (Abstract) – Peter Bergquist ....................................................................... 189
Environmental Justice and the Wood Preservation Industry – Amy Bauer, Dana McCue ...................................................... 190
Assessment of Metal Migration from Treated Vineyard Trellising and Garden Boxes into Soil and Plant Biomass –
Matthew Konkler, Gerald Presley .................................................................................................................................... 198
TECHNICAL SESSION 7
Durability of Mass Timber
The Current Status of Hardwood Cross Laminated Timber (Abstract) – Sailesh Adhikari, Brian Bond, Henry
Quesada, Daniel Hindman ................................................................................................................................................ 208
Service Life Prediction of Coated CLT: Is It Possible to Estimate When It’s Time to Recoat? – Gabrielly dos Santos
Bobadilha, Emily White, C. Elizabeth Stokes .................................................................................................................. 209

Resistance of Cross-laminated Timber (CLT) to Subterranean Termites (Abstract) – Tâmara França, C. Elizabeth
Stokes, Juliet Tang ............................................................................................................................................................ 217
Assessment of Termite and Decay Damage to Mass Timber Elements in AWPA Ground Proximity and Above
Ground Field Tests in Southern Mississippi – Mark E. Mankowski, Thomas G. Shelton, Grant Kirker, Jeffrey J.
Morrell .............................................................................................................................................................................. 218
Exploring the Use of Mass Timber Panels for Highway Noise Barrier – Laura Redmond, Weichiang Pang, Harsh
Bothra, Adelaide Heigel, Patricia Layton ......................................................................................................................... 227
AWPA Technical and Special Committees
Report of Technical Committee P-1 ........................................................................................................................................ 234
Report of Technical Committee P-3 ........................................................................................................................................ 235
Report of Technical Committee P-4 ........................................................................................................................................ 237
Report of Technical Committee P-5 ........................................................................................................................................ 239
Report of Technical Committee P-6 ........................................................................................................................................ 242
Report of Technical Committee P-9 ........................................................................................................................................ 244
Report of Technical Committee T-1 ........................................................................................................................................ 245
Report of Technical Committee T-2 ........................................................................................................................................ 246
Report of Technical Committee T-3 ........................................................................................................................................ 248
Report of Technical Committee T-4 ........................................................................................................................................ 249
Report of Technical Committee T-7 ........................................................................................................................................ 250
Report of Technical Committee T-8 ........................................................................................................................................ 252
Report of Technical Committee T-11 ...................................................................................................................................... 254
Report of Special Committee S-2 ............................................................................................................................................ 256
Report of Special Committee S-3 ............................................................................................................................................ 257
Report of Special Committee S-8 ............................................................................................................................................ 258
Technical and Special Committee Membership ...................................................................................................................... 259
AWPA Technical Committee Regulations (September 2021) ................................................................................................. 264
Attendees of the 2021 AWPA Fall Technical Committee Meetings ....................................................................................... 278
Fall Technical Committee Meeting History ............................................................................................................................. 280
Other Information
AWPA Membership Application ............................................................................................................................................. 283
Directory of AWPA Members ................................................................................................................................................. 285
Membership Listing by Classification ..................................................................................................................................... 298
In Memoriam ........................................................................................................................................................................... 311
AWPA’s 2022 Organizational Sponsors ................................................................................................................................. 312
118th AWPA Annual Meeting Individual Contributors ........................................................................................................... 330
