 |
|
A greater focus on air quality
has arisen, not only on the emissions of the vehicles we drive, our
factories and our manufacturing facilities, but also our HVAC systems,
carpets, wall coverings and even now furnishings. Chemical sensitivity
has evidenced itself in ever greater numbers over the past decade. An
awareness and in-depth analysis of the issues involved has begun.
The importance of understanding resins, relates primarily to
out-gassing issues. For all composite panel products, resins are
utilized as binding agents for the various particulates. These resins
pose certain potential risks - Certain resins, such as urea
formaldehyde, continue to outgas after initial cure, enabling a
potential exposure to unnecessary potentially harmful toxins. There is
a great movement within the Design and Environmental community to
eliminate the use of urea formaldehyde from the interior environment by
substituting for other binding agents. The elimination of added urea
formaldehyde from newly constructed environments is a goal considered
credit worthy by the LEED
rating system of the USGBC.
Out-gas chamber tests of particle board panels that utilize urea
formaldehyde as a binder completely sealed on six sides with
appropriate sealers and topcoats have provided results of no detectable
out-gassing of urea formaldehyde. This is not an effective preventative
method, as a concern results should the seal be broken, as in the use
of a grommet for wire passage on a work top.
So far, substituting resins with alternative binders has proven the
only solution for this issue. For availability and cost impacts see Substrates
Composite Panels. As studies of this issue continue and more
research is applied, we strive to stay abreast, and update this site as
this topic affects us all.
Resin Types
Defined by Fiber Futures
The main types of resin used in composite fiber product manufacturing
include:
1) MDI; 2) Urea-Formaldehyde; Phenol-Formaldehyde and; 4) Polyurethane.
Products made of urea formaldehyde can release formaldehyde gas;
products made of phenol formaldehyde generally emit lower levels of the
gas. An emerging class of “bio-based” adhesives derived from plant
materials (primarily soy) are also worth examining, however, none are
yet available on a competitive commercial basis.
MDI isocyanate is a newer resin (compared with UF and PF) that has
gained market share partly in response to public concern over
formaldehyde emissions. MDI is used in most of the strawboard plants.
MDI is a liquid binder based on 100% active ingredients. It is a very
efficient resin, due to the fact that it makes a molecular and an
adhesive bond. This also has drawbacks, in that it can stick firmly to
metal and various parts of the human anatomy. It does not off-gas after
use. However, workers must take great care in the production of the
resin itself, as it is highly volatile and has no odor. Major producers
of MDI include Dow Chemical and BASF. MDI tends to be more expensive
than the formaldehyde resins and it is shipped in liquid form, so the
cost of MDI has risen nearly 15% over the past year.
Urea-Formaldehyde (UF) is a colorless, pungent-smelling gas that can
cause negative effects to sensitive people. Sensitivities can include
watery eyes, burning sensations in the eyes and throat, nausea, and
difficulty in breathing in some humans exposed at elevated levels
(above 0.1 parts per million). High concentrations may trigger attacks
in people with asthma. According to the EPA, it has also been shown to
cause cancer in animals and may cause cancer in humans.
Phenol-Formaldehyde (PF) is a red/black-colored resin used in pressed
wood products such as softwood plywood and flake or oriented
strandboard for exterior construction. Although formaldehyde is present
in both types of resins, pressed woods that contain PF resin generally
emit formaldehyde at considerably lower rates than those containing UF
resin.
Polyurethane is used to produce rigid foams, flexible foams, sealants,
coatings, elastomers and agrifiber binders. Applications for these
products cover a wide range of end uses, including cushioning for
furniture and bedding, carpet backing, automotive seating and
instrument panels, office furniture, flooring, and insulation for
appliances, sheathing and roofing.
