Highly bulky spherosilicates as functional additives for polyethylene processing—Influence on mechanical and thermal properties

Abstract

In this work, a series of cage siloxanes (spherosilicate [SS] type) was tested as functional additives for preparation of polyethylene (PE)‐based nanocomposites. For this purpose, the compounds were prepared by condensation and olefin hydrosilylation reactions. The effect of these products on properties of obtained nanocomposites was analyzed by means of mechanical, microscopic (scanning electron microscopy‐energy dispersive spectroscopy), crystallographic (X‐ray diffraction), thermal (differential scanning calorimetry, thermogravimetry), rheological Melt flow rate (MFR), and thermomechanical (heat deflection temperature) analyses. The results were compared with similar reports on silsesquioxane‐ and SS‐reinforced PE systems. Effects of SS functional group structure on the behavior of the additive and properties of the composite system were discussed. Aspects of thermal decomposition of PE‐containing SS were studied and a probable mechanism of these polymer systems degradation was proposed.

Silsesquioxane Derivatives as Functional Additives for Preparation of Polyethylene-Based Composites: A Case of Trisilanol Melt-Condensation

“…It should be also noted that even at the polymer melting temperature, simple silsesquioxane additives with small substituents ( i Bu, Vi, substituted propyl) should not be expected to dissolve or melt, and rather only disperse/agglomerate, besides i Bu 7 SSQ-3OH during the initial compounding process. The above general conclusions are similar to the previous findings on spherosilicate/PE composites [ 54 ]. It can be speculated that the siloxane framework of the silsesquioxane molecule plays a role in a recombination or quenching of free radicals, as an average Si–C bond is weaker than a C–C bond, which results in elimination of an organic group and formation of a silyl radical [ 67 ].…”

“…The changes of the melting temperature can be linked to moderation of mean crystallite size, and larger crystallites being responsible for higher melting temperature [ 54 ]. By this principle, all the compounds mediated the PE crystallites size, with a tendency for most additives to reduce the main crystallite size at the highest additive loading.…”

“…Guo et al also suggested that when applying octa( iso butyl)silsesquioxane for UHMWPE, the additive segregated on the spherulite interfaces, where most of the polymer amorphous phase is located [ 37 ]. The non-linear relationship between the SSQ additive loading and the crystallinity levels of PE can be explained on the basis of two levels of dispersion of the additives, where at higher loadings more agglomerates form and the less numerous, large particles of the additive provide less nucleation sites for the crystallizing polymer [ 54 , 55 ]. For most examples, the highest crystallinity can be observed at 0.5% loading, so it can be speculated that it’s the concentration where most of the additive is well dispersed and provides the highest amount of small, nucleation-promoting particles, whereas at 1.0% and 1.5% loadings, multi-micron agglomerates predominate, limiting the number of available nucleation sites.…”

“…The dispersion level plays a huge factor on the properties of the obtained materials, and effective dispersing of the organosilicon additive is crucial to observe effects such as (nano)reinforcing action or thermal stabilization of the composition [ 11 , 12 , 13 , 14 , 15 ]. In the previous work, we showed how a proper choice of organic substituents for spherosilicate compounds, as well as a processing method applied, allowed for effective obtaining of micro-and nanodispersion of the compounds in PE together with limited agglomeration [ 54 ]. It is crucial to mention that often two levels of dispersion can be observed and above specific concentration (depending on the compound and polymer matrix) multi-micron agglomerates are formed, together with a fraction of the additive being well-dispersed at a sub-micron scale [ 55 ].…”

Biogenic Composite Filaments Based on Polylactide and Diatomaceous Earth for 3D Printing

“…The dry mass left after pyrolysis increased, as expected, with a growing concentration of the filler and with an increasing size of the filler fraction used. The differences between the dry mass left after pyrolysis ( Table 2 ) and the actual content of the filler in the composite follow from the fact that the process of pyrolysis is rapid (a steep mass loss curve) and pyrolytic gases carry out some fragments of diatom shells [ 27 ].…”