Structure and Property of Microinjection Molded Poly(lactic acid) with High Degree of Long Chain Branching

• Main Authors: Zhao, Z.-G., Yang, Q., Coates, Philip D., Whiteside, Benjamin R., Kelly, Adrian L., Huang, Y.-J., Wu, P.-P.
• Language: en
• Published: 2019
• Subjects: Polymer; Microinjection moulding
• Online Access: http://hdl.handle.net/10454/16981

Yes === Long chain branches (LCB) are successfully grafted to linear poly(lactic acid) (PLA) using functional group reactions with pentaerythritol triacrylate (PETA) and tetraethylthiuram disulfide (TETDS). Results show a high branching degree of PLA (∼49.5%) can be effectively obtained with adding only 1 wt % PETA, contributing remarkably to enhancing strain hardening. The density of the nuclei formed during nonisothermal crystallization for LCB-PLA samples is markedly increased contrasted with PLA, resulting in significantly enhancing crystallinity from 13.3% to 41%, the onset crystallization temperature (∼20 °C), and the crystallization rate. Interestingly, compared with mini-injection molding, the elevated wall shear rates (and corresponding shear stresses) prove to be beneficial to the creation of special crystalline morphologies (β-crystal form) and oriented structures under microinjection molding conditions, resulting in the improvement of tensile strength by ∼45 MPa. === Chinese Scholarship Council