Future plastic materials will be very different from those that are used today The increasing importance of sustainability promotes the development of bio-based and biodegradable polymers, sometimes misleadingly referred to as ‘bioplastics’ Because both terms imply “green” sources and “clean” removal, this paper aims at critically discussing the sometimes-conflicting terminology as well as renewable sources with a special focus on the degradation of these polymers in natural environments With regard to the former we review innovations in feedstock development (eg microalgae and food wastes) In terms of the latter, we highlight the effects that polymer structure, additives, and environmental variables have on plastic biodegradability We argue that the ‘biodegradable’ end-product does not necessarily degrade once emitted to the environment because chemical additives used to make them fit for purpose will increase the longevity In the future, this trend may continue as the plastics industry also is expected to be a major user of nanocomposites Overall, there is a need to assess the performance of polymer innovations in terms of their biodegradability especially under realistic waste management and environmental conditions, to avoid the unwanted release of plastic degradation products in receiving environments

Environmental performance of bio-based and biodegradable plastics: the road ahead

The current global plastics economy is highly linear, with the exceptional performance and low carbon footprint of polymeric materials at odds with dramatic increases in plastic waste. Transitioning to a circular economy that retains plastic in its highest value condition is essential to reduce environmental impacts, promoting reduction, reuse, and recycling. Mechanical recycling is an essential tool in an environmentally and economically sustainable economy of plastics, but current mechanical recycling processes are limited by cost, degradation of mechanical properties, and inconsistent quality products. This review covers the current methods and challenges for the mechanical recycling of the five main packaging plastics: poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) through the lens of a circular economy. Their reprocessing induced degradation mechanisms are introduced and strategies to improve their recycling are discussed. Additionally, this review briefly examines approaches to improve polymer blending in mixed plastic waste streams and applications of lower quality recyclate.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/marc.202000415

Mechanical Recycling of Packaging Plastics: A Review.

Carbon black: a promising electrode material for sodium-ion batteries

As the polymer industry evolved, considerable effort was made to understand the degradation processes of high polymers during weathering and ways were found to inhibit or at least retard their chemical modification and loss of their physical and mechanical properties. Weathering is particularly severe for polymers because it combines the photophysical and photochemical effects of ultraviolet radiation with oxidative and hydrolytic effects of the outdoor environment. This article discusses photo-oxidation degradation (the behavior of polymers as a result of outdoor factors) and mainly concentrates on the photo-oxidative degradation of polyolefins and poly(vinyl) chloride. Polymer photostabilization with ultraviolet screeners, quenchers, hydroperoxide decomposers, and radical scavengers is also described.

Polymer Weathering: Photo-Oxidation

The degradation study of the membrane electrode assembly (MEA) for proton exchange membrane fuel cells (PEMFCs) under low humidity conditions was conducted. The MEA degradation was observed during low humidity open-circuit voltage tests. To investigate the degradation mechanism, we conducted electron spin resonance studies of the degenerated MEA, and confirmed the formation of radicals in the catalyst layers. The MEA degradation mechanism that includes the radical formation reaction was verified. © 2004 The Electrochemical Society. All rights reserved.

https://iopscience.iop.org/article/10.1149/1.1739314/pdf

Degradation study of MEA for PEMFCs under low humidity conditions

Studies of synergism between carbon black and stabilisers in LDPE photodegradation

Interactions between carbon black and stabilisers in LDPE thermal oxidation

The surface activity of different types of carbon black with phenolic antioxidants is examined using flow micro-calorimetry (FMC), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FTIR). Significant differences in both the overall adsorption activity and the levels of probe adsorption are observed. Differences in behaviour between types of carbon black are evident and show that the specific surface area is not the most important factor affecting the adsorption activity, but also the chemical nature of its surface. Essentially, two factors were found to affect the behaviour of phenolic stabilisers: Phenolic hydroxyl and ester groups were found to form the strongest interactions with carbon black. Furthermore, steric hinderance of phenolic hydroxyls by alkyl groups is the main factor which influences adsorption activity. In order to characterise different carbon blacks, FTIR and XPS analysis have been used in an attempt to determine the nature of functional groups present on the surface of the carbon blacks. FTIR analysis also shows that some adsorbed antioxidants on the surface of the carbon black could be successfully detected. This provides valuable information regarding the adsorption mechanisms on to carbon black surfaces. Other techniques included thermogravimetric analysis (TGA), N2 BET adsorption studies and Karl Fisher analysis. The latter were performed in order to determine differences in the volatile and water contents, respectively, of the carbon black samples.

Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry and FTIR studies) Part I Primary phenolic antioxidants

Analysis of radical content on carbon black pigments by electron spin resonance: influence of functionality, thermal treatment and adsorption of acidic and basic probes

The interaction of hindered piperidine light stabilisers (HALS) with carbon black has been examined using flow micro-calorimetry (FMC) and Fourier transform infrared spectroscopy (FTIR). Significant differences in both the overall adsorption activity and molar heats of probe adsorption are observed. Differences in adsorption behaviour between different types of carbon black were clearly evident and, as with a previous paper (see reference 1, in the latter paper, surface chemistry of the carbon blacks investigated is extensively analysed by XPS, FTIR, N2 BET adsorption and Karl–Fischer analysis), were mainly to be due to differences in carbon black surface chemistry. The specific surface area merely physically affected the level and heat of adsorption (per unit mass of carbon black). Variation in the degree of substitution of the piperidine amine is an important factor that is found to influence the adsorption activity of HALS, as well as the number of adsorption active and sterically accessible functional groups per HALS molecule. In some cases the adsorbed HALS could be detected by FTIR; shifts in absorption frequencies associated with both the adsorbate and the substrate yielded significant insight into the mode of adsorption of several of the HALS investigated.

J.M. Peña

Papers

Studies of synergism between carbon black and stabilisers in LDPE photodegradation

Interactions between carbon black and stabilisers in LDPE thermal oxidation

Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry and FTIR studies) Part I Primary phenolic antioxidants

Analysis of radical content on carbon black pigments by electron spin resonance: influence of functionality, thermal treatment and adsorption of acidic and basic probes

Factors affecting the adsorption of stabilisers on to carbon black (flow micro-calorimetry studies): Part II : Hindered amine light stabilisers (HALS)