No abstract

Poly(lactic acid) (PLA) was plasticized with ester oligomers having different structure, molecular weight and carboxylic acid content as end‐functionalities. In particular PLA oligomers and a low‐molecular‐weight polyester of adipic acid and 1,2‐propanediol (an adipate‐based derivative) were used and compared. The plasticizing capability was tested and the final structural and thermal properties of PLA matrix were evaluated by correlating the various features to the chemical and physical characteristics of these additives. SEC, DSC, TGA, tensile tests, XRD and SEM results, even after annealing, were collected, and the related data analysed and evaluated with reference to additive starting properties. All the oligoesters were able to generate flexible compounds, but PLA oligomers provided mixtures with reduced structural and thermal stability. Finally, the best performing blend was tested for biodegradability to definitely assess the material suitability for the final application (sustainable packaging). © 2017 Society of Chemical Industry

In this paper, we present two novel experimental setups specifically designed to perform in situ long-term monitoring of the aging behaviour of commercial plastic granules (HDPE, PP, PLA and PBAT). The results of the first six months of a three year monitoring campaign are presented. The two experimental setups consist of: (i) special cages positioned close to the sea floor at a depth of about 10 m, and (ii) a box containing sand exposed to atmospheric agents to simulate the surface of a beach. Starting from March 2020, plastic granules were put into the cages and plunged in sea water in two different locations in the sand boxes. Chemical spectroscopic and thermal analyses (GPC, SEM, FTIR-ATR, DSC, TGA) were performed on the granules before and after exposure to natural elements for six months, in order to identify the physical-chemical modifications occurring in marine environmental conditions (both in seawater and in sandy coastal conditions). Changes in colour, surface morphology, chemical composition, thermal properties and molecular weight, and the polydispersity of the materials, showed the different influences of the environmental conditions. Photooxidative reaction pathways were prevalent in the sandbox. Abrasive phenomena acted specially in the sea environment. PLA and PBAT did not show significant degradation after six months, making the possible reduction of marine pollution due to this process negligible.

Polyvinyl butyral (PVB) is an amorphous polymer employed in many technological applications. In order to highlight the relationships between macroscopic properties and dynamics at a microscopic level, motions of the main-chain and of the propyl side-chains were investigated between Tg − 288 °C and Tg + 55 °C, with Tg indicating the glass transition temperature. To this aim, a combination of solid state Nuclear Magnetic Resonance (NMR) methods was applied to two purposely synthesized PVB isotopomers: one fully protonated and the other perdeuterated on the side-chains. 1H time domain NMR and 1H field cycling NMR relaxometry experiments, performed across and above Tg, revealed that the dynamics of the main-chain corresponds to the α-relaxation associated to the glass transition, which was previously characterized by dielectric spectroscopy. A faster secondary relaxation was observed for the first time and ascribed to side-chains. The geometry and rate of motions of the different groups in the side-chains were characterized below Tg by 2H NMR spectroscopy.