Conference Paper

Mechanical Properties and Anaerobic Biodegradation of Thermoplastic Starch/Polycaprolactone Blends

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Abstract

Thermoplastic starch (TPS) has emerged as a readily biodegradable and inexpensive biomaterial that can replace traditional plastics in applications such as food service and packaging. TPS is an abundant, renewable resource with a low processing temperature when compared with other biodegradable polymers. However, TPS has very low strength and it is brittle. Therefore, there is a need to modify it or blend it with other biodegradable polymers to achieve the desired performance. Polycaprolactone (PCL) is a rubbery biodegradable plastic that can be used to improve the ductile behavior of TPS. The goal of this research was to determine the viability of TPS as an inexpensive majority component in polymer blends with PCL. A ductile bioplastic that is cost-competitive can promote the use of compostable packaging. This study also evaluated biodegradation through anaerobic digestion under mesophilic (37±2°C) and thermophilic (52±2°C) conditions. Preliminary studies on the anaerobic degradation of PCL revealed that thermophilic degradation conditions were favorable compared to mesophilic conditions. While mesophilic digestion can work when a high percentage of TPS is blended with PCL, thermophilic conditions offer an advantage even at a lower TPS percentage. Addition of TPS improved the biodegradability of PCL significantly, possibly due to increased surface area of PCL exposed after TPS degrades from the blend.

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... A lower conversion into methane was reported by Abou-Zeid et al. (2004, 2001 and Day et al. (1994), between 29 and 55% in 40 and 42 days, respectively. Nunziato et al. (2018) reported a low degree of biodegradation for polyhydroxyoctanoate (PHO), which is a medium-chain PHA, with only 12% of the material being converted into methane after 56 days in a mesophilic digester. On the other hand, Federle et al. (2002) reported near-complete biodegradation (88%) for PHBO, a co-polymer of PHB and PHO (10% PHO), after 60 days of anaerobic digestion. ...
... PCL is often used in blends with TPS (Ali Akbari Ghavimi et al., 2015). Nunziato et al. (2018) showed that the addition of TPS increased the biodegradation rate of PCL in mesophilic and thermophilic anaerobic digesters. The biodegradation of PCL was reported to be very slow and in all cases, with the degradation level between 0 and 22% at the end of the tests ( Only 3 to 22% of the PCL was converted to methane, and they assumed that the same biodegradation mechanisms as with PLA were involved. ...
... No data regarding PHBV degradation by thermophilic digestion could be found in the scientific literature. As with mesophilic conditions, PHO was weakly degraded (6%) under thermophilic conditions in 50 days (Nunziato et al., 2018). ...
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