Physical Properties of Poly(trimethylene terephthalate)/Organoclay Nanocomposites Obtained via Melt Compounding and In Situ Polymerization

Two series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2-aminododecanoic acid (ADA)-intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3-propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1-5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide-angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA-MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA-MMT in PTT increases melt-crystallization (T-cm) peak temperature by 14-15 degrees C irrespective of the clay content. However, the melting temperature (T-m) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the T-cm and T-m peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (T-g) irrespective of clay content, and a noticeable decrease in T-g with increasing clay content for in situ polymerized samples. The PTT/ADA-MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 29:1328-1336, 2008. (C) 2008 Society of Plastics Engineers