Search results for "Gradation"

Anti-/Pro-Oxidant Behavior of Naturally Occurring Molecules in Polymers and Biopolymers: A Brief Review

2019

Polymers and biopolymers are continuously subjected to the action of different stress factors, such as oxygen, heat, UV light, mechanical stress, humidity, etc., during their processing and service life, undergoing overall oxidative degradation, that causes performance and property deterioration. To improve the resistance at high temperatures and long-term weatherability of the polymers and biopolymers, usually, during their manufacturing, synthetic antioxidants and UV-light stabilizers are added. In the past decade, several concerns related to the impact of the synthetic stabilizers have emerged, and to reduce their negative effect on human health and the environment, their replacement wit…

Quercetin as natural stabilizing agent for bio-polymer

2014

The introduction of antioxidants in polymers is the main way to prevent or delay the degradation process. In particular natural antioxidants receive attention in the food industry also because of their presumed safety. In this work bio-polymers, i.e. a commercial starch-based polymer (Mater-Bi®) and a bio-polyester (PLA), and a bio-polyether (PEO) were additivated with quercetin, a natural flavonoid antioxidants, in order to formulate bio-based films for ecosustainable packaging and outdoor applications. The photo-oxidation behavior of unstabilized and quercetin stabilized films was analyzed and compared with the behavior of films additivated with a commercial synthetic light stabilizer. Th…

On new chemical reactions of polymers

1968

Three major areas of work present themselves to a chemist who is concerned with polymer materials namely: synthesis and degradation of polymers; structure analysis of natural and synthetic polymers; and chemical transformations of polymers. Although these three fields are very closely related, I wish to concern myself only with the last of them.

1987

Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester

2011

Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester Hantzsch ester synthesis was investigated using (2-hydroxyethyl)-ammonium carboxylates, polar and hydrophilic ionic liquids possessing low toxicity and high biodegradability. The reaction rates and yields of the products in ionic liquids were greater than those in common organic solvents. The relationship between the structure of the ionic liquid used and the structure of the heterocyclic compound was investigated.

AN ENZYME-ENHANCED EXTRACTION OF ANTHOCYANINS FROM RED CABBAGE AND THEIR THERMAL DEGRADATION KINETICS

2020

There is a great demand for developing efficient anthocyanins extraction related to each plant material. Conventional methods have been replaced by novel techniques, but they might remain attractive when combined with the latter. Anthocyanins extraction from fresh and dried red cabbage was investigated by maceration, ultrasonication, and with enzymes. Pre-treatments through drying determined an improved extraction with respect to fresh samples, freeze-drying emerging as the best method. Combined enzyme-assisted extraction with maceration resulted in higher yield by conducting several extractions (1078.8±12.5 mg/100 g DW). The kinetic studies revealed good stability of anthocyanins at 50 °C,…

Wastewater COD characterization: analysis of respirometric and physical-chemical methods for determining biodegradable organic matter fractions

2010

BACKGROUND: In this work, a comprehensive study of the respirometric and physical–chemical methods has been performed to evaluate the information provided by these two methodologies in order to assess the biodegradable organic matter fractions of wastewater. RESULTS: First, an analysis was performed of the influence of the initial substrate on biomass ratio (F0/X0) in the assessment of readily biodegradable organic matter, SS, through respirometric experiments. In order to achieve an adequate assessment of the SS component, similar conditions (given by the initial F0/X0 ratio) must be employed in experiments that are carried to determine SS and YH (heterotrophic yield). Second, a comparativ…

Polymeric scaffolds based on blends of poly-l-lactic acid (PLLA) with poly-d-l- lactic acid (PLA) prepared via thermally induced phase separation (TI…

2012

Porous scaffolds based on blends of high crystalline Poly-L-lactic acid (PLLA) with low crystalline poly-D-L-lactic acid (PLA) were prepared via Ther- mally Induced Phase Separation (TIPS), with the aim of exploring the possibility to control the degradation behaviour of the PLA-based scaffold, simultaneously pre- serving the morphological characteristics required for tissue engineering applica- tions. Porous foams with different PLLA/PLA weight ratios (from 95/5 to 60/40) were produced and characterised in terms of pore size, porosity, and thermal properties. The scaffolds present an open porosity, with average pore sizes ranging from 30 to 70 lm. Results showed that, when dealing with a P…

Sorption of Hydrocarbons on Peat, and Possibilities for Using Peat-Based Oil Sorbent for Treatment of Polluted Areas

2017

The growing use and transport of crude oil and oil products has led to an increasing amount of spillages of various scales. In the event of an oil spill, it is important to stop the spill from spreading and to clean up the polluted environment. One of the possible ways of treating the polluted areas is the use of oil sorbents. The sorbents used for collecting oil in case of oil spills are mostly synthetic, which limits the possibilities of their disposal. The aim of our study is to investigate the possible use of peat and its modification products for oil and other hydrocarbon sorption. Peat is a prospective material for oil sorption because it has such advantages as low cost, biodegradabil…

A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production

2014

Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at th…