Poly(hydroxyalkanoate) Elastomers and Their Graphene Nanocomposites

Abstract

Medium-chain-length poly(hydroxyalkanoate)s (PHAmcl) are biodegradable and renewable biopolymers with elastomeric qualities. Here we report on the preparation and characterization of composite materials using thermally reduced graphene (TRG) nanoparticles as filler with three PHAmcl polymers. The matrices vary with respect to chain packing length, capacity for noncovalent bonding with the TRG surface, and the presence of covalent cross-linking. Results show that the addition of up to 2.5 vol % TRG to PHAmcl increases the melting temperature by 1–3 °C, the modulus by 200–590%, and the electrical conductivity by >7 orders of magnitude. Additionally, we use rheology and microscopy to characterize the composites. We discuss our results in light of polymer entanglement theory and the effects of polymer structure, filler loading volume, and the role of graphene-polymer interfacial forces. We extend our discussion by comparing the modulus enhancements of PHAmcl composites to those reported in other studies in which layered carbon nanofillers are combined with structurally related biopolyesters including: polylactide, polylactide-co-polyglycolide, polycaprolactone, and two other PHA copolymers.

Effect of polymer modifier chain length on thermal conductive property of polyamide 6/graphene nanocomposites

“…Chemical cross-links plus a fixed-constraint contribution is commonly associated with entanglements [40]. Second, the chains entangle and stack with each other more seriously as the NH 2 -PEG-NH 2 chain length increases [41]. The entanglement constrains the random arrangement of graphene; thus, the arrangement of graphene is regular in a certain direction (Fig.…”

Hybrid modification of high‐density polyethylene with hyperbranched polyethylene‐functionalized multiwalled carbon nanotubes and few‐layered graphene

“…They can act as nanofillers for polymer modification to render high‐performance polymer‐based nanocomposites (PNC), which have extensive applications in various fields, such as sensors, electromagnetic interference (EMI) shielding materials, and electrically/thermally conductive materials . So far, a great variety of methods have been explored for preparing PNC with CNT or graphene as filler, and their structures and properties have been intensively investigated . However, the large‐scale application of CNT and graphene as nanofillers for polymer modification remain a challenge, owing to their high cost and poor dispersibility in polymer matrix.…”

Effect of morphological state of graphene on mechanical properties of nanocomposites

“…Therefore, the main morphological states of graphene (and GO) are intercalated and exfoliated. As experiments showed [22,23], morphological differences caused a major effect on mechanical performance of composites. Lower stiffness reported for composites with intercalated graphene is mainly due to the fact that reinforcement in the matrix phase has a form of intercalated clusters -sandwiches of graphene and polymer.…”

“…However, depending on a manufacturing method and a type of materials constituting the nanocomposite, morphology of graphene flakes can differ. Barrett et al [22] studied an effect of molecular structure of three different polymer matrices on mechanical performance and physical changes of their nanocomposites reinforced with reduced GO (rGO). They applied the same preparation method for all the nanocomposites, but while rGO dispersed as exfoliated in a polyhydroxyoctanoate matrix, it exhibited an intercalated morphology in polyhydroxyoctenoate.…”