3 These systems are manufactured via radical copolymerization of silane-functional acrylates and (meth)acrylate monomers. The combination of these two curing mechanisms, organic and inorganic, provides outstanding properties to the coatings.Īcrylic-silane systems, on the other hand, cure only via the inorganic hydrolysis-condensation sequence of the silane groups.
This is complemented by an inorganic curing of silane groups, initiated by the ambient moisture (Figure 1). After mixing and coating application, the curing via epoxy-amine organic crosslinking occurs within hours. The amine and the aliphatic epoxy must therefore be kept in two separate cans and mixed shortly before coating application to avoid premature curing (2K). In the case of epoxy-polysiloxanes, the curing mechanism of the oxiranes is typically activated by an aminosilane monomer, like aminopropyltrimethoxysilane. 2 To achieve optimal performance, the typical level of a methy-phenyl polysiloxane ranges from 37 to 77 wt%, 2 which brings the cost of these systems to excessively high levels. In both cases, an inorganic polysiloxane resin is reacted with the organic epoxy or acrylic resin to balance and optimize properties like viscosity, durability, cohesive strength and adhesion. Today, most leading protective coatings suppliers offer silicone-containing coatings based on epoxy-polysiloxane and/or acrylic-polysiloxane chemistries. Instead, silicone coatings usually combine an inorganic polysiloxane with and organic resin.
Coatings based solely on polysiloxane resins, however, have limited market penetration. The extreme durability and resistance of glass, which is actually a giant polysiloxane network, exemplifies the outstanding properties of polysiloxanes well. Furthermore, the bond dissociation energy for the Si-O bond is about 33% higher than that of C-C bonds. The durability of polysiloxanes, can easily be understood considering that the Si-O bond is in an oxidized state and cannot be further oxidized, unlike carbon – carbon bonds in organic compounds. They are particularly appreciated for their very high durability and have often replaced polyurethanes. Today they are specified for a wide range of steel constructions, including highly demanding applications such as offshore platforms, storage tanks and pipes. Silicone-containing coatings play an ever-increasing role since their introduction in the mid-90’s. These factors make these vinyl silane copolymers an attractive alternative to 2K polyurethanes and acrylic-alkoxysiloxanes for several topcoat applications, especially protective coatings. Performance evaluation of 1- and 2K moisture-cure coatings based on this cost-efficient and highly versatile technology demonstrates that it brings high solids content, fast hardness development and very long shelf life, in addition to being isocyanate-free.
#Hexio level 22 series#
Variation of process parameters, monomer composition and alkoxysilane levels yielded a series of polymers with solids content between 70 and 100%, and exhibiting a wide range of attractive properties. This article presents a new family of polymers, which combine vinyl (neo)ester and vinyl alkoxysilane monomers.
However, these alternatives have seen limited market penetration, due to an unfavourable cost/performance ratio. Similar to 2K polyurethanes, these systems display a broad range of performance characteristics, depending on their structure and composition. Moisture-curing topcoats based on acrylic-and epoxy-alkoxysiloxane resins have been increasingly used as isocyanate-free alternatives in marine and protective applications. PCI - November 2019 Novel 1K and 2K Moisture-Curing Vinyl Alkoxysilane Technology, Hexion Inc.
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