Gas sorption-induced dilation of poly(4-methyl-1-pentene)

✍ Scribed by D. S. Pope; W. J. Koros

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 580 KB
• Volume: 34
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199608)34:11<1861::aid-polb3>3.0.co;2-v

✦ Synopsis

SYNOPSIS

Sorption and volume dilation isotherms of semicrystalline poly(4-methyl-1-pentene) (PMP) were measured using COP and C3Hs as penetrants, which have sieving diameters of 3.3 and 4.3 A, respectively. On the other hand, the PMP crystal has a void width of approximately 4 A as estimated by X-ray diffraction, so it was anticipated that CO, would be able to sorb into the PMP crystal while C3Hs would not. The data show that C3H8 has a constant partial molar volume of approximately 87 cc/mol, just above the value reported in other rubbery polymers, and are consistent with the hypothesis that the C3Hs molecules are too large to sorb into the PMP crystals. The partial molar volume of C 0 2 was found to be 39 cc/mol for CO, weight fractions of up to 0.03. Since the typical partial molar volume of COP in rubbery materials is 46 cc/mol, the lower values in this study were attributed to C 0 2 sorption into crystalline regions of the polymer, which provided no dilation. Application of a twophase model using the assumption of Henry's law sorption showed that apparently all C,H, sorption was occurring in the amorphous region but approximately 16% of COP sorption occurred in the crystalline regions. 0 1996 John Wiley & Sons, Inc.