1. Greening Plastics: Modifying plastics with functional additives based on condensed tannin esters Warren Grigsby Jamie Bridson, Cole Lomas Carmen Schrade and Jaime-Anne Elliot warren.grigsby@scionresearch.com

2. Overview  Highlights of a greater study evaluating tannin esters in plastics  Introduction Tannins & plastic additives  Tannin esters in plastics Filler v compatible, active ingredient Providing functional equivalence  Specific performance

3. Introduction: Condensed Tannins  Nature provides a range of condensed tannins Leaf, fruit, stem and bark  Provide a protection role for plant/tree  Secondary metabolites  Polyphenolic structure  Extractable Procyanidin: flavonoid base structure n

4. Tannins: Providing Function  Blueberries, bark, wine,… antioxidant, protein inhibition, UV absorption  Neutriceuticals, food, industrial oxidative stress-cognitive function protein inhibition antimicrobial tanning leather

5. Plastic Additives: Adding Performance  Additives provide functionality and longevity colour, flame retardant, plasticizers  Longevity antioxidants and UV stabilisers  not so well known synthetic, petrochemical  BHT, hindered amines  Why not bio?

6.  Tannin usually a crosslinked molecule in adhesives Phenol formaldehyde, Bakelite chemistry  PLA plastic modified with tannins reinforcement, melt-spun filaments  Electrospinning protein nanofibres tannin → functionality Tannins: Synthetics & Plastics Grigsby, Kadla, Macromolecular Materials and Engineering, 299(3) 2013 368–378. Dallmeyer, Grigsby, Kadla, J Wood Chem Tech 33(3) (2013) 197-207. 10m

7. Aims & Goals  Can functionality a tree uses be applied to plastics? Hypothesis  Tannin efficacy in bark can be applied to protect plastics from oxidative aging and UV-induced degradation  Evaluate tannins as bio-sourced plastic additives

8.  Tannins: water soluble extracts → inherently hydrophilic  Modify → change miscibility/compatibility with plastics Tannins & Chemical Modification Tannin + Alkyl Anhydride Tannin Esters C 2 –C 6 chain length Mixed Esters Vary: Degree of substitution (DS) Antioxidant Capacity Macromolecular properties UV absorption R 1,2 = Ac, Pr, Bu, Hex… Grigsby, et al. Polymers, 2013, 5(2), 344-360

9.  Tannins: water soluble extracts → inherently hydrophilic  Modify → change miscibility/compatibility with plastics Tannins & Chemical Modification Tannin + Alkyl Anhydride Tannin Esters C2–C6 chain length Mixed Esters Vary: Degree of substitution (DS) Antioxidant Capacity Macromolecular properties UV absorption Vary UV absorption Change melt behaviour

10. Plastic Processing & Evaluation  Tannin esters compounded in plastics 0-10% w/w Master Batch Tannin Ester (10%) compounded with plastic PP, PBS PLA, PHA, PHB Extrusion MB blended with plastic 0%, 0.5%, 1%, 3%, & 5%, 10% Injection Moulded ASTM Test specimens Flexural & Tensile bars Thermal Analysis DSC, TGA, DMTA Mechanical Testing Flex & Tensile Accelerated Aging Thermally UV & weathering Fluorescence & light microscopy

11. Plastic Additive or Filler?  Longer ester chains show progressive solubility and diminished particle domains within PLA TanAc (C 2 ) retained as distinct domains → poor miscibility or phase separation TanHex (C 6 ) → fully dispersed within the plastic TanAc TanPrTanBu TanHex (image 500 x 500 m) Confocal microscopy: PLA containing 5% tannin esters using tannin inherent autofluorescence Grigsby, et al. Polymers, 2013, 5(2), 344-360

12. Plastic Additive or Filler?  Tannin esters contribute up to 15% decreased PLA stiffness ester chain length & greater content decrease MOE native tannin stiffens PLA → acts as a filler Native Tannin TanAc C 2 Ester Longer Chain C 6 Esters Short Chain C 3 -C 4 Esters

