Abstract
Poly(3-hydroxybutyrate), PHB, has gathered a lot of attention for its promising properties—in particular its biobased nature and high biodegradability. Although PHB is prime candidate for the packaging industry, the applications are still limited by a narrow processing window and thermal degradation during melt processing. In this work, three novel additives based on ferulic acid esterified with butanediol, pentanediol, and glycerol (BDF, PDF, and GTF, respectively) were used as plasticizers and antioxidative additives to improve mechanical properties of PHB. Elongation at break up to 270% was obtained in presence of BDF and the processing window was improved nearly 10-fold. The Pawley method was used to identify the monoclinic space group P2 of the BDF. The estimated crystallite size (71 nm) agrees with a crystalline additive. With PHB70BDF30 blends, even higher elongations at break were obtained though dwindled with time. However, these properties could be recovered after thermal treatment. The high thermal stability of this additive leads to an increase in the fire retardancy property of the material, and the phenolic structure induced antioxidant properties to the samples as demonstrated by radical scavenging tests, further highlighting the possibilities of the PHB/additive blends for packaging applications.
Highlights
The objective of this study is to develop the appropriate plasticizer for improving mechanical properties
Synthesis of the Additives Based on Ferulic Acid
Three esters have been synthesized from ferulic acid (Figure 1)
Summary
Since their production method was streamlined a few decades ago, poly(3-hydroxyalkanoate)s (PHAs), which are produced by a fermentation process, have shown a growing amount of interest [1–3]. PHAs are one of the most promising renewable biocompatible and biodegradable polyesters [4–8]. Produced by microorganisms in presence of natural substrates, they offer an excellent alternative to petroleum-based plastics. Poly(3-hydroxybutyrate), PHB, is one of the simplest members of the PHAs family. PHB is a linear semi-crystalline isotactic polyester with high crystallinity, high melting temperature, and excellent resistance to solvents. To other PHAs, PHB exhibits complete biodegradability [9–14]. Its industrial applications are still limited today due to its high brittleness, low value for elongation at break and thermal degradation during melt processing. The short permanence above melting point induces degradation that involves a cis-elimination reaction and the formation of crotonic acid [15].
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