Attendees of the 118th AWPA Annual Meeting ....................................................................................................................... 331
Annual Meeting History .......................................................................................................................................................... 334

AWPA Award of Merit Honorees ........................................................................................................................................... 337
Articles of Incorporation .......................................................................................................................................................... 338
By-laws of the AWPA ............................................................................................................................................................. 341
Refereed Publication Policy ..................................................................................................................................................... 345
AWPA Award of Merit Policy and Regulations ...................................................................................................................... 346
AWPA Officers and Committees, 2022-2023 ......................................................................................................................... 348
Past and Present Officers and Executive Committee Members ............................................................................................... 349
Associations with Interests in Wood Protection ...................................................................................................................... 361
AWPA Publications and Order Form ...................................................................................................................................... 363
Index ........................................................................................................................................................................................ 365

Advances in Cottonseed-Guayule Resin Research
as a Bio-Based Adhesive for Hardwood Plywood
Edward D. Entsminger
Dercilio J.V. Lopes
Ramon F. Oliveira
Gabrielly dos Santos Bobadilha
Amy L. Rowlen
Rubin Shmulsky
Mississippi State University
Starkville, Mississippi
Michael K. Dowd
USDA ARS Southern Regional Research Center
New Orleans, Louisiana
ABSTRACT
This research focuses on the production of wood adhesives from upland cotton (Gossypium hirsutum L.) and guayule
(Parthenium argentatum A. Gray) plants. Literature indicates that the cottonseed protein meal can be used as an
environmentally safe and friendly, bio-based, formaldehyde-free wood-based adhesive. Harvested guayule woody biomass is
ground into bagasse (a fine fibrous wood pulp byproduct) from which solid latex rubber is chemically extracted, leaving a
guayule resin byproduct. Research shows that guayule resin has the potential as low-toxicity components of coatings, tackifiers,
adhesives, emulsifiers, bio-control agents, insecticides, antimicrobials, and antifungals. Guayule has demonstrated
performance as a natural biocide (termiticide and fungicide). This research focused on adding a guayule resin-acetone solution
to a cottonseed meal adhesive formulation to produce three-ply yellow poplar (Liriodendron tulipifera L.) plywood. Three
adhesives (53% protein cottonseed meal, cottonseed-guayule-acetone adhesive, and 49% protein in-house soybean meal) were
prepared and evaluated. Commercially manufactured soybean adhesive bonded yellow poplar plywood panels were also
purchased and tested for comparison. Each protein meal was mixed with deionized water, sodium metabisulfite (Na2S2O5),
and a polyamido-amine-epichlorohydrin (PAE). The plywood panels were hot pressed for 6 minutes at 135°C at a constant
pressure of 1.24 MPa. Then each panel was processed into four different test specimen regimes to conduct mechanical shear
strength, water resistance, decay resistance, and termite resistance as per national and international standards. Preliminary
results show similar water resistance and mechanical shear strength among the cottonseed, cottonseed-guayule resin, and in-
house soybean adhesive bonded plywood panels. The commercial soybean-based adhesive resulted in a lower mechanical
shear strength. The cottonseed and cottonseed-guayule adhesives show promise as formaldehyde-free bio-based hardwood-
plywood adhesives for interior applications. This research is ongoing with decay and termite resistance testing.
Keywords: Cottonseed Meal, Soybean Meal, Wood Adhesives, Water Resistance, Mechanical Shear Strength, Decay
Resistance, Termite Resistance, Yellow Poplar Plywood
INTRODUCTION
The most common adhesive types used in the wood composite industries are based on urea-formaldehyde, melamine-urea-
formaldehyde, polyurethane, or phenol-formaldehyde formulations (Dunky, 1998). Among them, urea-formaldehyde-based
adhesive is the primary resin applied for interior applications because of its bonding strength, rapid curing, and relatively low
cost (Conner, 1996). Due to concerns about formaldehyde toxicity and reclassification of the compound as a carcinogen by
the World Health Organization (WHO), there is an ongoing interest to reduce exposure and to eliminate the compound from
the workplace environment (Liteplo et al., 2002). Thus, there is a current and pressing need to develop applicable
formaldehyde-free, bio-based, environmentally safe, wood-based adhesives. One approach to this issue is to consider the re-
application of protein-based adhesives. Protein-based adhesives were commonly used in the wood products industry prior to
the development of petroleum-based formulations (Lambuth, 2003).
Because of the scale of the soybean oil industry and the large volumes of soybean-based meal that are available, much of
the research in this area focused on soybean proteins (Frihard and Birkeland, 2014), and interior plywood adhesives based on
defatted soybean meals are currently in the market (Malin, 2005). In addition, various other protein-based materials have been
AMERICAN WOOD PROTECTION ASSOCIATION
34

studied in this regard and reported to produce good wood bonding quality. Among these proteins are wheat gluten (Trischler
et al., 2018), pea protein (Santoni and Pizzo, 2013), peanut meal (Chen et al., 2018), and blood meal protein (Li et al., 2018).
