Properties Enhancement of High Molecular Weight Polylactide Using Stereocomplex Polylactide as a Nucleating Agent

Abstract

As one of the most attractive biopolymers nowadays in terms of their sustainability, degradability, and material tune-ability, the improvement of polylactide (PLA) homopolymer properties by studying the utilization of stereocomplex polylactide (s-PLA) effectively and efficiently is needed. In this sense, we have studied the utilization of s-PLA compared to poly D-lactide (PDLA) homopolymers as a nucleating agent for PLA homopolymers. The mechanical and thermal properties and crystallization behavior of PLA homopolymers in the presence of nucleating agents have been evaluated using a universal testing machine, differential scanning calorimeter, and X-ray diffractometer instruments, respectively. PDLA and s-PLA materials can be used to increase the thermal and mechanical properties of poly L-lactide (PLLA) homopolymers. The s-PLA materials increased the mechanical properties by increasing crystallinity of the PLLA homopolymers. PLLA/s-PLA enhanced mechanical properties to a certain level (5% s-PLA content), then decreased them due to higher s-PLA materials affecting the brittleness of the blends. PDLA homopolymers increased mechanical properties by forming stereocomplex PLA with PLLA homopolymers. Non-isothermal and isothermal evaluation showed that s-PLA materials were more effective at enhancing PLLA homopolymer properties through nucleating agent mechanism.

The Effect of Stereocomplex Polylactide Particles on the Stereocomplexation of High Molecular Weight Polylactide Blends

“…The high content of s-PLA crystallites may form aggregates, which counter the nucleation effect. It aligned with previous research where the addition of s-PLA crystallites improved polymer crystallinity [ 19 , 20 ]. For particle size effect, the PLLA/PDLA_B10 and PLLA/PDLA_C10 samples showed higher levels of s-PLA but lower total crystallinity values compared to PLLA/PDLA_A10.…”

“…The presence of s-PLA characteristic peak indicates that s-PLA crystallites act as an initiator for s-PLA formation in high molecular weight PLLA/PDLA blends. As reported in a previous study, the presence of s-PLA crystallites also initiates a nucleation site of PLA blends [ 20 ]. The possible mechanism may start with the initiating of s-PLA formation up to a certain portion, followed by the nucleation of homopolymers.…”

“…In previous studies, the utilization of s-PLA particles as a nucleating agent in polymer blends improved its mechanical and thermal properties [ 3 , 16 ]. The presence of s-PLA crystallites increased crystallization rates and nucleation sites in PLA blends through solution [ 19 , 20 ] and melt process [ 21 , 22 , 23 ]. The addition of s-PLA materials into homopolymers shows the potential application of s-PLA particles to improve the crystallization rate of PLA homopolymers [ 19 , 20 ].…”

“…The presence of s-PLA crystallites increased crystallization rates and nucleation sites in PLA blends through solution [ 19 , 20 ] and melt process [ 21 , 22 , 23 ]. The addition of s-PLA materials into homopolymers shows the potential application of s-PLA particles to improve the crystallization rate of PLA homopolymers [ 19 , 20 ]. In other studies, the combination of PLLA and PDLA in melt process affects the increasing crystallization degree of PLA blends [ 21 , 22 , 23 ].…”

Novel Poly(Methylenelactide-g-L-Lactide) Graft Copolymers Synthesized by a Combination of Vinyl Addition and Ring-Opening Polymerizations

“…Since these drawbacks in toughness and heat resistance confine specific applications of PLA, thereby, many attempts for improving PLA inferior properties via various modification methods have been investigated over the past decades [ 26 , 27 ]. The strategies include annealing, nucleating agents, plasticization, chain extending, copolymerization, blending, polymer (nano)composites, stereocomplexes, crosslinking, and functionalization [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”