Post on 11-May-2015
Durability of Wood Flour-Recycled Durability of Wood Flour-Recycled Thermoplastics Composites Under Thermoplastics Composites Under
Accelerated Environmental ConditionsAccelerated Environmental Conditions
Kamal Adhikary, Shusheng Pang and Mark Staiger
Department of Chemical and Process Engineering University of Canterbury
Christchurch, New Zealand
Ecocity World Summit 2008, San Francisco, USA22-26 April 2008
Background Objectives Experimental Programs Results and Discussions Conclusions
Presentation outlinePresentation outline
1. Total MSW generation in 2006 in USA was 251 million tons (USEPA 2006). Recycled 82 million tons of MSW (32.5 %).
2. 1.3 billion tonnes of MSW generated in Europe3. Worldwide plastics production: 245 million tonnes (PlasticEurope 2008).
BackgroundBackground
BackgroundBackground
Total MSW generation in 2006 in USA was 251 million tons.
– Plastics comprise 11.7 percent
– Wood follows at 5.5 percent – 9.4% of wood generated was recovered
– 6.9% of plastics waste generated was recovered/ or recycled
Recovery rate of post-consumer end-of-life plastics in Europe was 50% in 2006.
About 35,000 tonnes (13.48% of total imported virgin plastics) was recycled in 2004 in New Zealand
Increased use of recycled plastics and wood waste offers the prospect of lessening waste disposals and reducing the product costs
BackgroundBackground
Recycled plastics and wood waste are,
Lower cost than competitive materials (especially those based on synthetic polymer), For example, HDPE recycled pellet and flake is 31- 34% less expensive than virgin
Renewable resources Additional market for recycled plastics and
wood waste Reduce waste disposal burden Properties are comparable to virgin plastics
Development of new value added wood-plastic composite material utilizing recovered plastics and
wood waste will have a greater importance from both engineering and economic points of view
What is Wood-Plastic Composite?What is Wood-Plastic Composite?
Wood-plastic composite is manufactured by dispersing wood particles into molten plastic with coupling agent/ or additives to form composite material that can be processed
like a conventional plastic and has the best features of wood and plastics
Advantages over its constituent’s materials
Compare to wood it has lower water uptake, thickness swell, and highly durable against bio-deterioration, also reduce the machine wear and tear of processing equipment, and lowers the product cost against inorganic fillers
Compare to polymer it has higher mechanical properties, thermal stability, and more resistant to ultraviolet light and degradation
ObjectivesObjectives
Investigate the performance of wood-plastic composites (WPCs) made of recycled plastics and sawdust
Evaluate dimensional stability, mechanical properties, morphology and thermal properties of WPCs
Examine durability performance for outdoor applications
Experimental: Experimental: MaterialsMaterials
1: Wood filler Pinus radiata sawdustFresh sawdust was dried and
grounded to fine flour (0.18 and 0.5 mm) 0.00
20.00
40.00
60.00
80.00
7 10 18 35 45 80 120 140
Sieve num ber
Per
cen
tag
e re
tain
ed, %
Size distribution of radiata pine flour
Polymer typeMelt flow index, g/10min/(190°C / 2.16
kg)
Virgin HDPE 0.1
Recycled HDPE 0.07
Virgin PP 25
Recycled PP 21
2: Thermoplastic polymer Recycled thermoplastics (HDPE and
PP) collected from Local Plastics Recycling Company.
Virgin HDPE (grade GM4755) and virgin PP (Hyundai Séetec M1600, polypropylene co-polymer)
Coupling agent: Maleated polypropylene (Epolene G-3015)
Experimental: Composite preparationExperimental: Composite preparation
Mixing/compounding of wood flour and plastic: using a
co-rotating twin screw extruder. Composite formulation used:
Wood flour: 0, 30, 40, 50 and 60 wt. % MAPP content: 3-5 wt. %
Pressing mold temperature: 170 C for HDPE series and 190 C for PP series; hot pressed for 5 min under 5 MPa, and then cold pressed under same pressure.
