Crystallization Behavior of Poly(L-lactic acid) Containing
Octamethylenedicarboxylic Dibenzoylhydrazide

-1-1
1/2

Crystallization rate 1/t[s ]Crystallization rate 1/t

1/2

[s ]

Temperature [o C]

Kohei TAKAHASHI1, Masataka SUGIMOTO1, Takashi TANIGUCHI2, Kiyohito KOYAMA1
1
Graduate School of Science and Engineering, Yamagata University,2
Department of Chemical Engineering, Kyoto University,
takahashi@ckpss.yz.yamagata-u.ac.jp
1. Introduction:
Poly (L-lactic acid) (PLLA) have been focused owing to its various characteristics. Theapplications of PLLA are, however, limited because of the low crystallization rate and crystallity.
Generally, crystallization rate is enhanced by nucleating agent. Octamethylenedicarboxylic
dibenzoylhydrazide (OMBH) is one of excellent organic nucleating agent for PLLA [1]. In thisstudy, we investigated the effect of OMBH on the crystallization rate and crystalline morphology ofPLLA.
2. Experiment:
PLLA and nucleating agent (OMBH and talc) are mixed by twin-screwed mixer at 220 °C .
220 °C is above the melting point of OMBH. OMBH concentration was 0, 0.1, 0.2, 0.3, 0.4, 0.5
wt%. To observe crystallization process, polarizing optical microscope with hot stage was used. To
investigate crystallization rate, differential scanning calorimetry (DSC) measurement underisothermal condition was performed. The sample was heated to 220 °C , held for 3 min at 220 °C ,and then cooled to the crystallization temperature.
Spherulite/Needle mix
s Spherulite region
3. Result and discussion:
regionN Needle-like crystal region
600saFig.1 shows the crystalline morphology diagramin the early stage of crystallization. The crystalline 150 s s s s s Nmorphology of PLLA/OMBH changes from 140 s s s s N N240sbspherulite to needle-like crystal as increasing the 130 s s s N N N
OMBH concentration. Fig.2 shows the result of DSC 120 s s s N N N
measurement under isothermal condition. It is clear
0.1 0.2 0.3 0.4 0.5050µm
OMBH concentration [wt%]that the crystallization rate of the needle-like crystal isFig.1 Crystalline morphology diagram in themuch faster than that of spherulite. OMBH formed the early stage of crystallizationneedle structure in Needle-like crystal region in Fig.1, (a)140 °C , OMBH0.3wt%
though no structure derived from OMBH was (b)140 °C , OMBH0.4wt%
0.02
0.02
120℃
appeared in Spherulite region. This structure enhances
120℃
130℃
130℃
0.015
0.015
140℃
140℃
the crystallization of PLLA. At low OMBH
0.01
0.01
concentration, where OMBH does not form any
0.005
0.005
structure, the crystallization rate of PLLA/OMBH islower than that of talc/OMBH. It is suggested that0000.1
0.2
0.3
0.4
0.500.1
0.2
0.3
0.4
0.5
talc concentration [wt%]
OMBH concentration [wt%]needle-like crystal region shown in Fig.1 is suitable
Fig.2 Changes in crystallization rate 1/t1/2, as acondition to exert the nucleating ability of OMBH.
function of the concentration of nucleating agent
4. Summary:The crystalline morphology of PLLA/OMBH changed from spherulite or needle-like crystal
depending on the OMBH concentration and temperature. The crystallization rate of needle-likecrystal was much faster than that of spherulite.
5. Reference:[1] N. Kawamoto, A. Sakai, T. Horikoshi, T. Urushihara, E, Tobita, J.Appl.Polym.Sci, 103, 244-250 (2007)