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

Abstract

A linear variable differential transformer (LVDT) was employed to evaluate CO2‐polymer plasticization. Preliminary results on polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) elastomer are presented. At 22 °C under CO2 pressure, SBS undergoes compression due to hydrostatic pressure. However, sample expansion occurs upon depressurization. At 45 °C, SBS undergoes swelling of 0.7% due to CO2 plasticization, while no post‐pressurization expansion is observed. The contrasting result is explained by change in PS domain mobility and discontinuity in the density‐pressure relationship. Linear displacement of SBS as a function of time at 56 and 134 bar CO2.magnified imageLinear displacement of SBS as a function of time at 56 and 134 bar CO2.

On the CO 2 sorption and swelling of elastomers by supercritical CO 2 as studied by in situ high pressure FTIR microscopy

“…Indeed, for every polymer, the CO 2 mass uptake is increased by about 40 to 72% when the CO 2 pressure is raised from 5 MPa to 10 MPa whereas only a modest increase of about 4 to 20% CO 2 mass uptake is observed between 10 MPa and 15 MPa. This nonlinear relation between the solubility and the pressure increase has been reported for other rubbery polymers [22,27,[30][31][32]. Tomasko et al [33] explained that at high pressure, CO 2 sorption is no longer proportional to CO 2 pressure.…”

“…But depending on the polymer, the knowledge of CO2/polymer interactions is more or less accessible or sometimes poorly affordable. Glassy amorphous polymers are the most studied polymers [12,13], semi crystalline polymers are commonly studied [13][14][15][16] whereas reinforced, filled, or biphasic materials are becoming more and more studied [14,17,18] However studies (e.g refs [16,[19][20][21][22]) are rather scarce when dealing with the behavior of elastomers (neat or filled) in CO 2 . The reasons are twofold: i) rubbery polymers are expected to be highly deformable in CO 2 (involving a high swelling), ii) the sorption/desorption stages are fast.…”

Supercritical CO2 processing and annealing of polytetrafluoroethylene (PTFE) and modified PTFE for enhancement of crystallinity and creep resistance

“…Using solubility data for related polymers, Tuminello predicted that PTFE should be soluble in supercritical CO 2 (scCO 2 ) at very high temperatures and pressures [6]. In earlier studies, we found that scCO 2 plasticized perfluorinated polymers and acted as a processing aid [7][8][9]. Building on that work, we report here on post-processing properties, particularly creep, of PTFE treated with scCO 2 and compare these properties with those of PTFE annealed at ambient pressure.…”

Non-contact method used to determine the swelling/shrinking coefficients under CO2 sorption/desorption on an HNBR O-ring - Study of coupling with temperature and pressure

“…First of all, the swelling of polymers is a well-known consequence of fluid sorption [4,5] and this effect is severe with elastomer components [6][7][8][9][10]. The volume change phenomenon has been widely discussed in the literature, particularly in the case of carbon dioxide (CO 2 ) [1,6,9,[11][12][13][14] and to a lesser extent hydrogen (H 2 ) [15]. Reported data concern variety of thermoplastics (PEEK, PS, LLDPE, PTFE, PMMA, PET, PP, PVDF, … [12]) in CO 2 , but also rubbers and elastomers such as HNBR [1,13,16], NBR [14,16], EPDM [14,16], SBS block [12], PDMS [17,18], FKM [16], PTFE [16], ACM [16], VMQ [16], and rubber polymer [19].…”

“…The volume change phenomenon has been widely discussed in the literature, particularly in the case of carbon dioxide (CO 2 ) [1,6,9,[11][12][13][14] and to a lesser extent hydrogen (H 2 ) [15]. Reported data concern variety of thermoplastics (PEEK, PS, LLDPE, PTFE, PMMA, PET, PP, PVDF, … [12]) in CO 2 , but also rubbers and elastomers such as HNBR [1,13,16], NBR [14,16], EPDM [14,16], SBS block [12], PDMS [17,18], FKM [16], PTFE [16], ACM [16], VMQ [16], and rubber polymer [19]. As an illustration, Bonavoglia et al [11] with the same apparatus described by Rajendran et al measured by direct visualization the swelling [15].…”