Research, Education, and Economic Development 1Author name, [email protected]
Spray-dried Cellulose Nanofibrils Reinforced
Polypropylene Composites for Extrusion-
based Additive Manufacturing
Lu Wang, Ph.D. candidate
J. Elliott Sanders, Ph.D. student
Douglas J. Gardner, Professor
Advanced Structures and Composites Center
School of Forest Resources
University of Maine, Orono, MECollaborated with
Research, Education, and Economic Development 2Author name, [email protected]
Presentation outline
1. Introduction
2. Rheological properties of CNF-PP
composites
3. Non-isothermal crystallization
kinetics study on CNF-PP
composites
4. Mechanical properties of printed PP
Research, Education, and Economic Development 3Author name, [email protected]
Additive manufacturing
for the automotive
industry:
newer designs;
cleaner, lighter,
ergonomic products;
shorter lead times.
Introduction
(Giffi et al, 2016) https://media.ford.com/content/fordmedia/fna/us/en/news/2017/03/06/ford-tests-large-scale-3d-printing.html
Research, Education, and Economic Development 4Author name, [email protected]
Methods Advantages Disadvantages
SLA fast and accurate photo sensitive resins with poor mechanical properties; Leachates from under-cured resin is toxic
SLS dimensional stability limitation on suitable materials
LOM multiple material during printing (paper, ceramic, polymers or metals)
hard to create complex shape like embedded inserts
SMS reduced power density by using IR light, reduce building time by enlarging chamber, reduce degradation by laser
not suitable for polyamide
3DP colorful material by choosing inked binders
large void content (~50%), needs further infiltration
FDM use semi-finished product, prototype for functional testing, low cost
lower mechanical properties and low surface quality
CLIP Fast production rate and good mechanical properties
long post processing time
(Wendel et al 2008)
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• Alias:
• Fused Deposition Modeling
(FDM) Stratasys
• Fused Filament Fabrication
(FFF) RepRap
• Material Extrusion (ISO/ASTM
52900:2015)
http://www.custompartnet.com/wu/fused-deposition-modeling
Extrusion-based additive manufacturing
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• Polypropylene is a
versatile polymer with
many applications.
• World wide second largest
consumed polymer.
• Iso-PP cannot be easily
printed due to its
propensity to warp during
printing.
(Wang et al, 2017a ;Wang et al, 2017b)
Polypropylene
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• Abundant
• Renewable and biodegradable
• Low density
• High aspect ratio
• Low production cost
• High strength and modulus
(Moon et al, 20011; Peng et al, 2011)
Cellulose nanofibrils (CNF)
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Spray drying of CNF
(Wang et al 2017b)
Spray-dried CNF
Particle size distribution of spray-dried CNF
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Part 1: Rheological properties of CNF-PP composites for AM
• Shear rate during
extrusion-based AM is
100~200 S-1.
http://www.drawingartwiki.com/page/182/
?
Research, Education, and Economic Development 10Author name, [email protected]
• To investigate the effect of spray-dried CNF on the rheological properties of CNF-PP composites and evaluate the suitability of such composites for AM.
Objective
Research, Education, and Economic Development 11Author name, [email protected]
• Spray-dried CNF
• Homopolymer PP (H19G-01), density is 0.91 g/cm3 and MFI of 19 g/10min.
• CNF and PP was first compounded at 30 wt.% fiber content and dilute with fresh PP to final composition. Injection molded into flexural bars.
• Rheology. Bohlin Gemini rheometer (Malvern Instruments, UK). Temperature of 200 °C and parallel plates with a diameter of 25 mm.
Materials and methods
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Steady-state shear flow test results Flexural propertis of CNF-PP composites from injection molding
(Wang & Gardner 2017c)
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Polymer Mna (kg/mol) Tc
b
(°C)t1/2
c (s)
PP 41.8 120 2.93
PLLA 45 120 21.5
Crystallization rate comparison
(Seo et al, 2000; Fujisawa et al, 2014)
a number based molecular weight,b temperature for crystallization,c half crystallization time. Printed PLA sample
Part 2: non-isothermal crystallization kinetics study on CNF-iPP composites
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Objective
• To study if spray-dried CNF can be
used to retard the crystallization rate of
iPP.
