Elastomeric Polysiloxane Modifiers for Epoxy Networks

Abstract

Novel elastomeric polysiloxane modifiers for epoxy networks have been synthesized and characterized. In addition, curing studies of conventional epoxy resins incorporating these oligo mers have been conducted. Structures were prepared having either epoxide, primary amine and/or secondary amine endgroups. The polymerization step for the siloxanes consisted of a base cata lyzed equilibration of the appropriately functionalized disiloxane and octamethylcyclotetrasiloxane. In the case of hydroxy piperazine terminated modifiers, polymers were first synthesized with epoxy endgroups. These endgroups were then subsequently capped with an excess of piperazine prior to curing. The oligomers were characterized by FTIR, 'H and 13C NMR, GPC, endgroup analysis and vapor pressure osmometry. The secondary amine terminated oligomers basically act as linear modifiers. By contrast, the aminopropyl functional siloxanes produce a crosslinked network. Piperazine terminated oligomers show much better compatibility with the epoxy resins compared to the aminopropyl terminated oligomers. This is especially true if the modifier contains an amide group. The curing reactions of the epoxy resins (EPON resin-828) using these oligomers and a cycloaliphatic diamine (PACM-20) were followed under a variety of conditions by DSC. Percent conversion versus time plots showed that reactivities of the functional siloxanes are higher than the cycloaliphatic amine at comparable temperatures. X-ray photoelectron spectroscopy shows the surfaces of the polysiloxane modified materials to be predominantly siloxane even at quite low bulk levels of the reactive oligomers. Preliminary mechanical property studies are encouraging and detailed morphology-property studies are continuing.

Rubber‐modified epoxies. III. Analysis of experimental trends through a phase separation model

“…Further work may be related to the improvement of the thermodynamic and kinetic basis by removing some of the hypotheses carried out in the analysis, or to the extension to formulations using different rubbers than butadiene-acrylonitrile copolymers, like polysiloxanes or polyacrylates, [24][25][26][27] or to the use of engineering thermoplastics like PES or PEI in epoxy formulations.2a32 In this last case, new situations, like the vitrification curve of the epoxy copolymer-engineering thermoplastic, have to be considered in the analysis, because phase separation may be constrained by vitrification, depending on the location of the predicted composition for the dispersed phase and the Tg vs. composition curve. Of great interest will be also to follow the evolution of morphology at the early stages of phase separation.…”

Crosslinking of 1,9‐bis[glycidyloxypropyl]penta‐ (1′H,1′H,2′H,2′H‐perfluoroalkylmethylsiloxane)s with α,ω‐diaminoalkanes: The cure behavior and film properties

“…33,34 We have previously reported the synthesis of 1,9-bis[glycidyloxypropyl]decamethylpentasiloxane (I), 1,9-bis[glycidyloxypropyl]-3,5,7-tris(3Ј,3Ј,3Ј-trifluoropropyl)heptamethylpentasiloxane (II), and 1,9-bis-[glycidyloxypropyl]-3,5,7-tris(1ЈH,1ЈH,2ЈH,2ЈH-perfluorooctyl)heptamethylpentasiloxane (III). 35 In contrast to other studies with siloxane or fluorinated modified epoxies, 10,[32][33][34] these have well-defined microstructures. This may be useful in establishing structure-property relationships.…”

“…4 -16 These undergo phase separation during curing to form randomly dispersed particles within the epoxy matrix. Rubber or elastomeric modifiers that have been studied include carboxy-and amine-terminated butadiene-acrylonitrile copolymers, 4 polyacrylate elastomers, 5 poly(propylene oxide), 6 polysiloxanes, [7][8][9][10] and fluoroelastomers. 11 Unfortunately, small amounts of rubbery modifiers dissolved in the matrix cause a decrease in the T g and modulus values of epoxy resins.…”

“…30,31 ␣,-(Glycidyloxypropyl)oligosiloxanes 10 and poly(dimethylsiloxane) copolymers with pendant glycidyloxypropyl groups 32 have also been prepared. Fluorinated epoxy resins have been synthesized and cured with ␣,-(diamino)oligosiloxanes.…”

Surface properties and depth analysis of polyethylene/polydimethylsiloxane composite prepared by using supercritical carbon dioxide

“…It is also widely known owing to its extremely low glass transition temperature, flexibility and hydrophobic surface properties. [5][6][7][8] These properties of PDMS make it suitable for use in different industries. [9][10][11][12][13] Several studies have been reported on the phase behavior of PE/PDMS composites.…”