Thermal Characterization of Nanocrystalline Cellulose For Polymer Nanocomposite Applications

Transcription

1 Thermal Characterization of Nanocrystalline Cellulose For Polymer Nanocomposite Applications Andrew C. Finkle, C. Ravindra Reddy, Leonardo Simon University of Waterloo 200 University Av. W., Waterloo, ON, Canada

2 Outline Introduction: Motivation Materials: Nanocrystalline Cellulose sources Method: TGA, Flynn-Wall-Ozawa, Moisture Results: Onset of Degradation, EA, %MC Conclusion 2

3 Introduction Cellulose as a bio-based polymer reinforcement sustainable, recyclable, and non-toxic Interest to replace metal and glass with plastic High temperature polymer processing will cause thermal degradation of cellulose colour change, odour, reduction in strength and long-term stability Quantify thermal stability of cellulose 3

4 Materials: Cellulose Sources Alberta Innovates Technology Futures 1. Nanocrystalline Cellulose (NCC-Alb) Nanocrystalline Cellulose As received: small off-white flakes (~1mm) water soluble at few wt% 100nm fibers FP Innovations 2. Nanocrystalline Cellulose (NCC-FP) Nanocrystalline Cellulose from Canadian wood sources As received: low density translucent flakes water soluble at a few wt% 200nm x 10nm fibers 2 J. RETTENMAIER & SÖHNE GMBH+CO.KG 3. UltraFine Cellulose 100 (UFC-100) Microcrystalline cellulose As received: small off-white flakes (~1mm) water dispersible at few wt% ~4.5um microfibers 4. NanoDisperse Cellulose (MF 40-10) Nano/Microcrystalline Cellulose As received: dispersion, white paste ~1-5um microfibers 4

5 Methods Thermogravimetric Analysis (TGA) Weight change of cellulose as a function of a preprogrammed heating profile Thermal degradation is proportional to the conversion of cellulose from solid to gaseous products Temperature: ºC Heating rates: 5, 10, 20, 30, 40ºC per minute Gas atmosphere: Air and N2 5

6 Methods Flynn-Wall-Ozawa 3 Determine activation energy as a kinetic parameter of thermal degradation EA determined from plot of log β versus -1/RT at a constant conversion (over multiple heating rates) and will result in a line with a slope of *EA Focus on initial section of conversion (<40%) as this is of interest to polymer processing β is the heating rate E a is the activation energy of the reaction R is the gas constant T is the absolute temperature A is the pre-exponential factor α is the percent degradation 6

7 Methods Moisture Content Quantify the water content that is inherent in the solid cellulose material in ambient conditions Cellulose is very hydrophilic Moisture can cause compatibility issues between cellulose and polymer matrix Time (s) at 110ºC Sample heated at 110ºC until mass reaches steady state Does not account for any other volatile compounds that may be released 4 m i is the initial mass of the sample m f is the mass of the sample after reaching a steady-state mass following drying at 110 C 7

8 1. Results: NCC-Alb I II Air N 2 I II III IV III IV First region (I): mass decrease at very slow rate due to moisture content and other volatile components Second region (II): rate of mass loss increases significantly and about 40% of the mass is lost in a short time Third region (III): the rate of mass loss decreases again Fourth region (IV): In air, the rate of mass loss increases loss until it plateaus at a very small mass (residual ash) In nitrogen, the mass loss decreases slightly until end of the test 8 The reason for the difference in IV is manly the complete versus incomplete combustion between the oxygen-rich air and oxygen-free nitrogen.

9 1. Results: NCC-Alb A slower heating rate results in an earlier onset of degradation (i.e. 5ºC/min vs. 40ºC/min) The onset of degradation for samples heated in air occurs slightly earlier than samples in nitrogen (~2ºC) Residue after burning in air is ~2% whereas nitrogen is ~30% Onset of Degradation: The temperature at which the rate of mass loss increases significantly, temperature found at some arb. Conversion (%), here 5%. 9

10 2. Results: NCC-FP I II Air N I 2 II III IV III IV I: mass constant at 100% up to around 250ºC (%MC before 150ºC omitted) II: the rate of mass loss increases significantly and about 70% of the mass is lost in this short time higher than the 40% for NCC-Alb, suggesting more homogeneous III: the rate of mass loss decreases IV: In air, the rate of mass loss increases loss until it plateaus at a very small mass (residual ash) In nitrogen, the rate of mass loss decreases and continues to fall slightly until end of the test 10

11 2. Results: NCC-FP Slower heating rate = earlier onset of degradation Onset of degradation in air occurs slightly earlier than in nitrogen (~2ºC) Here 1 wt-% conversion has been assumed to calculate onset T Mass loss about 2% in air and only slightly higher in nitrogen (~2-5%) 11

