Interaction of supercritical carbon dioxide with polymers. II. Amorphous polymers

Abstract

In continuation of our goal to implement supercritical fluid (SCF) technology for various applications such as precision cleaning, foaming, and impregnation of materials, a systematic study has been performed involving amorphous polymers. Eleven different polymers of amorphous nature have been subjected to supercritical carbon dioxide (SC CO2) treatment under a wide pressure and temperature range (1000–3000 psi and 25–70°C, respectively). The influence and impact of such treatment on the appearance, weight change, and thermal and mechanical properties were followed systematically. In addition, the effect of treatment conditions and dimension of the samples on weight changes were also monitored. It has been found that amorphous polymers can absorb carbon dioxide to a greater extent than crystalline polymers and, in turn, the phenomenon of plasticization was also very high. In addition to morphology, the polarity of the polymer is also crucial in determining the solubility in carbon dioxide. Comparison was also made with the behavior of crystalline polymers. © 1996 John Wiley & Sons, Inc.

Solubility, swelling degree and crystallinity of carbon dioxide–polypropylene system

“…The upward trend of CO 2 solubility in PP as temperatures approached T m is most likely due to the melting or decrease of the crystalline regions of PP, which increased the amount of available amorphous regions, and thus lead to higher swelling. As noted in several works [1,27,28], CO 2 only dissolves in the amorphous region of a polymer, and specifically for PP, CO 2 has been shown to only dissolve into the amorphous regions for pressures as high as 20 MPa [27]. The higher CO 2 solubility in molten state PP than in rubbery state PP can be explained by the lack of crystalline regions in the molten state.…”

“…which assumes that the contribution of gas solubility in the polymer depends mainly on the amorphous region of the polymer, while the crystalline region has negligible contribution [1,27,28]. The denominator in the last term of Eq.…”

Critical ReviewAnalytical Extraction of Additives From Polymers

“…The amount of CO 2 absorbed will depend on temperature, pressure and the polymer concerned. Shieh et al 41,42 studied the effects of supercritical CO 2 on nine crystalline and 11 amorphous polymers. The appearance, mass changes, physical properties and solubility of CO 2 were examined after removal from the fluid.…”

Quantifying Plasticization and Melting Behavior of Poly(vinylidene fluoride) in Supercritical CO2 Utilizing a Linear Variable Differential Transformer

“…23,25,27,28 Effects of compressed CO 2 on semicrystalline polymers have also been investigated, mostly at relatively low pressures and temperatures. 20,21,29,[33][34][35][36][37][38][39][40][41][42][43] In semicrystalline polymers, solubility of CO 2 occurs solely in amorphous regions. Plasticization of strained amorphous regions, such as those adjacent to crystalline lamella, may result in CO 2 -induced crystallinity or "antiplasticization" 20,21 as found for poly(ethylene terephthalate) (PET) 34,36,37 and polycarbonate (PC).…”