Thermal and mechanical behavior of polyamide 6/polyamide 6I/6T blends

Abstract

'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.

Mechanical behavior of films of miscible polyamide 6/polyamide 6I‐6T blends

“…The variation of the storage modulus, E ′, with blend composition is markedly different on both sides of the α relaxation, as shown on Figure 5(b). In agreement with the larger stiffness of the semiaromatic amorphous copolyamide in the glassy state,23 E ′ slightly increases with aPA content for T < T α ; the opposite trend is clearly observed for T > T α . In the transition region, the storage modulus drops more rapidly as aPA content increases.…”

Melt rheology of miscible or compatibilized polymer blends obtained from polyamidic and polyolefinic polymers

“…In contrast to these rheological 2 analyses, this blend showed a positive deviation from additivity, typical of polymers not miscible in melt. 11 According to Han and Kim it can be observed 12 that the interaction parameter, , plays an impor- value of for iPP/HOCP blends is much smaller 1,2 than that of PB-1/HOCP blends. It is of interest to 3,4 observe ( Fig.…”

“…Thermal and crystallization behavior of polyamide 6 (PA6) blended with an amorphous aromatic copolyamide [PA6(6T/6I)] has previously been studied. Examination of isothermally crystal- 1 lized samples by optical microscopy has shown that the films were completely filled with spherulites and no segregation of PA6(6T/6I) could be observed. Spherulite growth rate and overall kinetic rate constants of crystallization were depressed by dilution of PA6 with PA6(6T/6I).…”

Morphology evolution of miscible blends between crystalline PA6 and amorphous PA6IcoT

“…In this work, morphology evolution of blends of a semicrystalline polyamide 6 (PA6) and an amorphous polyamide 6IcoT (PA6IcoT) was investigated. This system has been shown to be miscible over all range of compositions 22–25. Both the melting of polymers and the microstructure change via melt–melt mixing were considered to ascertain information on the phase morphology and phase dimensions, which are essential to understand the morphology transformation during mixing of miscible blend 26…”