Renewable and Tough Poly(l-lactic acid)/Polyurethane Blends Prepared by Dynamic Vulcanization

Abstract

Melt blending of homopolymers is an effective way to achieve an attractive combination of polymer properties. Dynamic vulcanization of fatty-acid-based polyester polyol with glycerol and poly( l -lactic acid) (PLLA) in the presence of hexamethylene diisocyanate (HDI) was performed with the aim of toughening PLLA. The dynamic vulcanization in an internal mixer led to the formation of a PLLA/PU biobased blend. Melt torque, Fourier transform infrared (FTIR), and gel fraction analysis demonstrated the successful formation of cross-linked polyurethane (PU) inside the PLLA matrix. Scanning electron microscopy (SEM) analysis showed that the PLLA/PU blends exhibit a sea–island morphology. Gel fraction analysis revealed that a rubbery phase was formed inside the PLLA matrix, which was insoluble in chloroform. FTIR analysis of the insoluble part shows the appearance of an absorption band centered at 1758 cm –1 , related to the crystalline carbonyl vibration of the PLLA component, thus suggesting the partial involvement of PLLA chains in the cross-linking reaction. The overall content of the PU phase in the blends significantly affected the mechanical properties, thermal stability, and crystallization behavior of the materials. The overall crystallization rate of PLLA was noticeably decreased by the incorporation of PU. At the same time, polarized light optical microscopy (PLOM) analysis revealed that the presence of the PU rubbery phase inside the PLLA matrix promoted PLLA nucleation. With the formation of the PU network, the impact strength showed a remarkable increase while Young’s modulus correspondingly decreased. The blends showed slightly reduced thermal stability compared to the neat PLLA.

Preparation and Characterization of Super-Toughened PLA/CPU Blends via One-step Dynamic Vulcanization

“…The torque value decreased rapidly with the addition of PEG in the second stage, which was attributed to the lubrication and plasticization of PEG. [43] The third stage was the in-situ reaction process of IPDIT, PEG and PLA. When IPDIT was added, the torque value dropped slightly.…”

“…The first stage and the second stage belong to PLA and CPU weightless, respectively. [43] The mass fractions of cross-linked PLA and CPU calculating according to TGA curves are shown in Figs. 1g-i.…”

4D Printing of Electroactive Triple-Shape Composites

“…PLA is an ideal FFF material, which enables a thermally induced SME [ 39 , 40 ]. However, incorporating nanofillers makes PLA brittle, thus limiting its deformability [ 41 ]. Therefore, blending polyurethanes (PUs) with PLA was investigated as an effective way to obtain multiphase SMPs with improved strength and elasticity.…”

Diisocyanate-Induced Dynamic Vulcanization of Difunctional Fatty Acids toward Mechanically Robust PLA Blends with Enhanced Luminescence Emission

“…Vegetable oils and their resulting derivatives ( e.g. , fatty acids) have received considerable interests for synthesizing renewable elastomers due to many advantages, such as abundant availability, flexible molecular backbone, versatile chemical structure, convenient functionalization as well as biodegradability. , Several attempts have been made to directly use vegetable oils or their epoxidized derivatives for PLA toughening via dynamic vulcanization, − yielding a moderate improvement in toughness that limits its engineering applications requiring a superior impact-resistance performance ( e.g. , automotive).…”