Morphological evaluation of silicone/clay slurries by small-angle/wide-angle x-ray scattering

Abstract

Pastas de argilas em siliconas foram obtidas por mistura mecânica de diferentes fluidos de silicona e argilas montmorillonitas. Duas séries de pastas contendo (1) montmorillonita natural (MMT) e (2) montmorillonita orgânica (O-MMT) foram preparadas usando poli(dimetilsiloxano) com finais de cadeias Si(CH 3) 2 OH (PDMS-OH), poli(dimetilsiloxanoco-metilpropilóxido de etileno siloxano) (PDMS-PEO) ou emulsão de poli(dimetilsiloxanoco-aminoetilaminopropilmetilsiloxano) em água (PDMS-NH 2). A morfologia das pastas foi caracterizada por espalhamento de raios-X em baixo/alto ângulo usando detector bidimensional (SAXS/WAXS-2D). As pastas preparadas com PDMS-OH apresentaram apenas um aumento discreto na separação das lamelas, enquanto aquelas preparadas com PDMS-PEO e PDMS-NH 2 apresentaram um aumento pronunciado, resultando em tactóides expandidos. Além disso, a análise da região de SAXS indicou a presença de lâminas finas (lamelas esfoliadas e/ou empilhamento de poucas lamelas) e tactóides expandidos nas pastas MMT/PDMS-PEO e MMT/PDMS-NH 2. Esta estrutura hierárquica também foi encontrada nas pastas preparadas com a O-MMT. Silicone/clay slurries were prepared by mechanical blending of different silicone fluids and montmorillonite clays. Two dispersion series containing (1) a natural montmorillonite (MMT) and (2) an organic montmorillonite (O-MMT) were prepared using poly (dimethylsiloxane) with-Si(CH 3) 2 OH end groups (PDMS-OH), poly(dimethylsiloxane-comethylpropylethylene oxide siloxane) (PDMS-PEO) or a poly(dimethylsiloxane-coaminoethylaminopropylmethylsiloxane)/water emulsion (PDMS-NH 2) as dispersion fluids. The resulting morphology of the silicone/clay slurries was characterized by small-angle/ wide-angle X-ray scattering using a two-dimensional imaging plate detector (2D-SAXS/ WAXS). The PDMS-OH/clay slurries showed only a slight increase in the layer separation while a more pronounced effect was found for the PDMS-NH 2 and PDMS-PEO slurries, which resulted in expanded tactoids. Analyses in the SAXS region also indicated the existence of thin platelets for the MMT slurries prepared with PDMS-NH 2 and PDMS-PEO fluids. This hierarchical structure, formed by thin platelets and expanded tactoids, was also found in the O-MMT/silicone slurries.

Improvement of toughness in polypropylene nanocomposite with the addition of organoclay/silicone copolymer masterbatch

“…Figure 8 shows a simplified illustration of the O‐MT/SCP masterbatch dispersion in the polymeric matrix. The proposed mechanism was based on earlier studies [20, 21] as well as on the results obtained in the present work.…”

“…Silicone polymers are known for their unique properties such as low‐temperature flexibility, excellent thermal and oxidative stabilities, low surface tension, chemical resistance and good dielectric properties, which contribute for the high performance of the silicone‐based elastomers [15, 16]. Evidence of silicone fluid intercalation in clay layers or clay delamination [17–20] without any solvent assistance or high shear [19, 20] were associated to the nature of this polymer and to the highly unusual surface properties, particularly of the poly(dimethylsiloxane), PDMS. These results motivated the use of silicone fluids as a swelling (or intercalating) agent in layered clays, giving rise to clay/silicone masterbatches.…”

Panorama da Pesquisa Acadêmica Brasileira em Nanocompósitos Polímero/Argila e Tendências para o Futuro

“…Por fim, um método menos comum também é empregado, no qual, uma pasta de argila é diretamente misturada com o polímero. A idéia desta técnica consiste no aumento do espaçamento basal da argila no primeiro estágio do processo, pela polimerização dos monômeros ou suspensão da argila em água/solventes e então a matriz polimérica é intercalada no espaçamento basal aumentado [16] .…”

A Direct SAXS Approach for the Determination of Specific Surface Area of Clay in Polymer-Layered Silicate Nanocomposites

“…Interfacial interactions, which can be tuned by surface modification, shape the properties of the interphase, and thus the macroscopic performance. Among the cited factors, established TEM, WAXD, and SAXS − techniques allow for the investigation and quantification of the size and morphology of dispersion of the filler in the matrix. As an example of the potential of SAXS analyses, for example, Krishnamoorti and colleagues exploited the anisotropy factor evaluated by SAXS to investigate shear induced orientation phenomena in polymer/clay dispersions or highlighted the disruptive effects that clay has on polymer lamellae. , …”