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PEER-REVIEWED REVIEW ARTICLE
Poly(butylene succinate-co-adipate) Poly(butylene succinate-co-adipate) (PBSA) is a random copolymer of PBS. Due to its flexibility of polymer chains and lower crystallinity and, it is more sensitive to biodegradation than PBS (Ray et al. 2007a,b). Ray et al. (2005) blended PBSA together with (3, 6, and 9 wt%) organically-modified clay to improve the mechanical properties (stiffness, and elongation), thermal stability of PBSA. The same authors investigated a PBSA/ organically modified synthetic fluorine mica (OSFM) blend (Ray et al. (2007a). An improvement in mechanical properties, such as in elastic modulus, as well as in thermal stability was noted. Ray et al. (2007b) also studied the morphology of a blend of 5 wt% organo-modified montmorillonite in poly(propylene) PP/PBSA (80:20) matrix. After the clay addition, the blend displayed a co-continuous structure and a lower viscosity ratio of the blend matrices. Likewise, improvements were noticed in mechanical, thermal, and rheological properties. Chen and Yoon (2005) produced twice- functionalized organoclays (TFC) and blended them with PBSA. They reported to increase the linear storage modulus of the blend compared to the organoclay /PBSA blend. In addition, PBSA/TFC blends displayed an improved tensile modulus and strength at break. PBS/biopolymer blends PBS has been blended with several bio-based polymers, such as cellulose, cellulose acetate, cellulose whiskers, starch, starch nanocrystal, chitosan, silk, plant- and red algae fibers, PLA, and PHAs (Lin et al. 2011). The PBSA/ starch blend (5 wt% to 30 wt%) has been investigated. In the study, it was found that starch addition did not considerably decrease mechanical properties, although the addition noticeably increased the degradation properties of the blend, starting from 5 wt% addition. Starch /PBS and starch/PBSA blends have been used in food packaging applications, for instance, as biodegradable biscuit trays or films (Tang et al. 2012). Poly(hydroalkanoates) Poly(hydroalkanoates) (PHAs) are a diverse group of linear thermoplastic biopolyesters (Liu 2006; Thellen et al. 2008; Bugnicourt et al. 2014). PHAs are naturally synthesized via bacterial fermentation under physiological stress (Liu 2006; Misra et al. 2006; Esteban et al. 2008; Johansson et al. 2012; Bugnicourt et al. 2014; Rastogi and Samyn 2015). PHA is obtained from the bacteria by extraction, which is followed by drying and powder or resin formation (Kuusipalo et al. 2008). The PHAs function as bacterial carbon and energy storage and their concentration can be from a marginal amount up to more than 80% of their cell dry mass, depending on the bacteria (Valentin et al. 1999; Esteban et al. 2008; Koller 2014). Sugar and glucose are common fermentation raw materials for the industrial production of PHAs. In addition to carbohydrates, lipids, such as vegetable oil and glycerin, have also been considered (Bugnicourt et al. 2014). Different types of wastes and wastewaters have been used for the production of PHAs (Bugnicourt et al. 2014; Rastogi and Samyn 2015). Some main processes used for PHA production are shown in Fig. 4. There are various monomer components enabling versatile properties and application fields of PHAs (Valentin et al. 1999; Liu 2006; Koller 2014). In addition to the structural variations, the fermentation process and its carbon source also affect the properties of PHAs (Liu 2006). The dominant and simplest polymers from the group of PHAs are poly(ß-hydroxybutyrate) (PHB) (Dubief et al. 1999; Liu 2006; Yu et al. 2006;
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Helanto et al. (2019). “ Bio-based barriers ,” B io R esources 14(2), Pg #s to be added.
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