Crystallization behavior and crystallite morphology control of poly(L‐lactic acid) through N, N′‐bis(benzoyl)sebacic acid dihydrazide

Abstract

Adding a nucleating agent is one of the best ways to accelerate the crystallization rate of poly(L-lactic acid) (PLLA) so as to obtain a high degree of crystallinity during the process, which will improve the heat distortion temperature of final products. In the work reported, N, N -bis(benzoyl)sebacic acid dihydrazide (BSAD) was synthesized and used as a nucleating agent for PLLA. Isothermal and non-isothermal crystallization behaviors were investigated using differential scanning calorimetry (DSC). The addition of BSAD successfully enhances the crystallization rate of PLLA. A unique phase separation behavior of PLLA/BSAD blends is found from DSC as well as from polarized optical microscopy, which explains the difference of optimal BSAD concentration between isothermal and non-isothermal crystallization. This is the first recording of a phase separation peak in PLLA/nucleating agent blends using DSC. In thermogravimetric analysis, the enhanced thermal stability indicates that there are strong hydrogen bonds between BSAD and PLLA matrix. BSAD can dissolve in PLLA melt below its melting point through intermolecular hydrogen bonding with PLLA and self-assemble upon cooling, leading to the surface being capable of nucleating PLLA. Different phase separation temperatures can be used to control the morphology of BSAD, which finally determines the crystallite morphology of PLLA.

Heterogeneous Nucleation Effect of N, N'-Adipic Bis(4-phenylbutyric Acid) Dihydrazide on Crystallization Process of Poly(L-lactic Acid)

“…Among these PLLA/APAD samples, PLLA/0.5 %APAD exhibits the highest onset crystallization temperature of 136.4 °C and crystallization peak temperature of 132.0 °C, as well as the largest non-isothermal crystallization enthalpy of 48.1 J/g, indicating that the enhancement of 0.5 wt.% APAD on the crystallization of PLLA is the best. On the other hand, under the same circumstance, the higher onset crystallization temperature and crystallization peak temperature, as well as the larger non-isothermal crystallization enthalpy of PLLA/APAD system further confirm the more powerful accelerating ability of APAD for PLLA crystallization comparing with other systems such as PLLA/BASD [11], PLLA/NA [33], PLLA/MCB [34]. Additionally, with increasing of APAD concentration, the crystallization peak shifts to the lower temperature, and the value of the non-isothermal crystallization enthalpy also becomes smaller.…”

“…However, the glass transition temperature of the amorphous PLLA is about 60 °C [10], which can not meet the using requirements of plastic products including disposable tableware, electronics enclosures and automotive interior parts [11]. For PLLA as a semicrystalline polymer, enhancing the crystallinity of PLLA is one of the most effective way to improve its heat resistance.…”

The Crystallization, Melting Behavior, and Thermal Stability of Poly(L-lactic acid) Induced byN,N,N′-Tris(benzoyl) Trimesic Acid Hydrazide as an Organic Nucleating Agent

“…Acid Dihydrazide. N,N,N -Tris(benzoyl) trimesic acid dihydrazide (TTAD) was prepared as shown in Scheme 1; the specific reaction process is similar to the other amide compounds reportedin our previous works [12,13].…”

Thermal Decomposition Kinetics of Poly(L-lactic acid) after Heat Treatment

“…There exist many literatures about PLLA and its composites based on PLLA [2,3], and the addition of a functional additive can significantly improve the properties of PLLA. For example, Fan et al [4] reported that N, N'-bis(benzoyl)sebacic acid dihydrazide was synthesized and used as a nucleating agent for PLLA. The addition of N, N'-bis(benzoyl)sebacic acid dihydrazide enhanced the crystallization rate of PLLA, and thermogravimetric analysis showed that the thermal stability of PLLA with N, N'-bis(benzoyl)sebacic acid dihydrazide was enhanced, indicating that there were strong hydrogen bonds between N, N'-bis(benzoyl)sebacic acid dihydrazide and PLLA matrix.…”