PLA Melt Stabilization by High-Surface-Area Graphite and Carbon Black

Abstract

Small amounts of carbon nanofillers, specifically high-surface-area graphite (HSAG) and more effectively carbon black (CB), are able to solve the well-known problem of degradation (molecular weight reduction) during melt processing, for the most relevant biodegradable polymer, namely poly(lactic acid), PLA. This behavior is shown by rheological measurements (melt viscosity during extrusion experiments and time sweep-complex viscosity) combined with gel permeation chromatography (GPC) experiments. PLA's molecular weight, which is heavily reduced during melt extrusion of the neat polymer, can remain essentially unaltered by simple compounding with only 0.1 wt % of CB. At temperatures close to polymer melting by compounding with graphitic fillers, the observed stabilization of PLA melt could be rationalized by scavenging traces of water, which reduces hydrolysis of polyester bonds. Thermogravimetric analyses (TGA) indicate that the same carbon fillers, on the contrary, slightly destabilize PLA toward decomposition reactions, leading to the loss of volatile byproducts, which occur at temperatures higher than 300 • C, i.e., far from melt processing conditions.

Production and Modification of Cellulose Nanocrystals fromAgave tequilanaWeber Waste and Its Effect on the Melt Rheology of PLA

“…Figure 9(a) presents the data for PLA and PLA/CNC nanocomposites showing that complex viscosity of PLA decreased continuously accounting for the~65% of initial value at the end of the experiment. The complex viscosity dropped rapidly during the first 15 min; the molecular weight of PLA resin usually decreases during processing due to thermal degradation as reported by others [23,[56][57][58][59]. On the other hand, the complex viscosity of PLA/CNC nanocomposites showed lower values than PLA sample suggesting that CNC promoted polymer degradation during the processing due to the lower thermal stability of CNC; in fact, sulfate groups on the CNC promote the degradation of the PLA as reported by others [60,61].…”

Micro powder poly lactic acid/carbon black composite as a bio printing ink

“…It shows that for PLA the terminal zone has been reached and the zero-shear viscosity can be obtained directly. 32 Image gloss properties in toner fusing process can be qualitatively expressed by viscoelastic behavior of toner resin. High image gloss can be gained under the condition that a rheological property of toner resin is in the terminal zone in the fusing process.…”

Towards sustainability in 3D printing of thermoplastic composites: Evaluation of recycled carbon fibers as reinforcing agent for FDM filament production and 3D printing

“…This resulted also in a more homogeneous filament diameter distribution. With the aim to, at least, roughly estimate the CFs content, as well as the overall thermal stability of the composites, all the obtained filaments were analysed by TGA adopting a temperature program able to selectively degrade the polymeric matrix without significant CFs damage [42]. Results of the tests are summarized in Table 2.…”