Properties of hemp fibre polymer composites -An optimisation of ...

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10 Conclusions and future work Hemp stems could be defibrated with the white rot fungus Phlebia radiata Cel 26 on at least the 100 g scale to make fibres for reinforcement of composites, since the pectin and wax rich epidermis was degraded. The fibres retained parallel orientation during the fungal defibration and water retting and are thereby useful for composites with aligned fibres. Lignin located in the middle lamellae between the single fibers made pectinase defibration difficult. Lignin degradation in the hemp fibres by cultivation of P. radiata Cel 26 resulted in more cellulose rich fibres (78%) than treatment with pectin degrading enzymes. Even though the hemp fibres were handled with mild methods like hand peeling and fungal defibration, fibre strength higher than 643 MPa was not obtained, which is similar to the strength of traditionally produced hemp yarn (677 MPa). Furthermore the fibre strength appeared to be linearly dependent on cellulose content and independent on cellulose crystallinity and microfibril angle. Pure cellulose had the estimated effective strength of 850 MPa that is about 10% of the strength on the molecular level. The plant fibre stiffness appeared to increase linearly with cellulose content, decrease with microfibril angle and increase with cellulose crystallinity. Pure crystalline cellulose had an estimated stiffness of 125 GPa. Future investigations could be to investigate the fracture mechanics in plant fibre reinforced composites. That will potentially explain if the obtained composite strength is lower than determined based on the fibre strength or if the reduction in strength is only due to the effect of the Weibull distribution. Such investigations should be performed at varied fibre content and will in addition reveal further information about the effect of fibre content on the resulting porosity content. Composites with various biodegradable matrix materials like starch or lignin could be tested to get a completely biodegradable material. This investigation should focus on the matrix properties and on how to get a good interface with the fibres. The fungal defibration method could be replaced with constructed enzyme mixtures by genetic engineering or a designed and stable bacterial strain could be applied in the retting procedure. 66 Risø-PhD-11
11 References Andersen TL, Lilholt H, 1999. Natural fibre composites: compaction of mats, press consolidation and material quality. Japanese Journal of Applied Physics Part 1-Regular Papers Short Notes & Review Papers, Presented at 7 th Euro-Japanese Symposium, 1-2 nd July 1999. Andersson S, Serimaa R, Paakkari T, Saranpaa P, Pesonen E, 2003. Crystallinity of wood and the size of cellulose crystallites in Norway spruce (Picea abies). Journal of Wood Science, 49: pp. 531-537. Bergander A, Brandstrom J, Daniel G, Salmen L, 2002. Fibril angle variability in earlywood of Norway spruce using soft rot cavities and polarization confocal microscopy. Journal of Wood Science, 48: pp. 255-263. Bjerre AB, Olesen AB, Fernqvist T, Plöger A, Schmidt AS, 1996. Pretreatment of wheat straw using combined wet oxidation and alkaline hydrolysis resulting in convertible cellulose and hemicellulose. Biotechnol Bioeng, 49: pp. 568-577. Bjerre AB, Schmidt AS, 1997. Development of chemical and biological processes for production of bioethanol: Optimization of the wet oxidation process and characterization of products. Risø-R-967(EN), Risø National Laboratory: pp 5-9. Bledzki AK, Sperber VE, Faruk O, 2002. Natural and wood fibre reinforcement in polymers. Rapra Review Reports, 13. Bócsa I, 1971. The realization of specific breeding goals in hemp breeding. Rostnövények: pp. 29-34. du Bois WF, 1982. Hemp as a raw material for the paper industry. Bedrijfsontwikkeling, 13: pp. 851-856. Bos HL, Molenveld K, Teunissen W, van Wingerde AM, van Delft DRV, 2004. Compressive behaviour of unidirectional flax fibre reinforced composites. J Mater Sci, 39: pp. 2159- 2168. Bos HL, Van den Oever MJA, Peters OCJJ, 2002. Tensile and compressive properties of flax fibres for natural fibre reinforced composites. J Mater Sci, 37: pp. 1683-1692. Boutelje JB, Rydell RR, 1986. Träfakta, 44 träslag i ord och bild. TräteknikCentrum Stockholm pp 27-29. Broge JL, 2000. Natural fibers in automotive components. Automotive Engineering International, 108: pp. 120. Browning BL, 1967. Methods of wood chemistry. New York: Interscience Publishers, A division of John Wiley & Sons. Brühlmann F, Leupin M, Erismann KH, Fiechter A, 2000. Enzymatic degumming of ramie bast fibers. Journal of Biotechnology, 76: pp. 43-50. Brüning HJ, Disselbeck D, 1992. Thermoplastic high-performance filament yarns and their use in fibre composites. International man-made fibres progress; Österreishisches Chemiefaser-Institut; Paper no. 31. Cappelsen J, 2004. Ugeberetning - klimadata