Considerable plywood manufacturing takes place in the southeastern region of the United States. This region has
considerable agricultural acreage invested in upland cotton (Gossypium hirsutum L.) production (Johnson et al., 2018). This
production generates not only cotton fiber, but also an under-utilized seed co-product. The meal contains gossypol, a
polyphenolic compound with toxic nutritional properties; therefore, other uses have been investigated for this type of protein,
as an example, wood adhesives compound.
Initial bench scale laboratory work has indicated that cottonseed protein in the form of an isolate (>90% protein), a protein
concentrate (>60% protein), or a meal (40-50% protein) have potential to bind wood veneers together to make softwood and
hardwood plywood products (Cheng et al., 2013; He et al., 2019; Shmulsky et al., 2021). This work has shown that significant
adhesive strength is possible, and it has demonstrated that the water resistance of cottonseed proteins appears to exceed that of
soybean proteins.
As recent literature indicates that cottonseed protein meal can be used as an environmentally safe and friendly, bio-based,
formaldehyde-free wood-based adhesive, we also incorporated the guayule resin into the adhesive for long-term durability.
Guayule (Parthenium argentatum A. Gray) is a shrub with large amounts of natural latex rubber in its stems. It is native to the
southwestern United States and throughout the northeastern parts of the Chihuahuan Desert from Mexico to the Big Bend
region of Texas, USA (Rasutis et al., 2015; Evancho and Dial, 2020). Guayule fields are established with genetically diverse
seed and are harvested mechanically for rubber production (Rasutis et al., 2015; Evancho and Dial, 2020). The harvested
materials are ground into bagasse and then the solid latex rubber is chemically extracted from its cells (Rasutis et al. 2015).
The guayule resin compounds have potential as low-toxicity components of coatings, tackifiers, adhesives, composite
components, emulsifiers, bio-control agents, insecticides, antimicrobials, and antifungals (Greenfield, 1992; Dehghanizadeh
and Brewer, 2020). Guayule resin has demonstrated properties as a natural biocide with termiticidal and fungicidal activity in
lumber and wood products (Bultman et al., 1991; Nakayama et al., 2001; Nakayama et al., 2003). Guayule resin has the
potential to provide longevity and protection to wood and forest products (Thames and Kaleem, 1991; Thames and Wagner,
1991).
However, despite what has been accomplished in the literature, there is a gap in the science and lack of research on guayule
resin being used as an adhesive additive for wood products like plywood. Therefore, as an environmentally safe alternative to
harsher chemicals that are in the adhesive market, we plan to use guayule resin and cottonseed meal as a novel bio-based
adhesive for hardwood plywood. The benefits of the proposed work include expansion of wood and wood products into
additional markets and development of novel applications of guayule as an adhesive additive for wood and wood products.
Therefore, this project’s objective is to develop and focus on the production of value-added wood products using hardwood
plywood forest products and under-utilized waste materials from the cottonseed meal and guayule resin to make bio-based
environmentally friendly adhesives for use in the hardwood plywood industry. This research focuses on adding a guayule
resin-acetone solution to a cottonseed meal adhesive formulation to produce three-ply yellow poplar (Liriodendron tulipifera
L.) plywood. This research used cottonseed meal preparations (53% protein new cottonseed and 53% protein new cottonseed
guayule-acetone adhesive) and an in-house soybean meal (49% protein) to make environmentally friendly bio-based plywood
adhesives. Hot press time, temperature, and pressure were 6 minutes, 135°C, and 1.24 MPa, respectively. A polyamido-amine-
epichlorohydrin (PAE) solution was included in each adhesive mix. Commercially manufactured yellow poplar plywood
bonded with soybean adhesive were also purchased and tested as controls against the three adhesive types. This work is a
collaborative effort of academia, federal, and industrial partners. Successfully conducting this project will help ensure the
leading position of the U.S. in wood products adhesive development for the future.
