THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

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structural weaknesses. To exploit the strength of native cellulose, the hierarchical structure needs to be broken down to harness the strength of microfibrils with higher crystallinity. There are three broad categories of treatments that can be used for the extraction of microfibrils: chemical, enzymatic or mechanical. Although these treatments can be used separately, a combination of these methods is typically used to achieve efficient yield of nanoparticles. To obtain high aspect ratios, chemical or enzymatic treatment is typically used to loosen up the macrostructure prior to mechanical delamination of long chains of microfibrils. The chemical approach relies on alkaline or acidic solvents. Mild alkaline treatments are typically applied to solubilize lignin, pectin and hemicellulose components surrounding the microfibrils (Moon et al. 2011). Cellulose fibers can also be partially hydrolyzed, and therefore the duration of hydrolysis treatment has to be taken into account to avoid undesirable degradation (Wang and Sain 2007a). Different acids have been previously employed for microfibril extraction, with hydrochloric and sulfuric acids being most frequently used by researchers (Hubbe et al. 2008). In practice, the diluted acid is mixed with cellulosic biomass at elevated temperatures for a length of time. For sulfuric acid, concentration does not vary much from 65% (w/w). However, temperatures could range from room temperature up to 70°C (Cherian et al. 2011). Reaction time could also vary from 30 min to overnight depending on temperature used. In terms of hydrochloric acid, reaction time varies with the cellulose source and hydrolysis is carried out at reflux temperature with a concentration ranging from 2.5N to 4N (Cherian et al. 2011). The reaction is then stopped via washing to neutralize and separate the biomass from residual acid and remaining neutralized salt. Subsequent filtration, centrifugation, and dialysis processes are often used to concentrate extracted fibers. Besides chemical treatments, enzymatic processes have also been previously used for ethanol production through the breakdown of biomass into simple sugars. By limiting the extent of cellulase hydrolysis, cellulose could be partially cleaved to yield nanofibers. Treatment effects 14
through the use of enzymes have produced more favorable characteristics compared to hydrolysis treatments. For instance, Henriksson et al. (2007) produced nanofibers with high molecular weights compared to mechanical and chemical methods. Janardhnan and Sain (2006) successfully obtained lower fiber diameters compared to acidic treatments using fungal culture OS1. The effectiveness of enzymatic treatments was attributed to its milder activity against cellulose where the cellulose fibrils were more intact in comparison to hydrolysis treatments. Mechanical extraction is achieved by refining, high-pressure homogenization, ultrasonication, and/or cryocrushing. Refining is similar to typical conventional paper making process except that rotating and stationary discs were used to compress and shear cellulose fibers to nano-scale dimensions. However this energy intensive method suffers a drawback that could yield aggregates of nano-sized particles rather than separated fiber strands (Hubbe et al. 2008). In comparison, homogenization is a process that uses refined cellulose suspensions that are pumped through a small orifice at high pressures. As the fibers exit the orifice, the impact and shearing forces result in a high degree of fibrillation of cellulose fibers bundles (Siró and Plackett 2010). Many reports have had success resulting in the production of MFC with high aspect ratios; diameters between 20 to 100 nm and estimated lengths of tens of micrometers have been reported (López-Rubio et al. 2007; Wang and Sain 2007a). In ultrasonication, high resonating frequencies are used to generate shock waves in liquids. When applied to a cellulose suspension, the high speed impinging jets and strong hydrodynamic shear forces disintegrates the suspension into short fibers with nano-dimensions (Pääkkö et al. 2007; Wang et al. 2008). Cryocrushing is done first by swelling cellulose with water, immersing in liquid nitrogen, and then crushing it using a mortar and pestle. This is an effective method for delamination but could also yield fibers that are brittle and short due to the extreme freezing combined with intense mechanical forces (Hubbe et al. 2008). 15
Page 1 and 2: A Study on the Extrusion of Soy Pro
Page 3 and 4: ACKNOWLEDGEMENTS My research would
Page 5 and 6: 4.3.9 Statistical Analysis.........
