Upgrading vegetable oil thermosets through copolymer reinforcement with

Upgrading vegetable oil thermosets through co-polymer reinforcement with tannin-lipid conjugates Warren Grigsby Chunhua Luo, Neil Edmonds, Jafar Al-Hakkak warren. grigsby@scionresearch. com

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? l ¡ A major challenge with feedstock replacement is performance l l ¡ strength and durability automotive and construction applications Natural oils investigated as raw materials for thermoset resins and co-polymers l l readily available, potential bio-degradability and multi-functionality differing fatty acid composition and unsaturation → ideal feedstocks Meier, Metzger, Schubert, Chem. Soc. Rev. , 2007. 36(11): p. 1788 -1802.

Natural Oil Thermosets ¡ Thermosets prepared via unsaturation or introduced functional groups l ¡ High degree of unsaturation for reactivity l ¡ radical, condensation, oxidative polymerization thermal or cationic polymerization Natural oils need co-monomers l styrene or divinyl benzene for performance Larock et al. , Polymer, 2000. 42(4): p. 1567 -1579; Biomacromolecules, 2005. 6(2): p. 797 -806.

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

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

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

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

Co-polymerization with vegetable oils ¡ Used different methods for radical polymerization l l l 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 l l loss of unsaturation auto-oxidation

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

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

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

Co-polymer cross-link density ¡ Kinetic theory of rubber elasticity → cross-linking density l E’ values taken 20˚C above Tg Cross-link density increase with tannin ester content Co-polymer Tannin (%) E 25°C (GPa) νe 103 (mol/m 3) Tg ( C) QTLA 100 28 1. 3 24 64 PTLA 100 32 1. 6 58 72 PTLA 75 -LIN 25 PTLA 50 -LIN 50 PTLA 25 -LIN 75 24 16 8 1. 3 0. 7 0. 1 23 10 1 56 43 38 LIN 100 0 0. 01 0. 08 24 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 l ¡ undertake at 60˚C, require post-cure at 100˚C Soft-flexible films l more oil, greater flexibility

What happens if we change oil/conjugate ? Tannin Oleate esters or lower oil unsaturation ¡ Slower reaction ¡ Soft-flexible films l more oil, greater flexibility Pine Quebracho ¡ More oil → stepwise decrease in softening onset l ¡ Tg’s typically 9 -13˚C Second broader increase >50˚C post-curing, second Tg 2 -phase system l 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 l l ¡ 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 l 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 l ¡ 20 -40 times slower Tannin oleates give rubber-like materials l l 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 copolymer 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 Ph. D 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 l Likely furthermal polymerization & post-cure l Higher oil content → broadens, lower temperature Consistent with DMTA l

What happens if we change oil/conjugate ? Tannin Oleate esters or lower oil unsaturation ¡ Slower reaction ¡ Soft-flexible films l more oil, greater flexibility Co-polymer Tannin E 25°C νe 103 (%) (GPa) PTLA 100 PTOA 100 32 25 1. 6 0. 3 58 -- 72 -- PTLA 75 -LIN 25 PTOA 75 -TUN 25 24 19 19 1. 3 0. 5 0. 8 23 9 8 56 37 9 (mol/m 3) Tg ( C)