Lauric Acid/Wood Fiber Blends for Shape Stable
Phase Change Material
Krista Stancombe, Fang Chen, Meng-Hsin Tsai and Michael Wolcott
Composite Materials and Engineering Center
Washington State University, P.O. Box 641806, Pullman, WA 99164, USA
Introduction
Polarized Optical Microscope (POM)
Thermogravimetric analysis (TGA)
Materials and Methods
100%
3.00
1
Deriv. Weight (%/oC)
2.50
80%
2.00
1.50
1.00
60%
Weight (%)
0.50
0.00
0
40%
100
200
o
300
400
500
Temp ( C)
•No effect on the
degradation with
varying processing
temperatures of the
LA/WF blends
20%
LA Crystals
Wood
Fiber
0%
0
100
200
300 Temp (oC) 400
500
600
Wood Fiber
700
Wood Fiber
Figure 3. TGA Results of LA, WF, and LA 80/WF 20 at different processing temperatures
100%
•LA and WF all
thermal degraded at
c.a. 210 and 380oC
2.50
Deriv. Weight (%/ oC)
•WF did not influence
the degradation of LA
in the blends system
80%
60%
2.00
Lauric Acid
LA 80/WF 20
LA 70/WF 30
LA 60/WF 40
Wood Fiber
1.50
3
1.00
0.50
0.00
40%
0
100
200
o
Temp ( C) 300
400
500
Lauric acid
20%
LA 80/WF 20 @ 100C
LA 60/WF 40 @ 100C
0
Wood Fiber Particle Size
100
200
300Temp (oC)400
500
600
700
Figure 4. TGA Results of LA, WF, and different LA/WF (wt%) blends
12%
23%
Differential Scanning Calorimetry (DSC)
3%
≥833 um
833 um
4%
Endo
180 um
150 um
≤125 um
•Thermal mechanical pulp of
softwood fiber (Plum Creek)
Method
WF content increased:
Lauric Acid
LA 80/WF 20
LA 70/WF 30
LA 60/WF 40
425 um
250 um
4%
•No effect on Tm
35
40
45
50
Temp. (oC)
55
60
WF content increases:
•Both of the ∆Hm and
∆Hc decreased
•Tc slightly reduced
Tm (oC) ∆Hm
(J/g)
47.0
198.7
47.4
184.0
48.2
169.3
47.6
168.7
Control*
80:20
70:30
60:40
Tc (oC) ∆Hc
(J/g)
41.5
209.4
40.6
196.8
38.7
186.2
39.2
185.9
Endo
Lauric Acid
Torque Rheometer
LA 80/WF 20 @ 60C
35
La 60/WF 40
LA 80/WF 20
25
LA 80/WF 20 @ 100C
•More WF, the
higher melting
torque occurred
(comparing after
3 mins. blended
LA 70/WF 30
Torque (Nm)
Processing temperatures
increased:
LA 80/WF 20 @ 80C
30
20
15
10
5
35
1
2
3
4
5
6
45
7
Time (Min.)
Figure 1. Varying LA/WF Ratios in Torque Rheometer
Processed temps.
Increased :
25
80/20 50C
80/20 80C
Torque (Nm)
•No effect with
varying processing
temperature
(comparing after 3
minutes blending
80/20 60C
20
•Slightly reduced the
∆Hm and ∆Hc
80/20 100C
15
10
5
0
0
1
2
3
4
5
6
50
55
•No effect on Tm and
Tc
60
7
Time (Min.)
Figure 2. Varying Temperatures with constant LA/WF Blend in Torque Rheometer
•Grafting lauric acid onto wood fiber for improving the stability
and thermal properties
Acknowledgements
This work was supported by the National Science Foundation’s REU
program under grant number DMR-0755055
Process
Temp.
