Used in a myriad of building products, such as fiberglass insulation, plywood, OSB, medium density fiberboard, particleboard, etc., as a binder (adhesive), formaldehyde has been the subject of much research and debate in recent years. Unfortunately, non-added formaldehyde alternatives are few and if available, typically significantly higher in cost. But things are changing.
This month, we'll begin a four-part series that takes an in-depth look at the progress that has been made with the goal of minimizing and/or replacing entirely formaldehyde as the primary binder in the manufacture of composite wood panel products. At the same time, we'll examine the potential for substituting agricultural fibers for wood fibers in the manufacture of composite wood panels.
In February 1998, the results of the most comprehensive study (up to that time) on the use of both waste agricultural fibers and soy-based binders, in whole or in part, as substitutes for wood fibers appeared in the Forest Products Journal. Conducted by Iowa State University, the study had two main motivations:
- Identify potential substitutes for wood fiber (to alleviate the growing worldwide shortage)
- Eliminate toxic emissions from building products such as MDF which release VOCs due to the presence of urea formaldehyde binders
The study focused on gauging the effects on the mechanical and dimensional properties of dry-formed MDF and hardboard, as well as wet-formed hardboard. Dry-formed MDF and hardboard typically use an 8 percent UF binder while wet-formed hardboard typically uses a 2 percent phenol formaldehyde binder. Using cornstalk and switchgrass as the waste agricultural fibers in test comparisons (100 percent wood fibers vs. 100 percent Ag fibers), the comparison was based on two criteria:
- Binder type (soy-based vs. UF)
- Ag-fiber ratio
For the binder, the study used a 50:50 ratio of 4 percent UF to 4 percent soy protein isolate binder in lieu of the conventional 8 percent for dry-formed MDF and hardboard. For the hardboard, there were no observed effects on the panel's structural properties. However, this was not the case for the MDF panels. Though the modulus of elasticity was unaffected, a reduction in the modulus of rupture was observed as well as a reduction in internal bonding strength. Known as thickness swell (the observed swelling effects upon water immersion) again, the hardboard came out on top. Though the MDF was unaffected by the change in binder formulation, the hardboard had a noticeably reduced thickness swell using the 50:50 ratio. When the PF binder used in the manufacture of wet-formed hardboard was substituted in whole (100 percent) with a soy-based binder, the results were disappointing:
- Increased thickness swell
- All structural properties negatively affected
Strawman bluesAs for the fiber comparisons (wood vs. Ag), the study proved cornstalk to be the better choice when compared with switchgrass. Though the study revealed that MDF and hardboard panels suffered from a reduction in structural performance when part of or all the wood fiber was substituted for Ag, it was less so for cornstalk. As well, thickness swell was significantly increased using Ag fibers. For the proponents of both Ag fibers and non-petroleum-based binders, the study proved disappointing but not debilitating-there were some positives to go along with the negatives.
In the late '90s, the time frame of this study, the green building movement was coming into its own and, with continued interest and research, the stage was being set for introducing "formaldehyde-free" composite wood panel products.
Baby stepsIn October of 1998, Portland, Ore.,-based Neil Kelly Signature Cabinets, in partnership with Endura Hardwoods and Environmental Building Supplies, introduced to the national market their Naturals Collection. Targeting mid-level consumers, the marketing strategy set out to limit the premium paid for the line's environmental attributes to only 7 to 12 percent above the cost of standard cabinets while providing optimal resource efficiency and indoor air quality benefits to the end-user.
Realizing the difficulty in finding "green" kitchen and bathroom cabinetry, Neil Kelly set out to begin the industry trend towards a green future for architectural cabinetry. The Naturals Collection feature components such as doors, drawers and veneers of particleboard frames made from certified wood sources/manufacturers. An "add-on" option includes substituting the particleboard case (with UF binder) for either certified plywood (with phenol formaldehyde binder-less off-gassing of formaldehyde than UF) or Medite II medium density fiberboard, which uses MDI (a polyurethane binder) making it formaldehyde-free. Neil Kelly's plans include a complete switchover to certified particleboard for all case construction. A natural oil/wax, which requires periodic renewal by the owner, provides the finish surface for the cabinets (a container of the finish is included with the cabinets).
In part two of this series, we'll see how the strategy of minimizing the harmful effects of formaldehyde off-gassing is paying off by substituting phenol formaldehyde (insoluble) for urea formaldehyde (water-soluble) as a binder for composite wood panel products.
If you read this article, please circle number 175.