13. Plastic Polymer Properties  10% C 6 esters lower PLA Tg reduced effect  lower ester quantity  shorter chain length  At typical additive content minimal impact on polymer properties Tg Crystallisation  Crystallization decreased melt temp. unchanged Melt DSC DMTA

14. Thermal & Oxidative Stability  Tannin esters promote plastic thermal stability  Oxidation induction time (OIT) TanHex in PP → increased OIT, TanHexAc → not  residual antioxidant capacity important Increased thermal stability Reprocessed PP (up to 10x) → reduced thermal stability 10% TanHex → increase thermal stability  potential to lower plastic oxidative degradation on processing TGA Grigsby, et al., Macromolecular Materials and Engineering, 299 (10) (2014)1251–1258.

15. Plastic Accelerated Aging  Tannin esters provide UV stability on aging polypropylene biopolyesters challenged by aging Native Tannin Mixed C 2 -C 6 Esters Longer Chain C 6 Ester Mechanical properties before/after UV and condensation exposure cycling

16. Accelerated Aging  Bionolle (PBS) samples increase in stiffness tannin hexanoate ester → excellent flexural strength retention  similar results on thermal aging  Functional equivalency comparable to commercial UV stabilisers Native Tannin Mixed C 2 -C 6 Esters Longer Chain C 6 Ester Grigsby et al, J. Appl. Polym. Sci., 132(11) (2014) 41626

17.  Accelerated Aging → plastic colour tended to surface bleach seen as undesirable, but gauge for tannin efficacy  Measure efficacy Colour Stability and UV inhibition Visible bleaching 0.24 mm Intensity across the surface  Tannin sacrificial  bleach depth → extent of UV inhibition PBS: TanHex 0.25 mm v. TanAc 0.47 mm  consistent with tannin dispersion by microscopy Grigsby et al, J. Appl. Polym. Sci., 132(11) (2014) 41626 White Intensity

18. Take home information  Tannin esters can be functional additives in biodegradable polyesters Longer chain C6 esters desirable for compatibility Do not impact plastic properties at typical additive loadings Provide stabilising role  reduce oxidative and UV-induced degradation  Similar to bark on a tree  PLA & Tannin esters C 6 ester chains lower Tg onset up to 5-6  C Can reduce flexural properties by 15% (TanAc to Hex) C 6 esters retain PLA flexural properties on aging Overall  Scope for tannin esters as sustainable additives for bioplastics

19. Acknowledgements  This work was supported by Biopolymer Network Ltd Funding through New Zealand Ministry of Business, Innovation and Employment.  Jamie Bridson, Cole Lomas and Jaime Elliot are grateful for studentships provided by Scion through BSc(Tech) placements with the University of Waikato (NZ)  Carmen Schrade (MSc thesis) is grateful to assistance provided by Department of Applied Chemistry, Reutlingen University (Germany)

22. Plastic Polymer Properties  DMTA → 10% TanHex/TanHexAc lower PLA Tg Lower ester quantity or shorter chain length → reduced effected  DSC → melt temperature unchanged Crystallization decreased with tannin ester content  At typical additive content minimal impact on polymer properties Tg Crystallisation

23. Accelerated Aging  Biopol samples show similar increases in flexural modulus longer chain tannin esters still maintain relatively lower flexural modulus than pure maintain flexural strength compared to pure polymer

24. Tannin Ester Modified Biopolyesters Microscopy:  Hexanoate C 6 chains compatible polyester plastics Mechanical & Polymer Properties  Do not detrimentally impact mechanical properties at loadings up to 5% (w/w)  Do not significantly influence polyester melt or Tg  As plastic additives provide: UV stability Antioxidant and thermal stability  Dependency on ester chain length, DS and content

25. Tannin Ester Modified Biopolyesters  Tannin ester addition contributes colour white/colourless preferred brown colour → undesirable for some applications ester modification reduces colour  Accelerated weathering revealed colour instability surface bleaching by UV light inherent property of tannins  biopolyesters unsuited to exterior conditions