By
A.Maheshwaran
BSF-04-012Presentation
on
Wood Composites
Course TeacherDr.I.Sekar
Wood plastic
•
Plastic ranging from polypropylene to PVC
Plastic ranging from polypropylene to PVC
•Binders/Fillers – Wood flour to Wax
Binders/Fillers – Wood flour to Wax
Benefits
• True hybrid materials & combine best features of True hybrid materials & combine best features of
wood & plastics
wood & plastics
• Use low cost & plentiful raw materialsUse low cost & plentiful raw materials • Competitively priced Competitively priced
• Easily produced & easily fabricated Easily produced & easily fabricated
• Available in broad range of finishes & appearanceAvailable in broad range of finishes & appearance • Easily recycled after useEasily recycled after use
• No further processing is neededNo further processing is needed • Weather, water, & mould resistantWeather, water, & mould resistant
Properties
•
High resistance to moisture (0.7%
High resistance to moisture (0.7%
compared to 17.2% in Pine)
compared to 17.2% in Pine)
•
Moisture not transmitted across plastic
Moisture not transmitted across plastic
boundaries
boundaries
•
Good stiffness & impact resistance
Good stiffness & impact resistance
•Dimensional stability
Dimensional stability
•
Resistance to rot
Resistance to rot
Environmental Benefits
•
Negligible waste & that produced is reused
Negligible waste & that produced is reused
•No volatile organic compound
No volatile organic compound
•
Recycled & reused after their service life
Recycled & reused after their service life
•Disposed using standard methods
Disposed using standard methods
•
Increase efficiency up to 40% compared to
Increase efficiency up to 40% compared to
traditional wood
•
Mix of wood & plastic - modified with
Mix of wood & plastic - modified with
process & additives - to improve
process & additives - to improve
processing / final properties of WPC
processing / final properties of WPC
•
Compatibiliser/coupling agent – Improve
Compatibiliser/coupling agent – Improve
blending
blending
•
Basic wood product – fine saw dust(40-60-
Basic wood product – fine saw
dust(40-60-mesh range)
mesh range)
•
Simple die can be used even for most
Simple die can be used even for most
complex profile
Wood filler
Wood putty or Plastic wood
wood dust combined with a binder that dries and a diluent and a pigment
fill imperfections, nail holes or pores in wood
Wood putty or plastic wood - thicker version Wood filler - thinner version
Plastic wood
The base product -100%
recycled High-Density Polyethylene (HDPE)
shampoo and detergent
bottles, to milk jugs
Some, entirely of HDPE recycled HDPE + with
wood fibers, rubber, fiberglass, or other plastics
Like Natural wood, Plastic lumber is
expand & contract with heat (Magnitude varies)
cut and shaped with traditional wood working tools
Plastic wood will not:
Rot (seawalls, docks) crack
warp splinter degrade
Plastic wood is:
denser than wood
virtually maintenance free long lasting stain resistant waterproof UV resistant aesthetically pleasing impervious to insects
Plastic wood also:
works with any deck fastener requires no painting or sealing
used in composite extruded panel plastic wood for flooring
Provides a good shock-absorbing surface for pedestrian traffic, such as runners and hikers.
Plastic lumber and Wood-plastic
composites - difference
fiber plastic lumber can
have less than 50% wood fiber.
balloted in ASTM by
Committee D20
Standard Test Method
for Shear Properties of Plastic Lumber and
Plastic Lumber Shapes.
