Preparation and characterization of hydroxyapatite reinforced PHBV nanocomposites

Poly(hydroxyalkanoates), PHAs have attracting considerable interest in scientific and industrial communities because of their remarkable physical properties and biodegradability. PHAs can be used in numerous applications, including the biomedical industry, molded articles of all sorts, packaging, coatings, films, electronics, sensor, foams and energy applications. However, the use of PHAs is limited due to availability of cheap petroleum based polymers. There is a therefore a critical need to evaluate and improve the properties of the biopolymers to make them fully competitive with common non-degradable thermoplastics. In recent years, nanoscale fillers in polymers have generated enormous interest in academia and industry because they exhibit improvements in material properties at small loading levels. Hydroxyapatite (HA) is one of the bioactive calcium phosphates, which exhibits excellent biocompatibility and bioactivity. In this work we aimed to develop biodegradable "green" composites prepared in a sustainable way. A composite system consisting of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) polymers as the semicrystalline matrix and the mineral hydroxyapatite (HAP) as particulate filler was chosen because of their intrinsic biodegradability and biocompatibility properties. For the primary characterization phase of this investigation, biobased composite specimens of PHBV with a reinforcing filler of HAP were fabricated using an extrusion process. The properties of the composites were characterized as a function of HAP loading. The effects of a silane treatment for surface modification of HAP were also investigated. Improved mechanical and barrier properties were observed for the composites compared to the individual PHBV suggesting potential applications for the new biodegradable materials.