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• Spray-dried CNF
• Homopolymer PP (H19G-01), density is 0.91 g/cm3 and MFI of 19 g/10min.
• Maleic anhydride polypropylene (MAPP) pellets (Polybond3200). Density of 0.91 g/cm3, melting point of 190 °C and MFI (190 °C/2.16kg) of 115 g/10min.
• CNF and PP was first compounded at 30 wt.% fiber content and dilute with fresh PP to final composition.
• Crystallization kinetics by DSC. 1-2 mg of injection molded samples, ramp to 190 °C at 50 °C/min, hold for 5 min, cool down to 50 °C at 4 different rates (5, 10, 15 and 20 °C/min), reheated to 190 °C at 10 °C/min to obtain melting information.
Materials and methods
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Table. Nonisothermal crystallization parameters at various cooling rate
Samples λa (K/min) Tob (°C) Tp
c (°C) Xcd (%) t1/2
e (min)
iPP 5 134.8 126.1 49.0 1.75
10 131.2 122.7 49.6 0.88
15 129.2 120.8 48.4 0.59
20 127.2 119.0 46.1 0.46
iPP/CNF3% 5 134.0 125.9 50.0 1.59
10 131.8 122.6 48.4 0.85
15 129.7 120.9 45.9 0.60
20 127.5 118.7 47.8 0.47
iPP/CNF10% 5 135.2 125.8 51.6 1.85
10 131.8 122.6 48.2 0.95
15 130.4 120.7 49.3 0.66
20 128.9 119.5 49.1 0.49
iPP/CNF30% 5 134.3 126.2 56.4 1.56
10 132.3 123.2 54 0.88
15 130.3 121.3 57.6 0.58
20 128.7 120.2 47.7 0.42
iPP/MA 5 133.4 125.8 53.4 1.51
10 130.9 122.8 51.9 0.81
15 129.4 121.0 49.3 0.56
20 127.2 119.3 47.1 0.41
iPP/MA/CNF10% 5 133.0 125.3 52.1 1.51
10 130.8 122.4 50.1 0.83
15 128.6 120.3 49.2 0.55
20 127.1 118.3 49.3 0.46
a λ-cooling rate, b To-onset temperature, c Tp-peak temperature, Xcd-crystallinity and t1/2
e -half crystallization time.
Research, Education, and Economic Development 17Author name, [email protected]
Effective activation energy calculated based on the Kissinger method.
Samples iPP iPPCNF3% iPPCNF10% iPPCNF30% iPP/MA/CNF10%
ΔE (kJ/mol) 264.1 262.5 291.6 305.5 265.2
R2 0.997 0.989 0.999 0.999 0.988
Samples Typical crystal diameter(µm)
PP 33
PP/MA 27
PP/CNF3% 21
PP/CNF10% 12
PPCNF30% 8
PP/MA/CNF10% 10
Polarized light microscopy micrographs of iPP and iPP/CNF composites. Scale bar 50 µm.
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Part 3: Mechanical properties of printed PP
Injection molded Printed
Mechanical properties: injection molded parts > printed parts
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Objective
To investigate whether printed PP
equally good in mechanical properties to molded PP.
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Impact-modified polypropylene
Materials and methods
Non-isothermal crystallization kinetic parameters for PP samples
(Nandi and Ghosh 2007)
Research, Education, and Economic Development 21Author name, [email protected]
• coPP went through two times of extrusion (200 °C and 100 rpm) before being made into 3-mm filaments using the same extruder (60 rpm). This coPP filament will be a control sample to our later experiments with coPP-CNF composites.
• Injection molding: 17 MPa, 200 °C, hold time 10s, mold temp (40 °C).
• Flexural and impact tests were performed.
• DSC. 1-2 mg of injection molded or printed samples, ramp from 40 °C to 190 °C at 10 °C/min.
