scholarly journals Multiple shape memory behavior of highly oriented long-chain-branched poly(lactic acid) and its recovery mechanism

2019 ◽  
Vol 107 (4) ◽  
pp. 872-883 ◽  
Author(s):  
Jiafeng Li ◽  
Xiaowen Zhao ◽  
Lin Ye ◽  
Phil Coates ◽  
Fin Caton-Rose
Keyword(s):  
Lactic Acid ◽  
Shape Memory ◽  
Poly Lactic Acid ◽  
Shape Memory Behavior ◽  
Recovery Mechanism ◽  
Long Chain

scholarly journals Star Shaped Long Chain Branched Poly (lactic acid) Prepared by Melt Transesterification with Trimethylolpropane Triacrylate and Nano-ZnO

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 796 ◽  
Author(s):  
Le Yang ◽  
Zaijun Yang ◽  
Feng Zhang ◽  
Lijin Xie ◽  
Zhu Luo ◽  
...  
Keyword(s):  
Lactic Acid ◽  
High Efficiency ◽  
Synergistic Effects ◽  
Transesterification Reaction ◽  
Poly Lactic Acid ◽  
Cell Diameter ◽  
Nano Zno ◽  
Melt Strength ◽  
Trimethylolpropane Triacrylate ◽  
Long Chain

Long chain branched poly (lactic acid) (LCBPLA) was prepared via transesterification between high molecular weight poly (lactic acid) (PLA) and low molar mass monomer trimethylolpropane triacrylate (TMPTA) during melt blending in the presence of zinc oxide nanoparticles (nano-ZnO) as a transesterification accelerant in a torque rheometer. Compared with the traditional processing methods, this novel way is high-efficiency, environmentally friendly, and gel-free. The results revealed that chain restructuring reactions occurred and TMPTA was grafted onto the PLA backbone. The topological structures of LCBPLA were verified and investigated in detail. It was found that the concentration of the accelerants and the sampling occasion had very important roles in the occurrence of branching structures. When the nano-ZnO dosage was 0.4 phr and PLA was sampled at the time corresponding to the reaction peak in the torque curve, PLA exhibited a star-shaped topological structure with a high branching degree which could obviously affect the melt strength, extrusion foaming performances, and crystallization behaviors. Compared with pristine PLA, LCBPLA showed a higher melt strength, smaller cell diameter, and slower crystallization speed owing to the synergistic effects of nano-ZnO and the long chain branches introduced by the transesterification reaction in the system. However, severe degradation of the LCBPLAs would take place under a mixing time that was too long and lots of short linear chains generated due to the excessive transesterification reaction, with a sharp decline in melt strength.

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