12 3. Results: UFC-100 I II Air N I 2 II III IV III IV I: mass constant at 100% up to around 275ºC II: the rate of mass loss increases significantly and about 90+% of the mass is lost in this short time higher than the 40% for NCC-Alb and 70% for NCC-FP, suggesting that UFC-100 is more homogeneous III: the rate of mass loss decreases slightly in air and plateaus in nitrogen IV: In air, the rate of mass loss increases loss until it appears to plateau at a very small mass (residual ash) In nitrogen, mass remains mostly constant (same as III) until end of test) 12

13 3. Results: UFC-100 Slower heating rate = earlier onset of degradation Onset of degradation in air occurs slightly earlier than in nitrogen (~2ºC) Here 1 wt-% conversion has been assumed to calculate onset T Mass loss about 0.2% in air and only slightly higher in nitrogen (~2-3%) 13

14 4. Results: MF I Air I N 2 II II III IV III IV I: mass constant at 100% up to around 225ºC II: the rate of mass loss increases significantly and about 70% of the mass is lost in this time, change in mass loss more gradual than other sources III: the rate of mass loss decreases, much more significantly in air IV: In air, the rate of mass loss plateaus at a very small mass (residual ash). In nitrogen, the rate of mass loss decreases and continues to fall slightly until end of the test. 14

15 4. Results: MF Slower heating rate = earlier onset of degradation Onset of degradation in air occurs slightly earlier than in nitrogen (~2ºC) Here 1 wt-% conversion has been assumed to calculate onset T Mass loss about 0.4% in air and only slightly higher in nitrogen (~10-15%) 15 gradual onset of degradation of MF may be attributed also to the fact that it had dried as a hard cake, whereas the other samples were in a low-density powder or flake morphology

16 Results: EAE Comparison Air N 2 16 cellulose sources have higher activation energy in nitrogen than in air (~20 kj/mol) Most R-square values for the fit of the log β versus -1/RT plots were >0.98 E A lines nearly parallel and constant, confirming that the activation energies do not depend on previous conversion (except NCC-Alb) NCC-FP > MF > UFC-100 > NCC-Alb varied from to kj/mol between the NCC-FP and NCC-Alb inconsistency and lower magnitude for the NCC-Alb source can be associated to inclusions of lignin, hemi-cellulose, or some other impurity

17 Results: Moisture Content Each cellulose source was tested for moisture content on four random days 17 The standard deviations are low as the %MC did not fluctuate too dramatically during the testing.

18 Conclusions E A and Onset of Degradation temperature was calculated for NCC-Alb, NCC-FP, UFC- 100 and MF using Flynn-Wall-Ozawa method E A for NCC-Alb were 122 kj/mol and 130 kj/mol in air and nitrogen respectively E A for NCC-FP were were higher at 184 and 202 kj/mol for air and nitrogen E A for UFC-100 were were higher at 136 and 145 kj/mol for air and nitrogen E A for MF were were higher at 152 and 166 kj/mol for air and nitrogen NCC-FP and UFC-100 sample contained less impurities than the other sources UFC-100 had the highest Onset of Degradation followed by NCC-FP, MF 40-10, and NCC-Alb E A for NCC-Alb appeared more dependent on conversion than the other cellulose sources The calculated E A and onset temperatures can be used to model and predict mass loss during a specific processing temperature profile as well as screening for the best candidate to use in a polymer nanocomposite 5 The moisture content for NCC-Alb is approximately 4.9%; for NCC-FP it is slightly higher at 6.4%; and UFC-100 and MF had %MC of 6.3% and 5.7% respectively 18

19 Acknowledgements The authors would also like to thank FP Innovations, Alberta Innovates, and JRS Inc. for donating the cellulose samples; and acknowledge financial support from the Natural Science and Engineering Council of Canada (Discovery Grant) and the Ontario Ministry of Research and Innovation (The Ontario BioCar Initiative). References 1. M.A. Hubbe, O.J. Rojas, L.A. Lucia, and M. Sain, Cellulosic nanocomposites: A Review, BioResources, vol. 3, 2008, pp FP Innovations Nanocrystalline Cellulose Green Nanoparticles. Brochure. Pointe-Claire, PQ. 3. JRS Inc., UFC-100 Material Specification Sheet, JRS Inc., MF Material Specification Sheet, T. Ozawa, Kinetic analysis of derivative curves in thermal analysis, Journal of Thermal Analysis, vol. 2, Sep. 1970, pp M. Golbabaie, Characterization of Ontario Crop Fibres for Use in Biocomposites (Wheat and Soybean), University of Guelph. MSc Thesis D.K. Misra. In: F. Hamilton, B. Leopold and M.J. Kocurek, Editors, (Version 5 Edition ed.),pulp and Paper Manufacture Vol. 3, Joint Textbook Committee of the Paper Industry TAPPI-CPPA, Montreal, Canada (1987), pp Secondary Fibers and Nonwood Pulping. 19

20 Thank you PRESENTED BY Andrew C. Finkle MASc ChemEng (Nano) University of Waterloo Please remember to turn in your evaluation sheet...