• DMA (dual-cantilever mode) were used to obtain the heat deflection temperature and E’, E’’ and tan_Delta of coPP samples (1Hz, 0.05% strain amp).
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Printing settings for coPP.
Parameters Fixed
Extruder temperature (ᵒC) 200
Platform temperature (ᵒC) 120
Extrusion speed (mm/s) 60
Infill density (%) 100
Layer height (mm) 0.3
Layer width (mm) 0.4
Number of shell 2
Raft, supports and bridging No
Orientation (ᵒ) +45/-45ºC
Air space (%) 0
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• Results and discussion
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0
10
20
30
40
coPPIM coPPAM
Mo
du
lus
(Gp
a)
Stre
ngt
h (
Mp
a)
Samples
Flexural properties
Modulus Strength
0
50
100
150
200
coPPIM coPPAM
Stre
ngt
h (
J/m
)
Samples
Izod impact strength
Izod impact strength
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Heat Deflection Temperatures of coPP samples
Sample HDT (⁰C)
coPPIM 83.8 (4.8)
coPPAM 91.8 (1.4)
DMA curves showing E’, E’’ and tan_Delta for injection molded and printed coPP
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DSC curves for injection molded and printed coPP.
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Conclusions
1. Spray-dried CNF can enhance the mechanical properties of iPP.
2. The addition of spray-dried CNF (up to 30 wt.%) did not significantly increase the viscosity of iPP at high shear rate (>10 S-1).
3. The addition of about 10 wt.% spray-dried CNF reduced the overall crystallization rate of iPP.
4. Printed coPP were as good as injection molded coPP in some mechanical properties. This is because the hot plate during printing increased the crystallinity and changed crystal form.
Research, Education, and Economic Development 27Author name, [email protected]
References1. Giffi CA, Gangula B, Illinda P. 3D opportunity in the automotive industry: Additive manufacturing hits the road. Deloitte
University Press.2. Wendel B, Rietzel D, Kühnlein F, Feulner R, Hülder G, Schmachtenberg E. Additive processing of polymers, Macromol. Mat.
Eng. 293 (10) (2008), 799-809.3. Wang L, Gardner DJ. Effect of fused layer modeling (FLM) processing parameters on impact strength of cellular
polypropylene. Polymer;113; 2017a:74-80.4. Wang L, Gardner DJ , Bousfiled DW. Cellulose Nanofibril-Reinforced Polypropylene Composites for Material Extrusion:
Rheological Properties. POLYM ENG SCI, 2017b.5. Moon RJ, Martini A, Nairn J, Simonsen J, Youngblood J. Cellulose nanomaterials review: structure, properties and
nanocomposites. Chem Soc Rev ;40(7);2011:3941-94.6. Peng Y, Gardner DJ, Han Y. Drying cellulose nanofibrils: in search of a suitable method. CELLULOSE,2011;19(1):91-102.7. Wang L, Gardner D J , Bousfiled D W (2017) Cellulose Nanofibril-Reinforced Polypropylene Composites for Material
Extrusion: Rheological Properties. POLYM ENG SCI. DOI 10.1002/pen.246158. Seo, Yongsok, Jinho Kim, Kwang Ung Kim, and Young Chul Kim. "Study of the crystallization behaviors of polypropylene and
maleic anhydride grafted polypropylene." Polymer 41, no. 7 (2000): 2639-2646.9. Fujisawa, Shuji, Jiaqi Zhang, Tsuguyuki Saito, Tadahisa Iwata, and Akira Isogai. "Cellulose nanofibrils as templates for the
design of poly (l-lactide)-nucleating surfaces." Polymer 55, no. 13 (2014): 2937-2942.10. Wang L and Gardner DJ. Enhanced cellulose nanofibril/polypropylene composites for 3D printing. SPE Plastic Research
Online.11. Nandi S, Ghosh AK. Crystallization kinetics of impact modified polypropylene. Journal of Polymer Research. 2007 Oct
1;14(5):387-96.
Research, Education, and Economic Development 28Author name, [email protected]
Thank you! Questions?