Chem. J. Chinese Universities ›› 2010, Vol. 31 ›› Issue (2): 397.

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Multiple Relaxation Behavior of Long Chain Branched Polylactic Acid

WANG Yong-Bin1,2, NIU Yan-Hua1, YANG Liang1,2, YU Feng-Yuan3, ZHANG Hong-Bin3, WANG Zhi-Gang1*   

  1. 1. Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
    2. Graduate School of Chinese Academy of Sciences, Beijing 100049, China;
    3. School of Chemistry and Chemical Engineering, Shanghai Jiaotong University, Shanghai 200240, China
  • Received:2009-05-05 Online:2010-02-10 Published:2010-02-10
  • Contact: WANG Zhi-Gang. E-mail: zgwang@iccas.ac.cn
  • Supported by:

    国家自然科学基金重大项目(批准号: 10590355)资助.

Abstract:

The long chain branched polylactic acid(PLA) samples were successfully fabricated by high energy irradiation in the presence of a small amount of poly-functional monomer. The branched structures of PLA were convinced by size exclusion chromatography(SEC) coupled with a multi-angle laser light scattering(MALLS). By the means of oscillatory shear and creep measurements, the shear rheological behavior of branched PLA was investigated. Meanwhile, the weighted relaxation spectra of PLA were calculated in light of the combined dynamic modulus data. The multiple relaxation behavior of PLA, which was attributed to the existence of different lengths of long chain branches, was actually observed. In addition, a novel procedure for quantificational determination of the lengths of branches and the arm molecular weight of PLA was put forward. It was found that the lengths of branches of PLA were extended and the arm molecular weight was enhanced with increasing amount of poly-functional monomer. The above results could facilitate the fabrication of long chain branched PLA with well-controlled branched structures and improved rheological properties that may dominate the future bio-plastics industry.

Key words: Polylactic acid; Long chain branching; Shear rheology; Multiple relaxation behavior; Degree of branching

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