Effects of L‐phenylalanine as a nucleation agent on the nonisothermal crystallization, melting behavior, and mechanical properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

Abstract

AbstractPoly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBHHx) is a thermoplastic biopolyester with a slow crystallization rate. L‐Phenylalanine (L‐PH) was used to improve the crystallization rate of PHBHHx. The nonisothermal crystallization kinetics and melting behaviors of PHBHHx and PHBHHx/L‐PH samples were characterized and compared with differential scanning calorimetry. At cooling rates of 2, 5, 10, and 20°C/min, PHBHHx/L‐PH could crystallize at higher temperatures than pure PHBHHx. A modified Avrami equation based analysis showed that the addition of L‐PH shortened the half‐time of crystallization of PHBHHx from 9.6 to 8.0 min and increased the composite rate constant of PHBHHx from 0.201 to 0.283 during the nonisothermal crystallization process at a cooling rate of 10°C/min. For other cooling rates, similar trends of changes were observed. These indicated a faster crystallization rate of PHBHHx in the presence of L‐PH. PHBHHx/L‐PH samples showed a higher melting temperature and a sharper melting peak than those of the pure PHBHHx, which suggested that L‐PH as a nucleation agent improved the perfection of the PHBHHx crystals. Stress–strain measurements showed that both PHBHHx and PHBHHx/L‐PH maintained their ductile and elastic properties during the 60 days of the aging study. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008