på ugebasis: oktober 1998 - december 2003. Technical report No 04-15, Danish Meteorological Institute. Cappelsen J, Jørgensen BV, 2002. The Climate of Denmark 2002. Technical report No 03- 02, Danish Meteorological Institute. Cichocki FR, Thomason JL, 2002. Thermoelastic anisotropy of a natural fiber. Compos Sci Technol, 62: pp. 669-678. Clemons C, 2000. Woodfiber-plastic composites in the United States – History and current and future markets. In the Proceedings of the 3rd International Wood and Natural Fibre Composites Symposium; Kassel, Germany: pp. 1-7. Coleman BD, 1958. On strength of classical fibres and fibre bundles. J mech phys solids, 7: pp. 60-70. Cromack HTH, 1998. The effect of cultivar and seed density on the production and fibre content of Cannabis sativa in southern England. Ind Crops Prod, 7: pp. 205-210. Risø-PhD-11 67
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Risø-PhD-11(EN) Properties of hemp
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Contents Preface 6 1 Resumé 7 2 Li
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PhD thesis: Properties of hemp fibr
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1 Resumé Karakterisering af hampef
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2.4 Oral presentations Anders Thyge
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4 Introduction Hemp (Cannabis sativ
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4.2 The outline of the thesis The f
Page 15 and 16: The only fertilizer used was 360/48
Page 17 and 18: Temperature [ o C] 35 30 25 20 15 1
Page 19 and 20: A B Figure 7. A: Model of transvers
Page 21 and 22: Figure 8. Lignin (a), pectin (b) an
Page 23 and 24: Figure 11. Microfibril angles (MFA)
Page 25 and 26: Teleman, 1997). The crystal structu
Page 27 and 28: to the computing effort and the sub
Page 29 and 30: Figure 15. The structure of hemicel
Page 31 and 32: fibre mats, which are made by air-d
Page 33 and 34: Figure 18. From fibre filament to a
Page 35 and 36: A B C D Figure 20. Chemical structu
Page 37 and 38: water vapour and air are removed fr
Page 39 and 40: 7 Defibration methods Defibration m
Page 41 and 42: Table 5. Fibre yield and cellulose
Page 43 and 44: a b c Composition [% w/w] 100 Compo
Page 45 and 46: 8 Fibre strength in hemp The streng
Page 47 and 48: 8.2 Effect of pre-treatment of hemp
Page 49 and 50: E-modulus [GPa] 90 80 70 60 50 40 3
Page 51 and 52: Second mode: Failure is controlled
Page 53 and 54: structure, which made much higher f
Page 55 and 56: Table 7. Porosity factors determine
Page 57 and 58: Thereby, the effective fibre streng
Page 59 and 60: a b Composite tensile strength σcu
Page 61 and 62: Table 9. Mechanical properties in a
Page 63 and 64: a σ c/ρ c [10 3 m 2 /s 2 ] b Ec/
Page 65: Fibre strength σ f [MPa] Fibre sti
Page 69 and 70: Kaar WE, Cool LG, Merriman MM, Brin
Page 71 and 72: Stowell EZ, Liu TS, 1961. On the Me
Page 73 and 74: Appendix A: Comprehensive composite
Page 75 and 76: The porosity constants can now be d
Page 77 and 78: Appendix D: Density and mechanical
Page 79 and 80: Paper I Changes in chemical composi
Page 81 and 82: Risø-PhD-11 81
Page 89 and 90: Paper II Hemp fiber microstructure
Page 91 and 92: ABSTRACT Characterization of hemp f
Page 93 and 94: METHODS AND TECHNIQUES Treatment of
Page 95 and 96: 2000) and their orientation gave th
Page 97 and 98: By TEM microscopy, the single fiber
Page 99 and 100: Table 1. Chemical composition of th
Page 101 and 102: Table 2. Tensile strength (σ) and
Page 103 and 104: Morvan, C., Jauneau, A., Flaman, A.
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Risø-PhD-11 117
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Paper IV Comparison of composites m
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ABSTRACT Aligned epoxy-matrix compo
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the calculation of volume fractions
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solution (pH 4) for 4 h at 85°C. L
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E ⎛ dσ c ⎞ = ⎜ ⎟ ⎝ dε
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Table 2. Chemical composition, stru
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transverse section of the small hem
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Long fibres that pass through the e
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Figure 6. Effect of composite fabri
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DISCUSSION The defibration of hemp
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This investigation showed that the
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Bos, H.L., Molenveld, K., Teunissen
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Thygesen, A., 2006. Properties of h
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Risø-PhD-11 145
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Risø’s research is aimed at solv
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