Rheology and Crystallization
of Long-Chain Branched
Poly(l‑lactide)s with Controlled Branch Length
- Publication date
- Publisher
Abstract
A series of long-chain branched poly(l-lactide)s
(LCB-PLAs)
with controlled branch length were prepared by a simple and efficient
method through a combination of ring-opening polymerization (ROP)
of l-lactide and a coupling reaction between the terminal
OH groups of the PLA prepolymers and the NCO groups of HDI. The influences
of reaction conditions on the synthesis of the LCB-PLAs were investigated,
and the structures of the resultant LCB-PLAs were characterized by <sup>1</sup>H NMR spectroscopy and SEC-MALLS. By adjusting the degree
of polymerization and the composition of the prepolymers, LCB-PLAs
with different branch densities and molecular weights between branch
points were obtained. The effect of macromolecular chain branching
on the rheology and crystallization of PLA was also investigated.
The LCB structure contributed to the enhancement of the zero-shear
viscosity, complex viscosity, storage modulus, melt strength, and
strain hardening under elongational flow. Thermal behavior indicated
that the branch structure resulted in a short nucleation induction
period and more rapid crystallization, which can be a guarantee of
high-strength foams