MATERIALS
Protein Preparation
The cottonseed and soybean protein meals used were prepared in house, through the United States Department of
Agriculture (USDA) Agriculture Research Service (ARS) Southern Regional Research Center in New Orleans, Louisiana,
USA. Glandless cottonseeds, a moderate gossypol genotype (0.75% total gossypol), were cracked and dehulled with a grinding
mill. The bulk of the hulls were separated with a vibratory shaker. The kernels were further cleaned to remove additional non-
kernel material. The cleaned kernels were then milled to produce the full-flat fine cottonseed flour.
The milled cottonseed kernel tissue flour was defatted using hexane. After extraction, the meal was washed with additional
fresh hexane to remove as much of the hold-up miscella volume. This material yielded an average nitrogen level of 8.90%,
resultant to an average of 53.4% protein level. This cottonseed meal is called “new cottonseed meal” from here on out.
The commercial source soybean protein meal used was Prolia 200/70 from Cargill, Inc. (Wayzata, Minnesota, USA). It
had an average nitrogen of 8.18%, corresponding to an average of 49.1% protein. This meal is called “in-house soybean meal”
product from here on out.
AMERICAN WOOD PROTECTION ASSOCIATION
35

Adhesive Preparation
All bio-based adhesives were synthesized at Mississippi State University in the Department of Sustainable Bioproducts
(DSB) Forest and Wildlife Research Center (FWRC) under controlled ambient conditions. A digital laboratory balance was
used to obtain weights of the dry and liquid products. In the first stage, each protein meal was mixed with deionized water at
a 2.5:1 ratio with moderate stirring using a laboratory overhead stirrer until fully dispersed, thoroughly mixed, and forming a
slurry. Next, sodium metabisulfite (Na2S2O5) and polyamido-amine-epichlorohydrin (PAE) Kymene™ Soyad™ CA1130
product (Solenis LLC, Wilmington, Delaware, USA) were added and stirred sequentially, forming the final adhesives. After
each mixture step, the viscosities of the adhesives were recorded using a digital viscometer.
Next, the pH values of the final adhesive were obtained using a benchtop meter. The sodium metabisulfite was added in
an effort to reduce the viscosity to be able to spread the adhesives. The PAE was added to enhance the water resistance and
wet-strength of each adhesive formulation. The PAE amounts were based on the manufacturer’s recommendation of 1:7 (PAE:
cottonseed or soybean powder by weight). Adhesive chemical formulation component amounts are as described in Table 1 to
yield adhesives with a suitable viscosity for spreading application rates.
Table 1. Adhesive Chemical Formulation
Adhesive Types PAE
(g)
Deionized Water
(g)
Dry Meal
(g)
Sodium Metabisulfite
(g)
Final Viscosity
(cP) pH
In-House Soybean 75 125 50 2.5 59,987 5.93
New Cottonseed 75 125 50 2.6 65,986 5.81
New Cottonseed-
Gua
y
ule Resin 75 125 50 2.6 47,990 5.79
Hydrated lime (calcium hydroxide, Ca(OH)2) was added to the soybean and cottonseed meal preparations to increase the
pH to ~10.0. The addition of a base was to better simulate current and historical industry practices (Lambuth, 2003). These
alkaline conditions were thought to complete the curing reaction and to simulate current practices in industry. However, all
the preliminary experimental trials using a hydrated lime powder or hydrated lime slurry produced very high viscosity
(>172,000 centipoise (cP)), which cannot be pushed out of spray nozzles or efficiently spread onto veneers within the industrial
parameters. Preliminary experiments revealed that the addition of hydrated lime or a hydrated lime slurry was detrimental to
the curing and water resistance of the specimens. Therefore, hydrated lime products were not added to the any of the
adhesive formulations.
Guayule Resin Acetone Solution Preparation
The USDA ARS Southern Regional Research Center in Lubbock, Texas, USA, provided the guayule resin. Prior to use,
the guayule resin was put in a laboratory conventional oven at ~70°C to reduce the viscosity for subsequent processing. The
team used a 1:1 ratio of liquefied guayule resin to pure acetone ((CH3)2CO) to create the guayule-acetone solution. Once the
solution was thoroughly mixed, using a vibrating mixer and stirrer, 4.0 g of the guayule solution was added to create the new
cottonseed-guayule adhesive treatment combination.
