Synthesis, Characterization and Properties of Biodegradable Poly(Butylene Sebacate-Co-terephthalate)

Abstract

In this study, poly(butylene sebacate-co-terephthalate) (PBSeT) was successfully synthesized using various ratios of sebacic acid (Se) and dimethyl terephthalate (DMT). The synthesized PBSeT showed a high molecular weight (Mw, 88,700–154,900 g/mol) and good elastomeric properties. In particular, the PBSeT64 (6:4 sebacic acid/dimethyl terephthalate mole ratio) sample showed an elongation at break value of over 1600%. However, further increasing the DMT content decreased the elongation properties but increased the tensile strength due to the inherent strength of the aromatic unit. The melting point and crystallization temperature were difficult to observe in PBSeT64, indicating that an amorphous copolyester was formed at this mole ratio. Interestingly, wide angle X-ray diffraction (WAXD) curves was shown in the cases of PBSeT46 and PBSeT64, neither the crystal peaks of PBSe nor those of poly(butylene terephthalate) (PBT) are observed, that is, PBSeT64 showed an amorphous form with low crystallinity. The Fourier-transform infrared (FT-IR) spectrum showed C–H peaks at around 2900 cm−1 that reduced as the DMT ratio was increased. Nuclear magnetic resonance (NMR) showed well-resolved peaks split by coupling with the sebacate and DMT moieties. These results highlight that elastomeric PBSeT with high molecular weight could be synthesized by applying DMT monomer and showed promising mechanical properties.

Characterization of PLA/PBSeT Blends Prepared with Various Hexamethylene Diisocyanate Contents

“…A peak corresponding to the –CH 3 of PLA at 2945 cm −1 , 2996 cm −1 [ 38 ] and the –CH– of PLA at 2997 cm −1 (asym), 2946 cm −1 (sym), and 2881 cm −1 stretch [ 39 ]. The –CH 2 of PBSeT was appeared at 2919 cm −1 , 2851 cm −1 [ 36 ]. However, it occurred nearby each other, so whole peaks were appeared in the range 2800–3000 cm −1 as small round curves.…”

“…Figure 4 and Table 3 shows the tensile-strength characteristics and stress–strain curves of the neat PLA, control, and blend specimens prepared with various HDI contents. According to previous research results, because PBSeT showed high elongation, it was expected to remarkably affect the tensile properties of the highly brittle PLA [ 36 ]. The neat PLA and simple-blend control specimens showed tensile strengths of approximately 93 and approximately 52 MPa, respectively.…”

“…All the specimens were pyrolyzed above approximately 340 °C, and the TGA curves of all the specimens exhibited peaks indicating two-stage decomposition because PLA and PBSeT show different decomposition temperatures. Previously reported main decomposition temperature of PBSeT was around 400 °C [ 36 ].…”

“…The PBSeT was synthesized using 60 mol% sebacic acid and 40 mol% DMT by esterification and subsequent polycondensation under vacuum in the range 200–240 °C, according to the method described by Kim et al (2020) [ 36 ], and the ratio (mol%) of BDO to dicarboxylic acid was fixed at 1.25:1. The blend was blended using a high-viscosity kneading machine (TEST ONE, Seoul, Korea) at 220 °C for 5 min.…”

“…However, fossil-based biodegradable polymers such as PBAT and PBS have been blended with PLA, thereby clearly decreasing the bio-based content or carbon footprint of the resulting blends [ 33 , 34 , 35 ]. Kim et al (2020) recently synthesized the random coblock polyester poly (butylene-sebacate– co –terephthalate) (PBSeT) from bio-based sebacic acid, and the resulting amorphous PBSeT showed a high elongation of over 1500% and high ductility [ 36 ]. Therefore, blending PBSeT with PLA is expected to decrease the PLA brittleness while preserving the decreased content of the biobased carbon content (BCC).…”