Chain Extension and Foaming Behavior of Poly(lactic acid) by Functionalized Multiwalled Carbon Nanotubes and Chain Extender

Abstract

A nanocomposited biofoam consisting of functionalized multiwalled carbon nanotubes (MWCNTs), a chain extender with multi-epoxy groups (CEME), and poly(lactic acid) (PLA) was prepared by a batch foam process. First of all, poly(acrylic acid) (PAA) was directly grafted onto the surface of MWCNTs by in situ polymerization. And then, the modified MWCNTs, CEME, and PLA were reacted by melt mixing through the esterification reaction between the epoxy groups of the CEME and the carboxyl groups of PAA or PLA. Finally, the resultant nanocomposites were foamed in a high-pressure stainless steel autoclave using CO 2 as a physical blowing agent. The functionalized MWCNTs were characterized using Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis. The crystallization and rheological properties of various samples were examined by a differential scanning calorimeter, rotational rheometer, and torque rheometer, respectively. The foaming properties of various samples were characterized by a scanning electron microscope and densimeter. It was found that the volume expansion ratio of modified MWCNT/PLA foam with a uniform cell size reached nearly 10 times. C

Antibacterial Property and Cytotoxicity of a Poly(lactic acid)/Nanosilver-Doped Multiwall Carbon Nanotube Nanocomposite

“…Therefore, strategies to improve its mechanical and thermal properties are necessary for commercial applicability. The most efficient strategy for improving its properties is reinforcement with nanomaterials [ 12 , 13 , 14 , 15 , 16 , 17 ], and various nanomaterials, such as sepiolite [ 13 ], carbon nanotubes [ 12 ], montmorillonite [ 13 , 14 ], zirconium phosphonate [ 13 ], graphene [ 15 ], and graphene oxide [ 16 ] have been used. PLA-based nanocomposites with varying content of multiwall carbon nanotubes (MWCNTs) have been suggested to for facilitating promising medical applications [ 17 , 18 , 19 ].…”

“…PLA-based nanocomposites with varying content of multiwall carbon nanotubes (MWCNTs) have been suggested to for facilitating promising medical applications [ 17 , 18 , 19 ]. For example, Wang et al [ 12 ] grafted poly(acrylic acid) onto MWCNTs to prepare modified MWCNTs to improve the expansion ratio of PLA after foaming with a chain extender. Park et al [ 20 ] reported the isothermal crystallization behavior and mechanical properties of PLA/MWCNT nanocomposites; specifically, they found that the MWCNTs effectively improved the isothermal crystallization rate of the PLA through heterogeneous nucleation.…”

Chemical recycling of polyesters

“…It was found that in supercritical CO 2 the process of crystallization of the extended PLA chains dramatically differs from that of pure PLA chains [27]. The multi-epoxide oligomer was also used by other authors to strengthen pure PLA [28,29], PLA blend with thermoplastic starch [30], PLA blend with poly(butylene succinate-co-adipate) and their composites with nanoclay [31] as well as PLA nanocomposites foamed with CO 2 [32]. Other researchers have shown that multi-epoxy ChEx can be successfully used as reactive compatibilizers of blends of two immiscible polyesters: PLA and poly(butylene adipate-co-terephthalate) (PBAT).…”

Foaming of PLA Composites by Supercritical Fluid-Assisted Processes: A Review

“…However, Li et al [73] showed that the solubility of CO 2 in PLA is approximately ten times that of N 2 . Therefore, the use of CO 2 increased for the different blowing process: batch [3,11,[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89], injection molding [2,90], and extrusion [13,49,[91][92][93][94][95][96].…”