Target panel density: 800-950 kg/m3 Composite panel size: size:
165 mm 152 mm 6.4 mm
Sawdust (wood-flour)
Mixing/Compounding
Recycled Plastics
WPC’s panel (Final product)
Hot/Cold pressing of pelletsWood-plastics Pellets
Wood-plastic composite manufacturing process flow
Composite formulations (% by weight)Composite formulations (% by weight)
Composite sample code
Polymer type
Polymer form
Polymer content (%)
Wood flour (%)
Coupling agent (%)
vPE50W50 HDPE Virgin 50 50 0
rPE50W50 HDPE Recycled 50 50 0
vPP50W50 PP Virgin 50 50 0
rPP50W50 PP Recycled 50 50 0
rPP45W50CA5 PP Recycled 45 50 5
Accelerated weathering testsAccelerated weathering tests1. Accelerated freeze-thaw cycles
Samples exposed to Accelerated Freeze–Thaw Cycles (ASTM D6662–01) for 12 full cycles.
One complete weathering cycle consisted of:(i) Water soaks until no further weigh gain (ii) Freezing for 24 h (Chest freezer at –27°±3°C)(iii) Thawing for 24 h (21°C±3°C and 50±5% RH)
2. Accelerated UV-exposure
Samples exposed to Fluorescent UV light-exposure apparatus (ASTM D4329-99).
Exposure for 2000 h Lamp type: UVA-340Irradiance: 0.77 W/m2 (~ wavelength of 340 nm)
Testing and analysisTesting and analysis
Water absorption & thickness swelling tests (ASTM D570-98). Mechanical properties: Flexural properties (ASTM D790) using
Universal Testing Machine. Morphology of the fracture surface of bending test specimens are
investigated by using high resolution field emission scanning electron microscopy.
Surface color of control and weathered samples are measured using Minolta Spectrophotometer (ASTM D2244).
Thermal properties are measured by using Differential Scanning Calorimetry- Scanned from 50 to 200oC at a heating and cooling rate of 2oC/min.
2 h Water Absorption
0
2
4
6
Wat
er a
bsor
ptio
n (%
)
Control
FT cycled
UV weathered
0
3
6
9
12
Wat
er a
bsor
ptio
n (%
)
Control
FT cycled
UV weathered
Water absorption by WPCs in Water Submersion
ResultsResults
24 h Water Absorption
24 h Thickness Swelling (%)
0
2
3
5
vPP5
0W50
rPP5
0W50
rPP4
5W50
CA5
vHDPE50
W50
rHDPE50
W50
Thi
ckne
ss S
wel
ling
(%)
Control
FT cycled
UV weathered
Results Contd……Results Contd……
Thickness Swelling by WPCs in Water Submersion
Flexural MOR of the WPCs Flexural MOE of the WPCs
0.0
1.0
2.0
3.0
MO
E (
GPa
)
Control
FT cycled
UV weathered
0
15
30
45
MO
R (M
Pa)
Control
FT cycled
UV weathered
Results Contd……Results Contd……
Flexural properties of WPCs
-90
-60
-30
0
30
60
90
vPP50
W50
rPP50
W50
rPP45
W50
CA5
vHDPE50
W50
rHDPE50
W50
% c
hang
e in
val
ues
MOR MOEYield stress Elongation at break
Results Contd……Results Contd……
Changes in flexural properties of WPCs after 12 FT cycles
Results Contd……Results Contd……
Surface colour measurement
ΔE – Discoloration; ΔL*- lightening; Δa*and Δb*-chromaticity coordinates
Δa* Δb* ΔL* ΔE Δa* Δb* ΔL* ΔE
vPP50W50 -2.3 -6.9 6.6 9.8 -3.3 -9.5 7.2 12.3
rPP50W50 0.2 1.2 10.4 10.5 -0.2 0.9 14.0 14.0
rPP45W50CA5 -0.3 -0.2 7.4 7.5 0.0 0.4 5.3 5.3
vHDPE50W50 -0.8 -4.7 -1.4 5.0 -1.1 -3.1 6.1 6.9
rHDPE50W50 0.3 1.8 4.8 5.2 0.1 0.6 2.6 2.7
Composite specimen code
After 12 FT cycles After 2000 h UV weatheing
0
4
8
12
16de
ltaE
Val
ue
500 h 1000 h
1500 h 2000 h
Discoloration values (ΔE) for UV-Weathered PP-wood flour Composites
Results Contd……Results Contd……
Results (contd.)Results (contd.)
