Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties

Abstract

Hybrid materials based on polyethylene and MCM-41 microparticles functionalized with silanes: Catalytic aspects of in situ polymerization, crystalline features and mechanical properties, Microporous and Mesoporous Materials (2016), doi: 10.1016/j.micromeso.2016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Mechanical response is observed to be dependent on the content in mesoporous MCM-41 and on the crystalline features of polyethylene. Accordingly, stiffness increases and deformability decreases in the nanocomposites as much as MCM-41 content is enlarged and polyethylene amount within channels is raised. Ultimate mechanical performance improves with MCM-41 incorporation without varying the final processing temperature.

Variation of Ultimate Properties in Extruded iPP-Mesoporous Silica Nanocomposites by Effect of iPP Confinement within the Mesostructures

“…They melt at low temperature because of their significant smaller size. On the contrary, this little endothermic event is not seen in the iPP−MCM-41 composites (the appearance of that endotherm is expected in the iPP−MCM-41 specimens at lower temperature than in those hybrids with SBA-15 particles, similarly to the features described for polyethylene materials with either MCM-41 [12][13][14] or SBA-15 [10,11]). Thus, it seems that there are not iPP chains within MCM-41 channels in a significant amount.…”

“…Other adverse circumstance that favors this poor pore filling is the preparation strategy since now the extrusion was used. In fact, it should be reminded that no secondary endotherm is seen in these extruded iPP−MCM-41 while a small endothermic peak was observed at same temperature interval for in situ polymerized PE−MCM-41 materials [12][13][14].…”

“…Another aspect to solve is to learn, without a doubt, whether or not there are iPP chains within the MCM-41 mesostructure. On one hand, the small endotherm usually observed in PE−MCM-41 [12][13][14], UHMWPE−SBA-15 [10,11] and iPP−SBA-15 nanocomposites [2][3][4], related to the melting of polymeric chains inside the pores, does not appear in the DSC curves during the first melting process of these iPP−MCM-41 materials. On the other hand, dependences on frequency of their rheological parameters seem to indicate the beginning of a transition from a liquid to a solid-like behavior, which could be ascribed to presence of iPP chains within MCM-41 channels.…”

“…These results confirmed the ones described in previous works performed at room temperature on in situ polymerized nanocomposites of poly(N-isopropylacrylamide)/SBA-15 [8] as well as on polyethylenimine (PEI)-based composites wet impregnated with either MCM-41 or 9].Regarding the existence of a small endothermic event in DSC, it should be said that this process was also observed for in situ polymerized materials based on ultra-high molecular weight polyethylene (UHMWPE) and 11] as well as in nanocomposites based on high density polyethylene (HDPE) and MCM-41. The temperature range was shifted to lower values [12][13][14] in the latest ones. These secondary processes were associated with the melting of crystallites with significantly smaller size than the thicker ones that melt at around 130 • C during the main endotherm [1].…”

UHMWPE/HDPE in-reactor blends, prepared by in situ polymerization: Synthetic aspects and characterization

“…This secondary process is less intense in sample FIM009 since its SBA-15 content is the lowest one. This small endothermic peak is attributed to those polyethylene crystallites, either those coming from the UHMWPE or from the HDPE component, that are developed inside the SBA-15 channels [19], similarly to evidence found in nanocomposites with MCM-41 [33,34]. Channel confinement prevents a further growth of the crystallites and, accordingly, these crystalline entities generated within SBA-15 particles are of much smaller size than those that can grow at its surface and in the UHMWPE and HDPE bulks.…”