S. Bastida

Phase and mechanical characterization of poly(ether imide)/polyarylate injection moulded blends

Abstract Poly(ether imide) (PEI)/polyarylate (PAr) blends were prepared throughout the composition range by direct injection moulding (IM) at 300 and 340 °C. The homogeneity and miscibility level obtained were comparable to that usually obtained by kneading. Whatever the moulding temperature, the 90 10 and 80 20 blends, although with a higher Tg than usual, appeared miscible by both DSC and SEM. The blends of other compositions were partially miscible. Unexpectedly, the mechanical properties were close or even above those predicted by the additivity rule for both miscible and partially miscible compositions. This took place not only in the case of the Youngs modulus or yield stress, but also in the case of a property as sensitive to immiscibility as ductility. Leaving aside orientation effects, it was concluded that full miscibility is not necessary for synergism in break properties to be obtained.

Phase behaviour, morphology and properties of poly(ether imide)/polyarylate blends

Abstract Poly(ether imide) (PEI)/polyarylate (PAr) blends of different compositions were obtained by melt blending followed by compression moulding. 90/10 and 80/20 blends appeared miscible by both differential scanning calorimetry and dynamic mechanical thermal analysis. The other compositions were biphasic; one phase was almost pure PAr and the other PEI with a fairly constant PAr content of roughly 25%. This phase behaviour agreed with both the observed transparency and the fracture surfaces observed by scanning electron microscopy. The mechanical properties of the blends as a function of composition showed values close to linearity or were even enhanced, with an unexpected synergism in ductility. This behaviour and that observed in other polymer blends, suggest that, assuming isotropy and constant crystallinity content, the relation between increased miscibility level and improved ductility is not a general rule.

The Vicat softening temperature as a method to assess the phase behaviour of amorphous polymer blends

Abstract The possibility of using the Vicat softening-point test as an additional method to find the phase behaviour of amorphous polymer blends is discussed. The comparison of the T g S by DSC to the Vicat temperatures of three blends, miscible, immiscible and partially miscible, allows us to interpret the different Vicat softening temperature-blend composition plots obtained and to be informed on the phase behaviour of the blends.

Effects of mixing procedure on the morphology and properties of poly(ether imide)/thermotropic copolyester blends

Poly(ether imide)/thermotropic copolyester (Rodrun) blends with liquid crystalline polymer contents of 5, 20 and 40% were obtained by injection moulding, both with and without previous extrusion, and at different melt temperatures and injection speeds. Previous extrusion or different injection speeds changed neither the morphology nor the mechanical properties of the blends, which improved significantly only at higher temperatures. The lack of significant increase in properties was due to the very low viscosity ratio-induced lack of fibrillation and overall poor mixing level of the blends, which was seen even in blends injected after previous extrusion.

Structure and properties of injection molded blends of poly(ether imide) and a thermotropic copolyester

The phase structure and mechanical properties of blends composed of poly(ether imide) and a thermotropic liquid-crystalline copolyester, Rodrun LC-5000, processed by injection molding were studied in the PEI-rich region. The addition of Rodrun to PEI produces fully immiscible blends and strongly improves the processability of PEI. Injection molding gave rise in very poor LCP blends to fine dispersed phases; in the rest of compositions it gave rise to coarse structures. This was probably due to the very large viscosity difference between the components of the blends. An increase in the melt temperature led to a smaller viscosity difference and as a consequence dispersed phase dispersion improved. The Youngs modulus clearly increased with the Rodrun content. The tensile strength was maintained up to a LCP content of 5% but decreased at higher contents because of the coarse morphologies obtained. The overall mechanical behavior was a main consequence of the lack of fibrillation and of the LCP dispersion level in the matrix.

Compatibilization of poly(ether imide)/Rodrun blends by means of a polyarylate

A compatibilization method for improving the mechanical properties of thermoplastic/liquid-crystalline polymer (LCP) blends has been tested in blends of poly(ether imide), PEI, with a thermotropic copolyester (Rodrun). It is based on the addition to the blend of a third component, both miscible with the matrix and also able to interact with the LCP. Given the miscibility of a polyarylate (PAr) with PEI up to 20% PAr content, and its probable interactions with Rodrun, a constant 20% PAr was added to the PEI matrix to test its possible compatibilizer activity in PEI/Rodrun blends. The observed decrease in the interfacial tension between the matrix and the dispersed phase induced by the PAr gave rise to a smaller size and to fibrillation of the dispersed phase. Fibrillation also gave rise to improved modulus of elasticity and tensile strength, thus proving the compatibilization activity of PAr.

Structure and physical properties of reprocessed poly(ether imide)

The effects of reprocessing by injection molding on the structure and properties of poly(ether imide) (PEI) were studied. The chemical structure of PEI does not change after reprocessing. However, the weight-average molecular weight decreases after the first and the second injection cycles, after which it stays constant. Despite the harsh conditions used, the thermal resistence and the small strain mechanical properties were unaffected by the application of successive injection molding processes to the 100% regrind PEI specimens. The tensile ductility and energy at break showed a decrease parallel to that of the molecular weight. However, the Izod impact strength was constant, probably due to the differences in strain rate and mode of deformation between the tensile and impact tests.

Effects of reprocessing on the nature and properties of SAN

Reprocessing of styrene-acrylonitrile copolymer (SAN) was carried out by means of repeated injection moulding up to five cycles. The chemical nature of SAN was apparently unchanged after reprocessing, but the molecular weight decreased slightly, detected by an increase in the MFI. SAN became progressively yellow with reprocessing but some of its most important mechanical properties remained unchanged.

Improved compatibilization in ternary poly(ether imide)/polyarylate–rodrun blends by means of interchange reactions

Abstract A possible compatibilization method in thermoplastic/liquid crystalline polymer blends based on the development of interchange reactions between the components of the blends has been tested in the case of the blends of Rodrun (Ro) with a miscible 80/20 poly(ether imide) (PEI)/polyarylate (PAr) thermoplastic matrix. The interchange reactions between PAr and Ro modified the nature of the PAr miscibilized in PEI, improving the adhesion between the modified matrix and Ro as seen by the improved ductility of the blends with 20% Ro. This indicated an additional compatibilization of the blend. The additional compatibilization was not able to overcome the brittle nature of the Ro at large Ro contents (40%), but in the case of the 20% Ro blends, led to blends with overall improved mechanical properties compared to those of the reference blends without additional time in the melt state.