Achievement of quasi-nanostructured polymer blends by solid-state shear pulverization and compatibilization by gradient copolymer addition

• Published in: Polymer (Guilford) Vol. 47; no. 19; pp. 6773 - 6781
• Main Authors: Tao, Ying, Kim, Jungki, Torkelson, John M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 07-09-2006; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Gradient copolymers; Machinery and processing; Miscellaneous; Nanoblend; Plastics; Polymer industry, paints, wood; Solid-state shear pulverization; Technology of polymers; Solid-state shear pulverization; Gradient copolymers; Nanoblend; Polymer blends; Dispersion degree; Methyl methacrylate polymer; Nanostructure; Experimental study; Solid phase extrusion; Compatibilizer; Heterogeneous mixture; Growth from solid state; Mechanical treatment; Morphology; Styrene polymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2006.07.041

Nanoblends, in which dispersed-phase domains exhibit length scales of order 100
nm or less, are made using a continuous, industrially scalable, mechanical process called solid-state shear pulverization (SSSP). An 80/20
wt% polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend processed by SSSP and consolidated by platen pressing, without melt processing, exhibits a quasi-nanostructured morphology with many irregular, minor-phase domain sizes of ∼100
nm or less. After short-residence-time single-screw extrusion, the pulverized blend exhibits spherical dispersed-phase domains with a number-average diameter of 155
nm. Thus, SSSP followed by certain melt-processing operations can yield nanoblends. However, the pulverized blend exhibits significant coarsening of the dispersed-phase domains during long-term, high-temperature static annealing, indicating that SSSP followed by other melt processes may yield microstructured blends. In order to suppress coarsening, a styrene (S)/methyl methacrylate (MMA) gradient copolymer is synthesized by controlled radical polymerization. When 5
wt% S/MMA gradient copolymer is added to the PS/PMMA blend during SSSP, the resulting blend exhibits a nanostructure nearly identical to that of the blend without gradient copolymer, and coarsening is nearly totally suppressed during long-term, high-temperature static annealing. Thus, SSSP with gradient copolymer addition can yield compatibilized nanoblends. Morphologies obtained in the pulverized PS/PMMA nanoblend are compared with those in blends of PS/poly(
n-butyl methacrylate) and PS/high-density polyethylene made using identical SSSP conditions, providing for commentary on the ability of SSSP to produce nanostructured blends as a function of blend components.