A X-ray study of β-phase and molecular orientation in nucleated and non-nucleated injection molded polypropylene resins

Abstract

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.

New piezoelectric composites based on isotactic polypropylene filled with silicate

“…7). The observed shape of diffraction profile can be attributed to the α-structure of i-PP [21,22]. The calculated degree of crystallinity of this polymer is about 55%.…”

Effect of porous zeolite on temperature-dependent physical properties of polypropylene/octadecane (PP/OD) composite films

“…The XRD pattern of ZL shows several sharp diffraction peaks at 2θ = 7.9, 8.7, 14.7, 23.0, 23.9 and 24.5°, which correspond to (011), (020), (031), (051), (303) and (313) planes of the ZSM-5 zeolite structure [14,32,33]. In contrast, the PP/OD composite film without ZL yielded an amorphous halo in the 2θ range of 15-25°a s well as four sharp diffraction peaks at 2θ = 14.0, 16.9, 18.5, and 21.5°, which are attributed to the (110), (040), (130), and (301) crystal planes of pure PP, respectively [34]. Furthermore, the XRD patterns of the five PP/OD/ZL composite films with 3-30 wt% ZL show several crystalline peaks that are almost identical to those observed for pure ZL in the 2θ range of 5-30°, with their intensities proportional to the ZL content [14,32].…”

The Effects of Thermoplastic Polyurethane on the Structure and Mechanical Properties of Modified Polypropylene Blends

“…Under common processing conditions, isotactic PP often shows an α crystalline form. Figure 3C shows that, in the XRD test, when 2θ was 14.1°, 16.8°, 18.5°, 21.3°, and 21.8°, the corresponding Bragg diffraction characteristic peaks of PP were accompanied by crystal plane diffraction of (110), (040), (130), (111), and (131) [1,[12][13][14]. The results illustrated that, for PP90/TPU10 and MPP/TPU, the diffraction peak remained the same, indicating that adding TPU did not create a new crystalline structure [15,16].…”