METHODOLOGY
Panel Preparation and Assembling
The hardwood yellow poplar veneers materials were obtained from a commercial mill in North Carolina, USA. Each full
sheet of veneer measured 0.38 x 122.0 x 244.0 cm3. Veneer was stored, processed, and cut up using a table saw in the
departmental woodshop to 0.38 x 30.5 x 30.5 cm3 for plywood specimen production. The veneer selected to compose the
panels was randomized. Thus, each three-ply panel contained veneer from three different parent veneer sheets. The four
plywood panel replicates within each treatment contained veneer from separate parent sheets.
From each of the three adhesive types (in-house soybean, new cottonseed, and new cottonseed-guayule), three-ply plywood
panels were produced. The adhesive was applied with a 10.2 cm-wide plastic roller onto one side of the top and bottom face
of the oven dry yellow poplar veneers. The core layer’s grain was oriented perpendicular to that of the top and bottom face
layers. The amount of adhesive applied to each panel was 38 + 1 gram (g). After preparation, the panels were cold pressed at
ambient temperature with 1.03 MPa pressure for 5 minutes, and then transferred immediately to the Dieffenbacher Hydraulic
Hot Press (Windsor, Ontario, Canada). The hot press conditions were 135°C, 1.24 MPa pressure, and 6 minutes press time.
AMERICAN WOOD PROTECTION ASSOCIATION
36

As a treatment factor, four panels were prepared with each of the three types of adhesive formulation. In total, 12 panels were
prepared. A completely randomized design with sub-sampling (adhesive types and panel replicates) was used. All other
parameters and processing factors were kept constant, such as veneer type, the PAE solution, adhesive spread rate, cold press
time, cold press pressure, hot press temperature, and hot press time and pressure.
Commercially manufactured soybean adhesive hardwood plywood control panels were purchased in July 2021. From
randomized locations within the full sheet of commercial plywood panel, water resistance, mechanical shear strength, decay
resistance, and termite resistance test specimens were cut to compare the three adhesive types against a commercially available
similar product.
Water Resistance Testing
The water resistance of the plywood panels for interior application was determined with a three-cycle soak test in
accordance with ANSI/HPVA HP-1 (ANSI/HPVA, 2020). Six specimens with a size of 5.08 x 12.70 cm2 were cut from each
panel and soaked in filtered deionized water at 24 + 3°C for 4 hours, and then dried between 49°C and 52°C for 19 hours with
sufficient air circulation to lower the MC of specimens to 12% or below of the oven-dry weight as per the standard
(ANSI/HPVA, 2020). The three-cycle soak test was conducted by submerging specimens in filtered deionized water using a
17.8 x 66.0 x 183.0 cm3 circulating water bath. Specimens were oven-dried following standard protocol. All panels underwent
this repeated three times soaking and drying cycle.
The degree of delamination of each specimen was measured and recorded after every cycle. According to the ANSI/HPVA
standard (ANSI/HPVA, 2020), delamination is considered as any continuous opening between two veneer layers that is longer
than 50.8 mm, deeper than 6.35 mm, and wider than 0.08 mm. The test requires that five of the six specimens shall pass the
first soak cycle and four of the six specimens shall pass the third soak cycle for a given plywood parent panel to pass the test.
The standard also requires that for any treatment to pass this test, 95% of the specimens tested must pass the first soak and dry
cycle, and 85% of the specimens tested must pass the third soak and dry cycle. To determine delamination of specimens, a
0.08 x 12.7 x 76.2 mm3 metal feeler gauge and digital caliper were used. Six test specimens were cut from each of the 12
panels that were made and the commercial plywood for a total of 96 specimens that went through the water resistance test.
