The development of α and β-phases and the molecular orientation of injection molded disks of two isotactic polypropylene (i-PP) resins were studied by wide angle X-ray diffraction (WAXD) and pole figures. A nucleated (NPP) and non-nucleated (HPP) polymers were analyzed. The main proposal of this article was the comprehensive study of the interrelations between the processing conditions, phase contents and PP α-phase molecular orientation of injection molded PP resins. In both resins, it was observed that the α-phase was present in all regions along the thickness while the β-phase was present mainly in the external layers, decreasing from the surface to the core; however this last phase was present in a very small amount in the NPP resin. For both polymers, the orientation of the macromolecules c-axis was higher along the flow direction (RD) than along the transverse direction (TD). The b-axis of the PP α-phase molecules was oriented to the thickness direction (ND). The orientation of the c-axis along RD and b-axis along ND of the NPP samples was considerably higher than of the HPP samples, due to the NPP faster crystallization kinetics. For both polymers, the most influential processing parameters on the molecular orientation were the mold temperature and flow rate. The results indicate that, as the mold temperature increased, the characteristic molecular orientation of PP α-phase, with c-axis along RD and b-axis along ND, decreased. With increase in the flow rate an increase of the c-axis molecular orientation of the samples along RD was observed.

The nonisothermal crystallization of polypropylene resins, i-PP, during injection molding, using an optical device inserted in the injection mold cavity was monitored. The device detected the change of optical properties which occurs in polymers during their crystallization process; thus the intensity of a laser beam after it passed through the crystallizing polymer was measured during an injection molding cycle. The collected light intensity after the end of the cycle was correlated with the morphologies and final crystallinity degree of the samples. The influence of nucleating agents and the change of the parameters of the injection molding process on the morphology and optical signals were also investigated. The morphologies were analyzed by polarized light optical microscopy, PLOM. The % of crystallinity of the samples was measured by wide angle X-rays diffraction, WAXS. It was concluded that the optical device was sensible to different polymer crystallization kinetics, morphology type, and changes in the injection molding parameters. It was also found that the mold temperature and packing pressure and time were the factors that affected most the kinetics of crystallization of these polymers in this particular disk geometry. The WAXS results showed that the lower the final light intensity the higher the % of crystallinity in the samples. POLYM. ENG. SCI.,

Intercalated polypropylene (PP)/clay nanocomposites were produced by twin screw extrusion; afterwards, the optical monitoring of their injection molding was done using a laser sensor. The transmitted light intensity as a function of molding time was measured. The mold and melt temperatures, packing pressure and flow rate were changed. The nanocomposite had higher induction times than the PP, that is, scattering structures were detected later in the nanocomposite than in the PP, which was attributed to a retardation effect promoted by the clay on the PP crystallization growth rate. The morphologies of the injection molded samples were analyzed by polarized light optical microscopy, differential scanning calorimetry and transmission electron microscopy. The nanocomposite samples showed a second core, a thicker skin layer, highly oriented nanoclay's tactoids in the skin region and average spherulites' sizes smaller than the PP. The final light intensity If was correlated with the spherulites' sizes: high values of If represented samples with large spherulites. The PP sample had average spherulites' sizes larger than the Nano samples. However, the surging of a second core with large spherulites in the Nano samples changed the expected pattern: the PP samples showed If lower than the Nano samples. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers

The use of a compatibilizer to improve the interactions between poly(trimethylene terephthalate) (PTT) and an organically treated montmorillonite (MMT) clay was studied. Nanocomposites, with and without compatibilizer, were obtained using a torque rheometer; their nanostructures were analyzed by wide angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), steady state and dynamic rheological measurements, and Fourier transform infrared analysis (FT‐IR). Only intercalated structures were obtained when no compatibilizer was added, independent of the mixing method (one or two steps); when the compatibilizer was added, however, intercalated and exfoliated structures were obtained, depending on the masterbatch composition. When the PTT was not present in the masterbatch, two‐phase exfoliated structures were obtained, with a disperse phase composed of nanoclay's lamellas and reticulated compatibilizer and a matrix phase composed of PTT. The compatibilizer cured due to the presence of the nanoclay's surfactant; a mechanism of cure was proposed in which the epoxide rings of the compatibilizer reacted with the hydroxyl groups of the nanoclay's surfactant, forming ether cross‐linkages. It was also concluded that in order to obtain one‐phase exfoliated structures the two steps mixing method using a masterbatch composition of 50 wt% of PTT, 25 wt% of compatibilizer, and 25 wt% of nanoclay gave the best results; after further dilution in the PTT, an exfoliated nanocomposite with a final concentration of 5 wt% of compatibilizer and 5 wt% of nanoclay was obtained. Copyright © 2008 John Wiley & Sons, Ltd.

Highly branched alkoxysilane (HB) units were prepared in situ via a Michael-type reaction between pentaerythrithol triacrylate and aminopropyltriethoxysilane. These units were used as an inorganic component for the modification of cellulose acetate (CA) films using the sol-gel process. The thermal and dynamic-mechanical behaviors, the morphology, and the dimensional stability of the modified CA films were analyzed. The siloxanemodified CA films showed thermal stability similar to pure CA, but the residue content at 900 C increased with the addition of HB units. The morphology of these films was characterized by siloxane nanodomains dispersed in the CA matrix, with good interfacial adhesion between the phases. Moreover, the CA/siloxane nanocomposite films showed improved dimensional stability in comparison with CA, i.e., in the presence of HB, the dimensional change was reduced to around 50% of the value observed for pure CA. Finally, a complex dynamic-mechanical behavior was obtained for the nanocomposite films, as a consequence of the heterogeneous morphology.