Polymer Degradation through Chemical Change: A Quantum-based Test of Inferred Reactions in Irradiated Polydimethylsiloxane

Chemical reaction schemes are key conceptual tools for interpreting the results of experiments and simulations, but often carry implicit assumptions that remain largely unverified for complicated systems. Established schemes for chemical damage through crosslinking in irradiated silicone polymers comprised of polydimethylsiloxane (PDMS) date to the 1950's and correlate small-molecule off-gassing with specific crosslink features. In this regard, we use a somewhat reductionist model to develop a general conditional probability and correlation analysis approach that tests these types of causal connections between proposed experimental observables to reexamine this chemistry through quantum-based molecular dynamics (QMD) simulations. Analysis of the QMD simulations suggests that the established reaction schemes are qualitatively reasonable, but lack strong causal connections under a broad set of conditions that would enable making direct quantitative connections between off-gassing and crosslinking. Further assessment of the QMD data uncovers a strong (but nonideal) quantitative connection between exceptionally hard-to-measure chain scission events and the formation of silanol (Si-OH) groups. Our analysis indicates that conventional notions of radiation damage to PDMS should be further qualified and not necessarily used ad hoc. In addition, our efforts enable independent quantum-based tests that can inform confidence in assumed connections between experimental observables without the burden of fully elucidating entire reaction networks.

LIGNOCELLULOSE WASTE VALORIZATION BY AN ENZYMATIC COCKTAIL OF P. ERYNGII AND P. PULMONARIUS

The present study aimed to characterize Pleurotus eryngii and P. pulmonarius ligninolytic enzymes and to determine their potential for polymer degradation in common agroforestry residues. The peak of laccase activity (36052.33 U L-1) was observed after P. pulmonarius cultivation on oak sawdust. The maximal Mn-dependent peroxidase activity was reached by P. eryngii (2511.36 U L-1), while the highest level of versatile peroxidase activity was noted in P. pulmonarius (3053.03 U L-1), after fermentation of corn stalks. The highest level of lignin loss (46.28%) was achieved after cultivation of P. pulmonarius on corn stalks, but the most selective degradation of lignocellulose polymers was observed after P. eryngii cultivation on wheat straw. The obtained results lead to the conclusion that the studied P. eryngii and P. pulmonarius strains are good producers of ligninolytic enzymes and effective and selective depolymerizers of agroforestry residues, and therefore their use would be beneficial in numerous environmentally friendly technologies.

Improvement of the wear resistance and energy efficiency of heavy-loaded metal-polymer transport tribosystems

The article describes the phenomena of electrification, and their effect on the processes of diffusion of polymer degradation products into metal surfaces in metal-polymer tribosystems, as well as the formation of secondary structures during friction. New methods of measuring tribo IV (tribo Internal Voltage) and the results of studies of various groups of materials are presented. The conducted studies made it possible, by combining multipolar polymer materials from fillers and nanoscale additives in the composite, to increase the wear resistance of heavily loaded metal-polymer tribosystems. For metal surfaces it was carried out by friction delivery of reinforcing elements to their surface layers, for polymer composites it was based on the developed technology of their modification, the formation of secondary surface structures in the process of metal-polymer friction was carried out.

Evaluation of Microalgae’s Plastic Biodeterioration Property by a Consortium of Chlorella sp. and Cyanobacteria sp.

Malaysia is one of the top eight countries that has a drawback of mismanaged plastic waste. This study intended to investigate polymer degradation using the biological technique with the help of microalgae to minimise the time required for biodegradation. This research article aims to identify the collected sample with the most suitable microalgae for the biodegradation of microplastic and to analyse the biodegradation of the polymer by microalgae. The results revealed that the consortium of Chlorella sp. and Cyanobacteria sp. were able to deteriorate low-density polyethene (LDPE sample) through several stages, and this was confirmed by UV-Spec, FESEM, EDX, CHNO, FTIR and DSC analysis. The results obtained revealed that microalgae producing exopolysaccharides (EPS) decreased the carbon and oxygen ratio. According to SEM micrographs, microalga may colonise, agglomerate, and adhere microplastics to its surface, regardless of its fractional size. The EDX analysis showed that the initial composition of carbon was 92.30 ± 1.23 %, while after the incubation, the carbon composition started decreasing from 53.18 % to 39.12 ± 1.08 %. Finally, there was a 37.91 % decrease in carbon weight from elemental analysise

Mangala Polymer Flood Performance: Connecting the Dots Through in Situ Polymer Sampling

The paper describes the in-situ polymer sampling in Mangala which helped explain the performance of a large polymer flood in Mangala field in India. The Mangala field contains medium-gravity viscous crude oil. Notably, it is the largest polymer flood in India and 34% of the STOIIP has been produced in 11 years of production. Mangala was put on full field polymer flood in 2015, six years after the start of field production on water flood in 2009. Polymer flood added 93 million barrels above the anticipated water flood recovery in 6 years. Reservoir simulation models could replicate the initial Mangala polymer flood performance. However, the performance of the lower layers of Mangala (FM-3 and FM-4) continued to progressively deviate from modeling estimates. Equally importantly, the prediction of polymer breakthrough deviated significantly from modeling estimates. After 6 years and 0.7 pore volumes of polymer injection, it is apparent that field performance is equivalent to only 50-60% of the viscosity of the polymer injected at the surface. To better understand and quantify the nature and extent of polymer degradation it is necessary to gather representative down hole samples of polymer which has stayed in the reservoir conditions for a considerable length of time. Accelerated ageing studies in the lab showed HPAM can lose viscosity and precipitate after prolonged exposure to Mangala reservoir conditions with an increase in the degree of hydrolysis as the primary reason for the degradation. The concept of transfer function based on first order kinetics was used to extrapolate the laboratory results to Mangala reservoir temperatures. To test the hypothesis, a multi-disciplinary team implemented a plan to gather a representative polymer sample from the reservoir. The polymer sample had been in the reservoir for nearly 120 days and was captured in low shear and anaerobic conditions to minimize shear and oxidative degradation. The sample was tested for degree of hydrolysis by NMR method. The results confirmed that the level of hydrolysis of the injected HPAM did increase in the reservoir leading to lower viscosity and reduced lower amide concentration. Preliminary simulation studies using the concept of viscosity half-life were used to mimic the polymer degradation with time in the reservoir. The method is quite a simplistic representation of the thermal degradation, but it significantly improved the model's water cut predictions for lower layers and the full field polymer breakthrough predictions. The impact of polymer precipitation in the reservoir on the permeability is under study and it will drive the next phase of more detailed modeling.