Supercritical carbon dioxide assisted blending of polystyrene and poly(methyl methyacrylate)

Abstract

A method for blending polystyrene and poly(methyl methacrylate), (PMMA), with the addition of supercritical carbon dioxide has been investigated. The first series of blends was a PMMA and polystyrene with similar melt viscosities. The second series of blends was a PMMA and polystyrene with a viscosity ratio (ηPMMA/ηpolystyrene) of about 20. The results show that a reduction in the size of the minor or dispersed phase is achieved when supercritical carbon dioxide is added to the blend system. A high‐pressure mixing vessel was used to prepare the blends under pressure with carbon dioxide for batch blending. The solubilities of CO2 in PMMA and polystyrene, measured in the high‐pressure mixing vessel at 200°C and 13.78 MPa (2000 psi) was 5.8 and 3.6 wt%, respectively. A single screw extruder was used to study the effects of carbon dioxide on the viscosity of polymer melts. The melt viscosity of PMMA was reduced by up to 70% with approximately 0.4 wt% CO2. The melt viscosity of polystyrene was reduced by up to 56% with a CO2 content of 0.3 wt%. A twin screw extruder was used to study the effects of injecting carbon dioxide in a continuous compounding operation.

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

“…If the latter effect is more pronounced than the former, the capillary number can be sufficiently increased to surpass j c , thereby resulting in CO 2 -enhanced droplet breakup. Experimental evidence confirms [173][174][175][176][177] that scCO 2 can substantially decrease the dispersion size of various polymer blends by lowering the viscosity and/or reducing the interfacial tension. For instance, the addition of scCO 2 to an immiscible PMMA/PS blend with an initial viscosity ratio of ca.…”

“…20 results in a significant reduction of the viscosity ratio, as well as the PMMA dispersion size. [173] In a comparable blend, an initial viscosity ratio of 7.3 is lowered to 3.4 upon addition of scCO 2 , and the dispersion size correspondingly decreases in both batch and continuous mixing processes. [176] Indeed, the dispersion size in a 25:75 (w/w) PMMA/PS blend systematically decreases with increasing CO 2 concentration, as illustrated by the sequence of TEM images displayed in Figure 10.…”

Phase Behavior of Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends in the Presence of High‐Pressure Carbon Dioxide

“…[46] In extrusion processes, exposure to CO 2 can facilitate intimate mixing of different polymers because of improved viscosity matching. [47][48][49][50][51] Polymer blends produced in this manner tend to exhibit finer dispersions and improved impact strength. The sorption of CO 2 in PMMA/PVDF blends, as well as the accompanying changes in blend properties, has been examined by Paul and co-workers.…”

Supercritical Fluids: Nanotechnology and Select Emerging Applications

“…Shows effects blending of two polymers under supercritical CO 2 on the morphology of the product as seen under a transmission electron microscope (TEM). Elkovitch et al (1999). Figure 32.…”

“…The monomer polymerizes in the matrix of the polymer, producing a new blend of polymers with different and improved physical and chemical properties that are difficult to synthesize by conventional methods, see Berens et al (1986). For example, Elkovitch, et al (1999) showed the effects of supercritical CO 2 on the blending of PMMA and polystyrene using both a batch mixer (with a single-screw extruder) and a continuous operation mixer (with a twin-screw extruder). Figure 31 shows the effects of SCF_CO 2 on the morphology of the final product.…”