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217. Super‐Elastic and Dimensionally Stable Polyether Block Amide Foams Fabricated by Microcellular Foaming with CO2&N2 as Co‐Blowing Agents.

Author

Yang, Haoqing, Dong, Guiwei, Wang, Guilong, Zhao, Jinchuan, and Zhao, Guoqun

Subjects
FOAM, BLOWING agents, SURFACE active agents, THERMOPLASTIC elastomers, ATMOSPHERIC pressure
Abstract

Polyether block amide (PEBA) is an important thermoplastic polyester elastomer (TPE) owing to its low density and high resilience. Microcellular foaming can endow PEBA with significant potential in sports, medical, and industrial applications. However, with the current microcellular foaming technology, it remains challenging to obtain PEBA foams with stable shapes, which are critical for their mechanical properties. Therefore, microcellular foaming with CO2 and N2 as co‐blowing agents is utilized in this study to achieve mechanically robust PEBA foams by reducing the dimensional shrinkage. The introduction of N2 can effectively slow the diffusion rate of blowing agents into the air, providing support for the foam to resist external atmospheric pressure and effectively reducing the dimensional shrinkage of PEBA foams. Consequently, a stable foam shape is achieved with an expansion ratio of 7.9. Finally, the PEBA foams with excellent shrinkage resistance and mechanical properties are prepared, and the cell shrinkage mechanism is analyzed to study the effects of blowing agents and foaming methods on the structural evolution of TPE foams. This promising outcome paves way for their practical industrial applications. [ABSTRACT FROM AUTHOR]

Published
2024
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218. Effects of Temperature on the Quality of Vacuum Concentrated Pear Juice and Construction of Quality Evaluation Model.

Author

YIN Ziying, ZHAO Jiangli, LIU Jinlong, ZHAO Guoqun, and GUAN Junfeng

Subjects
PEARS, VACUUM packaging, TEMPERATURE effect, FUMARATES, QUINIC acid, MALIC acid
Abstract

Objective: To compare the quality of vacuum concentrated pear juice at different temperatures and construct a quality evaluation method for concentrated pear juice. Method: Fresh pear juice was concentrated under decompression condition (vacuum degree 0.005 MPa) at concentration temperatures of 50, 60, 70 and 80 °C, respectively. The evaluation model of concentrated pear juice was constructed based on the browning degree, pH, total phenolic content, total flavonoid content, Fe3+ reducing power, soluble sugar, organic acid and volatile components of the concentrated pear juice. Results: The content of tartaric acid, fumaric acid and pH decreased significantly with the increasing temperature, while the browning degree, total phenolic content, total flavonoid content, Fe3+ reducing power, quinic acid, malic acid, citric acid increased significantly. The content of alcohols was the highest in concentrated pear juice of 50 °C (4.753 μg/mL), the esters was the highest in concentrated pear juice of 70 °C (2.808 μg/mL), the aldehydes and ketones were the highest in concentrated pear juice of 70 °C (12.478 μg/mL). This study obtained a model for evaluating the quality of concentrated pear juice and found that 70 °C was best vacuum concentration temperature for pear juice. Conclusion: The vacuum concentration temperature could affect the quality of concentrated pear juice, which could be well distinguished by the quality evaluation model. This study would provide references for the quality control of vacuum concentrated pear juice. [ABSTRACT FROM AUTHOR]

Published
2024
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