SEM images of rPP50W50 (a) control and (b) UV-weathered samples
Microstructural characterization
Results (contd.)Results (contd.)
SEM images of rPP45W50CA5 (a) control (b) FT-weathered samples
Microstructural characterization
Results contd…..Results contd…..
DSC thermograms (2nd heating) for PP based control and FT weathered composites
Thermal properties of WPCs
-0.35
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
50 80 110 140 170 200
Temperature (oC)
Hea
t flo
w (W
/g)
rPP100
vPP50W50
rPP50W50
FT-vPP50W50
FT-rPP50W50
Crystallization temperature (Tc) and enthalpy (ΔHc) were measured from 1st cooling run Peak melting temperature (Tm) and enthalpy (ΔHm) were measured from 2nd heating cycle Crystallinity (Xc):
ΔHf :Expt. heat of fusion, ΔHf100 is the theoretical heat of fusion for a 100% crystalline thermoplastic (ΔHf100=205 J/g for PP and ΔHf100=293 J/g for HDPE), and w is the mass fraction of thermoplastic in the composite samples
wH
HX
f
fc *
100
Results (contd.)Results (contd.)
Thermal properties
Melting enthalpy and crystallinity of UV-weathered composites was decreased compared to corresponding control samples.
Peak melting temperature and peak crystallization temperature changed slightly.
Wood fibers in composite act as nucleating agent and retards the crystallization rate.
Loss of crystallinity due to weathering degradation resulted the decrease in composite properties.
ConclusionsConclusions
The results of this work so far provided the evidence that the recycled thermoplastics (HDPE and PP) and wood sawdust can be successfully used to produce stable and strong wood plastic composites.
Improved stability can be achieved by increasing the polymer content or by addition of coupling agent.
Properties degradation is observed after Freeze-Thaw and UV weathering.
Property ComparisonProperty Comparison
Property HDPE based WPC
PP based WPC
PP lumber
Pine lumber
Regular MDF
(3mm)
Flexural MOR (MPa)
14.4-25.5 17.4-39.6 28.7 80.0 40.0
Flexural MOE (GPa)
1.06-1.97 1.7-2.5 1.39 7.9 3.0
24 h water absorption (%)
0.98-4.1 1.2-3.7 <0.01 17.2 2-3 (1h)
24 h thickness Swelling (%)
0.42-2.5 0.8-1.5 - 2.6 1.7-3.8 (1h)
Potential ApplicationsPotential Applications
Low Stress Applications:
Residential/Commercial decking products
Boardwalks and DocksWindows and door partsSiding and accessoriesFencingOthers: Roofing, Outdoor furniture,
Landscape timbers, Playground equipment
Exterior building trim Industrial flooring
AcknowledgementsAcknowledgements
Mr Jeremy Warnes and Mr Ross Anderson of Scion on extrusion experiments
Mr Murray Taylor and Mr Henry Baker of AgResearch (Lincoln) on hot press experiments
New Zealand Plastics Recycling Ltd. to supply the recycled plastics
Technicians from Departments of Mechanical Engineering, and Chemical and Process Engineering
New Zealand Development Scholarships (NZDS) scheme of NZAID
Funding from New Zealand Foundation for Research, Science and Technology
Thank you.Thank you.
Any questions, comments, suggestions??
Additives (Contd…)Additives (Contd…)
Modification scheme for esterification reaction between wood particles and maleated polyolefins: (a) monoester and (b) diester formation.