Effect of adding new phosphazene compounds to poly(butylene terephthalate)/polyamide blends. I: Preliminary study in a batch mixer

Poly(butylene terephthalate) (PBT) and a sample of polyamide have been melt processed in the presence of two new phosphazene compounds, namely 2,2-dichloro-4,4,6,6-bis[spiro(2′,2″dioxy-1′,1″biphenyl) ]cyclotriphosphazene (2Cl-CP) and 2,2-bis-(2-methoxy-4-methyleneoxy-phenoxy)-4, 4,6,6,-bis[spiro(2′,2″dioxy-1′,1″biphenyl)] cyclophosphazene (CP-2EPOX). The blends were prepared by using polyamide 6 (PA6) at 25/75 w/w and 75/25 w/w composition. In order to perform a preliminary analysis on the behaviour of the blends, the materials were prepared in a batch mixer. The materials have been completely characterized from a rheological, morphological, mechanical point of view. The results indicate that the additives used cause an increase of the rupture properties and of the viscosity especially in the PA-rich blend. This result can be attributed to a chain extension effect on the PA phase, even if some compatibilisation with the formation of PBT/PA6 copolymers cannot be excluded as evidenced by the reduction of particle dimensions and by the improvement of the adhesion between the phases. Between the two compatibilisers, the CP-2EPOX displays the best results for both the investigated compositions while 2Cl-CP seems to act simply as a PA6 chain extender with very low compatibilising effect.