Effect of CO2 exposure on free volumes in polystyrene studied by positron annihilation spectroscopy

被引：19

作者：

Chen, Hongmin ^{[1
]}

Cheng, Mei-Ling ^{[1
,2
]}

Jean, Y. C. ^{[1
,3
]}

Lee, L. James ^{[4
]}

Yang, Jintao ^{[4
]}

机构：

[1] Univ Missouri, Dept Chem, Kansas City, MO 64110 USA

[2] Yuan Ze Univ, Dept Chem Engn & Mat Sci, Chungli 320, Taiwan

[3] Chung Yuan Christian Univ, Ctr Membrane Technol, Chungli 320, Taiwan

[4] Ohio State Univ, Dept Chem & Biomol Engn, Columbus, OH 43210 USA

来源：

JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS | 2008年 / 46卷 / 04期

关键词：

absorption; free volume; glass transition; polystyrene; positron annihilation;

D O I：

10.1002/polb.21374

中图分类号：

O63 [高分子化学（高聚物）];

学科分类号：

070305 ; 080501 ; 081704 ;

摘要：

Free-volume properties, size and distribution, in amorphous polystyrene exposed to CO2 gases have been measured as a function of pressure to 800 psi (5.5 MPa), of time, and of temperature using positron annihilation lifetime spectroscopy. The free volume increases significantly and its distribution broadens as a function of pressure. The free volume relaxes as a function of time with a characteristic time of 15 h, and 5.7 h for 400, and 800 psi, respectively, after depressurizing under vacuum. A portion of free volume created by CO2 exposure remains permanently in the polymer after CO2 exposure. The glass transition temperature decreases significantly as a function of CO2 pressure from the free-volume data and is compared with the differential scanning calorimeter results. The observed free-volume variations as a function of pressure, time, and temperature are discussed in terms of hole expansion, creation, free-volume relaxation, plasticization, and hole filling in amorphous polymers. (c) 2008 Wiley Periodicals, Inc.

引用

页码：388 / 405

页数：18

共 83 条

[1] A comparison of concentration-glasses and temperature-hyperquenched glasses:: CO2-formed glass versus temperature-formed glass [J].