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PEER-REVIEWED REVIEW ARTICLE
compostable (Nam et al. 2011). Kanemura et al. (2012) observed that both the recycling of PBS is possible as well as the mechanical properties of PBS improve after reprocessing. A typical way to produce PBS film and coating is by melt extrusion casting (Wang et al. 2013). It might occur that, for high barrier demand products, the soft PBS material is not effective enough (Lin et al. 2011; Phua et al. 2012; Charlon et al. 2015). Moreover, the gas barrier properties of PBS are barely sufficient for gas sensitive products (Lin et al. 2011; Phua et al. 2012; Zhou et al. 2016). Melt viscosity and a relatively high price are also limiting the use of PBS (Lin et al. 2011). Furthermore, PBS has been studied as component in composites or blends, for example, to improve gas barrier (Bhatia et al. 2012; Boonprasith et al. 2013; Charlon et al. 2015; Zhou et al. 2016), mechanical, and thermal properties (Lin et al. 2011). PBS/filler composites PLA/PBS/nanoclay is a good example of related composites, where a lower oxygen permeability level is obtained through the addition of the clay. PBS (20 wt%) was found to increase the water vapor permeability (WVP) of PLA (80 wt%). Thus, the addition of nanoclay offered an 18% improvement in WVP (Bhatia et al. 2012). PBS/thermoplastic starch (TPS) blend with added nanoclays decreased the OTR and WVTR values significantly (Boonprasith et al. 2013). The improvement of gas barrier by adding clays or nanoclays relates to the tortuous path the gas molecules need to travel through the barrier (Zhou et al. 2016). Lin et al. (2011) blended 2 wt% and 5 wt% of cellulose nanocrystals (CNC) and starch nanocrystals (SN) separately with PBS. They improve the strength and elongation properties of the PBS matrices by both fillers. PBS/2 wt% CNC enhanced tensile strength by 11% and elongation by 17%, while PBS/5 wt% SN enhanced tensile strength by 8% and elongation by 28% (Lin et al. 2011). Someya et al. (2004) investigated different types of organo-modified montmorillonites blended with PBS. They found out that organo-modified montmorillonites promoted crystallization of PBS and therefore acted as nucleating agent. The addition of 3 wt% organo-modified montmorillonites resulted greater tensile and flexural modulus and weaker the tensile strength with most of the clay-types (Someya et al. 2004). Moreover, PBS has been blended with agro-fillers, such as wood and rice husk flour, wheat straw, and bagasse. Kim et al. (2005) studied the PBS/agro-filler blends in filler concentrations of 10, 20, 30, and 40 wt%, by preparing a blend of PBS/rice husk flour and PBS/wood flour. As a conclusion, the mechanical properties deteriorated when filler content was increased, whereas the reduction of filler particle size caused the tensile strength properties to increase moderately. Moreover, the tensile strength of the wood flour filled blend was higher than in the rice husk flour filled blend. Liu et al. (2009) studied the biodegradability of PBS/jute fiber composites. The composites containing 10, 20, and 30 wt% of jute fibers degraded faster than the plain PBS film or the plain jute fiber. The most significant weight loss (62.5% in 180 days) in a compost soil burial test was performed by the PBS/10 wt% jute fiber composite (Liu et al. 2009). Nam et al. (2011) studied PBS/alkali-treated coir fiber composites with a coir fiber concentration of 10 wt% to 30 wt%. As a result, they found the highest improvement in mechanical properties with an alkali-treated coir fiber concentration of 25 wt%. In the particular composite, the tensile strength, tensile modulus, and the flexural modulus increased by 54%, 141.9%, and 97.4%, respectively, in contrast to plain PBS.
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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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