1,720,962 research outputs found
Effect of basic and acid fillers on hydrolysis and biodegradation rate of poly-lactic acid (PLA)
No full textPoly(Lactic Acid)-based nanobiocomposites with modulated degradation rates
No full textIn the field of biodegradable polymers such as poly(Lactic Acid) (PLA), it is quite well known that their kinetics of hydrolysis strongly depend on the pH of the hydrolyzing medium. The idea explored during this study focused on PLA, is the addition of additives that are able to control the pH of water when it diffuses inside the polymer. For instance, acids (i.e. succinic acid, also used as food additive) are bio- and eco- friendly additives that are able to play this role. In order to control the release of these molecules and their dispersion inside the polymer, their intercalation in biocompatible nanofillers like layered double hydroxides (LDH) is here considered. The additives have been dispersed in the polymer by melt compounding, commonly used in the plastic industry. Several composites of PLA (4032D) and LDH intercalated with organic acids (succinic, fumaric, and ascorbic acid) have been obtained by an extrusion process. From all extruded materials, PLA films obtained by compression molding were then subjected to hydrolysis tests. The results showed that the mentioned molecules, dispersed in the polymer, are able to control the rate of hydrolysis, and experimental results show an increase of degradation time for samples containing LDH-organic acid (in particular with LDH-succinic acid), making such hybrid additives an appropriate and efficient solution for PLA
Modulating poly(lactic acid) degradation rate for environmentally sustainable applications
No full textThe huge amount of plastics generated by the massive use of packaging makes it difficult to manage waste safely. Introducing biodegradable polymers, such as poly(lactic acid) (PLA), can at least partially reduce the environmental pollution from plastic waste. Biodegradable polymers must have a degradation rate appropriate for the intended use to replace durable plastics. This work aims to introduce PLA fillers that can modulate the degradation rate during hydrolysis and composting. For this purpose, fumaric acid and magnesium hydroxide have been proposed. The experimental findings demonstrated that magnesium oxide makes hydrolysis faster than fumaric acid. A model describing the hydrolysis reaction, which also considers the effect of crystallinity, is proposed. The model can capture the filler effect on the kinetic constants related to the autocatalytic part of the hydrolysis reaction. Degradation of the PLA and compounds was also conducted in a composting medium. The compound with fumaric acid shows faster degradation than the compound with magnesium oxide; this behavior is opposite to what is observed during hydrolysis. Degradation in a composting medium is favored in a narrow pH window corresponding to the optimum environment for microorganism growth. Magnesium oxide leads to a pH increase above the optimum level, making the environment less favorable to microorganism growth. Vice-versa, fumaric acid maintains the pH level in the optimum range: it represents an additional carbon source for microorganism growth
Tuning the Hydrolytic Degradation Rate of Poly-Lactic Acid (PLA) to more Durable Applications
No full text
Tuning the hydrolytic degradation rate of poly-lactic acid (PLA) to more durable applications
No full textThe disposal of polymeric waste is increasingly becoming an issue of international concern. The use of biodegradable polymers is a possible strategy to face most of the problems related to the disposal of the durable (non-biodegradable) polymers. Among biodegradable polymers, PLA (obtained from renewable sources) is a very attractive one, due to its good processability, biocompatibility, interesting physical properties. Hydrolysis is the major depolymerisation mechanism and the rate-controlling step of PLA biodegradation in compost. The propensity to degradation in the presence of water significantly limits specific industrial applications such as automobile, biomedical, electronic and electrical appliances, agriculture. Therefore the control of biodegradation rate is somewhat even more important than the characteristic of biodegradability itself. This is the reason why it is critical to find additives able to modulate the biodegradation rate of biodegradable polymers in relationship to the expected lifetime. Since the kinetics of hydrolysis strongly depend on the pH of the hydrolyzing medium, in this work some fillers able to control the pH of water when it diffuses inside the polymer were added to PLA. In particular, fumaric acid, a bio- and eco-friendly additive, was used. In order to control the dispersion of this molecule inside the polymer, it was intercalated in a biocompatible nanofiller: layered double hydroxides (LDH). These fillers were added to the material using melt-compounding technique, suitable for industrial application. The preliminary results obtained are encouraging toward the possibility of effectively controlling the degradation rate
PLA-based nanobiocomposites with modulated biodegradation rate
No full textThe disposal of polymeric waste is increasingly becoming an issue of international concern. The use of biodegradable polymers is a possible strategy to face most of the problems related to the disposal of the durable (non-biodegradable) polymers. Among biodegradable polymers, polylactic acid (PLA), obtained from renewable sources, is a very attractive one, due to its relatively good processability, biocompatibility, interesting physical properties. Hydrolysis is the major depolymerization mechanism and the rate-controlling step of PLA biodegradation in compost. The propensity to degradation in the presence of water significantly limits specific industrial applications such as automotive, biomedical, electronic and electrical appliances, agriculture. Therefore the control of biodegradation rate is somewhat even more important than the characteristic of biodegradability itself. In this scenario, it is critical to find additives able to modulate the biodegradation rate of biodegradable polymers, in relationship to the expected lifetime. Since the kinetics of hydrolysis strongly depend on the pH of the hydrolyzing medium, in this work some fillers able to control the pH of water when it diffuses inside the polymer were added to PLA. In particular, fumaric acid, a bio- and eco- friendly additive, and magnesium hydroxide, a common antiacid, were used. These fillers were added to the material using a melt-compounding technique, suitable for industrial application. The results obtained are encouraging toward the possibility of effectively controlling the degradation rate
PLA-based bionanocomposites with modulated degradation rate: preparation and processing by microinjection molding
Full text link2016 - 2017The aim of this work has been to obtain bionanocomposites with a degradation rate which can be modulated in time, so that it can be possible to decide a priori the time after which the material will disappear in a given environment. At the same time, the material should preserve its properties during processing.
Several mixtures of PLA (4032D, 4060D) and LDH of cation composition Mg2Al organo-modified with organic acids (succinc, fumaric and ascorbic acid) have been obtained by extrusion. From the extruded materials there were obtained films by compression molding; these films were then subjected to hydrolysis tests. The experimental results show that for samples loaded with LDH-organic acid (in particular LDH-succinic acid), there is an increase in the time needed for degradation, and a decrease in this time for samples loaded with organic acid alone.
From the selected material (PLA + LDH-succinic acid) and from pure PLA, biphasic samples (half amorphous and the other half crystalline) have been obtained by micro-injection molding. Also in this case, the experimental results show an increase for the loaded samples in the time needed for degradation compared to pure PLA both for the crystal phase and for the amorphous one, and in particular the presence of a degradation profile within the same sample is observed. [edited by Author]XVI n.s. (XXX ciclo
PLA melt stabilization by high-surface-area graphite and carbon black
Full text linkSmall 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
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