The effect melt processing temperature on the isothermal crystallization of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

• Published in: Macromolecular research Vol. 32; no. 1; pp. 1 - 12
• Main Authors: Zhang, Tao, Jang, Yunjae, Jung, Minho, Lee, Eunhye, Kang, Ho-Jong
• Format: Journal Article
• Language: English
• Published: Seoul The Polymer Society of Korea 2024; Springer Nature B.V; 한국고분자학회
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Complex Fluids and Microfluidics; Copolymers; Crystallization; Enthalpy; Low molecular weights; Melt temperature; Melting; Nanochemistry; Nanotechnology; Physical Chemistry; Polymer Sciences; Soft and Granular Matter; Temperature; Thermal degradation; 고분자공학; 4-hydroxybutyrate; Relative crystallinity; Melt processing temperatures; Poly(3-hydroxybutyrate; Isothermal crystallization; Thermal degradation; Crystallization rate
• ISSN: 1598-5032; 2092-7673
• DOI: 10.1007/s13233-023-00205-x

The effect of melt processing temperature on the isothermal crystallization behavior of poly(3-hydroxybutyrate- co -4-hydroxybutyrate)[P(3HB- co -4HB)] is studied using differential scanning calorimetry and polarizing microscopy. P(3HB- co -4HB) undergoes thermal degradation above its melting temperature. The degree of degradation increases with increase in the 4HB content in copolymer. The formation of low molecular weight P(3HB- co -4HB) from thermal degradation reduces the crystallization temperature. Thus, the isothermal crystallization rate and crystallinity decrease at a processing of 190 ℃ compared with 180 ℃ where less thermal degradation occurs. This is more evident in the case of P(3HB- co -4HB) of high 4HB content. The P(3HB- co -4HB) crystals formed in the isothermal crystallization process have different perfectness in the 4HB rich phase and the 3HB rich phase depending on the melt processing temperature. This results in the appearance of two distinct melting peaks with different melting temperatures and melting enthalpies. Our results indicated that thermal history in the isothermal crystallization process will affect these crystals differently. Graphical abstract A 10 °C difference in the processing temperature of P(3HB- co -4HB) results in a clear difference in the temperatures where crystallization is possible. Samples processed at 180 °C have a higher crystallizable temperature and crystallize more readily during the cooling stage compared with those process ed at 190 °C. As a result, the effect of thermal degradation on the crystallization behavior is minimized for the samples processed at 180 °C, while it is greater when thermal degradation retards crystallization and the crystallization temperature decreases for the samples processed at 190 °C