Page 7 and 8: LIST OF TABLES Table 2.1: Compariso
Page 9 and 10: Figure 5.2: Light optical microscop
Page 11 and 12: 1.0 INTRODUCTION The production of
Page 13 and 14: einforcement material. Research int
Page 15 and 16: via centrifugation into four fracti
Page 17 and 18: zones are synonymous to feeding, tr
Page 19 and 20: Ralston (2008) investigated the ext
Page 21 and 22: onding between hydroxyl groups and
Page 23: Table 2.2: Summary of cellulose par
Page 27 and 28: matrix such as soy protein (Wang et
Page 29 and 30: 4) Explore the extraction process f
Page 31 and 32: 4.3 METHODS 4.3.1 SAMPLE PREPARATIO
Page 33 and 34: a Figure 4.2: a) Schematic of extru
Page 35 and 36: length at break by the initial grip
Page 37 and 38: 4.4 RESULTS AND DISCUSSION 4.4.1 SP
Page 39 and 40: Further experiments were carried ou
Page 41 and 42: Figure 4.5: Film with rough texture
Page 43 and 44: extrusion screw to continuously bre
Page 45 and 46: stopped which fixes the spherical s
Page 47 and 48: 4.4.3 MECHANICAL PROPERTIES Mechani
Page 49 and 50: Elongation at break (%) Figure 4.10
Page 51 and 52: Table 4.5: Water vapor permeability
Page 53 and 54: 4.4.5 FTIR ANALYSIS The main absorb
Page 55 and 56: 4.4.6 CONCLUSION The extrusion of S
Page 57 and 58: 5.3 METHODS 5.3.1 CELLULOSE EXTRACT
Page 59 and 60: For mechanical treatments, the obta
Page 61 and 62: initial soy biomass; SNF and SMF. T
Page 63 and 64: compiled by Moon et al. (2011), thi
Page 65 and 66: RSH: 5min HPH: 20 passes, 4000 - 60
Page 67 and 68: SMF micrographs, the presence of fi
Page 69 and 70: process as described. However, it m
Page 71 and 72: a peak at 22.6° is representative
Page 73 and 74: chemical and mechanical treatment h
Page 75 and 76:
6.3 METHODS 6.3.1 SAMPLE PREPARATIO
Page 77 and 78:
6.3.3 FILM CONDITIONING Similar to
Page 79 and 80:
increased in size. At fiber concent
Page 81 and 82:
6.4.2 MORPHOLOGY AND STRUCTURE Due
Page 83 and 84:
SEM images of the cryo-fractured su
Page 85 and 86:
Table 6.1: Mechanical properties of
Page 87 and 88:
cellulose and SPI. This high interf
Page 89 and 90:
concentrations at isolated sites. A
Page 91 and 92:
Similar to Section 4.4.5, dominatin
Page 93 and 94:
Further analysis of the Amide II ba
Page 95 and 96:
specimens that have been cryo-crush
Page 97 and 98:
crushing. Conversely, this could al
Page 99 and 100:
7.0 EXPLORATORY WORK WITH TIO 2 NAN
Page 101 and 102:
7.3.2 COMPOUNDING AND EXTRUSION Com
Page 103 and 104:
smaller size of P90, the ability to
Page 105 and 106:
Table 7.1: Mechanical Strength of T
Page 107 and 108:
Modulus of Elasticity (MPa) 120 110
Page 109 and 110:
(21 nm) particle was seen to have a
Page 111 and 112:
7.4.3 MECHANICAL PROPERTIES OF TIO2
Page 113 and 114:
Tensile Strenght (MPa) 12 11 10 9 8
Page 115 and 116:
Modulus of Elasticity (MPa) 200 180
Page 117 and 118:
8.0 CONCLUSIONS AND RECOMMENDATIONS
Page 119 and 120:
The viability of introducing a comp
Page 121 and 122:
acting as a coupling agent for furt
Page 123 and 124:
Cherian BM, Leao AL, Souza SFD, Tho
Page 125 and 126:
Kacurakova M, Capek P, Sasinkova V,
Page 127 and 128:
Pääkkö M, Ankerfors M, Kosonen H
Page 129:
Wang N, Ding E, Cheng R (2008) Prep
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THESIS - ROC CH ... - FINAL - resubmission.pdf - University of Guelph

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