Mechanical Shear Strength Testing
The mechanical shear strength of the plywood was determined using an Instron Universal Hydraulic Material Testing
System Machine (Norwood, Massachusetts, USA) located in the Department of Sustainable Bioproducts (DSB) Forest and
Wildlife Research Center (FWRC) in accordance with American Society of Testing Materials D906-20 standard test method
for strength properties of adhesives in plywood type construction in shear by tension loading (ASTM, 2020). Test specimens
were three-ply, 25.4 x 82.6 mm2. Each had a bonded shear test area of 25.4 x 25.4 mm2. The outer veneer layers from each
specimen were scored in order to yield a 25.4 x 25.4 mm2 bonded area for testing. Specimens were moisture conditioned in an
environmentally controlled chamber before testing. In addition, the specimen’s moisture content (MC) values were checked
and recorded at the time of testing. Eight test specimens were cut from each of the 12 test panels as well as the commercial
plywood panel. This scheme yielded a total of 104 shear strength test specimens. The speed of the testing machine crosshead
was 23 mm/min. The shear strength values were calculated using Equation 1:
𝑆ℎ𝑒𝑎𝑟 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ 󰇛𝑀𝑃𝑎󰇜  𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑇𝑒𝑛𝑠𝑖𝑜𝑛 𝐹𝑜𝑟𝑐𝑒 𝑎𝑡 𝐵𝑟𝑒𝑎𝑘󰇛𝑁󰇜
𝐺𝑙𝑢𝑖𝑛𝑔
𝐴
𝑟𝑒𝑎󰇛𝑚𝑚󰇜 (1)
Termite and Decay Resistance Biological Assessments
From each adhesive and panel replicate, five sub-sample specimens were cut and randomized. Approximately 45 grams
of native eastern subterranean termites (Reticulitermes flavipes) were obtained from Dorman Lake Test Plot, Starkville, MS,
USA. Each individual specimen was placed into a sterilized glass jar containing 150 g oven dry sand and 28 mL of deionized
water, and then inoculated with 1.0 gram of termites (~400 termites). Jars were placed in an incubator at 27°C and monitored
for 28 days. Mass of each specimen and control specimens were taken before and will be taken after termite exposure at oven
dry conditions. Southern yellow pine (Pinus spp. L.) specimens were used as the control for the termite resistance test. Choice
and no-choice tests were used for the termite resistance test (AWPA, 2017). This work is ongoing. When complete, visual
ratings from 0-10 will be assigned per the AWPA E1-17 standard laboratory method for evaluating the termite resistance of
wood-based materials (AWPA, 2017).
In addition, the AWPA E10-16 standard laboratory method for evaluating the decay resistance of wood-based material
against pure basidiomycete cultures: soil/block test was used for decay resistance test (AWPA, 2016). Sweetgum (Liquidambar
styraciflua L.) specimens were used as the control for the decay resistance test. Results are not available at this time as these
tests and research are ongoing.
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STATISTICAL ANALYSES
For the delamination, decay, and termite resistance tests, ANSI/HPVA (2020), AWPA E1-17 (2017), and AWPA E10-16
(2016) standards were followed. The shear strength data were analyzed in a full factorial arrangement of treatments (protein
meal types and four replicate panel) in a completely randomized with sub-sampling design, based on the replicated panels. The
treatment factors will be evaluated using analysis of variance (ANOVA) and when detected as a statistical difference (F-test: p
< 0.05), a Fisher’s least significant difference (LSD) test will be performed at α = 0.05. All data analyses will be conducted
using SAS/SAT™ software version 9.4 (SAS Institute, 2013). Statistical analysis is ongoing.
PRELIMINARY RESULTS
Water Resistance Testing
The four adhesive types (in-house soybean, new cottonseed, new cottonseed-guayule, and commercial soybean-based
plywood) plywood specimens passed the three-cycle water resistance tests (ANSI-HPVA, 2020) between 91.7% to 100%
specimen success at 1.24 MPa constant pressure and 135°C temperature at 6 minutes hot press time (Figure 1). The new
cottonseed adhesive had 100% specimen success with 24/24 specimens passing this test (Figure 1). The new cottonseed-
guayule and commercial soybean-based adhesives each had 95.8% specimen success with 23/24 specimens passing this test
(Figure 1). The in-house soybean adhesive produced the lowest results of 91.7% specimen success with 22/24 specimens
passing this test (Figure 1). Based on the ANSI-HPVA (2020) standard, 85% of the specimens in each treatment must pass all
three-cycle water resistance tests. All adhesive types passed the three-cycle water resistance tests.
