Adverse effects of air pollutants on wood products and a method for preventing resulting degradation
A study of wood surface in hostile environments was undertaken to elucidate the degradation mechanism and develop a method to protect wood in outdoor applications. In this investigation, wood was exposed to SO[sub 2] and NO[sub 2] in the presence and absence of ultraviolet light for up to 4 weeks. The effect of the simulated acid rain on wood with and without an epoxy film was evaluated by intermittent spraying of the wood with either sulfuric, nitric acid or water and irradiated with and without the xenon light in a weatherometer for up to 8 weeks. The surface properties of degraded wood and protective epoxy films were analyzed. UV light changed the wood color. The samples lost weight and generated water-soluble degradation products after the photoirradiation. Sulfur dioxide lighted the wood color; nitrogen dioxide changed wood color to brown. Wood increased its weight during the exposure of SO[sub 2] and NO[sub 2], however, the presence of such gases triggered photo-induced degradation. Lignin was degraded and carbonyl groups were formed at irradiated wood. Sulfur and nitrogen dioxides reduced the intensity of carbonyl groups due to degradative hydrolysis. Water-soluble products were derived from polysaccharides and lignin, nitric acid, sulfuric acid and its dissociated ions. During the simulated acidic weathering, xenon light changed the wood color. The color change rate of earlywood was greater than latewood. The presence of acids and water facilitated the wood degradation, and eventually caused leaching. The primary photodegradation phenomena of lignin was confirmed by the FTIR and UV analyses of the irradiated samples. Transparent anhydride-cured epoxy films partially protected wood against the acidic degradation and photoirradiation. Epoxy film cracked, yellowed and had O-ring shapes cavities after the exposure. Salol-added film provided the best protection for wood, followed by a film without an UV stabilizer and Tinuvin 770-added film last.
- Research Organization:
- Clemson Univ., SC (United States)
- OSTI ID:
- 6113537
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
ACID RAIN
BIOLOGICAL EFFECTS
WOOD
DECOMPOSITION
PROTECTIVE COATINGS
AIR POLLUTION
CHEMICAL RADIATION EFFECTS
LEACHING
LIGNIN
NITRIC ACID
NITROGEN DIOXIDE
PHOTOCHEMICAL REACTIONS
POLLUTANTS
POLYSACCHARIDES
SULFUR DIOXIDE
SURFACE PROPERTIES
ULTRAVIOLET RADIATION
WEATHERING
ATMOSPHERIC PRECIPITATIONS
CARBOHYDRATES
CHALCOGENIDES
CHEMICAL REACTIONS
COATINGS
DISSOLUTION
ELECTROMAGNETIC RADIATION
HYDROGEN COMPOUNDS
INORGANIC ACIDS
NITROGEN COMPOUNDS
NITROGEN OXIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POLLUTION
RADIATION EFFECTS
RADIATIONS
RAIN
SACCHARIDES
SEPARATION PROCESSES
SULFUR COMPOUNDS
SULFUR OXIDES
560300* - Chemicals Metabolism & Toxicology
360604 - Materials- Corrosion
Erosion
& Degradation
360605 - Materials- Radiation Effects