Wood-plastic
composites have at
least 50% or more wood
balloted in ASTM by
committee D07
Standard Test Methods
for Evaluating the Mechanical and
Physical Properties of Wood-Plastic Composite Products
New technology in plastic
composite lumber
post-consumer plastics such as high density polyethylene (HDPE)
mixed environmental wastes and plastic material into extruded composite lumber 65% recycled Cellulostics materials and
CATEGORIES
1. Material Preparation 2. Extruder Design 3. Screw Design 4. Cooling Technology 5. Die technology 6. FillersWood cement
wood wool cement boards (WWCB) cement bonded particleboard (CBPB)
General Properties
durable and resistant to frost/thaw, fire,
moisture, rot, vermin, fungus and termites easy workability
MANUFACTURING PROCESSES
Manufacture of Wood Wool Cement Board
Manufacture of Cement Bonded Particle Boards
Manufacture of WWCB
Long wood + cement wool strands (or excelsior) - cut from debarked logs
400-500mm length prior to cutting the wood wool treated to prevent blue-staining
The logs stored on racks a month to reduce the moisture & sugar content
wood is shredded
salt (CaCl2) solution + Portland cement (2:1 ratio)
spread onto plywood moulds & stacked
The mats pressed at room temperature under 10 psi.
stack is clamped under pressure for another 24 hours then
removed from the moulds & cured for 2-3 weeks.
They are subsequently trimmed and finished.
Manufacture of CBPC
wood is in particle rather than strand form softwood logs debarked & stored to reduce
moisture and sugar content
Portland cement: wood: water in ratio 3:1:1 Water evaporation is monitored
CaCl2 added - cement setting The mixture fed to a conveyor
Manufacture of CBPC
mat subsequently cut
These stacked & compressed together to 1/3rd of its original height over a 2-3 minute
period.
The mats are clamped and heated in a
chamber at 70-80 degrees Celsius for 6-8 hours.
boards dried, trimmed and stored for 12-18 days until the cement cures.
Manufacture of CBFB
wood pulped cellulose
fibre (with an air-dry
moisture content of 12-16%)
Silica + alumina + water +
pulped cellulose
Binders added
water removed and mixture
is rolled onto mats, cut, and sized, or moulded
Properties
Properties of WWCB
insulation
fire retardation
water resistance
resistance to organism attack
Insulation
WWCB provides very good insulation, both thermally and
acoustically.
Acoustic Insulation
Resistance of a plastered wall of 5cm Wood Wool Cement
Boards 36-40dB
Resistance of a plastered double wall with air space between
WWCBs 53-57dB
Resistance of a permanent shuttered wall with 12cm concrete
core 354-56dB
Noise Reduction Coefficient for 2.5cm board 0.7 Thermal Insulation (Evans,1996)
Fire Resistance
5cm boards 1 hour resistance 10cm boards 2 hours resistance
Water Resistance
Dimensional change after soaking in water for 48 hours:
0.84% thickness swelling 0.21% linear expansion 22% water absorption
Resistance to Organism Attack
WWCB is highly resistant to dry rot and other fungal growth as well as to termites.
Mechanical Properties
Specific Gravity
light boards for insulation only 360kg per cubic metre
denser boards for roofs and permanent shuttering 450kg per cubic metre
Bending Strength = 20-30kg per cubic centimeter Design load for 2cm board = 50psf
Ultimate load for 2cm board = 200psf Allowable span for 2cm board = 122cm Deflection at design load = 0.2cm
Properties of CBPB
insulation
machinability
water resistance
Insulation
Thermal Insulation
Thermal conductivity (k value) = 0.35W/m.K Linear thermal expansion =
0.01W/m.K
Electrical Insulation
CBPB is resistant to tracking and does not build up static charges, thus be
used as backing panelling for electrical appliances.
Acoustic Insulation
The sound reduction for boards of various thicknesses is as follows:
6mm - 28dB 10mm - 31dB 20mm - 33dB 30mm - 36.5dB 40mm - 38dB
Machinability
working - CBPB can be worked using hard tipped tools in a similar
manner to timber,plywood or chipboard.
sawing - can be sawn with handsaws, jigsaws with suitable blades
or power saws with tungstentipped blades.
drilling - use hand drill or high speed power drill
sanding - manual sanding or mechanical sander preferably applied
to both sides of board simultaneously.
