Upgrading vegetable oil thermosets through co-polymer reinforcement with tannin-lipid conjugates Warren Grigsby Chunhua Luo, Neil Edmonds, Jafar Al-Hakkak

Overview: Unsaturated Copolymer Thermosets Polyester Resins Petrochemical-based Maleic anhydride Bisphenol A Styrene Divinyl benzene Unsat. Oil Systems Partial replacement Vegetable oils Styrene Divinyl benzene - req for cross-linking Unsat. Oil Systems Totally bio-based Vegetable oils Polyphenols - assist cross-linking

Introduction  Thermoset resins → performance materials polyesters and epoxies  renewables substitution?  A major challenge with feedstock replacement is performance strength and durability automotive and construction applications  Natural oils investigated as raw materials for thermoset resins and co-polymers readily available, potential bio-degradability and multi-functionality differing fatty acid composition and unsaturation → ideal feedstocks Meier, Metzger, Schubert, Chem. Soc. Rev., (11): p

Natural Oil Thermosets  Thermosets prepared via unsaturation or introduced functional groups radical, condensation, oxidative polymerization  High degree of unsaturation for reactivity thermal or cationic polymerization  Natural oils need co-monomers styrene or divinyl benzene for performance Larock et al., Polymer, (4): p ; Biomacromolecules, (2): p

 Nature provides a range of condensed tannins Leaf, fruit, stem and bark Polyphenolic, flavanyl sub-unit  Tannin usually a cross-linked molecule in adhesives Phenol formaldehyde, Bakelite chemistry Structural applications requiring durability, strength Provide reinforcement in modified PLA plastics Condensed Tannins

 Tannins are oligomeric polyphenolics typically n = 4 to 13 Possess rigid aromatic structures Easily functionalised – esters, ethers  Potential to substitute petroleum-based co-monomers in natural oil-based co-polymer formulations  Thermoset completely composed of renewable resources n

Aims  Produce a totally biobased thermoset resin based on vegetable oils and tannins  Utilise flavanyl structure → rigidity & cross-linking networks Evaluate differing tannin types, content and fatty acid ester DS natural oils with varying unsaturation & reactivity

Conjugating fatty acids by esterification  Tannin Linoleate and Oleate esters formed differing unsaturation → reactivity & cross-linking  Two tannin types similar degree of substitution (DS = 2) residual hydroxyls capped by acetate groups ArH HC= X X -CH 2 - -COCH 3 -CH 3 Pine Tannin Quebracho Tannin Luo, Grigsby, Edmonds, Al-Hakkak Acta Biomaterialia 9 (2013) 5226–5233.

Co-polymerization with vegetable oils  Used different methods for radical polymerization Co/Zr oxidative catalyst Range of tannin ester contents (PTLA 0→100%) Linseed and tung oils  Solvent cast films = hard, rigid → soft, flexible  Monitor co-polymerization loss of unsaturation auto-oxidation

Chemical analysis of co-polymer films  Cast films evaluated by 13 C NMR and solvent extraction Esterification retained Decrease of C=C Tannin Tannin Linoleate Co-polymer film

Co-polymer material properties DMTA  Comparable to typical polyester thermosets  PTLA has greater film stiffness (E’) Pure oil least  Lower tannin ester content contributes to decreasing E’ and at lower temperatures PineQuebracho

Co-polymer material properties Tan  profiles  Higher Tg with tannin ester content → greater cross-linking Quebracho tannin Tg 32 to 64˚C Pine tannin Tg 36 to 72 ˚C Higher tannin → peak intensity decrease, over a broader range PineQuebracho

Co-polymer cross-link density  Kinetic theory of rubber elasticity → cross-linking density E’ values taken 20˚C above Tg  Cross-link density increase with tannin ester content Co-polymer TanninE 25°C ν e 10 3 Tg (%)(GPa) (mol/m3) (C) QTLA PTLA PTLA75-LIN PTLA50-LIN PTLA25-LIN LIN Luo, Grigsby, Edmonds, Al-Hakkak Acta Biomaterialia 9 (2013) 5226–5233

What happens if we change oil/conjugate ? Tannin Oleate esters or lower oil unsaturation  Slower reaction undertake at 60˚C, require post-cure at 100˚C  Soft-flexible films more oil, greater flexibility

What happens if we change oil/conjugate ? Tannin Oleate esters or lower oil unsaturation  Slower reaction  Soft-flexible films more oil, greater flexibility  More oil → stepwise decrease in softening onset Tg’s typically 9-13˚C  Second broader increase >50˚C post-curing, second Tg  2-phase system PineQuebracho Luo, Grigsby, Edmonds, Al-Hakkak Macromolecular Materials and Engineering, 2014, 299(1) pp 65–74.

Summary  Tannin fatty acid esters and vegetable oils give varying co-polymerization rates and material properties  Tannin esters provide additional cross-linking sites for co-polymerization beyond the triglyceride

Summary  Tannin fatty acid esters and vegetable oils give varying co-polymerization rates and material properties  Tannin esters provide additional cross-linking sites for co-polymerization beyond the triglyceride Tannin Linoleates  Linoleates give greater range in properties and Tg’s Dependent on tannin ester content Single Tg → single co-polymer phase and homogeneity in films  Tannin linoleates and oils have similar polymerization rates and cross-linking not case in analogous vegetable oil – styrene/divinyl benzene

Summary  Tannin fatty acid esters and vegetable oils give varying co-polymerization rates and material properties  Tannin esters provide additional cross-linking sites for co-polymerization beyond the triglyceride Tannin Oleates  Introducing lower unsaturation reduces reactivity times slower  Tannin oleates give rubber-like materials reduced cross-linking with 1-2 Tg features Offer differing dampening properties → rubbers with relatively rigid domains

Conclusions  Tannin fatty acid conjugates can replace styrene and divinyl benzene in vegetable oil co-polymers  Tuning reactivity gives co-polymers ranging from soft rubbers to hard thermosets  Lineolate esters and >20% tannin content give co-polymer properties reported for styrene-vegetable oil systems  Using tannin conjugates realizes a totally bio-based co- polymer thermoset

Acknowledgements  The work presented in this study was supported through funding provided through the New Zealand Ministry of Business, Innovation & Employment  C.L. thanks the Biopolymer Network Ltd for financial support and PhD scholarship stipend  This presentation is dedicated to the late Prof. Allan Easteal who was a supervisor, colleague and contributor to this work

Polymer Properties DSC  Thermograms exhibit exothermic peak >100˚C Likely further thermal polymerization & post-cure Higher oil content → broadens, lower temperature Consistent with DMTA

What happens if we change oil/conjugate ? Tannin Oleate esters or lower oil unsaturation  Slower reaction  Soft-flexible films more oil, greater flexibility Co-polymerTanninE 25°C ν e 10 3 Tg (%)(GPa) (mol/m3) (C) PTLA PTOA PTLA75-LIN PTOA75-LIN PTOA75-TUN