Toughening Poly(lactide) with Bio-Based Poly(farnesene) Elastomers

Abstract

The development and application of bio-sourced elastomers which can be blended with poly(lactide) (PLA) to enhance its poor material properties are of great interest as we move toward replacing petroleum-derived plastics with viable alternatives. As such, this work focused on the valorization of the terpene-based monomer, trans-β-farnesene (farnesene), as a building block to design rubber toughening agents to improve the impact strength of PLA blends. Ternary blends consisting of copolymers of farnesene−glycidyl methacrylate (PFGMA), farnesene−methacrylic acid (PFMAA) (20−30 wt % farnesene copolymers), and PLA exhibited significant improvements in impact strength and elongation at break (i.e., approximately 16-fold and 10-fold, respectively) over neat PLA. Torque mixer measurements and FTIR spectroscopy confirmed the occurrence of epoxy− acid/epoxy−hydroxyl interfacial compatibilization reactions catalyzed through hydrogen-bonding interactions. Phase morphologies of the ternary blends were evaluated with scanning electron microscopy (SEM) and showed an approximate 4-fold reduction in particle diameter relative to the binary systems (i.e., from 4.3 to 1.1 μm) with the compatibilized blend morphology deemed stable upon annealing. The toughening mechanism responsible for the improved mechanical properties observed with the ternary blends was also investigated by examining the impact fractured surface morphologies with SEM. A combination of enhanced interfacial adhesion coupled with shear yielding of the matrix was proposed as the main contributing factor to the improvement in mechanical properties observed in the ternary blends.

Vitrification: Versatile Method To Modulate Properties of Myrcene-Based Rubbers

“…To achieve the first strategy, we synthesized a statistical prepolymer of Myr and AAEMA with M n of 22 kg/mol (coded as MyrAA-30-Long), which is slightly higher than the critical entanglement molecular weight (M e ) of poly(Myr) homopolymer (M e ∼ 18 kg/mol). 36,59 Figure S9 shows the GPC traces of all prepolymers. A clear shift toward higher molecular weights was observed for MyrAA-30-Long.…”

“…35 Similar to other 1,3-dienes, such as butadiene and isoprene, poly(Myr) also forms low glass transition temperature (T g ) (∼ −75 °C) rubbery polymers. 36 In addition to renewability, an advantage of Myr over butadiene and isoprene is its lower volatility with a boiling point of 167 °C, meaning that Myr does not require pressurized equipment to handle. 37 However, the longer pendant side chain in poly(Myr) results in a higher entanglement molecular weight of ∼18 kg/mol compared to that of poly(butadiene) and poly(isoprene) with ∼3 and ∼6 kg/mol, respectively.…”

“…37 However, the longer pendant side chain in poly(Myr) results in a higher entanglement molecular weight of ∼18 kg/mol compared to that of poly(butadiene) and poly(isoprene) with ∼3 and ∼6 kg/mol, respectively. 36,38 This in general can result in lower tensile strength, elongation, and toughness of poly(Myr), which could potentially limit its applications. 33,39 Although some in-depth studies involving various polymerization techniques and properties of poly(Myr) have been reported, thorough investigations on the applications of poly(Myr)based elastomers in the rubber industry are generally lacking in the literature.…”

“…Myr can be isolated from various sources such as pine, hops, bay leaves, lemongrass, celery, nutmeg, and rosemary. , Additionally, Myr is industrially produced by pyrolysis of β-pinene, which is a major constituent of natural turpentine oil . Similar to other 1,3-dienes, such as butadiene and isoprene, poly­(Myr) also forms low glass transition temperature ( T g ) (∼ −75 °C) rubbery polymers . In addition to renewability, an advantage of Myr over butadiene and isoprene is its lower volatility with a boiling point of 167 °C, meaning that Myr does not require pressurized equipment to handle .…”

Fabrication of Biodegradable Poly(Lactic Acid) Composites with High Toughness via In Situ Fibrillation Method and Facile Annealing Process

“…Blending modification was considered to be a simple and economical method, and its mechanism has been widely studied. − For example, blending with flexible or elastic biodegradable polymers such as poly­(caprolactone) (PCL), , poly­(butylene adipate- co -terephthalate) (PBAT), , poly­(butylene succinate) (PBS), , and starch has been extensively studied. However, due to the large particle size of the dispersed phase, the toughening efficiency of these materials to PLA is not ideal.…”