'Stazione Sperirnentale per la Cellulosa, Carta e Fibre Tessili Vegetali ed Artificiali, Piazza Leonard0 da Vinci 26, 201 33 Milan, Italy; 'Stazione Sperirnentale per i'lndustria delle Conserve Alirnentari. Viale Tanara 33, 431 00 Parrna, Italy
SYNOPSISThe thermal and mechanical properties of blends, obtained by mixing polyamide 6 (PA6) and an amorphous aromatic copolyamide G21 (IS0 nomenclature P A 61/6T), were investigated by differential scanning calorimetry, dynamic mechanical analysis, and mechanical tensile tests. Quenched blends show a single glass transition temperature; the T,-composition trend was interpreted by means of the Gordon-Taylor equation. The half-time of crystallization decreases by increasing the G21 content and this indicates a depression of the overall crystallization rate. A small decrease in the equilibrium melting temperature of PA6 in the blends was observed; this finding suggests that the interaction parameter in PA6/G21 blends is probably very small. The dynamic mechanical analysis of crystallized blends suggests the presence of a homogeneous amorphous phase even if the crystallization of PA6 occurred. The tensile mechanical properties reveal that G21 acts as stiffener of PA6. The collected experimental data suggest that PA6 and G21 are miscible in the composition range investigated. 0 1996 John Wiley & Sons, Inc.
I NTRODUCTI ONPolyamide 6 (PA6) films show good performances such as chemical and mechanical resistance, barrier properties to gas and aromas, thermoforming and shrink properties, transparency, and printability. Due to these peculiarities, PA6 film is widely used in medical and food packaging.A great increase of the applications is expected when PA6 is modified by adding a second component to improve some properties. G21 (IS0 nomenclature P A 61/6T) is an amorphous aromatic copolyamide obtained from the condensation of examethylenediamine with terephthalic and isophthalic acids, whose structural formula is ~ ~ * To whom correspondence should be addressed.Journal of Applied Polymer Science, Vol. 60, 1757-1764 (1996) C) 1996 John Wiley & Sons. lnc.
CCC 002l-S995/96/l01757-08G21 has good mechanical and gas barrier properties; moreover, in contrast to polyamide 6, the barrier properties improve with increasing relative humidity.'s2 In a recent series of articles, Ellis extensively studied the phase behavior of polyamide-based These works pointed out the existence of simple relationships between structure and miscibility that are explained by a theory based upon a binary interaction model? An estimation of the Flory interaction parameter (Xblend) for various aliphatic/aromatic polyamide blends was performed; in particular, for a system composed of PA6 and an aromatic copolyamide with the same structure as that of G21, an Xblend value of -0.0104,4 suggesting the existence of a favorable interaction between the components, was found. The aim of the present work was to investigate the thermal and mechanical properties of PA6/G21 blends.