fixing - drilling of pilot holes for nails and screws is recommended
Water Resistance
Thickness swelling
<1.0% after 2 hours soaking <1.5% after 24 hours soaking <2.0% after >24 hours soaking
Longitudinal and Transverse Swelling
2.7mm/m from air dry to water saturated
0.1mm/m for each 1% change in moisture content of the
board
1.4mm/m for each 30% change in relative humidity of
Mechanical Properties
modulus of elasticity = 4500N per cubic
mm
bending strength = 10-15N per cubic mm
(depending on density and raw materials)
compressive strength = 15N per cu mm density = 1250kg per cubic metre
APPLICATIONS
Applications of
Applications of
CBPB
CBPB
External Applications
External Applications
• flat roofing
• prefabricated structures(including housing) • mobile homes
• permanent formwork
• balcony parapets and floors
• cladding for industrial and warehouse
buildings
External Applications
External Applications
• sound barrier walls on highways • fire barriers
• pavillions
• separating and party walls • soffits
• agricultural buildings
Internal Applications
Internal Applications
• sound insulation and fire
resistant partitions and doors
• linings for timber frame
housing
• fire resistant doors, walls
and ceilings
• built-in furniture
Internal Applications
Internal Applications
• lift shaft and duct linings • back boards for electrical
and gas appliances
• glue laminated structural
members
• flooring in greenhouses • linings for bathrooms and
Applications of
Applications of
WWCB
WWCB
Most important
Most important
applications
applications
•
thermal and acoustic insulation
thermal and acoustic
thermal and acoustic
insulation
insulation
• basements • floor units • permanent shuttering • partitioning• sound insulation in walls, ceilings and floors
• roofs
• sound barriers
• thermal insulation (often combined with
other insulation products such as polystyrene and polyurethane)
Applications for Low-Cost
Applications for Low-Cost
Housing
Housing
• relative low price of products since wood wool
can be produced from inferior quality wood which is unsuitable for sawmills
• simple technology required to produce boards,
etc - see photograph below of plant in the Philippines
• in most countries in the world wood and the
components of cement are readily available
• low enough weight to allow handling panels
Applications for Low-Cost
Applications for Low-Cost
Housing
Housing
• highly skilled labourers are not required for board
manufacture or building construction which allows boards to be made and buildings to be constructed locally and cheaply
• the construction process is quite fast and simple • high insulation value
• easy handling and workability
• important properties such as fire, water, termite and
References:
References:
• http://www.umeciv.maine.edu/rla/images/DSC00088.JPG • http://www.tangram.co.uk/TI-Polymer-Plastic&Composite_Windows.html • http://www.tangram.co.uk/TI-Wood_Plastic_Composites.html • http://www.tangram.co.uk/TI-Wood_Plastic_Composites_Review.pdf • http://www.cis.tennessee.edu/EPAMACT/other/Plywood/pcwpVT1.shtml • http://www.renewresources.com • http://www.machinerydata.com/HowToMakePlasticWood.htm • http://www.cierraindustries.com/plasticlumber.asp • http://en.wikipedia.org/wiki/Wood-plastic_composite• http://www.awc.org/Publications/download.html • http://www.awc.org/HelpOutreach/faq/FAQfiles/Plastic_Wood-Lumber.html • http://www.panelworldmag.com/vserver/hb/display.cfm? MagazineKey=6&IssueKey=461&SectionKey=389&ArticleKey=620 • http://www.fpl.fs.fed.us/documnts/pdf1997/wolfe97a.pdf#search=%22wood %20cement%20products%22 • http://www.ccaconference.org/pre/pdf/Gong.pdf#search=%22wood%20cement %20products%22 • http://www.anu.edu.au/Forestry/wood/cfb/contents.html • http://www.fpl.fs.fed.us/documnts/pdf1996/geime96b.pdf#search=%22cement %20wood%22 • http://www.aciar.gov.au/web.nsf/doc/JFRN-5J47AH • http://www.anu.edu.au/Forestry/wood/nwfp/woodwool/woodwoolphil.html • http://www.toolbase.org/Technology-Inventory/walls/wood-fiber-composite-forms
