spray-dried cellulose nanofibrils reinforced polypropylene...

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


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


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


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)


• 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


• 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


• 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)


Spray drying of CNF

(Wang et al 2017b)

Spray-dried CNF

Particle size distribution of spray-dried CNF


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/

?


• 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


• 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


Steady-state shear flow test results Flexural propertis of CNF-PP composites from injection molding

(Wang & Gardner 2017c)


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


Objective

• To study if spray-dried CNF can be

used to retard the crystallization rate of

iPP.


• 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.



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.


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.


Part 3: Mechanical properties of printed PP

Injection molded Printed

Mechanical properties: injection molded parts > printed parts


Objective

To investigate whether printed PP

equally good in mechanical properties to molded PP.


Impact-modified polypropylene


Non-isothermal crystallization kinetic parameters for PP samples

(Nandi and Ghosh 2007)


• 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).


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


• 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


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


DSC curves for injection molded and printed coPP.


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.


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.


Thank you! Questions?

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