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An Effective Package of Antioxidants for Avoiding Premature Failure in Polypropylene Random Copolymer Plastic Pipes under Hydrostatic Pressure and High Temperature.

ABSTRACT: Pipes of polypropylene random (PP-R) copolymers are the best choice for hot- and cold-water networks. Validation of a severe test, accomplishing the ISO 1167 standard, is mandatory to assess their service lifetime expectancy. This work evaluates the behavior shown by three commercial pipes, either the original ones (new pipes) or after being subjected to a hydrostatic pressure test at elevated temperature (aged pipes). Several features with relevance for the final performance have been examined: crystalline characteristics, phase transitions in crystalline regions, effect of high temperature and pressure on these transitions, and oxidation induction time. Moreover, the presence of inorganic fillers, and the content of different antioxidants together with their depletion, have also been analyzed. Films from the new pipes were also prepared for replication of the different environments in order to achieve a better and complete understanding of the phase transitions in the crystalline regions and of the consumption of antioxidants. Distinct environments surrounded the inner and outer parts of the pipes exposed to the failure aging test at 110 °C: hot water and warm dry air, respectively. These features play a key role in the loss of additives and in the subsequent initiation of degradation. Even if the crystalline characteristics are appropriate in the polymeric matrix, the success of a pipe lies in the homogeneous dispersion of components for avoiding damage at interfacial properties, and in a correct package of antioxidants used in its formulation.

SUBMITTER: Blazquez-Blazquez E

PROVIDER: S-EPMC8400617 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Food waste is a promising resource for the production of fuels and chemicals. However, increasing plastic contamination has a large impact on the efficiency of conversion for the more established biological routes such as anaerobic digestion or fermentation. Here, we assessed a novel route through the hydrothermal liquefaction (HTL) of a model waste (pistachio hulls) and polypropylene (PP). Pure pistachio hulls gave a biocrude yield of 34% (w/w), though this reduced to 16% (w/w) on the addition of 50% PP in the mixture. The crude composition was a complex blend of phenolics, alkanes, carboxylic acids, and other oxygenates, which did not change substantially on the addition of PP. Pure PP does not breakdown at all under HTL conditions (350 °C, 15% solids loading), and even with biomass, there is only a small synergistic effect resulting in a conversion of 19% PP. This conversion was enhanced through using typical HTL catalysts including Fe, FeSO4·7H2O, MgSO4·H2O, ZnSO4·7H2O, ZSM-5, aluminosilicate, Y-zeolite, and Na2CO3; the conversion of PP reached a maximum of 38% with the aluminosilicate, for example. However, the PP almost exclusively broke down into a solid-phase product, with no enhancement of the biocrude fraction. The mechanism was explored, and with the addition of the radical scavenger butylated hydroxytoluene (BHT), the conversion of plastic reduced substantially, demonstrating that radical formation is necessary. As a result, the plastic conversion was enhanced to over 50% through the addition of the co-solvent and hydrogen donor, formic acid, and the radical donor, hydrogen peroxide. The addition of formic acid also changed the crude composition, including more carboxylic acids and oxygenated species than the conversion of the biomass alone; however, the majority of the carbon distributed to the volatile organic gas fraction producing an array of short-chain volatile hydrocarbons, which potentially could be repolymerized as a polyolefin or combined with the biocrude for further processing. Catalytic HTL was therefore shown to be a promising method for the valorization of polyolefins with biomass under typical HTL conditions.

Project description:BackgroundMicrosatellite instability (MSI) is a common genomic alteration in colorectal cancer, endometrial carcinoma, and other solid tumors. MSI is characterized by a high degree of polymorphism in microsatellite lengths owing to the deficiency in the mismatch repair system. Based on the degree, MSI can be classified as microsatellite instability-high (MSI-H) and microsatellite stable (MSS). MSI is a predictive biomarker for immunotherapy efficacy in advanced/metastatic solid tumors, especially in colorectal cancer patients. Several computational approaches based on target panel sequencing data have been used to detect MSI; however, they are considerably affected by the sequencing depth and panel size.ResultsWe developed MSIFinder, a python package for automatic MSI classification, using random forest classifier (RFC)-based genome sequencing, which is a machine learning technology. We included 19 MSI-H and 25 MSS samples as training sets. First, we selected 54 feature markers from the training sets, built an RFC model, and validated the classifier using a test set comprising 21 MSI-H and 379 MSS samples. With this test set, MSIFinder achieved a sensitivity (recall) of 1.0, a specificity of 0.997, an accuracy of 0.998, a positive predictive value of 0.954, an F1 score of 0.977, and an area under the curve of 0.999. To further verify the robustness and effectiveness of the model, we used a prospective cohort consisting of 18 MSI-H samples and 122 MSS samples. MSIFinder achieved a sensitivity (recall) of 1.0 and a specificity of 1.0. We discovered that MSIFinder is less affected by a low sequencing depth and can achieve a concordance of 0.993 while exhibiting a sequencing depth of 100×. Furthermore, we realized that MSIFinder is less affected by the panel size and can achieve a concordance of 0.99 when the panel size is 0.5 M (million bases).ConclusionThese results indicate that MSIFinder is a robust and effective MSI classification tool that can provide reliable MSI detection for scientific and clinical purposes.

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An Effective Package of Antioxidants for Avoiding Premature Failure in Polypropylene Random Copolymer Plastic Pipes under Hydrostatic Pressure and High Temperature.

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