Tm (oC) ∆Hm (J/g) Tc (oC) ∆Hc (J/g)
Control*
50oC
60oC
80oC
100oC
47.0
47.6
47.8
47.9
47.4
198.7
195.0
179.0
186.5
184.1
•Evaluating the shape stable stability of hot-pressed sample by
heat deflection temperature test
I would like to thank Dr. Wolcott for all of his support throughout this
project. Also, I would like to thank Fang Chen, Meng-Hsin Tsai and Brent
Olsen because none of this would have been possible without them.
Temp. (oC)
Figure 6. DSC curves of pure lauric acid and LA 80/WF 20 (wt%)
at different processing temperatures.
0
0
40
•Analyzed results showed that the LA/WF blends can still
maintain the thermal properties as the requirements of
phase change materials for thermal energy storage.
Future Work
Table 1. Thermal properties of the varying ratio blends at 100ºC
LA 80/WF 20 @ 50C
•WF absorbed molten lauric acid during the melt mixing
•LA crystallized along the wood fiber direction with an angle)
appeared only bottom of the WF, not surface of WF)
•The crystals may indicate that the lauric acid was melt flew
out from wood fiber (during heating), and further crystallized
after temperature below Tc
•The thermal analysis and morphology results indicated that
not enough evidence can prove if any interaction between
lauric acid and the wood fiber.
*Virgin Lauric Acid
Results and Discussions
Figure 7. POM photos of (1) pure lauric acid at room temperature;
(2), (3), (4) LA80/WF20 (wt%) blend at room temperature
•WF absorbed molten LA (LA penetrated into WF) as
function of stabilizing the phase change material.
Figure 5. DSC curves of pure lauric acid and various LA/WF (wt %) ratio blends
LA/WF.
4
Wood Fiber
Conclusion
•Wider range of energy
absorbing temperatures
51%
•Wood fiber (WF) was oven dried with a 2.73% moisture
content
•Lauric acid (LA) and WF mixtures were prepared in 60/40,
70/30, and 80/20 (wt %) ratios, respectively
•Mixtures of LA/WF were melt blended in a torque rheometer
with 50, 60 ,80, 100oC processing temperatures
•The thermal properties of the blends were analyzed by
differential scanning calorimetry (DSC) and thermogravimetric
analyses (TGA)
•The morphology properties of the LA/WF blends were
analyzed by the polarized optical microscope (POM)
LA crystals
3.00
LA 70/WF 30 @ 100C
3%
LA crystals
Wood Fiber
0%
•Purity >99% Lauric Acid (Palmac
99-12, Acidchem International
Sdn. Bhd.)
LA Crystals
2
LA crystals
Wood Fiber
Materials
LA Crystals
Lauric acid
LA 80/WF 20 @ 50C
LA 80/WF 20 @ 60C
LA 80/WF 20 @ 80C
LA 60/WF 20 @ 100C
Wood Fiber
Weight (%)
Energy saving, a major issue today, is one of the main
components in green building systems which can be achieved
by using phase change materials (PCM) as energy storage in
buildings. Fatty acids have greater properties over other PCMs
because of its: (1) high capacity of latent heat for thermal
energy storage, (2) suitable melt and crystallization
temperatures (Tm, Tc), (3) potential for sustainable production,
(4) non toxic and non-corrosive properties. However, the low
melt viscosity of fatty acids present challenges in retaining
shape at temperatures greater than its melting temperature. In
this project, lauric acid (LA) is as a matrix in preparing wood
fiber (WF) composites. The goal in developing this material is
to produce a shape stabilized PCM for use in building products.
To understand the effects of processing temperatures and
mixing ratios on the thermal properties of the LA/WF blends, the
composites were first melt blended in a torque rheometer, and
further characterized by thermogravimetric analysis (TGA),
differential scanning calorimetry (DSC) and polarized optical
microscopy (POM).
41.5
41.0
40.8
40.6
40.5
209.4
208.7
191.3
199.8
196.8
*Virgin Lauric Acid
Table 2. Thermal properties of varying the processing temperatures of the LA80/WF20 (wt%)
References
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Sari, A., Kaygusuz, K. (2007). Poly(vinyl alcohol)/Fatty Acid Blends for Thermal
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