Assessing Thermal Characteristics of Polyhydroxybutyrate Based - - PowerPoint PPT Presentation

Assessing Thermal Characteristics of Polyhydroxybutyrate Based Composites Reinforced with Different Natural Fibres

Mikael Skrifvars 1, Rathish Rajan2 and Kuruvilla Joseph3

1) School of Engineering, University of Borås, S-501 90 Borås, Sweden

2) St. Berchmans College , Mahatma Gandhi University, Kerala, India 3) Indian Institute of Space Science and Technology, ISRO.P.O, Thiruvananthapuram, Kerala, India

University of Borås, Sweden

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Professor Mikael Skrifvars

• Project manager at Neste

Chemicals company, Finland, 1986 to 1999

• Group manager at SICOMP

Research Institute, Sweden, 1999-2003

• Professor in polymer

technology at UCB since 2003 Borås, Sweden

¨The Textile Center of Sweden¨

Aim of work

• Study the injection moulding of

polyhydroxybutyrate composites reinforced with natural fibres

• Study the thermal and mechanical properties

for prepared composites

• Study the possibilities to enhance

processability and properties for polyhydroxybutyrate by incorporating natural fibres

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Poly(3‐hydroxybutyrate)

• An aliphatic polyester
• Semicrystalline

– Crystallinity 60 – 80 % – Tm = 170 – 180 °C

– Tg = 4 °C – Density 1.25 g/cm3

• Biodegradable
• Technical properties

similar as isotactic polypropylene

O O R

n

R name hydrogen Poly 3‐hydroxypropionate methyl Poly 3‐hydroxybutyrate ethyl Poly 3‐hydroxyvalerate propyl Poly 3‐hydroxyhexanoate

Polyhydroxyalkanoate polymers

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Polyhydroxybutyrate synthesis

• Bacterial fermentation
• f organic sources
• Accumulation in

granules in cell cytoplasm

• A super‐clean polymer

with high molecular weight ( 2 million g/mol)

• Conventional organic

synthesis gives lower molecular weights

Ref: Stubbe et al., Chemical & Engineering News, Sep 27, 2004

PHB granules starting to grow in cell wall PHB granules

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Natural fibre characteristics

Properties Flax Sisal Coconut (Coir) Banana Density (g/cm3) 1.5 1.45 1.15 1.3 Tensile Strength (MPa) 345-1100 468-640 131-175 600-700 Modulus (GPa) 27.6 9.4-22.0 4-6 29-32 Elongation at break (%) 2.7-3.2 3-7 15-40 2-4 Cellulose content (wt %) 64.1-71 36-43 63-64 Liginin content (wt%) 1.7-2.0 41-45 5

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Materials

Polymer

• Polyhydroxybutyrate (PHB 209) from Biomer, GmbH,

Krailling, Germany Natural fibres

• Sisal fibres, from Sheeba fibres and handicrafts,

Tamilnadu, India

• Banana fibres, from Sheeba fibres and handicrafts,

Tamilnadu, India

• Coconut/coir fibres, from local producer in Kollam,

Kerala, India

• Flax yarn, from Nordic Flax, Finland

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Material processing

• Compounding

– DSM Xplore conical twin screw microcompounder, 15 cc – 15 g sample batch – T = 175 °C, 60 rpm – 10 min mixing time

• Injection moulding

– DSM Xplore micro injection moulding machine, 10 cc – T = 175 °C

• Composition of samples

– 5, 10, 20 and 30 weight‐% fibre content – 5 specimens for each composition

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Thermal characterisation

• Thermogravimetric analysis

– TA Instruments TGA Q‐500 – 25 °C to 800 °C, 10 °C/min, N2 atmosphere

• Differential scanning calorimetry

– TA Instruments Q‐1000 – From ‐ 20 °C to 200 °C, 10 °C/min, N2 atmosphere – Tm, Tc, ∆Hm (normalized relative to weight fraction) – Degree of crystallinity: χ = ∆Hm/ ∆H0

m,

– ∆H0

m = 146 J/g for 100 % crystalline PHB

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Mechanical testing

• Tensile testing

– ISO 527‐5B – ltotal = 75 mm, lnarrow = 25 mm, w = 12.5 mm – Tinius Olsen H10 kT – 500 N load cell, 2 mm/min, 25 mm gauge length – 5 specimens/composition

• Charpy unnotched impact testing

– l = 80 mm, w = 10 mm, t = 4 mm – Zwick pendulum impact tester, 2.7 J – Flatwise impact

• Fracture surfaces inspected by SEM

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Thermogravimetric analysis

Neat PHB compared with 10 wt‐% sisal PHB‐composite

Neat PHB 5 % weight loss at 234 °C At 340 °C complete degradation

• f neat PHB

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PHB-Sisal 5 % weight loss at 254 °C At 430 °C complete degradation of PHB-Sisal

Thermogravimetric analysis

Neat PHB compared with 30 wt‐% coconut, banana, flax and sisal PHB‐composites

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Differential scanning calorimetry

