Search

The comparison of the degree of crystallinity and the micromechanical properties in the blends of recycled amorphous polyethylene terephthalate PET with isotactic polypropylene iPP and highdensity polyethylene HDPE with a compatibilizer in different proportions is reported. The physical study of the composites of the compatibilized blends and clay is also discussed. The analysis, performed by means of wideangle Xray scattering and differential scanning calorimetry techniques, permits us to describe, at microscale level, the role of the compatibilizer on the structure and microhardness of the polymer blends that we studied. The results reveal that PET was incompatible with both iPP and HDPE. However, the presence of the compatibilizer, a styrene–ethylenebutylene–styrene block copolymer grafted with maleic anhydride, allowed the compatibilization of these polymers. In the PETiPP blends, the clay seemed to have a nucleating effect on the iPP and also induced a hardness increase in the compatibilized blends. On the other hand, in case of PETHDPE, the crystallinity of these samples pure blends, blends with compatibilizer, and blends with compatibilizer plus clay only depended on their composition. Similarly to the PETiPP blends, the addition of clay induced an increase in the hardness of the compatibilized blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

A new route based on reversibly crosslinking reactive extrusion is applied for the development of iPPclay nanocomposites. Analysis of smallangle Xray scattering SAXS reflections of isotactic polypropylene iPPclay nanocomposites, prepared by two different mixing and chemical crosslinking methods i.e., conventional and in situ, is presented and results are compared with preceding wideangle Xray diffraction WAXD results. It is shown that the presence of clay significantly affects the value of long spacing in iPP, as well as the coherence length of lamellar stacks. Results show that the size of the coherently diffracting nanodomains decreases in two stages, first rapidly and then slowly as a function of increasing clay content. This can be attributed to the influence of confined iPP lamellae under the effect of rising number of clay particles. The appearance of the γcrystalline form in the crosslinked iPPclay nanocomposites is related with the difficulty in chain folding of iPP chains introduced by the chemical crosslinking process, as well as by the presence of clay particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

The microhardness of a series of biodegradable polyesters was determined. The nanostructural features of these materials were studied by wideangle Xray scattering WAXS, smallangle Xray scattering SAXS, and differential scanning calorimetry. Analysis of the SAXS and WAXS patterns allowed direct derivation of the degree of crystallinity and crystal thickness values, and correlations of the micromechanical properties are presented. The differences in the thermal and mechanical properties exhibited by the studied systems and the ones found in other aromatic polyesters are explained as due to the different chemical natures of the monomeric units. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [ABSTRACT FROM AUTHOR]

Reversibly crosslinked isotactic polypropylene (iPP) was prepared in the presence of dicumyl peroxide. The effects of the peroxide oxy‐radicals in the melt were investigated in relation to the modification of the polymer. The dynamic rheology analysis of the crosslinking process was carried out by using a plastograph. The crosslinking reaction was evaluated by the Monsanto method. The resulting structure of the modified samples was studied by means of differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), microhardness, and mechanical properties. The degree of crystallinity of the modified iPP, derived from DSC and WAXS, remains almost unchanged, i.e., the crystalline structure is unaffected, though the lamellar thickness slightly decreases. The impact strength of the crosslinked iPP is greatly improved with reference to that of the unmodified material. A transition from brittle to ductile behavior appears in the modified iPP for all the crosslinking agents studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2968–2976, 2007 [ABSTRACT FROM AUTHOR]