Figure 1. Combined Summary of Water Resistance Test Results of Yellow Poplar Hardwood Plywood Specimen
Success for In-House Soybean, New Cottonseed, New Cottonseed-Guayule, and Commercial Soybean Grouped by
Adhesive Types.
Mechanical Shear Strength Testing
No industry or standard minimum mechanical shear strength levels exist for these types of products. Commercial
acceptability is ultimately governed by wood failure and wood strength. If the primary location of shear failure is in the wood
and not in the adhesive, then the adhesive is considered to be developing sufficient minimum shear strength. Figure 2 shows
the preliminary average mechanical shear strength load test results of yellow poplar hardwood plywood specimen for in-house
soybean, new cottonseed, new cottonseed-guayule, and commercial soybean grouped by adhesive types. Figure 3 shows the
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preliminary average maximum mechanical shear strength load test results of the plywood specimen grouped by adhesive types.
The average mechanical shear strength of in-house soybean, new cottonseed, and new cottonseed-guayule adhesive panels had
statistically similar values of 1.75, 1.60, and 1.57 MPa, respectfully (Figures 2 and 3). However, the commercial soybean panel
had a much lower mechanical shear strength value of 1.22 MPa (Figures 2 and 3). By analyzing the data using an ANOVA, it
was determined that the in-house soybean, new cottonseed, and new cottonseed-guayule adhesive panels were not statistically
different from each other, but the commercial soybean panel was statistically different from the others (Figure 3). Note that
the in-house soybean and commercial soybean panels exhibited more uniform shear strength as compared to the slightly broader
average shear strength range of the new cottonseed and new cottonseed-guayule panels. Two reasons for this difference include
potential differences in wood moisture content of the specimens at the time of testing and differences in the source veneer as
the three treatments were from one manufacturing shift, albeit randomized, of veneer, while the commercially produced panel
was manufactured from veneer from a different production shift.
Figure 2. Preliminary Average Mechanical Shear Strength Load Test Results of Yellow Poplar Hardwood Plywood
Specimen for In-House Soybean, New Cottonseed, New Cottonseed-Guayule, and Commercial Soybean Grouped by
Adhesive Types.
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Figure 3. Preliminary Average Maximum Mechanical Shear Strength Load Test Results of Yellow Poplar Hardwood
Plywood Specimen for In-House Soybean, New Cottonseed, New Cottonseed-Guayule, and Commercial Soybean
Grouped by Adhesive Types.
Termite and Decay Resistance
Results are not available at this time. These tests are underway and research is ongoing.
PRELIMINARY SUMMARY AND CONCLUSIONS
 There is a great need for an environmentally safe and friendly, bio-based, formaldehyde-free wood-based adhesive.
 High shear strength was achieved for in-house soybean, cottonseed, and cottonseed-guayule adhesives.
o Commercial soybean-based plywood shear strength was statistically lower.
 Shear results indicate cottonseed meal can be used as an alternative to soybean adhesives.
 Similar water resistance was achieved among all treatments.
 Both cottonseed and cottonseed-guayule adhesives showed superior water resistance.
 The cottonseed meal showed promise for use in interior applications as a hardwood plywood adhesive.
 Guayule resin can be used as an additive with cottonseed meal adhesive.
 Decay resistance and termite resistance testing research are ongoing.
ACKNOWLEDGEMENT
Authors acknowledge the funding support of the United States Department of Agriculture (USDA), Research, Education,
and Economics (REE), Agriculture Research Service (ARS), Administrative and Financial Management (AFM), Financial
Management and Accounting Division (FMAD), and Grants and Agreements Management Branch (GAMB), under Agreement
No. 58-0204-9-164. Any opinions, findings, conclusion, or recommendations expressed in this publication are those of the
author and do not necessarily reflect the view of the U.S. Department of Agriculture. Mention of trade names or commercial
products in this publication is solely for the purpose of providing specific information and does not imply recommendation or
endorsement by the USDA. The USDA is an equal opportunity provider and employer. The authors also acknowledge USDA
ARS Dr. Greg Holt’s contributions with the guayule resin for this research. This publication article is a contribution of the
Forest and Wildlife Research Center (FWRC) at Mississippi State University.
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