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RESULTS The effect of defibration on hemp fibres The defibration of hemp by cultivation of P. radiata resulted in hemicellulose, pectin and lignin degradation, and the cellulose content in the fibres increased to 78% after 14 days of cultivation (Table 2). The content of crystalline cellulose in the fibres increased from 60 to 66 g/100 g dry matter (DM) due to the increased cellulose content after the fungal cultivation (Table 2). However the cellulose crystallinity decreased from 94 to 84 g/100 g cellulose due to conversion of crystalline cellulose into its amorphous form. The recovery of cellulose was 87% after 14 days using medium scale cultivation (Table 3) so there appeared to be decay of crystalline cellulose. Using small-scale experiments for 31 days there was no further cellulose decay due to the constant fibre yield (Table 3). Previous observations with transmission electron microscopy have also shown the fibre wall to remain intact (Thygesen et al., 2005a). The fibre bundle strength was reduced from 950 MPa in raw hemp bast to 820 MPa after the fungal defibration (Table 2). The defibration of hemp fibres by cultivation of C. subvermispora resulted in cellulose degradation as shown by the cellulose recovery of 87% after 14 days cultivation (Table 3) and by further reduction of the fibre yield after 31 days cultivation (Table 3). The fungus formed a lot of mycelia above the water surface, while hemp stem pieces below the surface were not colonised and the obtained cellulose content was 72% (Table 2). The fungus grew well with low and medium scale cultivation resulting in reduction of pH from 6 to 4.6 (Table 3). The fibre bundle strength was reduced by the cultivation to 780 MPa (Table 2). At large-scale cultivation, sterilisation was insufficient resulting in lower fibre yield after 14 days cultivation (27 g/100 stem) and unchanged pH in the culture broth (Table 3). Lignin degradation was obtained during the cultivation of P. radiata on the hemp due to peroxidase enzymes, as suggested by the presence of H2O2 in the cultivation broth (Table 3). Smaller hemp fibre bundles were also obtained by cultivation of P. radiata (3×10 3 μm 2 ) than by water retting and by C. subvermispora cultivation (Table 2), due to the greater degradation of the lignin rich middle lamellae between the fibres. Water retting was a faster process than fungal defibration (Table 1) due to the lacking of sterilisation and the higher temperature (35°C). However, a more variable quality was obtained due to inhomogeneous colonisation by bacteria and fungi resulting in lower fibre bundle strength (590 MPa, Table 2) and unchanged cellulose crystallinity (Figure 3). 128 Risø-PhD-11
Table 2. Chemical composition, structural properties and strength in fibres from hemp Raw hemp Hemp fibres defibrated with: bast Water retting C. sub. P. rad. Chemical composition Cellulose % w/w 64 74 72 78 83 Hemicellulose % w/w 15 12 14 13 11 Lignin % w/w 4 5 5 3 1 Pectin % w/w 6 3 4 2 1 Water soluble % w/w 6 3 3 3 1 Wax % w/w 1 2 1 1 2 Ash % w/w 4 2 2 1 1 Structure and strength Sample crystallinity % w/w 60 68 63 66 68 Cellulose crystallinity % w/w 94 92 88 84 82 Fibre bundle transverse section 10 3 μm 2 160 10 50 3 1 Hemp yarn Fibre bundle strength MPa 950 ± 230 590 ± 260 780 ± 170 820 ± 100 660 ± 100 Notes: - 14 days at medium scale (Table 1). - Comprehensive fibre analysis used for determination of chemical composition. - Sample crystallinity Cellulose crystallinity = Cellulose content Fibre yield [g/100 g bast] 100 75 50 25 0 Hemp stems treated with: No fungus C. sub P. rad 0 10 20 30 Incubation time [days] Figure 2. Yield of hemp fibres after small-scale cultivation with P. radiata and C. subvermispora versus time. Risø-PhD-11 129 40
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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
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The only fertilizer used was 360/48
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Temperature [ o C] 35 30 25 20 15 1
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A B Figure 7. A: Model of transvers
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Figure 8. Lignin (a), pectin (b) an
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Figure 11. Microfibril angles (MFA)
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Teleman, 1997). The crystal structu
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to the computing effort and the sub
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Figure 15. The structure of hemicel
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fibre mats, which are made by air-d
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Figure 18. From fibre filament to a
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A B C D Figure 20. Chemical structu
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water vapour and air are removed fr
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7 Defibration methods Defibration m
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Table 5. Fibre yield and cellulose
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a b c Composition [% w/w] 100 Compo
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8 Fibre strength in hemp The streng
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8.2 Effect of pre-treatment of hemp
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E-modulus [GPa] 90 80 70 60 50 40 3
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Second mode: Failure is controlled
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structure, which made much higher f
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Table 7. Porosity factors determine
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Thereby, the effective fibre streng
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a b Composite tensile strength σcu
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Table 9. Mechanical properties in a
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a σ c/ρ c [10 3 m 2 /s 2 ] b Ec/
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Fibre strength σ f [MPa] Fibre sti
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11 References Andersen TL, Lilholt
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Kaar WE, Cool LG, Merriman MM, Brin
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Stowell EZ, Liu TS, 1961. On the Me
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Appendix A: Comprehensive composite
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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.
Page 119 and 120: Paper IV Comparison of composites m
Page 121 and 122: ABSTRACT Aligned epoxy-matrix compo
Page 123 and 124: the calculation of volume fractions
Page 125 and 126: solution (pH 4) for 4 h at 85°C. L
Page 127: E ⎛ dσ c ⎞ = ⎜ ⎟ ⎝ dε
Page 131 and 132: transverse section of the small hem
Page 133 and 134: Long fibres that pass through the e
Page 135 and 136: Figure 6. Effect of composite fabri
Page 137 and 138: DISCUSSION The defibration of hemp
Page 139 and 140: This investigation showed that the
Page 141 and 142: Bos, H.L., Molenveld, K., Teunissen
Page 143 and 144: Thygesen, A., 2006. Properties of h
Page 147: Risø’s research is aimed at solv
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