Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

Abstract

We report on enhancing crystallization and heat resistance of poly­(l-lactic acid) (PLLA) by d-sorbitol as a small molecule nucleating agent via melt blending. During the reheating process, the cold crystallization disappeared and the crystallinity of nucleated PLLA exceeded 50%. The heat deflection temperature of PLLA was elevated from 56 to 132 °C by simply increasing the mold temperature (90 °C) without an additional annealing treatment. We also observed the polymorphic crystals of PLLA during melt crystallization, i.e., the coexistence of hexagonal and lenticular crystals, along with their various geometrical aggregates in addition to plenty of conventional spherulites. On the basis of the fact that the nonisothermal crystallization temperature of PLLA (110 °C at a cooling rate of 10 °C/min) was higher than the melting point of d-sorbitol (about 93 °C), we speculated that d-sorbitol promoted the crystallization of PLLA through a homogeneous nucleation mechanism.

Flexibly Controlling the Polycrystallinity and Improving the Foaming Behavior of Polylactic Acid via Three Strategies

“…On cooling, the hydrogen bonding interaction between the hydroxyl groups of DS and the carbonyl groups of PLA chains could be effectively developed. This hydrogen bonding twisted and folded the PLA chain segments to promote the orderly stacking of PLA chains, which favored the crystallization nucleation . The detailed mechanism is shown in Supporting Information, Figure S3.…”

“…This hydrogen bonding twisted and folded the PLA chain segments to promote the orderly stacking of PLA chains, which favored the crystallization nucleation. 37 The detailed mechanism is shown in Supporting Information, Figure S3. Moreover, in PPZn's chemical structure, the metal ions, Zn 2+ , could form an inner polar layer shielded by two non-polar layers of aromatic rings.…”

Isotactic-Alternating, Heterotactic-Alternating, and ABAA-Type Sequence-Controlled Copolyester Syntheses via Highly Stereoselective and Regioselective Ring-Opening Polymerization of Cyclic Diesters

“…Thus the crystallization progress will be accelerated when there are some seed crystals in the polymers. Like the research on polylactides, 77 the enhancement of the crystallinities of these polymers incorporated with mandelic acid units is an interesting research topic that is still going on in our lab.…”

Role of Interfacial Postreaction during Thermal Treatment: Toward a Better Understanding of the Toughness of PLLA/Reactive Elastomer Blends

“…Polylactide (PLLA), biodegradable aliphatic thermoplastic polyester derived from annually renewable resources, has been attracting increasing attention due to its excellent mechanical strength, biocompatibility, and processability. − Nevertheless, the inherent brittleness of PLLA prevents it from being applied widely, such as in automotive industries, biomedical devices, − packaging, − and electric appliance industries. , Extensive approaches have been developed to modify the properties of PLLA. Blending with reactive elastomers, such as poly­(ethylene- n -butylene-acrylate-co-glycidyl methacrylate) (EBA-GMA), − ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) random terpolymer, − natural rubber-glycidyl methacrylate (NA-GMA), , and polyurethane prepolymer (PUP), is regarded as the most efficient and economic strategy to toughen PLLA.…”