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Developed in the early 1960s in the U.S., MDF is actually based on a hardboard product first created accidentally by William H. Mason (of Masonite
fame) in 1925. He was trying to turn wood chips discarded by lumber mills
into an affordable insulation product. One evening he forgot to shut down his
equipment, and instead of a lightweight sheet of insulation he created a thin,
very durable composite wood panel.
The wood fiber, or “furnish,” for MDF comes from many sources. Most commonly
it is pre-consumer wood waste that would otherwise be landfilled or incinerated—
forest thinnings and wood residuals from lumber, plywood, and furniture
plants. Additional sources include post-consumer items like wood pallets and
retired wood furniture (after impurities are removed). It should be noted that
different fiber sources may require different bonding systems.
A few vertically integrated forest products companies have streamlined
their sourcing of furnish for MDF and other composite panels by optimizing
transfer from their other lumber, engineered wood, and panel operations.
The remaining material is pre-steamed, where low-pressure steam is injected
to heat and soften the lignin. After pre-steaming, fibers are fed into a plug
screw feeder where they are compressed to remove the water from the
steaming process. Fibers are then transferred into the pressurized vessel, or
digester, and finally to a refiner where the material is separated into usable
fibers by two grinding discs.
Resins and a wax emulsion are applied to the fiber at the inlet pipe to
the drying tube. This is also the stage were additives to enhance flame
retardancy, moisture resistance, or other properties are introduced. Ratios of
resin, fiber, additives, and catalysts are carefully controlled by weighing each
ingredient. Single- or multiple-stage tube dryers dry and blend the fibers.
To create a panel, the dried fiber is pushed through scalping rolls to produce
a thick, fluffy mat of uniform thickness.
The mechanical stability of MDF is attributable to three primary variables:
physical and mechanical properties of individual wood fibers, fiber-to-fiber
stress transfer, and fiber orientation. These origins of fiber properties and
stress transfer can be traced to the fiber generation method wherein fiber
orientation is associated with mat formation.
A continuous or “feed-through” press equipped with a steel band running over
large heated drums compresses the mat at a uniform rate, or a multi-opening
vertical “daylight” press that creates several panels in a single pressing operation.
Modern MDF presses are equipped with electronic controls to prevent
resin pre-curing, creating MDF with the desired density and uniform strength
as efficiently as possible.
As the finished board emerges from the press it is cut to panel lengths
using automated saws before the MDF cools.
After cooling, the panels are sanded on both sides by large belt sanding
machines using either silicon carbide abrasives, or for finer surfaces, ceramic
abrasives like zirconia alumina and aluminum oxide.
Most MDF plants use computerized process control to monitor each manufacturing step and to maintain product quality. Product consistency is maintained
by a combination of continuous weight belts, basis weight gauges, density
profile monitors, and thickness gauges. In addition, the American National
Standards Institute has established product specifications for each application,
as well as formaldehyde emission limits. As environmental regulations and
market conditions continue to change, these standards are revised.
The standard for MDF (ANSI A208.2-2016 Medium Density Fiberboard for
Interior Applications) is the most recent version of this industry standard. This
standard classifies MDF by density and use (interior or exterior) and identifies four
interior product grades. Specifications identified include physical and mechanical
properties, dimensional tolerances, and formaldehyde emission limits.
Specifications are presented in both metric and inch-pound limits.
Physical and mechanical properties of the finished product that are
measured include density and specific gravity, hardness, modulus of rupture,
abrasion resistance, impact strength, modulus of elasticity, and tensile
strength. In addition, water absorption, thickness swelling, and internal bond
strength are also measured. The American Society for Testing of Materials
has developed a standard (D-1037) for testing these properties.
Few materials on earth are as perfect for their purpose as wood. Trees grow
essentially by building themselves, efficiently creating their own construction
materials along the way. The lignocellulose fibers that form the essence of
wood create a unique combination of strength, resilience, workability, and
renewability that no other material can even come close to.
The inherent properties of wood are what make MDF and other composite
wood panels an environmentally positive choice for furniture, fixtures, and interiors.
A brief overview:
w WOOD IS ONE OF THE PLANET’S MOST EASILY RENEWED
• During the past 60 years, net growing-stock growth has consistently
exceeded growing-stock removals in the United States.
• In terms of percent of standing volume, removals are at the lowest level
in the past 60 years and growth has also slowed.
• The volume of annual net growth is currently two-times higher than the
volume of annual removals.
Source: “U.S. Forest Service Resource Facts and Historical Trends,” FS-1035, August 2014
• North American panel producers have proven themselves to be
exceptional stewards of their resources.
w COMPOSITE WOOD PANELS MAKE USE OF WOOD FIBER LEFT
OVER FROM OTHER MANUFACTURING PROCESSES.
• This material would otherwise be destined for landfills and incinerators.
• These panels are more stable than solid wood, and may be engineered
for specific applications and performance characteristics: moisture
resistance, fire resistance, strength, weight, machinability, etc.
• These properties ensure a longer useful life, requiring less frequent
• Composite wood panels have been shown to be “better than carbon
neutral” in a recent lifecycle inventory analysis.
• The wood in composite panels acts as a carbon sink, sequestering more
carbon than is expended in their production, transportation, and installation.
Source: “Cradle to Gate Life Cycle Assessment of U.S. Medium Density Fiberboard
Production”; see sources section
• Rare and endangered wood species are spared by the use of
decorative composite wood panels.
• High-definition printed and textured decorative surfaces offer the
beauty of any wood, with better design consistency and durability.
• Carefully cut veneers maximize the decorative square footage of
responsibly harvested trees.
80 interiors+sources october2016 interiorsandsources.com
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