Miscible blends of styrene‐acrylic acid copolymers with aliphatic, crystalline polyamides

Abstract

AbstractStyrene‐acrylic acid copolymers exhibit miscibility with various aliphatic, crystalline polyamides (e.g., nylon 6, 11, and 12) at 20% acrylic acid content in the copolymer. At 8% acrylic acid, phase separation is observed with the crystalline polyamides. At 14% acrylic acid, partial miscibility is observed with each polyamide, resulting in the Tg's of the constituents shifted toward the other constituent. The miscibility of the styrene‐acrylic acid copolymers ( > 14 wt % AA) can be ascribed to hydrogen bonding interactions with the polyamides. Styrene‐acrylic acid (20% AA) copolymers are miscible with other nylons with alternating amide orientation along the chain (e.g., nylon 6,6 and nylon 6,9). These samples tend to crosslink upon exposure to temperatures above the polyamide melting point unlike the nylon 6, 11, and 12 blends in which branching may only occur. Nylon 11/styrene‐acrylic acid blends were chosen for crystallization rate studies. A melting point depression of nylon 11 occurs with addition of the styrene‐acrylic acid (20% AA). The Flory‐Huggins interaction parameter from the melting point depression is calculated to be ‐0.27. The crystallization rate of nylon 11 is significantly reduced with the addition of the miscible SAA copolymers (20% AA). The spherulitic growth rate equation predicts this behavior based on a Tg increase with SAA addition.