RESEARCH ARTICLE

Nucleation, melting behaviour and mechanical properties of poly(L-lactic acid) affected by the addition of N, N'-bis(benzoyl) suberic acid dihydrazide

Yan-Hua Cai^*

College of Materials, Chongqing University of Arts and Sciences, Yongchuan, Chongqing-402160, P.R. China

ABSTRACT

A new category of nucleating agent for poly(L-lactic acid) (PLLA) was developed. An organic nucleating agent; N,N'-bis(benzoyl) suberic acid dihydrazide (NA) was synthesized from benzoyl hydrazine and suberoyl chloride which was deprived from suberic acid via acylation. The nucleation, melting behaviour and mechanical properties of the PLLA containing NA were investigated. NA showed excellent nucleating effects on PLLA crystallization. Compared to the neat PLLA, with the addition of 0.8 % NA, the crystallization temperature (T_o) increase from 105.88 °C to 125.57 °C and the crystallization enthalpy( AH_c) increase from 1.379 J g^-1 to 31.63 J g^-1 at a cooling rate of 1 °C min^-1 from melt. In the presence of NA, the melting behaviour of PLLA was affected significantly, and a double-melting peak resulted during melting-recrystallization. The tensile strengths and tensile modulus increase with the increase of NA content and possesses a maximum value for the critical NA loading of 0.8 %. However, the elongations at break of the samples decreased significantly.

Keywords: Poly (L-lactic acid), crystallization, melting behaviour, benzoyl hydrazine

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Received 7 October 2010
Revised 2 July 2011
Accepted 19 July 2011

* E-mail: caiyh651@yahoo.com.cn