title: Viscoelastic properties of linseed oil-based medium chain length poly(hydroxyalkanoate) films: effects of epoxidation and curing.
abstract: Medium-chain-length poly(hydroxyalkanoate) (mcl-PHA) polymers derived from linseed oil (PHA-L) have a relatively small molar mass and contain a high concentration of unsaturated side-chains. As such, these polymers are amorphous and take on the consistency of a viscous liquid at room temperature. In order to increase the application potential of this material, the side-chain olefinic groups of PHA-L were converted to epoxy derivatives (PHA-LE) using m-chloroperoxybenzoic acid (m-CPBA). Epoxidation resulted in a 37% conversion of olefinic to epoxy groups. The epoxy groups enhanced the PHA-LE film susceptibility to crosslinking upon exposure to air. PHA-LE films began to crosslink and stiffen in less than 25 days, whereas PHA-L films began to crosslink between days 50 and 75. The PHA-LE films showed an increase in tensile strength (TS, from 4.8 to 20.7 MPa) and Young's modulus (YM, from 12.9 to 510.6 MPa) between 25 and 100 days. In contrast, PHA-L had a TS of 25.0 MPa and YM of 767.8 MPa after 100 days. Epoxidation helped induce crosslink formation; however, aging for 100 days ultimately resulted in crosslinked films from both PHA-L and PHA-LE with higher strength and durability than the original materials.
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038, USA. rashby@arserrc.gov
authors.forename: R D
authors.initials: RD
authors.lastname: Ashby
authors.forename: T A
authors.initials: TA
authors.lastname: Foglia
authors.forename: D K
authors.initials: DK
authors.lastname: Solaiman
authors.forename: C
authors.initials: C
authors.lastname: Liu
authors.forename: A
authors.initials: A
authors.lastname: Nuñez
authors.forename: G
authors.initials: G
authors.lastname: Eggink
mesh_terms: D001696:Biomechanical Phenomena; D004548:Elasticity; D004852:Epoxy Compounds / Q000737:chemistry; D019597:Flax / Q000737:chemistry; D006880:Hydroxy Acids / Q000737:chemistry*; D008043:Linseed Oil / Q000737:chemistry*; D014783:Viscosity
chemical_list: D004852:Epoxy Compounds; D006880:Hydroxy Acids; D008043:Linseed Oil