Assessing Thermal Characteristics of Polyhydroxybutyrate Based Composites Reinforced with Different Natural Fibres Mikael Skrifvars 1 , Rathish Rajan 2 and Kuruvilla Joseph 3 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 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¨ MSK 20080918 2
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 MSK 20090407 3
Poly(3 ‐ hydroxybutyrate) • An aliphatic polyester Polyhydroxyalkanoate polymers • Semicrystalline O R – Crystallinity 60 – 80 % – T m = 170 – 180 ° C O – Tg = 4 ° C n – Density 1.25 g/cm 3 R name • Biodegradable hydrogen Poly 3 ‐ hydroxypropionate • Technical properties methyl Poly 3 ‐ hydroxybutyrate similar as isotactic ethyl Poly 3 ‐ hydroxyvalerate polypropylene propyl Poly 3 ‐ hydroxyhexanoate MSK 20090407 4
Polyhydroxybutyrate synthesis • Bacterial fermentation of organic sources • Accumulation in granules in cell cytoplasm • A super ‐ clean polymer with high molecular weight ( 2 million g/mol) PHB granules PHB granules • Conventional organic starting to grow in cell wall synthesis gives lower molecular weights Ref: Stubbe et al., Chemical & Engineering News, Sep 27, 2004 MSK 20090407 5
Natural fibre characteristics Properties Flax Sisal Coconut Banana (Coir) Density (g/cm 3 ) 1.5 1.45 1.15 1.3 Tensile Strength 345-1100 468-640 131-175 600-700 (MPa) Modulus (GPa) 27.6 9.4-22.0 4-6 29-32 Elongation at 2.7-3.2 3-7 15-40 2-4 break (%) Cellulose 64.1-71 36-43 63-64 content (wt %) Liginin 1.7-2.0 41-45 5 content (wt%) MSK 20090407 6
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 MSK 20090407 7
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 MSK 20090407 8
Thermal characterisation • Thermogravimetric analysis – TA Instruments TGA Q ‐ 500 – 25 °C to 800 °C, 10 °C/min, N 2 atmosphere • Differential scanning calorimetry – TA Instruments Q ‐ 1000 – From ‐ 20 °C to 200 °C, 10 °C/min, N 2 atmosphere – T m , T c , ∆ H m (normalized relative to weight fraction) – Degree of crystallinity: χ = ∆ H m / ∆ H 0 m, – ∆ H 0 m = 146 J/g for 100 % crystalline PHB MSK 20090407 9
Mechanical testing • Tensile testing – ISO 527 ‐ 5B – l tota l = 75 mm, l narrow = 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 MSK 20090407 10
Thermogravimetric analysis Neat PHB compared with 10 wt ‐ % sisal PHB ‐ composite PHB-Sisal 5 % weight loss at 254 °C Neat PHB 5 % weight loss at 234 °C At 430 °C complete degradation of At 340 °C PHB-Sisal complete degradation of neat PHB MSK 20090407 11
Thermogravimetric analysis Neat PHB compared with 30 wt ‐ % coconut, banana, flax and sisal PHB ‐ composites MSK 20090407 12
Differential scanning calorimetry χ (%) T m 1 ( 0 C) T m 2 ( 0 C) ∆ H m (J/g) Sample code Fibre content (%) Neat PHB 0 158.9 166.7 70.34 48.17 5 155.5 165.2 69.77 47.78 SISAL 10 156.1 165.8 67.47 46.21 20 78.43 53.71 158.5 167.0 30 156.8 166.4 80.42 53.08 5 155.6 165.3 68.72 47.06 FLAX 10 71.14 158.5 166.9 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 5 156.2 166.8 68.32 46.79 COIR 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 5 158.8 166.5 71.49 48.96 BANANA 10 64.46 157.1 165.9 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 % MSK 20090407 14
Differential scanning calorimetry χ (%) T m 1 ( 0 C) T m 2 ( 0 C) ∆ H m (J/g) Sample code Fibre content (%) Neat PHB 0 158.9 166.7 70.34 48.17 5 155.5 165.2 69.77 47.78 SISAL 10 156.1 165.8 67.47 46.21 20 78.43 53.71 158.5 167.0 30 156.8 166.4 80.42 53.08 5 155.6 165.3 68.72 47.06 FLAX 10 71.14 158.5 166.9 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 5 68.32 156.2 166.8 46.79 COIR 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 5 158.8 166.5 71.49 48.96 BANANA 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 MSK 20090407 15
Differential scanning calorimetry χ (%) T m 1 ( 0 C) T m 2 ( 0 C) ∆ H m (J/g) Sample code Fibre content (%) Neat PHB 0 158.9 166.7 70.34 48.17 5 155.5 165.2 69.77 47.78 SISAL 10 156.1 165.8 67.47 46.21 20 78.43 53.71 158.5 167.0 30 156.8 166.4 80.42 53.08 5 155.6 165.3 68.72 47.06 FLAX 10 71.14 158.5 166.9 48.72 20 153.2 164.2 74.41 50.96 30 153.8 164.9 73.34 50.23 5 68.32 156.2 166.8 46.79 COIR 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 5 158.8 166.5 71.49 48.96 BANANA 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 MSK 20090407 16
Tensile modulus for prepared composites at different fibre loadings Sisal 3500 Flax Coir Banana 3000 Youngs modulus (MPa) 2500 2000 1500 1000 0 5 10 15 20 25 30 Fibre content (wt %) MSK 20090407 19
Tensile strength for prepared composites at different fibre loadings 12 Sisal Flax 11 Coir Banana 10 Tensile strength (MPa) 9 8 7 6 5 4 0 5 10 15 20 25 30 Fibre content (wt %) MSK 20090407 20
Elongation at break for prepared composites at different fibre loadings Banana 0.9 Coir Flax 0.8 Sisal Elongation at break (%) 0.7 0.6 0.5 0.4 0.3 0.2 0 5 10 15 20 25 30 Fibre content wt(%) MSK 20090407 21
Sample Fibre content (%) Impact strength (kJ/m 2 ) code Neat PHB 0 102,8 5 52,1 SISAL 10 50,0 20 33,1 30 33,8 5 62,1 FLAX 10 61,9 20 30,0 30 36,2 5 42,1 COIR 10 30,7 20 25,7 30 24,6 5 59,4 BANANA 10 45,9 20 43,2 30 35,4 MSK 20090407 22
Impact strength for prepared composites at different fibre loadings 1100 Sisal 1000 Flax Coir 900 Banana Impact strength(kJ/m2) 800 700 600 500 400 300 200 0 5 10 15 20 25 30 Fibre content (wt %) MSK 20090407 23
Scanning electron microscopy of fracture surfaces from impact testing Banana Coconut 2 mm 2 mm Sisal Flax 2 mm 2 mm MSK 20090407 24
Fibre – matrix interfacial adhesion Banana Coir 200 μ m 200 μ m Sisal Flax 200 μ m 200 μ m MSK 20090407 25
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 MSK 20090407 26
On ‐ going work: Melt spinning of fibre filaments for microfibrillar composites MSK 20090407 27
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 MSK 20090407 28
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