silane-crosslinking efficiency in wood-polyethylene...
TRANSCRIPT
Silane-crosslinking efficiency in wood-polyethylene composites:
Göran Grubbström and Kristiina Oksman
Division of Design and Manufacturing of Wood and Bionanocomposites,Luleå University of Technology, Sweden
Study of different polyethylenes
10th International Conference on Wood & Biofiber Plastic Composites
Outline
Conclusions
Background
ProcessingDegree of crosslinkingMechanical properties
Testing and Results
MaterialsReactive extrusionCuring
Materials and Processing
Background
Challenges for WPCs
Improving long-term material properties
Strength and toughness
Lowering the weight
Challenges for WPCs
Improving long-term material properties
Crosslinking:
Strength and toughness
Lowering the weight
Higher strength and toughness
Creep resistance
Crosslinked WPCs
Crosslinked
Polymer matrix
Non-crosslinked
Crosslinked WPCs
Crosslinked
Polymer matrix
Non-crosslinked
Creep resistance
Crosslinked WPCs
Crosslinked
Polymer matrix
Non-crosslinked
Strength and toughness
Previous studies
Sapieha et al. (1990), Kuan et al. (2004), Xiong et al (2008), etc.Pre-treated wood flour/fibers
Add reactants during compoundingNogellova et al. (1998), Janigova et al. (2001), Bengtsson et al. (2006)
Previous studies
Sapieha et al. (1990), Kuan et al. (2004), Xiong et al (2008), etc.Pre-treated wood flour/fibers
Add reactants during compoundingNogellova et al. (1998), Janigova et al. (2001), Bengtsson et al. (2006)
Silane-crosslinkingPeroxide-crosslinking
Crosslinked polyethylene
Peroxide-crosslinking
PE
Crosslinked polyethylene
Peroxide-crosslinking Silane-crosslinking
PE
Crosslinked polyethylene
Peroxide-crosslinking Silane-crosslinking
PE
Crosslinked polyethylene
Peroxide-crosslinking Silane-crosslinking
PE
Molten state
Solid state
Crosslinked polyethylene
Peroxide-crosslinking Silane-crosslinking
PE
Side-reactio
n
(Scorch)
Molten state
Solid state
Silane-crosslinked polyethylene
Differences between type of polyethylene
HDPE LDPE
More
Faster
More
Lazar et al. (1990), Wong and Varrall (1994), Shieh and Liu (1999).
Slower
Less
Less
Curing
Polymer chain scission
Scorch
High-density polyethylene Low-density polyethylene
Silane crosslinked WPC
One-step process: CompoundingSilane-graftingProfiling
(Bengtsson et al., 2006)
Silane crosslinked WPC
Store composite
One-step process: CompoundingSilane-graftingProfiling
(Bengtsson et al., 2006)
H2O
Objective for the study
Compare results to our previous
study of crosslinked HDPE-WPC
Investigate possibility to use
silane-technology for LDPE-WPCs
Materials and Processing
Materials
Wood flourSoftwood, 300-500μm
Lubricant TPW113 (Struktol, U.S.A.)
47 wt-%
50 wt-%
3 wt-%
MFI 0.4 MFI 12HDPE LDPE (recycled)
Materials
Wood flourSoftwood, 300-500μm
Lubricant TPW113 (Struktol, U.S.A.)
VinyltrimethoxysilaneVTMS 97% (Sigma Aldrich, U.S.A.)
Dicumyl peroxide DCP 98% (Sigma Aldrich, Japan)
47 wt-%
50 wt-%
3 wt-%
Solution
MFI 0.4 MFI 12HDPE LDPE (recycled)
Materials
Wood flourSoftwood, 300-500μm
Lubricant TPW113 (Struktol, U.S.A.)
VinyltrimethoxysilaneVTMS 97% (Sigma Aldrich, U.S.A.)
Dicumyl peroxide DCP 98% (Sigma Aldrich, Japan)
47 wt-%
50 wt-%
3 wt-%
+ 4 wt-% 12:1 w/w
MFI 0.4 MFI 12HDPE LDPE (recycled)
Materials
Wood flourSoftwood, 300-500μm
Lubricant TPW113 (Struktol, U.S.A.)
VinyltrimethoxysilaneVTMS 97% (Sigma Aldrich, U.S.A.)
