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Quantifying Polymer Swelling Employing a Linear Variable Differential Transformer: CO2 Effects on SBS Triblock Copolymer

“…Since the depressurization rate affects expansion, care was taken to maintain similar depressurization rates and similar sample sizes. [9] Preliminary experiments show that by releasing the pressure over shorter times higher expansions are obtained.…”

“…Paralleling explanations of Ender and Gent, exposure to high-pressure CO 2 for a substantial length of time (2.5 h) allows diffusion-controlled solubility and CO 2 condensation. [9,14] Perhaps the condensed state involves adsorption of CO 2 at the interface between the glassy phase and the rubbery phase as well as general distribution due to free volume. In any event, during rapid depressurization, the rate of diffusion of the entrapped gas is lower than the rate of pressure reduction resulting in expansion.…”

“…In testing several commercial elastomers, Ender noted irreversible damage for expansions ''greater than several percent''. [9] In this case, some combination of filler effects or chemical (rather than physical) crosslinking in the proprietary materials may account for the difference.…”

“…Elastomer compression in high-pressure CO 2 has been previously observed on ''inflation resistant'' nitrile rubber. [9] The effect of sample size and the weight of the follower rod on SBS compression was investigated at 134 bar and 22 8C. For a sample weighing 0.2 g (%0.138 cm 3 ) as opposed to the original 0.03 g (%0.024 cm 3 ) SBS compression is 4.2%.…”

“…[5,7,8] Ender developed a linear variable differential transformer (LVDT) method to measure o-ring swelling. [9] An LVDT method was also employed as a sensor to obtain the creep compliance of polystyrene in high pressure CO 2 . [10] In initiating the development of an LVDT-based technique, we note Ender's results on Viton TM and nitrile rubber o-rings of ''proprietary composition''.…”