writer：Yongbin Wang, Liang Yang, Yanhua Niu, Zhigang Wang*, Jun Zhang, Fengyuan Yu, Hongbin Zhang
keywords：聚乳酸，长链支化，流变学,辐照
source：期刊
specific source：J Appl Polym Sci 2011，122，1857–1865.
Issue time：2011年

In this study, a series of linear- and long chain branched polylactic acid (PLA) samples was prepared by electron beam irradiation without or with addition of a trifunctional monomer, trimethylolpropane triacrylate (TMPTA). The chain structures of the PLA samples were characterized by size-exclusion chromatography coupled with a light scattering detector (SEC-MALLS) and shear and extensional rheology. PLA tends to degrade while keeps linear structures with increasing irradiation dose and without addition of TMPTA, as evidenced by decreased molecular mass Mw and reductions of storage modulus and the zero shear viscosity. Long-chain branched PLA samples were successfully prepared with irradiation and addition of TMPTA, which shows prominent higher zero shear viscosity and apparent flow activation energy, longer characteristic relaxation time, and pronounced strain-hardening behaviors. With increasing amount of TMPTA, Mw dependences of zero shear viscosity and the root mean square radius of gyration Rg obviously deviate from the scaling relation of linear PLA samples, which strongly indicates the increased long-chain branching degree for the branched PLA samples.