Dicumyl peroxide DCP 98% (Sigma Aldrich, Japan)
47 wt-%
50 wt-%
3 wt-%
+ 3 wt-% 12:1 w/w
MFI 0.4 MFI 12HDPE LDPE (recycled)
Materials
Wood flourSoftwood, 300-500μm
Lubricant TPW113 (Struktol, U.S.A.)
VinyltrimethoxysilaneVTMS 97% (Sigma Aldrich, U.S.A.)
Dicumyl peroxide DCP 98% (Sigma Aldrich, Japan)
47 wt-%
50 wt-%
3 wt-%
+ 3 wt-% 12:1 w/w
MFI 0.4 MFI 12HDPE LDPE (recycled)
25:1 w/w
Reactive extrusion
Twin screw extrusion
(Coperion W&P ZSK18 MEGAlab)
- Compounding and profiling
Throughput 5.2 kg/hResidence time 55-60 s.Melt temp. ~195oC
Curing conditions
Room temperature (RT)
Sauna (SA)90˚CRH close to 100%
21˚CRH 30-40%
Storing times: 0, 3, 6, 12 hours,1, 2, 3, 4, 6, 9 days
Sample coding
LDPE-composites HDPE-composites
HD-X LD-X
HD Non-X LD Non-X
LD-X (low)
Testing and Results
Processing
LDPE-compositeHDPE-composite
Non HD-X Non LD-X LD-X(low)
Processing
Extruder torque: 45% 60-70%35% 60%
LDPE-compositeHDPE-composite
Non HD-X Non LD-X LD-X(low)
Processing
Extruder torque: 45% 60-70%35% 60%
Die swelling: 4% 20% 40%Not significant
LDPE-compositeHDPE-composite
Non HD-X Non LD-X LD-X(low)
Degree of crosslinking
(ASTM D2765)Measure insoluble gel content
- Sample in 120 Mesh pouch- In boiling xylene for 12 hours- Extracted mass (%) measured- Degree of crosslinking = 100 – Extract (%)
Degree of crosslinking
RTSA
0%
20%
40%
60%
80%
100%
0 1 2 3 4 5 6 7 8 9
LD-X
56%
Storing time (days)
HD-X
0%
20%
40%
60%
80%
100%
0 1 2 3 4 5 6 7 8 9
35%
Storing time (days)
Degree of crosslinking
RTSA
LD-X (Low)
0%
20%
40%
60%
80%
100%
0 1 2 3 4 5 6 7 8 9
39%
Storing time (days)
56%
0%
20%
40%
60%
80%
100%
0 1 2 3 4 5 6 7 8 9
HD-X
Storing time (days)
35%
Mechanical testing
LDPE-compositesFlexural properties (ISO 178)
HDPE-composites*Tensile properties (ASTM D638)
* Grubbström and Oksman 2009
Mechanical properties
HDPE-composites
0
5
10
15
20
25
Tens
ile s
tres
s (M
Pa)
RTSA
HD-X
Non-X
Strain (%)0 1 2 3 4 5
Mechanical properties
0
5
10
15
20
25
30
Flex
ural
str
ess
(MPa
)
Non-X LD-X
LD-X (low)
Strain (%)
LDPE-compositesRTSA
0 2 3 4 5 6 7 8 91
Morphology
LDPE-Composite
HDPE-Composite
CrosslinkedNon-X
Short-term creep
DMA
- Specimen: 60.0 x 12.5 x 2.5 (mm)
- Dual cantilever mode- Static stress 5 MPa- 30˚C - 5 hours + 1 hour recovery
(TA Instruments)
Short-term creep
LDPE-composites
0,0
1,0
2,0
3,0
4,0
5,0
0 1 2 3 4 5 6
Non-XLD-X
LD-X (low)
Time (hours)
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0 1 2 3 4 5 6
HDPE-composites
Non-X
HD-X
Time (hours)
RTSA
Stra
in(%
)
Conclusions
Conclusions
There are differences in crosslinking efficiencydepending on type of polyethylene in the WPC
LDPE-composite: More sensitive for reactants
Cures faster
Do not need storing in Sauna
The technology works for both HDPE and LDPE
Future work
Minimize crosslinking in extrusion process
Silane-crosslinking process: RT, SA
Long-term properties
Acknowledgements
Skellefteå Kraft and Nordea for financial support
Questions?