Fibers & Wood
Wood
• Next to food crops, perhaps human-kind’s most
important plant product.
• Used for housing, furniture, paper, fuel (wood &
charcoal), and raw materials for synthetics (rayon,
cellophane, cellulose acetate)
• Forests covered ca. 1/3 of Earth’s land surface.
• Ca. 50% of original forest gone.
• Current rate of deforestation > rate of reforestation
(especially in tropics; where used mostly for fuel
& land for crops/ranching).
• U.S. & Canada leading producers of wood &
wood products (including paper) (In U.S, mostly
from pines & firs in SE & NW).
Wood, cont.
• Mostly cellulose & lignin from secondary cell
walls; mostly vessels and/or tracheids and fibers.
• From secondary xylem – most cells are
impregnated with lignin and are dead.
• Hardwoods - angiosperms
– wood mostly vessels + some tracheids
• Softwoods - gymnosperms
– wood mostly tracheids, more uniform
Cell structure
• Cell wall : primary: 9-25%
cellulose, microfibrils,
hemicelluloses (20-50%),
pectic substances (1035%), and proteins (10%).
Primary cell walls have a
high tensile strength and
are porous
• Middle lamella : pectin
– Glue holding cells together
• Secondary cell wall: 45%
cellulose, 30%
hemicellulose and 22-28%
lignin
Includes:
Wood products
Paper,
Veneers,
Plywood,
Particle board,
Charcoal,
Resins & oils
(pitch, turpentine),
Cork
Biological Properties: Xylem
• Conducts water and
minerals from soil upward
– gymnosperms
• Tracheids
• “Softwoods; e.g., pine,
spruce, cedar, fir, hemlock
– angiosperms
• Tracheids
• Vessel elements
• Hardwoods; e.g., maple,
oak, mahogany, poplar,
walnut, ash, hickory
Fig. 38.13a
Stems: Secondary growth
•Vascular tissue, (xylem) makes up the bulk of the stem
•Forms tree rings
Wood characteristics
• Porosity - manner in
which large vessels are
dispersed, only in
hardwoods. Diffuse or
ring-porous wood.
• Grain - alignment of
xylem cells.
• Knots - Inclusion of
branch in xylem.
Sapwood: functional xylem next to cambium
Heartwood: older non-functional (for transport) xylem cells
(still functions in support); best for solid wood
Physical Properties of Wood
• Tensile Strength
• Compression Strength
• Splitting Strength
Cork
• Characteristics due to
many air-filled cells,
good insulating
material, lightweight,
floats
• Cork cambium
develops within the
secondary phloem
• Quercus suber - cork
oak
What is paper?
• Paper derives from the word
"papyrus“.
• Paper includes a wide range of
products with very different
applications: communication,
cultural, educational, artistic,
hygienic, sanitary, as well as
storage and transport of all
kinds of goods. It's almost
impossible to imagine a life
without paper.
• The best paper is pure cellulose
(lignin is undesirable).
Paper trivia
• Each American uses about 144 pounds of paper per year!
• More than 500,000 trees per week are used to produce the
2/3 of newspapers that are never recycled.
• Every ton of paper that is recycled saves 17 trees, 7,000
gallons of water, & 4,100 kilowatts of electricity.
• Producing paper from recycled fibers reduces air pollutants
by as much as 74% and water pollutants by as much as
35%.
• Paper making is one of the most polluting of industries.
• Ca. 50% of harvestable wood in industrial nations goes to
paper making.
Historical writing surfaces
• papyrus (Cyperus papyrus; Cyperaceae) – from
Egyptians, ca. 4500 years ago, learned by Greeks
& Romans
• rice paper (Fatsia papyrifera, Araliaceae) - Orient
• mulberry paper (Broussonetia papyrifera,
Moaraceae) – Mayans
• Also, non-plant substances; e.g., parchment, clay
Paper
• separated plant fibers that have been matted together to form a
sheet
• can come from various sources (e.g., straw, rags), but wood most
common
• alternate sources being considered include hemp (Cannabis sativa)
and kenaf (Hibiscus cannibinus)- these make better paper (lower
lignin)
• true paper (origin from China, second century)
– thin sheets must be made from fiber (vessel, tracheid, fiber) that
has been macerated until each individual filament is a separate
unit
– fibers are then intermixed with water, and, by the use of a sieve
like screen, are lifted from the water in the form of a thin
stratum, the water draining through the small openings of the
screen leaving a sheet of matted fiber upon the screen's surface
– this thin layer of intertwined fiber is paper
Making Paper
•
•
•
•
Harvesting
Cooking with lye
Rinsing
Beating or blend to make
pulp
– Add laundry starch to size
• Mould and Deckle
•
http://www.missioncreekpress.com/plants.htm
Bamboo
• Over 1000 diverse species from across globe; in
Grass family.
• No secondary xylem, primary growth only.
• Segmented, hollow tubes, typical grass stem
(woody culm produced from rhizome).
• Many many uses: e.g., fishing poles, caning for
furniture, house construction in tropics, skyscraper
scaffolding in Japan, paper making in India.
• Pandas feed on young leaves & stems of bamboo.
• Bamboos have unusual life cycle: some species
grow for decades without flowering, then all the
members of a species worldwide will flower and
die the same year.
Plant Fibers & Their Uses
Chapter 18, Table 18.1, pg 288
Chapter 18, Table 18.A, pg 298
Historical perspective
• Plant fibers have been used throughout
human history, initially as strips of bark,
stems, or leaves to make mats, baskets, etc.
• Wild cotton used for spinning and twining is
traceable to Peru 12,000 ybp.
