Accelerated ageing of polylactide in aqueous environments: Comparative study between distilled water and seawater

Abstract

Pollution of nature by plastics is a major environmental problem and the challenge for the future is to manage the lifetime of polymers better. The aim of this study is to establish a baseline on degradation mechanism and degradation kinetics for lifetime prediction of polylactide (PLA) in a marine environment. The ageing of PLA was accelerated by raising temperature in distilled water, filtered and renewed seawater and natural seawater. Samples were immersed in distilled water for six months at different temperatures (25, 30, 40 and 50°C) in order to evaluate the influence of temperature on PLA degradation kinetics and to predict lifetime. Then, samples were immersed in seawater both in the laboratory and at sea, in order to compare the effects of environment, marine organisms and salt, on degradation. The different degradation steps were followed by gravimetry, tensile tests, scanning electron microscopy (SEM), steric exclusion chromatography (SEC) and differential scanning calorimetry (DSC). In distilled water, accelerated ageing of PLA is complex with deviation from Fickian behaviour at higher temperature. Moreover, immersion in distilled water induces morphological changes, in particular holes, which are absent in seawater at 40°C for the same immersion time. Indeed, seawater has little impact on the diffusion kinetics but affects M ∞ values, which are slightly lower compare to the distilled water uptake.

Environmental degradability of polycaprolactone under natural conditions

“…The very small changes of weight might be explained by very slow nonenzymatic hydrolytic ester cleavage, what is complied with literature reports that the hydrolytic degradation of PCL is slow because of its hydrophobic nature [23]. One reason of slightly higher weight losses of PCL after incubation in pond water with NaN3 is the lack of mineral salts which facilitates the diffusion of water within the polymer [24]. Salt contents in laboratory sea water probably have an influence on slow chemical hydrolysis of PCL during incubation in this environment.…”

Mechanical Recycling of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Polylactide Based Blends

“…The specimen was a thin rectangular strip with dimensions around 30 9 6 9 2 (mm) 3 prepared from the compression molded. A temperature scan from -40°C up to 150°C was performed at the rate of 3°C min -1 while a dynamic tensile test was performed at a frequency of 1 Hz with amplitude of 10 lm.…”

“…Biopolymers have generated great interest in this decade due to rapid growth in consumer awareness and stricter government regulation of municipal waste [1][2][3]. Biodegradable polymers derived from renewable resources have attracted increasing attention due to the great demand in biomedical field, including resorbable sutures, drug delivery systems, tissue scaffolds [4] and also for food packaging applications [5,6].…”

Estudo da influência do condicionamento higrotérmico nas propriedades viscoelásticas de compósitos termoplásticos

“…A maioria dos compósitos utilizados atualmente é constituída de matrizes termorrígidas que apresentam problemas de tensões em virtude do processamento e da natureza quebradiça da resina, falta de resistência à erosão e, quando aquecidos, podem apresentar mudanças químicas e estruturais limitando sua aplicação em algumas regiões de maior temperatura de serviço e não podem ser reciclados devido à presença de ligações cruzadas. Entretanto, os polímeros termoplásticos reforçados com fibras contínuas vêm se mostrando importantes substitutos aos termorrígidos e conquistando uma grande versatilidade de aplicações [6,7] . Atualmente, muita atenção vem sendo dada à utilização de compósitos termoplásticos para aplicações estruturais, podendo ser citados o PEI (poli(éter-imida)), o PEKK (poli(éter-cetona-cetona)), o PEEK (poli(éter-éter-cetona)) e o PPS (poli(sulfeto de fenileno)), todos reforçados com fibras de vidro ou carbono [7,8] .…”

“…Entretanto, os polímeros termoplásticos reforçados com fibras contínuas vêm se mostrando importantes substitutos aos termorrígidos e conquistando uma grande versatilidade de aplicações [6,7] . Atualmente, muita atenção vem sendo dada à utilização de compósitos termoplásticos para aplicações estruturais, podendo ser citados o PEI (poli(éter-imida)), o PEKK (poli(éter-cetona-cetona)), o PEEK (poli(éter-éter-cetona)) e o PPS (poli(sulfeto de fenileno)), todos reforçados com fibras de vidro ou carbono [7,8] .…”