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Aging of polyamide 11. Part 1: Evaluating degradation by thermal,mechanical, and viscometric analysis 下载免费PDF全文
Hydrolytic degradation at elevated temperatures is a key reason for failure in offshore flexible risers. In this article, the aging of polyamide 11 in deoxygenated water at 90°C and 120°C was studied. Tensile and dynamic mechanical thermal analysis tests were performed to measure changes in mechanical properties. Viscometry, gravimetric measurements, differential scanning calorimetry, and thermogravimetric analysis were used to link these properties with morphological changes. General trends are increased stiffness, tensile strength, and glass transition temperature as well as decreased glassy state damping efficiency with increased aging times. Changes can be initially ascribed to plasticizer depletion and then to interplay between molecular weight decrease and crystallinity increase. Viscosity at hydrolysis equilibrium indicates that brittle failure typically involves oxidation or UV exposure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41971. 相似文献
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Didar Sevim Oya Köseoğlu Hasan Ertaş Durmuş Özdemir Mehmet Ulaş Salih Günnaz Veysel Umut Çelenk 《Journal of the American Oil Chemists' Society》2023,100(5):355-367
Isotope ratio mass spectroscopy (IRMS) and nuclear magnetic resonance (NMR) spectroscopy techniques are two of the analytical methods that are used to characterize food products. The aim of this study is to classify extra virgin olive oil (EVOO) samples collected from different regions of Turkey based on 1H and 13C NMR spectra along with IRMS δ13C carbon isotope ratio data by using chemometrics multivariate data analysis methods. A total of 175 EVOO samples were analyzed in 2014/15 and 2015/16 harvest seasons. Multivariate classification and clustering models were used to identify geographical and botanical origins of the EVOOs. IRMS results showed that there was no significant difference in terms of δ13C values between the years in terms of harvest year (p > 0.05), only extraction phase and variety were statistically significant factors (p < 0.05). The interactions of the factors showed that the harvest year × variety interaction is important. The outcomes of this research clearly indicated that considering the partial least squares discriminant analysis result with NMR spectra, the percent success of the model in the South Marmara, North Aegean, and South Aegean region samples were 95%, 95.7%, and 96.4% in the model set, respectively. The results showed that by using classification and clustering models, geographic marking and labeling of these oils can be carried out regardless of differences in year and production systems (2 and 3 phase extraction system) according the NMR analysis. 相似文献