Synthesis, characterization and degradation of poly (butylene adipate-co-terephyhalate (PBAT) based biodegradable foams

The purpose of this thesis is to synthesize PBAT and PBAT/TPS polymeric foam materials in a batch system and in a continuous system with twin screw extruders. Within this scope, the optimization and characterization of the synthesized foams by FTIR, TGA, DTG, SEM, Micro-CT and elemental analysis were performed. The characteristic peaks of both PBAT and TPS were observed in FTIR analysis. C = O bond that found in both the aromatic and aliphatic groups of PBAT was observed at 1708 cm -1. Also peak of the C-H bond in the phenyl ring in the aromatic group was observed at 2957 cm-1. In PBAT/TPS, broadband due to hydroxyl groups was observed at of 3200 cm-1 to 3400 cm-1. After foaming process, PBAT undergoes the esterification reaction due to the foaming agent and temperature. According to the results of TG analysis, PBAT foam lost its weight between 310℃ - 460℃ with single step and PBAT/TPS foam lost its weight in three stage between 25℃ - 150℃, 270℃ - 320℃ and 320℃ - 450℃. These losses represent the degradation of water, TPS and PBAT in the structure, respectively. According to the Micro-CT and SEM analysis, the average pore number in the cross-sectional area of the PBAT foam is 577, the total pore area in the cross-sectional area is 5.73 × 106 m, the mean pore size in the cross-sectional area is 9.95 × 103 m and the porosity rate is 31.5%. The density of PBAT was reduced from 1.26 g/cm3 to 0.86 g/cm3 by foaming and the cell density was calculated as 2.63 × 〖10〗^5 (cells / cm3). The average pore number in the cross-sectional area of PBAT/TPS foam is 378, the total pore area in the cross-sectional area is 1.41 × 106 m, the mean pore size in the cross-sectional area is 3.75 × 103 m and the porosity rate is 17.3%. The density of the PBAT/TPS was reduced from 1.29 g/cm3 to 1.06 g/cm3 by foaming and cell density density was calculated as 3.93 × 〖10〗^5 (cells / cm3). In order to investigate the biodegradability of the synthesized foams in controlled compost medium, degradation test was performed according to ISO 14855-1: 2013 standard. After 15 days PBAT foam was degraded 17.56%, PBAT/TPS foam was degraded 27.43% and cellulose was degraded 57.39%. According to FTIR and TG analysis after composting, there was no change in the structure of PBAT and PBAT/TPS foam in the compost medium. Both analyzes showed that biodegradation firstly started from TPS and the TPS in the structure was significantly degraded after composting. According to the SEM analysis after composting, the biodegradation of the closed cell structure foams that synthesized from PBAT and PBAT/TPS proceeded from the outer surface to the inner surface. The biodegradation process did not deteriorate the porous structure of the foams, but increased surface area accelerated biodegradability.