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Sample code Fibre content (%) T m 1 (0C) T m2 (0C) ∆Hm (J/g) χ (%) Neat PHB 158.9 166.7 70.34 48.17 SISAL 5 155.5 165.2 69.77 47.78 10 156.1 165.8 67.47 46.21 20 158.5 167.0 78.43 53.71 30 156.8 166.4 80.42 53.08 FLAX 5 155.6 165.3 68.72 47.06 10 158.5 166.9 71.14 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 COIR 5 156.2 166.8 68.32 46.79 10 151.1 162.7 66.01 45.21 20 157.6 166.2 62.06 42.50 30 156.8 166.1 69.61 47.67 BANANA 5 158.8 166.5 71.49 48.96 10 157.1 165.9 64.46 44.15 20 157.3 166.1 65.47 44.84 30 157.3 166.2 74.32 50.90

Reported in literature: Χ ~ 60 – 80 %

Differential scanning calorimetry

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Sample code Fibre content (%) T m 1 (0C) T m2 (0C) ∆Hm (J/g) χ (%) Neat PHB 158.9 166.7 70.34 48.17 SISAL 5 155.5 165.2 69.77 47.78 10 156.1 165.8 67.47 46.21 20 158.5 167.0 78.43 53.71 30 156.8 166.4 80.42 53.08 FLAX 5 155.6 165.3 68.72 47.06 10 158.5 166.9 71.14 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 COIR 5 156.2 166.8 68.32 46.79 10 151.1 162.7 66.01 45.21 20 157.6 166.2 62.06 42.50 30 156.8 166.1 69.61 47.67 BANANA 5 158.8 166.5 71.49 48.96 10 157.1 165.9 64.46 44.15 20 157.3 166.1 65.47 44.84 30 157.3 166.2 74.32 50.90

Differential scanning calorimetry

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Sample code Fibre content (%) T m 1 (0C) T m2 (0C) ∆Hm (J/g) χ (%) Neat PHB 158.9 166.7 70.34 48.17 SISAL 5 155.5 165.2 69.77 47.78 10 156.1 165.8 67.47 46.21 20 158.5 167.0 78.43 53.71 30 156.8 166.4 80.42 53.08 FLAX 5 155.6 165.3 68.72 47.06 10 158.5 166.9 71.14 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 COIR 5 156.2 166.8 68.32 46.79 10 151.1 162.7 66.01 45.21 20 157.6 166.2 62.06 42.50 30 156.8 166.1 69.61 47.67 BANANA 5 158.8 166.5 71.49 48.96 10 157.1 165.9 64.46 44.15 20 157.3 166.1 65.47 44.84 30 157.3 166.2 74.32 50.90

Tensile modulus for prepared composites at different fibre loadings

5 10 15 20 25 30 1000 1500 2000 2500 3000 3500

Youngs modulus (MPa) Fibre content (wt %)

Sisal Flax Coir Banana

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Tensile strength for prepared composites at different fibre loadings

5 10 15 20 25 30 4 5 6 7 8 9 10 11 12

Tensile strength (MPa) Fibre content (wt %)

Sisal Flax Coir Banana MSK 20090407 20

Elongation at break for prepared composites at different fibre loadings

5 10 15 20 25 30 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Elongation at break (%) Fibre content wt(%)

Banana Coir Flax Sisal

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Sample code Fibre content (%) Impact strength (kJ/m2) Neat PHB 102,8 SISAL 5 52,1 10 50,0 20 33,1 30 33,8 FLAX 5 62,1 10 61,9 20 30,0 30 36,2 COIR 5 42,1 10 30,7 20 25,7 30 24,6 BANANA 5 59,4 10 45,9 20 43,2 30 35,4

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Impact strength for prepared composites at different fibre loadings

5 10 15 20 25 30 200 300 400 500 600 700 800 900 1000 1100

Impact strength(kJ/m2) Fibre content (wt %)

Sisal Flax Coir Banana

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Scanning electron microscopy of fracture surfaces from impact testing

2 mm 2 mm 2 mm 2 mm

Banana Coconut Sisal Flax

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Fibre – matrix interfacial adhesion

Banana Coir Sisal Flax

200 μm 200 μm 200 μm 200 μm

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Conclusions

• PHB composites containing 5 to 30 wt‐% of flax, coir, banana

respective sisal fibres have been prepared by injection moulding

• The degree of crystallinity increased for sisal and banana fibre

at high fibre loadings, while the degree of crystallinity decreased for coir fibres

• Tensile modulus increased with fibre content for all

reinforcements, as expected

• A clearly lower impact strength was achieved for all

reinforcements, due to poor interfacial adhesion

• Modification of PHB with natural fibres might be a possibility

to prepare cost‐efficient composite material

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On‐going work:

Melt spinning of fibre filaments for microfibrillar composites

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Acknowledgements

• Albany International is acknowledged for

performing the SEM analysis

• Haike Hilke is acknowledged for the

mechanical testing Thank you for your attention! mikael.skrifvars@hb.se

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