Optical monitoring of the injection molding of intercalated polypropylene nanocomposites

Abstract

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

Mechanical properties and stem cell adhesion of injection‐molded poly(ether ether ketone) and hydroxyapatite nanocomposites

“…The thickness of the skin of all of the samples was measured, and it is shown in Table ; we observed that, as expected, the lower Q was, the lower the shear rate and the higher the time for the beginning of the flow‐induced crystallization to occur were, as confirmed by other works . Therefore, the thickness of the frozen skin layer was higher.…”

“…All of the samples also showed cold crystallization, even the thermally treated ones; this indicated that the thermal treatment was not enough to attain the highest amount of crystallinity in the samples. The addition of HA slightly increased the amount of crystallinity of the thermally and non thermally treated samples; this was in contrast to other results . The amount of crystallinity was also dependent of the injection‐molding conditions, as expected; for example, PEEK and the nanocomposite injected under condition 1 (lowest Q ) had the lowest X c _DSC because a low Q favored the formation of a thicker skin (frozen layer) and a low X c _DSC .…”

“…This makes nucleation and crystal growth more difficult and delays crystallization. Another work of ours on optical monitoring during the injection molding of polypropylene (PP) and MMT nanocomposites showed that the PP/MMT nanocomposites had higher induction times for the beginning of crystallization than the pure PP; this confirmed the retardation effect in the growth rate promoted by the MMT nanoparticles.…”

Preparação e Caracterização de Nanofibras de Nanocompósitos de Poliamida 6,6 e Argila Montmorilonita

“…As concentrações finais dessas soluções estão descritas na Tabela 1. uma escala competitiva com outros materiais convencionais. A nanoargila montmorilonita vem sendo fonte de constantes estudos de intercalação química e esfoliação, pois possui origem natural e vantagens como boas capacidade de delaminação, alta resistência a solventes, estabilidade térmica para suportar os processos de transformação e elevada razão de aspecto [1,[5][6][7][8][9][10][11][12] . Nanofibras de nanocompósitos obtidas pelo processo de eletrofiação e com propriedades especiais têm sido amplamente apresentadas na literatura recente [13][14][15][16][17][18][19] .…”

Trends in the multifunctional performance of polyolefin/clay nanocomposite injection moldings

“…With respect to the structure that nanocomposites develop, Moretti et al [49] observed that intercalated PP/clay nanocomposites produced by twin-screw extrusion showed a second core, a thicker skin layer, highly oriented nanoclay's tactoids in the skin region, and average spherulite size smaller than PP. They also noted that the neat PP sample had average spherulite size larger than the nanocomposite samples.…”