Comparison of anhydrous and monohydrated forms of orotic acid as crystal nucleating agents for poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

A small molecule nucleating agent, orotic acid (OA), was investigated to enhance crystallinity and crystallization kinetics in poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) for the purpose of addressing embrittlement and reducing solidification time after thermal processing. In particular, the effectiveness of monohydrated (OA-m) and anhydrous (OA-a) forms of OA as nucleating agents for isothermal and non-isothermal crystallization of PHBV films was investigated and compared. Both forms of OA were able to increase crystallization temperature of PHBV as well as form more uniform crystal structures, based on differential scanning calorimetry. It was found that OA-a at 1–2 wt% was most effective in PHBV crystal nucleation because of the increase in overall polymer crystallinity and faster crystallization rate. Additionally, the faster crystallization of OA-a led to fibrillar film morphology of the PHBV/OA blends.