Grafted α-cellulose-poly(hydroxybutyrate-co-hydroxyvalerate) Biocomposites. Liqing Wei and Armando G. McDonald Renewable Materials Program June 2015

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1 Grafted α-cellulose-poly(hydroxybutyrate-co-hydroxyvalerate) Biocomposites Liqing Wei and Armando G. McDonald Renewable Materials Program June 2015

2 1.1 Why Use Bioplastics Issues with Conventional Plastic >300 million tons of plastics are produced annually >40 % of these conventional plastics are used in short-term applications Environmental pollution both terrestrial & marine How to overcome these issues Need to introduce bioplastics from renewable resources into the market with comparable or improved properties Biodegradable

3 1.2 Bacterial polyhydroxyalkanoates Carbon Cycle of PHA PHA granules PHA R PHB - CH 3 PHV -CH 2 CH 3 PHBV - CH 3 & CH 2 CH 3 PHHp -(CH 2 ) 3 CH 3 PHBO -CH 3 & -(CH 2 ) 4 CH 3 HB: 3-hydroxybutyrate; HV: 3-hydroxyvalerate H O R x O OH n PHA general structure R = C 1 -C 13 x = 1 to 3 or more

4 Packaging films: Shopping bags, containers & paper coatings, single-use items Biomedical implant materials: Sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples Limitations 1.3 Applications of PHA PHA s poor melt strength limits processing & product options en.european-bioplastics.org ducation/bioplastics

5 1.4 Biocomposites Both reinforcement (e.g., wood & cellulose) & matrix (PLA, PHA, starch) from renewable sources Fiber reinforcement improves performance Work required to improve compatability & properties

6 1.5 Summary of bioplastics BIOPLASTICS (e.g., PHB/PLA) ADVANTAGES SHORTCOMINGS Excellent biodegradability Environmentally-friendly synthesis Brittleness (PHB) Narrow processing window From renewable resource Thermal degradation Good biocompatibility Poor interaction with natural fibers Good compostability Relatively higher prices How to over come the shortcomings of bioplastics?

7 2. Objectives 1. Produce α-cellulose fibers from small diameter lodgepole pine 2. Prepare α-cellulose-graft-phbv biocomposites via the grafting onto strategy during in-situ reactive extrusion 3. Evaluation of α-cellulose-graft-phbv biocomposite materials

8 3. Grafting approach Enhance the interphase between α-cellulose & PHBV by grafting Grafting by reactive processing with peroxide radicals initiation PHBV

9 3.1 Experimental: α-cellulose Isolation Lodgepole pine logs Lodgepole Pine wood fibers Acetone Extractive free fibers Wiley milled <1 mm Delignification NaClO o C Ф <10 cm Aspect ratio = 29, L = 0.5 mm Holocellulose 17.5% NaOH α-cellulose 96% purity

10 3.2 Experimental: grafting Processing: 175 o C using Dynisco mixing molder-extruder α-cellulose; PHBV (22 mol% HV, Tianan Biopolymer) Reactive extrusion: DCP (2%), reaction time (10 min) Controls - PHBV & α-cellulose/phbv (αcell-phbv) blend Rheometry Bohlin CVO-100 Molded specimens

11 1 PHBV G' T=175 C Cell-PHB G' Cell-g-PHB G' 4.1 Results: Rheometry (a) (rad/s) G c = 4600 Pa G c = 970 Pa G'' (Pa) T=170 C G c = 574 Pa PHBV G'' Cell-PHBV G'' Cell-g-PHBV G'' PHBV G' Cell-PHBV G' Cell-g-PHBV G' G' (Pa) (b) (rad/s) Melt viscosity increased due to grafting & crosslinking

12 4.2 Results: morphology Melt blended α-cellulose -PHBV α-cellulose-graft-phbv

13 Stress, σ (MPa) 4.3 Results: tensile properties MPa, 18.8% αcell-g-phbv 13.9MPa 14.4% 11.8Mpa 19.8% 9 αcell-phbv PHBV Strain, ε (%)

14 Storage modulus, E (MPa) 4.4 Results: Viscoelastic properties αcell-g-phbv A 30 C Interfacial adhesion factor Samples Tanδ 30 C V f (%) A 30 C αcell-phbv PHBV Temperature ( o C) Neat PHBV αcell-phbv αcell-g-phbv A = (1/(1-V f )) (tan δ c /tan δ m ) 1 Lower A better adhesion

15 Crystallinity 4.5 Results: FTIR spectroscopy Cellulose total crystallinity index TCI = A 1370 /A 2900 PHBV crystallinity I PHBV/C=O = A 1720 /A Cell PHBV αcell PHBV αcell-phbv αcell-g-phbv DSC analysis showed similar trends for PHBV crystallinity

16 Crystallite size (Å) Crystallinity index 4.7 Results: XRD Crystallinity indicies: CrI αcell = 1 (I am /I 002 ) CrI PHBV = I 17 /I total Crystal size D hkl = K x λ / (β 1/2 x cosɵ) Cellulose PHBV Cellulose PHBV αcell PHBV αcell-phbv αcell-g-phbv 0 αcell PHBV αcell-phbv αcell-g-phbv

17 Weight (%) 4.8 Results: Thermal stability αcell-g-phbv αcell-phbv αcell 20 PHBV Temperature ( o C)

18 5. Conclusions Successfully made α-cellulose-g-phbv by reactive extrusion Melt viscosity (elasticity) increased by grafting Observed good interfacial bonding/compatibility between cellulose & PHBV Crystallinity and crystal size decreased for PHB & cellulose as a result of grafting The α-cellulose-g-phbv was more thermally stable & improved tensile properties than simple composite blend In-situ reactive extrusion is a practical approach for improving biocomposite performance

19 Thank you! Questions? Acknowledgements: Financial support from Grant number 08-JV