• Flax has been used for 8000 years, so plant
fibers were apparently used in weaving
before animal fibers.
cellulose
• plant fibers are composed of cellulose long chain of glucose molecules
• animal fibers are protein (collagen)
Properties of cellulose
• Withstand high temperature
• Does not incorporate colors easily
• Resistant to animal pests, but susceptible to
fungi and termites
• Less elastic than animal fibers and have
higher affinity for water
Most synthetic fibers are
produced from petroleum
• Nylon, polyester, etc.
• Exception is rayon
Plant fibers that are short, brittle,
or slippery
• cannot be twined, woven, plaited, or spun
• can be used for paper, fiberboard,
cellophane, and rayon (synthetic “silk”
made from cellulose, mostly from wood
pulp)
Fibers must stand up to twisting
in spinning process, which holds
the fibers together mechanically
• Surface fibers – from seeds, leaves, fruits (mostly
hairs)
• Bast (soft) fibers - phloem tissues (mostly fibers)
of dicots
• Hard (leaf) fibers – vascular bundles (xylem,
phloem, fibers) leaves of monocots
Fiber characteristics
•
•
•
•
•
Look and feel
Strength
Elasticity
Density
Resistance to heat, chemicals, sun, etc.
Fiber extraction
• Retting - produces bast fibers
– plant stems placed in water or wet area to rot
– thick-walled xylem remains and must be
removed by scutching
– fibers are hackled (separated and aligned) by
drawing them across a comb
• Ginning - seed fibers
– fibers are removed from seed
Cotton: Seed & Fruit Fibers
•
•
•
•
Most important fiber plant.
Easily processed mechanically.
Fibers dye well and withstand vigorous washing.
Origins 10-12,000 ybp in New World, 5000 ybp in
Old World.
• Tremendous influence on history; especially U.S.
history.
• Top producers: China, U.S., India, Egypt,…
Cotton species
• Member of Mallow family; shrubby perennial.
• Needs warm climate and lots of water.
• Fibers from seed hairs (e.g., 20,000 per seed);
seeds packaged in a capsule (cotton boll).
• Hairs are 90% cellulose.
• Four main species grown:
– Gossypium hirsutum and G. barbadense (New World;
tetraploids, N=52) (G. hirsutum = 95% of world
production; upland cotton) (G. barbadense = pima,
Egyptian cotton)
– G. arboreum & G. herbaceum (Old World; diploids)
Cottons
• perennials, but are grown as annuals
• tremendous amount of pesticides are used in
cotton culture
• plants are defoliated chemically and
machine harvested
• Eli Whitney's invention of cotton gin led to
explosion of cultivation of cotton in U.S.
and increased need for slaves to work fields
Cotton Processing
• Ginning - removal of seeds and debris
• Carding - fibers are combed parallel to produce a
web
• Sliver - made by twisting web into a large rope
• Drawing - more alignment
• Spinning
• Cleaning - boiled in caustic soda and bleached
Cotton processing II
• Mercerization - stretched and placed in cold
caustic soda, increases luster, dye uptake
and durability.
• Sizing - stiffening agent (e.g., starch) before
weaving.
• Permanent press - chemicals used to crosslink polymers.
Bast: Flax
• Linum usitatissimum – linen and
linseed oil.
• Annual from Flax family.
• May be oldest plant fiber used for
cloth (> 10,000 ybp; New & Old
World).
• Used to wrap mummies.
• Fibers are long, smooth, straight,
lusturous & yellow (from waxes)
and 2 to 3 times as strong as
cotton; 70% cellulose.
• Flax industry never became fully
mechanized, since mechanically
processed flax is not as good as
that produced by hand, so linen is
expensive.
• Linen is durable, but wrinkles.
• Ca. 2% of world’s textiles.
Flax products
• Linen
• Linseed oil
– oil paints, varnishes and stains
• Linoleum
– Latin name, linum, which means flax, and oleum, which
means oil.
– Manufactured by oxidizing linseed oil to form a thick
mixture called linoleum cement.
– Cement is cooled & mixed with pine resin, & wood
flour to form sheets on a jute backing.
• Candle wicks: braided cordage made of flax fibers
‘tow-head’
• silky strands of the flax plant were oft-times
compared to hair
– a 'flaxen haired maiden‘
– a 'tow-head' referring to a blond approaching
whiteness
• Tow = short, coarse fibers of flax not used
in the higher grades of spinning
Bast: Jute
Jute - Corchorus sapsularis
– Annual native to Asia (wet tropics)
• fibers are rough, brittle, and don't take dyes easily
• used in sacks (burlap), twine, carpet backing
• easily grown and processed
– Bangladesh – primary world producer
Bast: Hemp
• Cannabis sativa - used for at least 6000
years.
• Fibers are stiffer than flax, used in cordage,
rope, canvas, and sailcloth.
• Made original set of Levis from hemp.
– jeans are currently made of cotton.
Bast: Ramie
• Boehmeria nivea - China grass
– cultivated for centuries in Asia
– problems with growing and processing
– makes among the longest, strongest, and silkiest
of all plant fibers
– mechanization may result in it becoming an
important fiber
Hard (Leaf) Fibers
• monocot leaf fibers: make better ropes than bast
• Sisal - Agave sisatana - Needle and thread plant
– Rope, mats
• Henequen - Agave fourcroydes
– Mayans and Aztecs made them into rough garments
– Processed by squeezing leaves and scraping away fibers
• Abaca - Musa textilis - banana relative
– used in tea bags, dollar bills, manila envelopes,
cigarette filters, rope
Other fibers
• Coir from coconuts, a seed fiber
– fibers are used as mattress stuffing, bristles in
brooms and brushes, mats
• Kapok, surface fiber from seed pods
– water-proof fibers used in life preservers,
padding
• Pineapple cloth, from leaf fibers
– used in clothing