Norner (Norway)

Abstract Biocatalytic degradation of non-hydrolyzable plastics is a rapidly growing field of research, driven by the global accumulation of waste. Enzymes capable of cleaving the carbon-carbon bonds in synthetic polymers are highly sought-after as they may provide tools for environmentally friendly plastic recycling. Despite some reports of oxidative enzymes acting on non-hydrolyzable plastics, including polyethylene or poly(vinyl chloride), the notion that these materials are susceptible to efficient enzymatic degradation remains controversial, partly driven by a general lack of studies independently reproducing previous observations. We attempted to replicate two recent studies reporting that deconstruction of polyethylene and poly(vinyl chloride) can be achieved using an insect hexamerin from Galleria mellonella (so-called “Ceres”) or a bacterial catalase-peroxidase from Klebsiella sp. , respectively. Reproducing previously described experiments with the recombinant proteins, we did not observe any activity on plastics using multiple reaction conditions and multiple substrate types. Digging deeper into the discrepancies between the previous data and our observations, we show how and why the original experimental results may have been misinterpreted, leading to the erroneous claim that enzymatic deconstruction of polyethylene and poly(vinyl chloride) had occurred. Our results should lead to caution when interpreting the growing amount of literature claiming enzymatic degradation of non-hydrolyzable plastics.

How to deal with plastic waste is an important question, as it may affect both the climate and environment. A method that may be beneficial to dispose some kinds of plastic waste that cannot be material-recycled is thermochemical conversion and, more specifically, pyrolysis. To be able to optimize such a process models are important. This paper describes the results of a study where the main aim was to identify and compare existing published models identifying the important variables regarding the pyrolysis of Polyethylene (PE) and Polypropylene (PP), published in open literature, and to compare these methods with experimental data. Several models were found, of which three were chosen for implementation and further evaluation.

We present an alternative polymer modification of poly (propylene carbonate) (PPC). A conventional practice for PPC melt processing is the melt - modification with maleic anhydride (MAH) - a di-carboxylic anhydride -. In our work, PPC is melt-modified with pyromellitic di-anhydride (PDAH) - a tetra-carboxylic dianhydride -. Using MAH modified PPC as reference, the polymer degradation and the thermal and viscoelastic properties of the materials are studied. Both anhydrides after their melt compounding have similar efficiency in the conservation of the molecular weight. Strikingly, the use of PDAH is advantageous over MAH considering the improvement of the thermal stability, the decrease of the complex melt viscosity and higher storage modulus (stiffness) of the modified PPC. It is speculated that the changes in the material performance arise from the occurrence of long chain branching and non-covalent interactions from the PDAH modifier.

Approximate analytic expressions for haze (and gloss) of Gaussian randomly rough surfaces for various types of correlation functions are derived within phase-perturbation theory. The approximations depend on the angle of incidence, polarization of the incident light, the surface roughness, $\ensuremath{\sigma}$, and the average of the power spectrum taken over a small angular interval about the specular direction. In particular it is demonstrated that haze (gloss) increase (decrease) with $\ensuremath{\sigma}/\ensuremath{\lambda}$ as $\text{exp}[\ensuremath{-}A{(\ensuremath{\sigma}/\ensuremath{\lambda})}^{2}]$ and decreases (increase) with $a/\ensuremath{\lambda}$, where $a$ is the correlation length of the surface roughness, in a way that depends on the specific form of the correlation function being considered. These approximations are compared to what can be obtained from a rigorous Monte Carlo simulation approach, and a good agreement is found over large regions of parameter space. Some experimental results for the angular distribution of the transmitted light through polymer films and their haze are presented and compared to the analytic approximations derived in this paper. A satisfactory agreement is found. In the literature haze of blown polyethylene films has been related to surface roughness. Few authors have quantified the roughness and others have pointed to the difficulty in finding the correct roughness measure.

Pharmaceutical trade-marks function as symbols and essential lines of scientific research and progress of medical science. Protection laws for trade-mark rights in foreign countries and United States against infringement, misappropriation, and piracy are discussed. International conventions contain valuable stipulations to harmonize conflicts of law to protect the rightful owner. Transformation of trade-marks into generic names are to be avoided.